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1.  Pharmacokinetics and skin-tissue penetration of daptomycin in rats 
Background
Daptomycin is recommended for complicated skin and skin-structure infections. However, information on the penetration of daptomycin into skin is limited. Therefore, the aim of this in vivo investigation was to determine the pharmacokinetics and skin penetration of daptomycin in rats.
Materials and methods
Concentrations of daptomycin were determined by high-performance liquid chromatography. A noncompartmental pharmacokinetic analysis was conducted to estimate the rate and extent of daptomycin penetration from the systemic circulation into skin tissue. Since protein binding of daptomycin in rat serum was 89.3%, the free maximum concentration (Cmax) and free area under the curve from time 0 to infinity (AUC0–∞) for plasma were calculated as follows: fCmax, plasma = (1 – 0.893) × Cmax, plasma, fAUC0–∞, plasma = (1 – 0.893) × AUC0–∞, plasma.
Results
The following values (mean ± standard deviation) were obtained: 0.06±0 L/h/kg for total clearance (CLtotal), 0.44±0.06 hours for elimination-rate constant, 1.58±0.23 hours for half-life, 0.14±0.02 L/kg for steady-state volume distribution, and 2.28±0.33 hours for mean residence time. Time to Cmax was 3.0 hours for plasma and skin tissue. Cmax and AUC0–∞ for plasma were 175.8±5.1 μg/mL and 811.8±31.9 μg × h/mL, respectively. Cmax and AUC0–∞ for skin tissue were 19.1±1.7 μg/mL and 113.9±21.8 μg × h/mL, respectively. Furthermore, fCmax and fAUC0–∞ for plasma were 18.8 μg/mL and 86.9 μg × h/mL, respectively. The degrees of skin-tissue penetration, defined as the Cmax, skin tissue/fCmax, plasma ratio and AUC0–∞, skin tissue/fAUC0–∞, plasma ratio, were 1.0 and 1.3, respectively.
Conclusion
Daptomycin exhibited good penetration into skin tissue, supporting its use for the treatment of complicated skin and skin-structure infections. However, further studies are needed in infected patients in order to investigate the relationship between the antimicrobial efficacy of daptomycin and its drug concentrations in skin tissues.
doi:10.2147/CPAA.S83447
PMCID: PMC4445693  PMID: 26056496
daptomycin; pharmacokinetics; rat; skin-tissue penetration
3.  Pharmacokinetic equivalence study of two formulations of the anticonvulsant pregabalin 
Purpose
The present study was conducted to evaluate whether the bioavailability of pregabalin capsules 150 mg manufactured by PT Dexa Medica was equivalent to the reference formulation.
Methods
This was a randomized, open-label, two-period, two-sequence, and crossover study under fasting condition, with a 1-week washout period. Plasma concentrations of pregabalin from 20 subjects were determined by using a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) detection method. Pharmacokinetic parameters assessed in this study were: area under the plasma concentration–time curve from time zero to last observed quantifiable concentration (AUC0–t), area under the plasma concentration–time curve from time zero to infinity (AUC0–∞), maximum plasma concentration (Cmax), time to maximum plasma concentration (tmax), and terminal half-life (t1/2). The 90% confidence intervals (CIs) for the geometric mean ratios of test formulation/reference formulation were calculated for the AUC and Cmax parameters; while tmax difference was analyzed nonparametrically on the original data using the Wilcoxon matched-pairs test, and t1/2 difference was analyzed using Student’s paired t-test.
Results
The mean (standard deviation [SD]) AUC0–t, AUC0–∞, Cmax, and t1/2 of pregabalin from the test formulation were 27,845.86 (4,508.27) ng · h/mL, 28,311.70 (4,790.55) ng · h/mL, 3,999.71 (801.52) ng/mL, and 5.66 (1.20) hours, respectively; while the mean (SD) AUC0–t, AUC0–∞,Cmax, and t1/2 of pregabalin from the reference formulation were 27,398.12 (4,266.28) ng · h/mL, 27,904.24 (4,507.31) ng · h/mL, 3,849.50 (814.50) ng/mL, and 5.87 (1.25) hours, respectively. The median (range) tmax of pregabalin from the test formulation and reference formulation was 1.00 (0.67–2.00) hours and 1.00 (0.67–3.00) hours, respectively. The 90% CIs for the geometric mean ratios of test formulation/reference formulation for pregabalin were 101.54% (98.75%–104.41%) for AUC0–t, 101.35% (98.66%–104.11%) for AUC0–∞, and 104.19% (98.75%–109.93%) for Cmax.
Conclusion
The study concluded that the two formulations of pregabalin capsules studied were bioequivalent.
