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1.  Simulation of In Vitro Dissolution Behavior Using DDDPlus™ 
AAPS PharmSciTech  2014;16(1):217-221.
Dissolution testing is a performance test for many dosage forms including tablets and capsules. The objective of this study was to evaluate if computer simulations can predict the in vitro dissolution of two model drugs for which different dissolution data were available. Published montelukast sodium and glyburide dissolution data was used for the simulations. Different pharmacopeial and biorelevant buffers, volumes, and rotations speeds were evaluated. Additionally, a pH change protocol was evaluated using these buffers. DDDPlus™ 3, Beta version (Simulation Plus, Inc.), was used to simulate the in vitro dissolution data. The simulated data were compared with the in vitro data. A regression coefficient between predicted and observed data was used to assess the simulations. The statistical analysis of Montelukast sodium showed that there was a significant correlation between the in vitro release data and the predicted data for all cases except for one buffer. For glyburide, there was also a significant correlation between the experimental data and the predicted data using single pH conditions. Using the dynamic pH protocol, a correlation was significant for one biorelevant media. The simulations showed that both in vitro drug releases were sensitive to solubility effects which confirmed their BCS class II category. Computer simulations of the in vitro release using DDDPlus™ have the potential to estimate the in vivo dissolution at an early stage in the drug development process. This might be used to choose the most appropriate dissolution condition to establish IVIVC and to develop biorelevant in vitro performance tests to capture critical product attributes for quality control procedures in quality by design environments.
PMCID: PMC4309826  PMID: 25409918
biorelevant media; DDDPlus; dissolution testing; QbD; QC
2.  Investigating the Dissolution Profiles of Amoxicillin, Metronidazole, and Zidovudine Formulations used in Trinidad and Tobago, West Indies 
AAPS PharmSciTech  2014;15(5):1060-1069.
Trinidad and Tobago is a twin-island Republic in the Caribbean and like many developing countries, it has included generic drugs on the national drug formulary to decrease the financial burden of pharmaceutical medications. However, to ensure that medications received by patients are beneficial, generic drugs need to be interchangeable with the innovator which has demonstrated safety, efficacy, and quality. The objective of the study was to compare the dissolution profiles and weight variations for different formulations of amoxicillin, metronidazole, and zidovudine that are on the national drug formulary and marketed in Trinidad and Tobago. All the products investigated are categorized as class 1 drugs according to the Biopharmaceutics Classification System (BCS) and the dissolution profiles were assessed according to the World Health Organization (WHO) criteria for interchangeability between products. The similarity factor, f2, was used to determine sameness between the products. No generic formulation was found to be similar to Amoxil® 500-mg capsules. The two generic products for metronidazole 200-mg tablets demonstrated more than 85% drug release within 15 min in all three of the buffers; however, their 400-mg counterparts did not fulfill this requirement. The zidovudine 300-mg tablet complied with the requirements in buffer pH 4.5 and simulated gastric fluid (SGF) but not for simulated intestinal fluid (SIF). Some Class 1 pharmaceutical formulations may possess the same active ingredient and amount of drug but may show significant differences to in vitro equivalence requirements. Nevertheless, the dissolution process is suitable to detect these variations.
PMCID: PMC4179665  PMID: 24848758
biopharmaceutics classification system; dissolution; generic drugs; interchangeability; in vitro equivalence
3.  In Vitro Dissolution of Generic Immediate-Release Solid Oral Dosage Forms Containing BCS Class I Drugs: Comparative Assessment of Metronidazole, Zidovudine, and Amoxicillin Versus Relevant Comparator Pharmaceutical Products in South Africa and India 
AAPS PharmSciTech  2014;15(5):1076-1086.
