The workshop “Bioequivalence, Biopharmaceutics Classification System, and Beyond” was held May 21–23, 2007 in North Bethesda, MD, USA. This workshop provided an opportunity for pharmaceutical scientists to discuss the FDA guidance on the Biopharmaceutics Classification System (BCS), bioequivalence of oral products, and related FDA initiatives such as the FDA Critical Path Initiative. The objective of this Summary Workshop Report is to document the main points from this workshop. Key highlights of the workshop were (a) the described granting of over a dozen BCS-based biowaivers by the FDA for Class I drugs whose formulations exhibit rapid dissolution, (b) continued scientific support for biowaivers for Class III compounds whose formulations exhibit very rapid dissolution, (c) scientific support for a number of permeability methodologies to assess BCS permeability class, (d) utilization of BCS in pharmaceutical research and development, and (e) scientific progress in in vitro dissolution methods to predict dosage form performance.
bioavailability; bioequivalence; biopharmaceutics classification system (BCS); oral absorption; permeability; regulatory science; solubility
The FDA Biopharmaceutical Classification System guidance allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release solid oral dosage forms only for BCS class I. Extensions of the in vivo biowaiver for a number of drugs in BCS Class III and BCS class II have been proposed, particularly, BCS class II weak acids. However, a discrepancy between the in vivo- BE results and in vitro- dissolution results for a BCS class II acids was recently observed. The objectives of this study were to determine the oral absorption of BCS class II weak acids via simulation software and to determine if the in vitro dissolution test with various dissolution media could be sufficient for in vitro bioequivalence studies of ibuprofen and ketoprofen as models of carboxylic acid drugs.
The oral absorption of these BCS class II acids from the gastrointestinal tract was predicted by GastroPlus™. Ibuprofen did not satisfy the bioequivalence criteria at lower settings of intestinal pH=6.0. Further the experimental dissolution of ibuprofen tablets in the low concentration phosphate buffer at pH 6.0 (the average buffer capacity 2.2 mmol L-1/pH) was dramatically reduced compared to the dissolution in SIF (the average buffer capacity 12.6 mmol L -1/pH). Thus these predictions for oral absorption of BCS class II acids indicate that the absorption patterns largely depend on the intestinal pH and buffer strength and must be carefully considered for a bioequivalence test. Simulation software may be very useful tool to aid the selection of dissolution media that may be useful in setting an in vitro bioequivalence dissolution standard.
weak acid; ibuprofen; ketoprofen; pH; simulation; GastroPlus; in vitro dissolution; dissolution media
The Biopharmaceutics Classification System (BCS) is based on the mechanistic assumptions that the rate and extent of oral drug absorption are governed by drug solubility, intestinal permeability, and dissolution rate from the dosage form administered. One of the goals of BCS is to identify classes of drugs for which bioequivalence may be established based solely on the in vitro dissolution data, i.e., which would be eligible for biowaiver. On the basis of BCS, currently, the biowaiver concept is adopted and recommended for immediate release of drug products containing highly soluble and highly permeable compounds (BCS class 1 drugs). Dissolution testing properties are proposed to be more stringent: very rapid dissolution is demanded when generic drug application is submitted with the exemption of in vivo bioequivalence study. In the present paper, Gastrointestinal Simulation Technology has been applied in order to evaluate the potential for different in vitro drug dissolution kinetics to influence dosage forms in vivo behavior and the relevance of “very rapid dissolution” criteria to be met (i.e., more than 85% of dose dissolved in 15 min).