Video abstract
doi:10.2147/CPAA.S82143
PMCID: PMC4408967  PMID: 25945069
antiepileptic; bioavailability; bioequivalence; generic product
4.  Expanding antitumor therapeutic windows by targeting cancer-specific nicotinamide adenine dinucleotide phosphate-biogenesis pathways 
Nicotinamide adenine dinucleotide phosphate (NADPH) biogenesis is an essential mechanism by which both normal and cancer cells maintain redox balance. While antitumor approaches to treat cancers through elevated reactive oxygen species (ROS) are not new ideas, depleting specific NADPH-biogenesis pathways that control recovery and repair pathways are novel, viable approaches to enhance cancer therapy. However, to elicit efficacious therapies exploiting NADPH-biogenic pathways, it is crucial to understand and specifically define the roles of NADPH-biogenesis pathways used by cancer cells for survival or recovery from cell stress. It is equally important to select NADPH-biogenic pathways that are expendable or not utilized in normal tissue to avoid unwanted toxicity. Here, we address recent literature that demonstrates specific tumor-selective NADPH-biogenesis pathways that can be exploited using agents that target specific cancer cell pathways normally not utilized in normal cells. Defining NADPH-biogenesis profiles of specific cancer-types should enable novel strategies to exploit these therapeutic windows for increased efficacy against recalcitrant neoplastic disease, such as pancreatic cancers. Accomplishing the goal of using ROS as a weapon against cancer cells will also require agents, such as NQO1 bioactivatable drugs, that selectively induce elevated ROS levels in cancer cells, while normal cells are protected.
doi:10.2147/CPAA.S79760
PMCID: PMC4381889  PMID: 25870517
reactive oxygen species (ROS); NQO1-bioactivatable drugs; nicotinamide adenine dinucleotide phosphate (NADPH); glutathione (GSH); biogenic pathways; antioxidant
5.  Carbon monoxide: a critical quantitative analysis and review of the extent and limitations of its second messenger function 
Endogenously produced carbon monoxide (CO) is commonly believed to be a ubiquitous second messenger involved in a wide range of physiological and pathological responses. The major evidence supporting this concept is that CO is produced endogenously via heme oxygenase-catalyzed breakdown of heme and that experimental exposure to CO alters tissue function. However, it remains to be conclusively demonstrated that there are specific receptors for CO and that endogenous CO production is sufficient to alter tissue function. Unlike other signaling molecules, CO is not significantly metabolized, and it is removed from cells solely via rapid diffusion into blood, which serves as a near infinite sink. This non-metabolizable nature of CO renders the physiology of this gas uniquely susceptible to quantitative modeling. This review analyzes each of the steps involved in CO signaling: 1) the background CO partial pressure (PCO) and the blood and tissue CO binding; 2) the affinity of the putative CO receptors; 3) the rate of endogenous tissue CO production; and 4) the tissue PCO that results from the balance between this endogenous CO production and diffusion to the blood sink. Because existing data demonstrate that virtually all endogenous CO production results from the routine “housekeeping” turnover of heme, only a small fraction can play a signaling role. The novel aspect of the present report is to demonstrate via physiological modeling that this small fraction of CO production is seemingly insufficient to raise intracellular PCO to the levels required for the conventional, specific messenger receptor activation. It is concluded that the many physiological alterations observed with exogenous CO administration are probably produced by the non-specific CO inhibition of cytochrome C oxidase activity, with release of reactive oxygen species (ROS) and that this ROS signaling pathway is a potential effector mechanism for endogenously produced CO.
doi:10.2147/CPAA.S79626
PMCID: PMC4348054  PMID: 25750547
cytochrome; oxygenase; Krogh cylinder model; ROS; heme
6.  Severe iatrogenic bradycardia related to the combined use of beta-blocking agents and sodium channel blockers 
Purpose
Drug-induced bradycardia is common during antiarrhythmic therapy; the major culprits are beta-blockers. However, whether other antiarrhythmic drugs are also a significant cause of this, alone or in combination with beta-blockers, is not well known.
Methods
We retrospectively investigated the records of all patients hospitalized at our institution for drug-related bradycardia from the years 2004 to 2012. Patients with cardiac disease and electrolytic or hormonal abnormalities that could cause bradyarrhythmias were excluded.
Results
Eight patients were identified (mean age, 79±5 years; range, 71–85 years; 6 women). Three patients were taking only beta-blockers (hereafter referred to as the BB group), while five patients were on both beta-blockers and Na channel blockers (hereafter referred to as the BB + Na group). Heart rates ranged from 20∼49 beats/minute on arrival. The initial electrocardiogram showed sinus bradycardia (n=6) or sinus arrest with escape beats (n=2). QRS duration was 80–100 ms. The clinical presentation of the BB + Na group was considerably worse than that of the BB group, and included cardiogenic shock and heart failure. Four of the BB + Na patients had been on their medications for over 300 days. The BB group recovered solely with drug discontinuation, while 4 of the 5 patients in the BB + Na group needed additional treatments, such as intravenous administration of atropine or adrenergic agonist and temporary pacing. Bradycardia did not recur during follow-up (median, 687 days).
Conclusion
Although wide QRS ventricular tachyarrhythmia is a better known proarrhythmic effect of Na channel blockers, life-threatening bradycardia may also occur in combination with beta-blockers in the elderly, even months after the start of medication, and at plasma concentrations that do not prolong QRS width.
doi:10.2147/CPAA.S77021
PMCID: PMC4337503  PMID: 25733934
proarrhythmia; elderly; QRS duration
7.  Heparin requirements for full anticoagulation are higher for patients on dabigatran than for those on warfarin – a model-based study 
Purpose
Dabigatran (D) is increasingly used for chronic anticoagulation in place of warfarin (W). These patients may present for catheter-based procedures requiring full anticoagulation with heparin. This study compares the heparin sensitivity of patients previously on dabigatran, on warfarin, or on no chronic anticoagulant during ablation of atrial fibrillation.