Biowaivers are recommended for immediate-release solid oral dosage forms using dissolution testing as a surrogate for in vivo bioequivalence studies. Several guidance are currently available (the World Health Organization (WHO), the US FDA, and the EMEA) where the conditions are described. In this study, definitions, criteria, and methodologies according to the WHO have been applied. The dissolution performances of immediate-release metronidazole, zidovudine, and amoxicillin products purchased in South African and Indian markets were compared to the relevant comparator pharmaceutical product (CPP)/reference product. The dissolution performances were studied using US Pharmacopeia (USP) apparatus 2 (paddle) set at 75 rpm in each of three dissolution media (pH1.2, 4.5, and 6.8). Concentrations of metronidazole, zidovudine, and amoxicillin in each dissolution media were determined by HPLC. Of the 11 metronidazole products tested, only 8 could be considered as very rapidly dissolving products as defined by the WHO, whereas 2 of those products could be considered as rapidly dissolving products but did not comply with the f2 acceptance criteria in pH 6.8. All 11 zidovudine products were very rapidly dissolving, whereas in the case of the 14 amoxicillin products tested, none of those products met any of the WHO criteria. This study indicates that not all generic products containing the same biopharmaceutics classification system (BCS) I drug and in similar strength and dosage form are necessarily in vitro equivalent. Hence, there is a need for ongoing market surveillance to determine whether marketed generic products containing BCS I drugs meet the release requirements to confirm their in vitro bioequivalence to the respective reference product.
PMCID: PMC4179660  PMID: 24848760
BCS; dissolution testing; generic drug; immediate-release solid oral dosage forms; WHO criteria
4.  Challenges and Opportunities to Use Biowaivers to Compare Generics in China 
AAPS PharmSciTech  2014;15(5):1070-1075.
Biowaivers for class I drugs according to the biopharmaceutics classification system (BCS) were first introduced in 2000. The in vitro equivalence can be used to document bioequivalence between products. This study compared the in vitro dissolution behavior of two BCS class I drugs, amoxicillin and metronidazole, which are sold in China. Identifying a reference product on the Chinese domestic market was impossible. Three 250-mg and two 500-mg amoxicillin capsules and four metronidazole tablet products were tested. None of the amoxicillin products and three of the four metronidazole tablets were found to be equivalent to each other when the same strengths were compared. The bioequivalence of products that fail the in vitro test can be established via in vivo clinical studies which are expensive and time consuming. Establishing nationally or globally accepted reference products may provide regulatory agencies with an efficient mechanism approving high quality generics.
PMCID: PMC4179670  PMID: 24848759
bioequivalence; biopharmaceutics drug classification system (BCS); biowaiver; dissolution; generic drugs
5.  Antiulcerogenic Potential Activity of Free and Nanoencapsulated Passiflora serratodigitata L. Extracts 
BioMed Research International  2014;2014:434067.
This paper provides evidence that the leaves and stem of Passiflora serratodigitata L. dry crude extract (DCE), ethylacetate fraction (EAF), and residual water fraction show potential antiulcerogenic activity. Interestingly, the polymeric nanocapsule loaded with EAF had 10-fold more activity than the free EAF. Furthermore, the polymer nanoparticles provided homogeneous colloidal drug delivery systems and allowed overcoming challenges such as poor aqueous solubility as well as the physical-chemical instability of the organic extract, which presented 90% (w/w) of the flavonoid content. The entrapment efficiency of the total flavonoid was 90.6 ± 2.5% (w/v) for the DCE and 79.9 ± 2.7% (w/v) for the EAF. This study shows that nanoencapsulation improves both the physicochemical properties and the efficacy of the herbal formulations. Therefore, free and encapsulated extracts have the potential to be suitable drug design candidates for the therapeutic management of ulcer.
PMCID: PMC4122002  PMID: 25126557
6.  Evaluation of the DDSolver Software Applications 
BioMed Research International  2014;2014:204925.
When a new oral dosage form is developed, its dissolution behavior must be quantitatively analyzed. Dissolution analysis involves a comparison of the dissolution profiles and the application of mathematical models to describe the drug release pattern. This report aims to assess the application of the DDSolver, an Excel add-in software package, which is designed to analyze data obtained from dissolution experiments. The data used in this report were chosen from two dissolution studies. The results of the DDSolver analysis were compared with those obtained using an Excel worksheet. The comparisons among three different products obtained similarity factors (f2) of 23.21, 46.66, and 17.91 using both DDSolver and the Excel worksheet. The results differed when DDSolver and Excel were used to calculate the release exponent “n” in the Korsmeyer-Peppas model. Performing routine quantitative analysis proved to be much easier using the DDSolver program than an Excel spreadsheet. The use of the DDSolver program reduced the calculation time and has the potential to omit calculation errors, thus making this software package a convenient tool for dissolution comparison.