BCS; bioequivalence; dissolution; gastrointestinal simulation
The Biopharmaceutics Classification System (BCS) is not only a useful tool for obtaining waivers for in-vivo bioequivalence studies but also for decision making in the discovery and early development of new drugs. Measurement of solubility and permeability in the discovery/development settings is described. These data can be utilized for the preliminary BCS classification of pipeline compounds. A decision tree is described in the prioritization of salt and polymorph screening studies prior to in vivo studies in animals. For BCS class 1 and 3 compounds, polymorphism is less likely to impact on bioavailability. The polymorph screening study may be postponed after animal studies. The BCS classification can also be used in the design of animal and human formulations. A BCS-based animal formulation development decision tree is presented. A compound is triaged based on a series of decision points into one of the five formulation strategies. Human formulation has different requirements than animal formulation. A comparison between animal and human formulation strategies is presented. In conclusion, for non-BCS 1 compounds, the right-first-time polymorph and formulation selection ensures consistent pharmacokinetic performance and avoids bridging BA/BE studies. It is in line with FDA’s initiative to reduce R&D cycle time through quality by design for pharmaceutical products.
biopharmaceutics classification; decision tree; formulation; polymorphism; salt
The biopharmaceutical classification system (BCS) classifies compounds based on their solubility and permeability. Regulatory agencies and health organizations have utilized this classification system to allow dissolution to be used to establish bioequivalence for highly soluble and highly permeable compounds. The pharmaceutical industry has taken advantage of this and BCS-based waivers are becoming more routine and result in significant savings. Further, there is strong scientific rationale to allow BCS-based waivers for even more compounds to realize even more savings. Yet just as clear as the benefits are the barriers that limit application: lack of international regulatory harmonization, uncertainty in regulatory approval, and organizational barriers within the pharmaceutical industry. Once these barriers are overcome and additional applications are fully allowed, the full benefits of BCS applications will be realized.
biopharmaceutical classification system; dissolution; formulations development; permeability; solubility
The Biopharmaceutics Classification System (BCS) categorizes drugs into one of four biopharmaceutical classes according to their water solubility and membrane permeability characteristics and broadly allows the prediction of the rate-limiting step in the intestinal absorption process following oral administration. Since its introduction in 1995, the BCS has generated remarkable impact on the global pharmaceutical sciences arena, in drug discovery, development, and regulation, and extensive validation/discussion/extension of the BCS is continuously published in the literature. The BCS has been effectively implanted by drug regulatory agencies around the world in setting bioavailability/bioequivalence standards for immediate-release (IR) oral drug product approval. In this review, we describe the BCS scientific framework and impact on regulatory practice of oral drug products and review the provisional BCS classification of the top drugs on the global market. The Biopharmaceutical Drug Disposition Classification System and its association with the BCS are discussed as well. One notable finding of the provisional BCS classification is that the clinical performance of the majority of approved IR oral drug products essential for human health can be assured with an in vitro dissolution test, rather than empirical in vivo human studies.
BA/BE; biopharmaceutics classification system; biowaiver; intestinal absorption; molecular biopharmaceutics; oral drug product
The aim of this study was to investigate the influence of experimental conditions on levothyroxine sodium release from two immediate-release tablet formulations which narrowly passed the standard requirements for bioequivalence studies. The in vivo study was conducted as randomised, single-dose, two-way cross-over pharmacokinetic study in 24 healthy subjects. The in vitro study was performed using various dissolution media, and obtained dissolution profiles were compared using the similarity factor value. Drug solubility in different media was also determined. The in vivo results showed narrowly passing bioequivalence. Considering that levothyroxine sodium is classified as Class III drug according to the Biopharmaceutics Classification System, drug bioavailability will be less sensitive to the variation in its dissolution characteristics and it can be assumed that the differences observed in vitro in some of investigated media probably do not have significant influence on the absorption process, as long as rapid and complete dissolution exists. The study results indicate that the current regulatory criteria for the value of similarity factor in comparative dissolution testing, as well as request for very rapid dissolution (more than 85% of drug dissolved in 15 min), are very restricted for immediate-release dosage forms containing highly soluble drug substance and need further investigation. The obtained results also add to the existing debate on the appropriateness of the current bioequivalence standards for levothyroxine sodium products.
bioequivalence; dissolution; immediate release; levothyroxine sodium; solubility
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.