Patients and methods
In a retrospective study of patients treated with D, W, or neither drug (N) undergoing atrial ablation, the timing of heparin doses and resulting activated clotting times were collected. First, the initial activated clotting time response to the first heparin bolus was compared. Then, a non-linear mixed effects modelling (NONMEM) analysis was performed, fitting a pharmacokinetic and -dynamic model to the entire anticoagulation course of each patient. Resulting model coefficients were used to compare the different patient groups.
Results
Data for 66 patients on dabigatran, 95 patients on warfarin, and 27 patients on no anticoagulation were retrieved. The last dose of dabigatran or warfarin had occurred 27 hours and 15 hours before the procedure. Groups D and N both responded significantly less (P<0.05) to the initial heparin bolus than Group W (approximately 50%). Likewise, the model coefficients resulting from the fit to each group reflected a significantly lower heparin sensitivity in groups D and N compared to W. Clearances of the heparin effect in the model did not differ significantly among groups.
Conclusion
Patients on warfarin with an average INR of 1.5 or higher are more sensitive to heparin than patients not previously anticoagulated or patients who discontinued dabigatran 27 hours earlier (approximately two half-lives) warfarin.
doi:10.2147/CPAA.S72185
PMCID: PMC4327399  PMID: 25709508
atrial fibrillation; electrophysiology; NONMEM; PKPD model
8.  Bioavailability of everolimus administered as a single 5 mg tablet versus five 1 mg tablets: a randomized, open-label, two-way crossover study of healthy volunteers 
Background
The mammalian target of rapamycin (mTOR) inhibitor everolimus has a well-established pharmacokinetics profile. We conducted a randomized, single-center, open-label, two-sequence, two-period crossover study of healthy volunteers to assess the relative bioavailability of everolimus administered as one 5 mg tablet or five 1 mg tablets.
Methods
Subjects were randomized 1:1 to receive everolimus dosed as one 5 mg tablet or as five 1 mg tablets on day 1, followed by a washout period on days 8–14 and then the opposite formulation on day 15. Blood sampling for pharmacokinetic evaluation was performed at prespecified time points, with 17 samples taken for each treatment period. Primary variables for evaluation of relative bioavailability were area under the concentration–time curve from time zero to infinity (AUCinf) and maximum blood concentration (Cmax). Safety was assessed by reporting the incidence of adverse events (AEs).
Results
Twenty-two participants received everolimus as one 5 mg tablet followed by five 1 mg tablets (n=11) or the opposite sequence (n=11). The Cmax of five 1 mg tablets was 48% higher than that of one 5 mg tablet (geometric mean ratio, 1.48; 90% confidence interval [CI], 1.35–1.62). AUCinf was similar (geometric mean ratio, 1.08; 90% CI, 1.02–1.16), as were the extent of absorption and the distribution and elimination kinetics. AEs, all grade 1 or 2, were observed in 54.5% of subjects.
Conclusion
Although the extent of absorption was similar, the Cmax of five 1 mg tablets was higher than that of one 5 mg tablet, suggesting these formulations lead to different peak blood concentrations and are not interchangeable at the dose tested.
doi:10.2147/CPAA.S73472
PMCID: PMC4310326  PMID: 25653564
absorption kinetics; healthy volunteers
9.  Effects of food and alcohol on the pharmacokinetics of an oral, extended-release formulation of hydrocodone in healthy volunteers 
Background
The purpose of this study was to evaluate the pharmacokinetics, bioavailability, and safety of oral extended-release hydrocodone (HC-ER) when administered with food or alcohol.
Methods
Two single-center, open-label, randomized, crossover studies were conducted in healthy volunteers. In a two-period food-interaction study, 12 subjects received HC-ER 20 mg after an overnight fast and a high-fat meal. In a three-period alcohol-interaction study, 30 naltrexone-blocked subjects received HC-ER 50 mg with a 0%, 20%, or 40% alcohol/orange juice solution after an overnight fast. Pharmacokinetic parameters were derived from plasma concentrations of hydrocodone and its metabolites.
Results
Exposure to hydrocodone after HC-ER 20 mg was similar in the fed and fasted states, as assessed by area under the plasma concentration versus time curve from time of dosing to time of last detectable concentration (AUC0–t; 316.14 versus 311.94 ng · h/mL); relative bioavailability (Frel) was 101.74%. Differences (fed versus fasted) in hydrocodone mean maximum plasma concentration (Cmax; 28.86 versus 22.74 ng/mL) and median time to Cmax (tmax; 6 versus 8 hours) were not clinically significant. Administration of 20% alcohol with HC-ER 50 mg did not increase systemic exposure relative to 0% alcohol (AUC0–t 878 versus 832 ng · h/mL; Frel 105%) or result in clinically meaningful changes in Cmax (51.8 versus 46.3 ng/mL) or tmax (5.44 versus 6.16 hours). Administration with 40% alcohol increased AUC0–t (1,008 ng · h/mL versus 832 ng · h/mL; Frel 120%) and Cmax (109 versus 46.3 ng/mL), and shortened tmax (2.43 versus 6.16 hours). Adverse events occurred in 10.0%, 24.1%, and 66.7% of subjects after 0%, 20%, and 40% alcohol, respectively.