PMCID: PMC4022259  PMID: 24877067
7.  In Vitro Release Kinetics of Antituberculosis Drugs from Nanoparticles Assessed Using a Modified Dissolution Apparatus 
BioMed Research International  2013;2013:136590.
The aim of this study was to assess the in vitro release kinetics of antituberculosis drug-loaded nanoparticles (NPs) using a “modified” cylindrical apparatus fitted with a regenerated cellulose membrane attached to a standard dissolution apparatus (modifiedcylinder method). The model drugs that were used were rifampicin (RIF) and moxifloxacin hydrochloride (MX). Gelatin and polybutyl cyanoacrylate (PBCA) NPs were evaluated as the nanocarriers, respectively. The dissolution and release kinetics of the drugs from loaded NPs were studied in different media using the modified cylinder method and dialysis bag technique was used as the control technique. The results showed that use of the modified cylinder method resulted in different release profiles associated with unique release mechanisms for the nanocarrier systems investigated. The modified cylinder method also permitted discrimination between forced and normal in vitro release of the model drugs from gelatin NPs in the presence or absence of enzymatic degradation. The use of dialysis bag technique resulted in an inability to differentiate between the mechanisms of drug release from the NPs in these cases. This approach offers an effective tool to investigate in vitro release of RIF and MX from NPs, which further indicate that this technique can be used for performance testing of nanosized carrier systems.
PMCID: PMC3723057  PMID: 23936771
8.  Toward Global Standards for Comparator Pharmaceutical Products: Case Studies of Amoxicillin, Metronidazole, and Zidovudine in the Americas 
The AAPS Journal  2012;14(3):462-472.
This study compared in vitro dissolution characteristics and other quality measures of different amoxicillin, metronidazole, and zidovudine products purchased in the Americas to a comparator pharmaceutical product (CPP). These three drugs are classified as Biopharmaceutics Classification System Class I drugs with the possibility that dissolution findings might be used to document bioequivalence. All investigated zidovudine products were found to be in vitro equivalent to the CPP. Only 3 of 12 tested amoxicillin products were found to be in vitro equivalent to the CPP. None of the tested metronidazole products were in vitro equivalent to the CPP. These findings suggest but do not confirm bioinequivalence where in vitro comparisons failed, given that an in vivo blood level study might have confirmed bioequivalence. At times, identifying a CPP in one of the selected markets proved difficult. The study demonstrates that products sold across national markets may not be bioequivalent. When coupled with the challenge of identifying a CPP in different countries, the results of this study suggest the value of an international CPP as well as increased use of BCS approaches as means of either documenting bioequivalence or signaling the need for further in vivo studies. Because of increased movement of medicines across national borders, practitioners and patients would benefit from these approaches.
Electronic supplementary material
The online version of this article (doi:10.1208/s12248-012-9350-9) contains supplementary material, which is available to authorized users.
PMCID: PMC3385829  PMID: 22528504
bioequivalence; Biopharmaceutics Classification System; comparator pharmaceutical products; equivalence; standards
9.  Microcalorimetric Method to Assess Phagocytosis: Macrophage-Nanoparticle Interactions 
The AAPS Journal  2010;13(1):20-29.
This study evaluated the use of isothermal microcalorimetry (ITMC) to detect macrophage–nanoparticle interactions. Four different nanoparticle (NP) formulations were prepared: uncoated poly(isobutyl cyanoacrylate) (PIBCA), polysorbate-80-coated PIBCA, gelatin, and mannosylated gelatin NPs. Changes in NP formulations were aimed to either enhance or decrease macrophage–NP interactions via phagocytosis. Alveolar macrophages were cultured on glass slabs and inserted in the ITMC instrument. Thermal activities of the macrophages alone and after titration of 100 μL of NP suspensions were compared. The relative interactive coefficients of macrophage–NP interactions were calculated using the heat exchange observed after NP titration. Control experiments were performed using cytochalasin B (Cyto B), a known phagocytosis inhibitor. The results of NP titration showed that the total thermal activity produced by macrophages changed according to the NP formulation. Mannosylated gelatin NPs were associated with the highest heat exchange, 75.4 ± 7.5 J, and thus the highest relative interactive coefficient, 9,269 ± 630 M-1. Polysorbate-80-coated NPs were associated with the lowest heat exchange, 15.2 ± 3.4 J, and the lowest interactive coefficient, 890 ± 120 M-1. Cyto B inhibited macrophage response to NPs, indicating a connection between the thermal activity recorded and NP phagocytosis. These results are in agreement with flow cytometry results. ITMC is a valuable tool to monitor the biological responses to nano-sized dosage forms such as NPs. Since the thermal activity of macrophage–NP interactions differed according to the type of NPs used, ITMC may provide a method to better understand phagocytosis and further the development of colloidal dosage forms.