bioequivalence; Biopharmaceutics Classification System; comparator pharmaceutical products; equivalence; standards
The aim of the present paper is to summarize the revised European Union (EU) Guideline on the Investigation of Bioequivalence and to discuss critically with respect to previous European requirements and present US Food and Drug Administration guidelines its more relevant novelties such as the following: in order to facilitate the development of generic medicinal products, the EU guideline includes the eligibility for Biopharmaceutics Classification System (BCS)-based biowaivers not only for BCS class I drugs but also for class III drugs with tighter requirements for dissolution and excipient composition. The permeability criterion of BCS classification has been substituted with human absorbability, as per the Biopharmaceutical Drug Disposition Classification System. The widening of the acceptance range for Cmax is possible only for highly variable reference products with an additional clinical justification. This scaled widening is carried out with a proportionality constant of 0.760 which is more conservative than the FDA approach and maintains the consumer risk at a 5% level when the intra-subject CV is close to 30%, due to the smooth transition between the scaled and the constant criteria. The guideline allows for the possibility of two-stage designs to obtain the necessary information on formulation differences and variability from interim analyses as a part of the pivotal bioequivalence study, instead of undertaking pilot studies. The guideline also specifies that the statistical analyses should be performed considering all factors as fixed, which has implications in the case of replicate designs.
bioequivalence; generic medicinal products; regulatory requirements
The present study was aimed to predict the absorption profile of a risperidone immediate release tablet (IR) and to develop the level A in vitro–in vivo correlation (IVIVC) of the drug using the gastrointestinal simulation based on the advanced compartmental absorption and transit model implemented in GastroPlus™. Plasma concentration data, physicochemical, and pharmacokinetic properties of the drug were used in building its absorption profile in the gastrointestinal tract. Since the fraction absorbed of risperidone in simulation was more than 90% with low water solubility, the drug met the criteria of class II of the Biopharmaceutics Classification System. The IVIVC was developed based on the model built using the plasma data and the in vitro dissolution data in several dissolution media based on the Japanese Guideline for Bioequivalence Studies of Generic Products. The gastrointestinal absorption profile of risperidone was successfully predicted. A level A IVIVC was also successfully developed in all dissolution media with percent prediction error for Cmax and the area under the curve less than 10% for both reference and test drug.
GastroPlus™; immediate release tablet; in vitro–in vivo correlation; risperidone
The Biopharmaceutics Classification system (BCS) classifies drug substances based on aqueous solubility and intestinal permeability. The objective of this study was to use the World Health Organization Model List of Essential Medicines to determine the distribution of BCS Class 1, 2, 3, and 4 drugs in Abbreviated New drug Applications (ANDA) submissions. To categorize solubility and intestinal permeability properties of generic drugs under development, we used a list of 61 drugs which were classified as BCS 1, 2, 3, and 4 drugs with certainty in the World Health Organization Model List of Essential Medicines. Applying this list to evaluation of 263 ANDA approvals of BCS drugs during the period of 2000 to 2011 indicated 110 approvals (41.8%) for Class 1 drugs (based on both biowaiver and in vivo bioequivalence studies), 55 (20.9%) approvals for Class 2 drugs, 98 (37.3%) approvals for Class 3 drugs, and no (0%) approvals for Class 4 drugs. The present data indicated a trend of more ANDA approvals of BCS Class 1 drugs than Class 3 or Class 2 drugs. Antiallergic drugs in Class 1, drugs for pain relief in Class 2 and antidiabetic drugs in Class 3 have received the largest number of approvals during this period.