Conclusion
HC-ER can be administered without regard to meals. While there was no evidence of “dose-dumping” (an unintended, rapid release in a short time period of all or most of the hydrocodone from HC-ER), even with 40% alcohol, as with all opioids, alcohol should not be ingested while using HC-ER.
doi:10.2147/CPAA.S70831
PMCID: PMC4307648  PMID: 25653563
opioid; food interaction; alcohol interaction; bioavailability; norhydrocodone; hydromorphone
10.  Enantiomer-selective pharmacokinetics, oral bioavailability, and sex effects of various alpha-lipoic acid dosage forms 
The present study aimed to examine the enantiomer-selective pharmacokinetics (PK), relative bioavailability (Frel), and sex effects of various oral dosage forms of racemic alpha-lipoic acid (ALA). In an open-label, randomized, four-period, four-sequence crossover study, 24 healthy adult subjects (12 males and 12 females) received single doses of 600 mg of ALA in fasted state at four different occasions as follows: three 200 mg tablets (T 200); two 300 mg tablets (T 300); one 600 mg tablet (T 600); and a racemic ALA solution (OS). All tablet formulations (Thioctacid HR) were considered test treatments, while the OS (Thioctacid, 600 T) served as the reference treatment. Serial blood samples were collected over 8 hours postdose to quantify R-(+)- and S-(−)-ALA enantiomer plasma concentrations for the PK evaluation. The maximum observed plasma concentration (Cmax) and total exposure (area under the curve [AUC]0–t) were compared between treatments by analysis of variance. Weight-normalized Cmax and the AUC data of male and female study subjects were applied to examine the presence of sex effects. All treatments displayed rapid absorption of both enantiomers with median time to maximum concentration (tmax) values ranging from 0.33–0.5 hours. The Frel of all tablet formulations was comparable, with R-(+)-enantiomer Cmax test/reference ratios ranging from 36% (T 600) to 43% (T 200), and R-(+)-enantiomer AUC test/reference ratios ranging from 64% (T 600) to 79% (T 300), indicating a favorable Frel of all tablet formulations, especially in terms of the total extent of absorption (AUC). An examination of weight-normalized female/male Cmax and AUC sex ratios for both ALA enantiomers indicated the absence of a significant sex effect for Cmax, as well as 20%–26% and 25%–32% higher R-(+)- and S-(−)-ALA enantiomer AUC outcomes in females when compared to males. The observed modest sex effect was comparable for both ALA enantiomers and across all formulations, and it did not appear to require a dose adjustment in clinical practice.
doi:10.2147/CPAA.S71574
PMCID: PMC4258503  PMID: 25506250
alpha-lipoic acid; thioctic acid; enantiomers; sex effect; formulation effect; bioavailability
11.  Parkinson’s disease: carbidopa, nausea, and dyskinesia 
When l-dopa use began in the early 1960s for the treatment of Parkinson’s disease, nausea and reversible dyskinesias were experienced as continuing side effects. Carbidopa or benserazide was added to l-dopa in 1975 solely to control nausea. Subsequent to the increasing use of carbidopa has been the recognition of irreversible dyskinesias, which have automatically been attributed to l-dopa. The research into the etiology of these phenomena has identified the causative agent of the irreversible dyskinesias as carbidopa, not l-dopa. The mechanism of action of the carbidopa and benserazide causes irreversible binding and inactivation of vitamin B6 throughout the body. The consequences of this action are enormous, interfering with over 300 enzyme and protein functions. This has the ability to induce previously undocumented profound antihistamine dyskinesias, which have been wrongly attributed to l-dopa and may be perceived as irreversible if proper corrective action is not taken.
doi:10.2147/CPAA.S72234
PMCID: PMC4238750  PMID: 25484598
vitamin B6; PLP; irreversible; pyridoxal 5’-phosphate
12.  A randomized direct comparison of the pharmacokinetics and pharmacodynamics of apixaban and rivaroxaban 
Background
Currently, there are no direct comparisons of apixaban and rivaroxaban, two new oral direct factor Xa inhibitors approved for management of thromboembolic disorders.
Objective
Compare the pharmacokinetics and anti-factor Xa activity (AXA) of apixaban and rivaroxaban.
Methods
In this randomized, open-label, two-period, two-treatment crossover study, healthy subjects (N=14) received apixaban 2.5 mg twice daily (BID) and rivaroxaban 10 mg once daily (QD) for 4 days with a ≥4.5-day washout. Plasma samples were obtained for pharmacokinetic and AXA assessments; parameters were calculated using noncompartmental methods.
Results
Median time-to-maximum concentration was 2 hours for both compounds, and the mean half-life was 8.7 and 7.9 hours for apixaban and rivaroxaban, respectively. Daily exposure, the area under the curve (AUC(0–24)), appeared similar for rivaroxaban (1,094 ng · h/mL) and apixaban (935 ng · h/mL), whereas mean peak-to-trough plasma concentration ratio was 3.6-fold greater for rivaroxaban (16.9) than apixaban (4.7). Coefficient of variation for exposure parameters (AUC0–24, Cmax, Cmin) was 20%–24% for apixaban versus 29%–46% for rivaroxaban. Peak AXA, AXA AUC(0–24), and AXA fluctuation were ~2.5-, 1.3-, and 3.5-fold higher for rivaroxaban than apixaban, respectively. Trough concentrations and AXA were lower for rivaroxaban (10 ng/mL and 0.17 IU/mL vs 17 ng/mL and 0.24 IU/mL for apixaban, respectively). Rivaroxaban exhibited a steeper concentration–AXA response (slope: 0.0172 IU/ng vs 0.0134 IU/ng for apixaban, P<0.0001).