Electronic supplementary material
The online version of this article (doi:10.1208/s12248-010-9240-y) contains supplementary material, which is available to authorized users.
PMCID: PMC3032094  PMID: 21057907
flow cytometry; isothermal microcalorimetry; macrophages; nanoparticles; phagocytosis
10.  Investigation of the Performance of the Disintegration Test for Dietary Supplements 
The AAPS Journal  2010;12(4):602-607.
The aim of this study was to investigate how beaker size, basket assembly, use of disk, and immersion medium impact the disintegration time of dietary supplements. The disintegration times were determined for five tablet and two capsule products. A two-station disintegration tester was used with Apparatus A or Apparatus B as described in the United States Pharmacopeia (USP) chapters, <701> and <2040>. Two beakers complying with the harmonized specifications were used, one with a volume of 1,000 mL and one with a 1,500-mL volume. The disintegration data were analyzed using ANOVA for the following factors: beaker size, equipment (App A and B) and condition (with/without disk). Two tablet products were not sensitive to any changes in the test conditions or equipment configurations. One product was only partially sensitive to the test conditions. The other products showed impact on the disintegration time for all test conditions. The results revealed that these tablet products might pass or fail current USP disintegration requirements depending on the equipment configuration. Similar results were obtained for the two investigated capsule formulations. One product might fail current USP disintegration requirements if the large beaker was used, but might pass the disintegration requirements when the small beaker was used. Hydroxy propyl methyl cellulose capsules were mostly influenced if sodium instead of a potassium buffer was used as the immersion medium. The results demonstrate that the current harmonized ICH specifications for the disintegration test are insufficient to make the disintegration test into reliable test for dietary supplements.
PMCID: PMC2977009  PMID: 20652779
dietary supplements; disintegration; ICH; quality by design; USP
11.  Isothermal Microcalorimetry as a Quality by Design Tool to Determine Optimal Blending Sequences 
The AAPS Journal  2010;12(3):417-423.
This study was designed to assess the value of isothermal microcalorimetry (ITMC) as a quality by design (QbD) tool to optimize blending conditions during tablet preparation. Powder mixtures that contain microcrystalline cellulose (MCC), dibasic calcium phosphate dihydrate (DCPD), and prednisone were prepared as 1:1:1 ratios using different blending sequences. ITMC was used to monitor the thermal activity of the powder mixtures before and after each blending process. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) were performed on all final powder mixtures. Final powder mixtures were used to prepare tablets with 10 mg prednisone content, and dissolution tests were performed on all tablet formulations. Using ITMC, it was observed that the powder mixtures had different thermal activity depending on the blending sequences of the ingredients. All mixtures prepared by mixing prednisone with DCPD in the first stage were associated with relatively fast and significant heat exchange. In contrast, mixing prednisone with MCC in the first step resulted in slower heat exchange. Powder mixture with high thermal activity showed extra DSC peaks, and their dissolution was generally slower compared to the other tablets. Blending is considered as a critical parameter in tablet preparation. This study showed that ITMC is a simple and efficient tool to monitor solid-state reactions between excipients and prednisone depending on blending sequences. ITMC has the potential to be used in QbD approaches to optimize blending parameters for prednisone tablets.
PMCID: PMC2895446  PMID: 20461485
isothermal microcalorimetry; powders blending; quality by design; tablets
12.  Pulmonary Toxicity of Polysorbate-80-coated Inhalable Nanoparticles; In vitro and In vivo Evaluation 
The AAPS Journal  2010;12(3):294-299.
PMCID: PMC2895437  PMID: 20405258
inhalable nanoparticles; polysorbate 80; pulmonary toxicity; surface pressure-area isotherm

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