ANDA; BCS biowaiver; bioequivalence; Biopharmaceutics Classification System; generic drug product
A Biopharmaceutics Drug Disposition Classification System (BDDCS) was proposed to serve as a basis for predicting the importance of transporters in determining drug bioavailability and disposition. BDDCS may be useful in predicting: routes of drug elimination; efflux and absorptive transporters effects on oral absorption; when transporter-enzyme interplay will yield clinically significant effects (e.g. low drug bioavailability and drug-drug interactions); and transporter effects on post-absorptive systemic drug levels following oral and i.v. dosing. For highly soluble, highly permeable Class 1 compounds, metabolism is the major route of elimination and transporter effects on drug bioavailability and hepatic disposition are negligible. In contrast for the poorly permeable Class 3 and 4 compounds, metabolism only plays a minor role in drug elimination. Uptake transporters are major determinants of drug bioavailability for these poorly permeable drugs and both uptake and efflux transporters could be important for drug elimination. Highly permeable, poorly soluble, extensively metabolized Class 2 compounds present the most complicated relationship in defining the impact of transporters due to a marked transporter-enzyme interplay. Uptake transporters are unimportant for Class 2 drug bioavailability, (ensure space after,) but can play a major role in hepatic and renal elimination. Efflux transporters have major effects on drug bioavailability, absorption, metabolism and elimination of Class 2 drugs. It is difficult to accurately characterize drugs in terms of the high permeability criteria, i.e. ≥90% absorbed. We suggest that extensive metabolism may substitute for the high permeability characteristic, and that BDDCS using elimination criteria may provide predictability in characterizing drug disposition profiles for all classes of compounds.
We recommend that regulatory agencies add the extent of drug metabolism (i.e., ≥90% metabolized) as an alternate method in defining Class 1 marketed drugs suitable for a waiver of in vivo studies of bioequivalence. That is, ≥90% metabolized is an additional methodology that may be substituted for ≥90% absorbed. We propose that the following criteria be used to define ≥ 90% metabolized for marketed drugs: Following a single oral dose to humans, administered at the highest dose strength, mass balance of the Phase 1 oxidative and Phase 2 conjugative drug metabolites in the urine and feces, measured either as unlabeled, radioactive labeled or nonradioactive labeled substances, account for ≥ 90% of the drug dosed. This is the strictest definition for a waiver based on metabolism. For an orally administered drug to be ≥ 90% metabolized by Phase 1 oxidative and Phase 2 conjugative processes, it is obvious that the drug must be absorbed. This proposal, which strictly conforms to the present ≥90% criteria, is a suggested modification to facilitate a number of marketed drugs being appropriately assigned to Class 1.
Background and the purpose of the study
The relative in vivo bioavailability and in vitro dissolution studies of three chemically equivalent amiodarone generic products in healthy volunteers was evaluated in three separate occasions. The possibility of a correlation between in vitro and in vivo performances of these tablet formulations was also evaluated.
The bioequivalence studies were conducted based on a single dose, two-sequence, cross over randomized design. The bioavailability was compared using AUC0–72, AUC0–8, Cmax and Tmax. Similarity factor, dissolution efficiency (DE), and mean dissolution time (MDT) was used to compare the dissolution profiles. Polynomial linear correlation models were tested using either MDT vs mean residence time (MRT) or fraction of the drug dissolved (FRD) vs fraction of the drug absorbed (FRA).
Significant differences were found in the dissolution performances of the tested formulations and therefore they were included in the development of the correlation. The 90% confidence intervals of the log-transformed AUC0-72, AUC0–8, and Cmax of each two formulations in each bioequivalence studies were within the acceptable range of 80–125%. Differences were not observed between the untransformed Tmax values. Poor correlation was found between MRT and MDT of the products. A point-to-point correlation which is essential for a reliable correlation was not obtained between pooled FRD and FRA. The dissolution condition which was used for amiodarone tablets failed for formulations which were bioequivalent in vivo and significant difference between the dissolution characteristics of products (f2<50) did not reflect their in vivo properties.
Bioequivalence studies should be considered as the only acceptable way to ensure the interchangeability and in vivo equivalence of amiodarone generic drug products. The dissolution conditions used of the present study could be used for routine and in-process quality control of amiodarone tablet formulations.
Bioequivalence; Bioavalability; Dissolution; Correlation
It is widely believed that acceptable bioequivalence studies of drugs with high within-subject pharmacokinetic variability must enroll higher numbers of subjects than studies of drugs with lower variability. We studied the scope of this issue within US generic drug regulatory submissions.