Conclusion
Apixaban 2.5 mg BID demonstrated less intersubject variability in exposure, lower AXA AUC, and higher trough and smaller peak-to-trough fluctuations in plasma concentration and AXA, suggesting more constant anticoagulation compared with rivaroxaban 10 mg QD. However, the clinical impact of these differences on the relative efficacy and safety of apixaban and rivaroxaban remains to be determined.
doi:10.2147/CPAA.S61131
PMCID: PMC4235474  PMID: 25419161
apixaban; pharmacodynamics; pharmacokinetics; rivaroxaban; safety
13.  Evaluating the effects of dexmedetomidine compared to propofol as adjunctive therapy in patients with alcohol withdrawal 
Background
In severe alcohol withdrawal (AW), benzodiazepines may be inadequate to control symptoms. In many situations, benzodiazepine dosing escalates despite no additional efficacy and introduces potential toxicities. Severe cases of AW may require additional agents to control symptoms. Case reports and studies have shown benefits with dexmedetomidine and propofol in severe AW, but these agents have not been compared with one another. This study compares the effects of dexmedetomidine and propofol on benzodiazepine and haloperidol utilization in patients with AW.
Methods
A retrospective chart review was completed on 41 patients with AW who received adjunctive dexmedetomidine or propofol. The primary objective was to compare benzodiazepine and haloperidol utilization before and after initiation of dexmedetomidine or propofol. Secondary measures included AW and sedation scoring, analgesic use, intensive care unit length of stay, rates of intubation, and adverse events.
Results
Among the dexmedetomidine and propofol groups, significant reductions in benzodiazepine (P≤0.0001 and P=0.043, respectively) and haloperidol (P≤0.0001 and P=0.026, respectively) requirements were observed. These reductions were comparable between groups (P=0.933 and P=0.465, respectively). A trend toward decreased intensive care unit length of stay in the dexmedetomidine group (123.6 hours vs 156.5 hours; P=0.125) was seen. Rates of intubation (14.7% vs 100%) and time of intubation (19.9 hours vs 97.6 hours; P=0.002) were less in the dexmedetomidine group. Incidence of hypotension was 17.6% in the dexmedetomidine group vs 28.5% in the propofol group. Incidence of bradycardia was 17.6% in the dexmedetomidine group vs 0% in the propofol group. No differences were observed in other secondary outcomes.
Conclusion
In patients with severe AW who require sedation, both dexmedetomidine and propofol have unique and advantageous properties. Both agents appear to have equivalent efficacy in reducing AW-related symptoms and benzodiazepine and haloperidol requirements. These results should be validated in a larger, prospective trial.
doi:10.2147/CPAA.S70490
PMCID: PMC4222895  PMID: 25382987
dexmedetomidine; propofol; benzodiazepines; alcohol; withdrawal
14.  The Parkinson’s disease death rate: carbidopa and vitamin B6 
The only indication for carbidopa and benserazide is the management of L-3,4-dihydroxyphenylalanine (L-dopa)-induced nausea. Both drugs irreversibly bind to and permanently deactivate pyridoxal 5′-phosphate (PLP), the active form of vitamin B6, and PLP-dependent enzymes. PLP is required for the function of over 300 enzymes and proteins. Virtually every major system in the body is impacted directly or indirectly by PLP. The administration of carbidopa and benserazide potentially induces a nutritional catastrophe. During the first 15 years of prescribing L-dopa, a decreasing Parkinson’s disease death rate was observed. Then, in 1976, 1 year after US Food and Drug Administration approved the original L-dopa/carbidopa combination drug, the Parkinson’s disease death rate started increasing. This trend has continued to the present, for 38 years and counting. The previous literature documents this increasing death rate, but no hypothesis has been offered concerning this trend. Carbidopa is postulated to contribute to the increasing Parkinson’s disease death rate and to the classification of Parkinson’s as a progressive neurodegenerative disease. It may contribute to L-dopa tachyphylaxis.
doi:10.2147/CPAA.S70707
PMCID: PMC4211847  PMID: 25364278
L-dopa; levodopa; vitamin B6; pyridoxal 5′-phosphate
15.  Lack of effect of ezogabine/retigabine on the pharmacokinetics of digoxin in healthy individuals: results from a drug–drug interaction study 
Introduction
The potential for ezogabine/retigabine (EZG/RTG) and its N-acetyl metabolite (NAMR) to inhibit the transporter protein P-glycoprotein-(P-gp)-mediated digoxin transport was tested in vitro. EZG/RTG did not inhibit P-gp. However, NAMR inhibited P-gp in a concentration-dependent manner. Based on these in vitro results, NAMR had the potential to inhibit P-gp at therapeutic doses of EZG/RTG (600–1,200 mg/day). As digoxin has a narrow therapeutic index, inhibition of digoxin clearance may have an impact on its safety.
Methods
An open-label, single-center, two session, fixed-sequence study was conducted to assess the effect of co-administration of therapeutic doses of EZG/RTG on digoxin pharmacokinetics in healthy adults. In session 1, subjects received a single dose of digoxin 0.25 mg. In session 2, EZG/RTG was up-titrated over 6 weeks. Digoxin 0.25 mg was co-administered at EZG/RTG steady-state doses of 600, 900, and, based on tolerability, 1,050/1,200 mg/day. Blood samples were collected over 144 hours for determination of digoxin, EZG/RTG, and NAMR concentrations. Urine samples were collected over 48 hours for determination of digoxin concentrations.
Results
Of 30 subjects enrolled, 29 were included in the pharmacokinetic analysis. Compared with digoxin alone, co-administration with EZG/RTG led to small increases in the digoxin plasma area under the concentration–time curve (AUC)0–120 at doses of 600, 900, and 1,050/1,200 mg (geometric mean ratio 1.08, 90% confidence interval [CI] 1.01–1.15; 1.18, 90% CI 1.10–1.27; 1.13, 90% CI 1.05–1.21, respectively). Safety was consistent with previous repeat-dose studies of EZG/RTG in healthy subjects.
Conclusion
Co-administration of EZG/RTG across the therapeutic range resulted in small, non-dose-dependent and non-clinically relevant increases in digoxin systemic exposure, suggesting that digoxin dose adjustment is not necessary.
doi:10.2147/CPAA.S64131
PMCID: PMC4206209  PMID: 25342921
digoxin; retigabine; ezogabine; drug–drug interactions
16.  Arbekacin: another novel agent for treating infections due to methicillin-resistant Staphylococcus aureus and multidrug-resistant Gram-negative pathogens 
Arbekacin sulfate (ABK), an aminoglycoside antibiotic, was discovered in 1972 and was derived from dibekacin to stabilize many common aminoglycoside modifying enzymes. ABK shows broad antimicrobial activities against not only Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) but also Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. ABK has been approved as an injectable formulation in Japan since 1990, under the trade name Habekacin, for the treatment of patients with pneumonia and sepsis caused by MRSA. The drug has been used in more than 250,000 patients, and its clinical benefit and safety have been proven over two decades. ABK currently shows promise for the application for the treatment of multidrug-resistant Gram-negative bacterial infections such as multidrug-resistant strains of P. aeruginosa and Acinetobacter baumannii because of its synergistic effect in combination with beta-lactams.
doi:10.2147/CPAA.S44377
PMCID: PMC4186621  PMID: 25298740
synergistic effect; Habekacin; MRSA; multidrug-resistant Gram-negative bacteria
17.  Melatonergic drugs in development 
Melatonin (N-acetyl-5-methoxytryptamine) is widely known as “the darkness hormone”. It is a major chronobiological regulator involved in circadian phasing and sleep-wake cycle in humans. Numerous other functions, including cyto/neuroprotection, immune modulation, and energy metabolism have been ascribed to melatonin. A variety of studies have revealed a role for melatonin and its receptors in different pathophysiological conditions. However, the suitability of melatonin as a drug is limited because of its short half-life, poor oral bioavailability, and ubiquitous action. Due to the therapeutic potential of melatonin in a wide variety of clinical conditions, the development of new agents able to interact selectively with melatonin receptors has become an area of great interest during the last decade. Therefore, the field of melatonergic receptor agonists comprises a great number of structurally different chemical entities, which range from indolic to nonindolic compounds. Melatonergic agonists are suitable for sleep disturbances, neuropsychiatric disorders related to circadian dysphasing, and metabolic diseases associated with insulin resistance. The results of preclinical studies on animal models show that melatonin receptor agonists can be considered promising agents for the treatment of central nervous system-related pathologies. An overview of recent advances in the field of investigational melatonergic drugs will be presented in this review.
doi:10.2147/CPAA.S36600
PMCID: PMC4172069  PMID: 25258560
MT1/MT2 ligands; circadian rhythms; melatonin
18.  Reducing medication errors in critical care: a multimodal approach 
The Institute of Medicine has reported that medication errors are the single most common type of error in health care, representing 19% of all adverse events, while accounting for over 7,000 deaths annually. The frequency of medication errors in adult intensive care units can be as high as 947 per 1,000 patient-days, with a median of 105.9 per 1,000 patient-days. The formulation of drugs is a potential contributor to medication errors. Challenges related to drug formulation are specific to the various routes of medication administration, though errors associated with medication appearance and labeling occur among all drug formulations and routes of administration. Addressing these multifaceted challenges requires a multimodal approach. Changes in technology, training, systems, and safety culture are all strategies to potentially reduce medication errors related to drug formulation in the intensive care unit.
Video abstract
doi:10.2147/CPAA.S48530
PMCID: PMC4155993  PMID: 25210478
medication safety; drug design; drug formulation; patient safety
19.  Differential renal adverse effects of ibuprofen and indomethacin in preterm infants: a review 
Objective
The objective of this study was to evaluate the extent of renal adverse effects caused by ibuprofen or indomethacin in order to choose the safer drug to administer to preterm infants.
Methods
The following three parameters of renal function were taken into consideration: 1) the urine output; 2) the serum creatinine concentration; and 3) the frequency of oliguria. The bibliographic search was performed using PubMed and Embase databases as search engines.
Results
Urine output ranged from 3.5±1.2 to 4.0±1.4 mL/kg/h after ibuprofen treatment, and from 2.8±1.1 to 3.6±1.4 mL/kg/h after indomethacin treatment. The values for ibuprofen are significantly (P<0.05) higher than those for indomethacin. The serum creatinine concentrations ranged from 0.98±0.24 to 1.48±0.2 mg/dL after ibuprofen treatment, and from 1.06±0.24 and 2.03±2.10 mg/dL after indomethacin treatment. The values for ibuprofen are significantly (P<0.05) lower than those for indomethacin. The frequency of oliguria ranged from 1.0% to 9.6% (ibuprofen) and from 14.8% to 40.0% (indomethacin), and was significantly lower following ibuprofen than indomethacin administration. In infants with body weight lower than 1,000 g, oliguria appeared in 5% (ibuprofen) and 40% (indomethacin; P=0.02).
Conclusion
Indomethacin is associated with more severe renal adverse effects than ibuprofen. Ibuprofen is less nephrotoxic than indomethacin and should be used to treat patent ductus arteriosus in preterm infants. Immaturity increases the frequency of adverse effects of indomethacin.
doi:10.2147/CPAA.S59376
PMCID: PMC4124049  PMID: 25114597
ibuprofen; indomethacin; patent-ductus-arteriosus; renal-side-effects
20.  Administration of supplemental L-tyrosine with phenelzine: a clinical literature review 
The subject of this literature review is the alleged relationship between L-tyrosine, phenelzine, and hypertensive crisis. Phenelzine (Nardil®) prescribing information notes: “The potentiation of sympathomimetic substances and related compounds by MAO inhibitors may result in hypertensive crises (see WARNINGS). Therefore, patients being treated with NARDIL should not take […] L-tyrosine […]”. Interest in the scientific foundation of this claim was generated during routine patient care. A comprehensive literature search of Google Scholar and PubMed revealed no reported cases of hypertensive crisis associated with concomitant administration of L-tyrosine and phenelzine. Review of current US Food and Drug Administration nutritional guidelines relating to ongoing phenelzine studies reveals no mention and requires no consideration of L-tyrosine ingestion in combination with phenelzine. This paper is intended to provide an objective review of the science to then allow the reader to formulate the final opinion.
doi:10.2147/CPAA.S67271
PMCID: PMC4112771  PMID: 25092999
hypertensive crisis; phenelzine; tyrosine; tyramine; stroke; phenelzine
21.  Effect of age and sex on warfarin dosing 
Objective
We examined the potential effect of sex and age on warfarin dosing in ambulatory adult patients.
Methods
We conducted a retrospective chart review of patients attending an anticoagulation clinic. We included patients anticoagulated with warfarin for atrial fibrillation or venous thromboembolism who had a therapeutic international normalized ratio of 2–3 for 2 consecutive months. We excluded patients who had been on any drug that is known to have a major interaction with warfarin, smokers, and heavy alcohol consumers. Out of 340 screened medical records, 96 met the predetermined inclusion criteria. The primary outcome assessed was warfarin total weekly dose (TWD).
Results
There was a statistically significant difference in the TWD among the ages (P<0.01); older patients required lower doses. However there was no statistically significant difference in the TWD between sexes (P=0.281).
Conclusion
Age was found to have a significant effect on warfarin dosing. Even though women did require a lower TWD than men, this observation was not statistically significant.
doi:10.2147/CPAA.S66776
PMCID: PMC4103915  PMID: 25050078
warfarin; INR; anticoagulation; vitamin K antagonists; age
22.  In vitro microdialysis membrane efficiency of broad-spectrum antibiotics in combination and alone 
Purpose
Microdialysis is a valuable technique for studying the distribution of drugs into interstitial fluid, the target site for a pharmacologic effect. Due to incomplete equilibrium, retrodialysis is a method used to correct for relative recovery. The impact of two-drug combinations on probe recovery, however, remains unknown.
Methods
In vitro microdialysis was conducted for five antibiotics (avibactam, cefepime, ceftaroline, piperacillin-tazobactam, and vancomycin), representing three empiric antimicrobial regimens, to assess the impact of two-drug combinations on probe recovery. Recoveries were compared between single and two-drug treatments.
Results
Recoveries by gain and loss were linear with their molecular weight. During all gain experiments, recoveries were similar when tested alone or in combination with another antibiotic. Unacceptable differences in recovery by loss were observed for cefepime in the presence of vancomycin (−21%) and vancomycin in the presence of piperacillin-tazobactam (−22%).
Conclusion
Differences among in vitro recovery by loss suggest two-drug combinations may impact dialysate recovery during in vivo retrodialysis procedures, particularly when larger molecular weight drugs (ie, vancomycin) are involved. Importantly, there were no differences during gain experiments. In vitro studies, as performed here, should be conducted for each potential two-drug combination, prior to their combined use for in vivo retrodialysis.
doi:10.2147/CPAA.S65389
PMCID: PMC4051625  PMID: 24940084
microdialysis; retrodialysis; combination therapy
23.  Incidence and management of adverse events in patients with relapsed and/or refractory multiple myeloma receiving single-agent carfilzomib 
Carfilzomib, a selective proteasome inhibitor approved in the USA in 2012, is a single agent for relapsed and refractory multiple myeloma. Carfilzomib is administered as a 2–10-minute infusion on days 1, 2, 8, 9, 15, and 16 of a 28-day cycle at a starting dose of 20 mg/m2 for cycle 1 and a target dose of 27 mg/m2 thereafter. In the pivotal Phase II study (PX-171-003-A1), carfilzomib 20/27 mg/m2 provided durable responses in a heavily pretreated population with relapsed and refractory multiple myeloma (n=266), with an overall response rate of 22.9% and a median duration of response of 7.8 months. In an integrated safety analysis of four Phase II studies, common adverse events (32.7%–55.5%) included fatigue, anemia, nausea, thrombocytopenia, dyspnea, and diarrhea. Grade 3/4 adverse events were generally hematologic and included thrombocytopenia (23.4%), anemia (22.4%), and lymphopenia (18.1%). Serious adverse events included pneumonia (9.9%), acute renal failure (4.2%), pyrexia (3.4%), and congestive heart failure (3.4%). New or worsening peripheral neuropathy was infrequent (13.9% overall, 1.3% grade 3, no grade 4). This review discusses findings of the integrated safety analysis and provides practical experience from a single institution in managing treatment-related and disease-related adverse events. Individualized treatment with proactive management of side effects and complications allows patients with advanced multiple myeloma to remain on carfilzomib for extended periods.
doi:10.2147/CPAA.S62512
PMCID: PMC4020895  PMID: 24855395
carfilzomib; relapsed; refractory; myeloma; safety; adverse events; toxicity
24.  Effects of irbesartan on serum uric acid levels in patients with hypertension and diabetes 
Background
Hyperuricemia has been proposed to be a risk factor for cardiovascular disease and chronic kidney disease. Since diabetes is often complicated by hypertension and hyperuricemia, efficient therapeutic strategy against these two complications is very important in diabetic treatment. It has been reported that the antihypertensive drug, irbesartan, inhibits the renal uric acid reabsorptive transporters, URAT1 and GLUT9; this result suggests that irbesartan decreases serum uric acid level (SUA).
Subjects and methods
A retrospective study of 107 patients with hypertension and diabetes was performed to analyze the effects of irbesartan on blood pressure, estimated glomerular filtration rate (eGFR), and SUA. The follow-up period was 6–12 months. Seventy percent of the patients were diagnosed with diabetic nephropathy stage II–IV. We excluded patients treated with drugs that influenced SUA. The multiple logistic regression analysis was introduced to identify the relative factors for SUA decline. The time-dependent SUA changes were examined in a mixed-linear model.
Results
Irbesartan reduced blood pressure significantly after 1, 6, and 12 months’ treatment. No subject showed significant change in eGFR from baseline level throughout the period. The multiple logistic regression analysis revealed that SUA baseline significantly influenced SUA decline after 6–12 months. In patients whose SUA baseline was ≥5.9 mg/dL, the SUA was significantly decreased from 6.6±0.16 mg/dL to 6.2±0.16 mg/dL (P=0.010), after 12 months’ irbesartan treatment. In the SUA baseline <5.9 mg/dL group, the SUA did not show significant change over the monitoring period.
Conclusion
Our results demonstrate that irbesartan reduces the risk of hyperuricemia. No decline in renal function was observed after the initiation of irbesartan treatment. The present report determines the criteria of SUA baseline for introducing an antihyperuricemic effect using irbesartan. Its antihypertensive effect coupled with SUA decline would be effective for the treatment of hypertension complicated by hyperuricemia.
doi:10.2147/CPAA.S61462
PMCID: PMC4014383  PMID: 24833923
angiotensin-receptor blocker; diabetes; hypertension; hyperuricemia; serum uric acid
25.  Analysis of factors affecting rehospitalization of patients with chronic kidney disease after educational hospitalization 
Background
Chronic kidney disease (CKD) is associated with a high risk of cardiovascular disease complications. Therefore, medical institutions conduct educational hospitalization for early treatment and education of CKD patients. However, patients who have been discharged after achieving educational targets can end up showing poor symptoms at home. There also have been several cases of rehospitalization or disease aggravation. In this study, we analyzed rehospitalized patients who were discharged from the hospital after CKD educational hospitalization and investigated the purpose of analyzing rehospitalization factors.
Materials and methods
This was an observational case-control study conducted at Yokosuka Kyousai Hospital. We performed univariate analysis using patient background features and laboratory data between a rehospitalization group and a no-rehospitalization group. Next, we performed multiple logistic regression analysis using the results of the univariate analysis.
Results
From the results of this study, we identified independent risk factors, such as serum albumin level, heart-failure complications, and estimated glomerular filtration rate (eGFR). Moreover, the serum Alb level was identified as the most important risk factor for rehospitalization. Therefore, we considered that it is important to live a life that makes it possible to maintain CKD stage G3b for a long time after discharge, because the cutoff level of eGFR is 31 mL/minute/1.73 m2.
Conclusion
We believe that it is important to educate patients, their families, and medical staff on the importance of early detection and treatment, and we consider that this approach is important to inclusively protect the kidney.
doi:10.2147/CPAA.S57442
PMCID: PMC3986110  PMID: 24748823
albumin; glomerular filtration rate; cardiovascular disease; stages of chronic kidney disease

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