Materials and Methods
We collected data from all in vivo bioequivalence studies reviewed at FDA’s Office of Generic Drugs (OGD) from 2003–2005. We used the ANOVA root mean square error (RMSE) from bioequivalence statistical analyses to estimate within-subject variability. A drug was considered highly variable if its RMSE for Cmax and/or AUC was ≥0.3. To identify factors contributing to high variability, we evaluated drug substance pharmacokinetic characteristics and drug product dissolution performance.
Results and Discussion
In 2003–2005, the OGD reviewed 1,010 acceptable bioequivalence studies of 180 different drugs, of which 31% (57/180) were highly variable. Of these highly variable drugs, 51%, 10%, and 39% were either consistently, borderline, or inconsistently highly variable, respectively. We observed that most of the consistent and borderline highly variable drugs underwent extensive first pass metabolism. Drug product dissolution variability was high for about half of the inconsistently highly variable drugs. We could not identify factors causing variability for the other half. Studies of highly variable drugs generally used more subjects than studies of lower variability drugs.
About 60% of the highly variable drugs we surveyed were highly variable due to drug substance pharmacokinetic characteristics. For about 20% of the highly variable drugs, it appeared that formulation performance contributed to the high variability.
bioequivalence; generic drugs; highly variable drugs; presystemic drug metabolism; variable drug product dissolution
The Food and Drug Administration (FDA) Guidance for Bioavailability and Bioequivalence Studies for Levothyroxine has been challenged by companies that manufacture brand-name products. Their contention is that the current guidance does not adequately address the endogenous background levels of the drug, and that the ratios of the PK parameters, a basis for approval of equivalence, are not assessed correctly. In particular, they conclude that products that have a potency differing by 12.5% cannot be differentiated using the present guideline and criteria for acceptance of bioequivalence. They claim that such a difference can be a public health hazard because of the perception among practitioners that levothyroxine is a narrow therapeutic index drug. This article describes the procedure recommended in the current Guidance for Levothyroxine and demonstrates that the methods recommended are adequate and will accept products that are therapeutically equivalent. To date, no generic product accepted as equivalent using FDA Guidances has been shown to result in a safety and efficacy profile different from its brand counterpart.
Ritonavir is an antiretroviral drug characterized by low solubility and high permeability which corresponds to BCS class II drug. The purpose of the study was to develop solid dispersion by different methods and investigate them for in vitro and in vivo performance for enhancing dissolution and bioavailability, respectively. Since the drug possesses food-related absorption, the effect of biorelevant media (FaSSIF and FeSSIF state) on dissolution behavior was also studied. The solid dispersion was prepared using Gelucire as carrier in 1:4 ratio by different methods and were characterized for differential scanning calorimetry (DSC), X-ray diffractometry, scanning electron microscopy, and FT-IR. Oral bioavailability of 10 mg of ritonavir in solid dispersion prepared by solvent evaporation (SE1) and melt method (MM1) was compared with pure drug after oral administration of solid dispersion and pure drug to Albino Wistar rats of either sex. The results suggested formation of eutectic solid dispersion. In vitro dissolution studies was performed in 0.1 N HCl and biorelevant media showed enhanced dissolution rate as compared to pure drug in both FeSSIF media and 0.1 N HCl. The apparent rate of absorption of ritonavir from SE1 (Cmax 20221.37 ng/ml, tmax 0.5 h) was higher than that of MM1 (Cmax 2,462.2, tmax 1 h) and pure drug (Cmax 1,354.8 ng/ml, tmax 0.5 h). On the basis of the result obtained, it was concluded that solid dispersion is a good approach to enhance solubility and bioavailability of poorly water-soluble ritonavir.
bioavailability; gelucire; poorly soluble drug; ritonavir; solid dispersion
FDA’s critical path initiative documents have focused on the challenges involved in the development of new drugs. Some of the focus areas identified apply equally to the production of generic drugs. However, there are scientific challenges unique to the development of generic drugs as well. In May 2007, FDA released a document “Critical Path Opportunities for Generic Drugs” that identified some of the specific challenges in the development of generic drugs. The key steps in generic product development are usually characterization of the reference product, design of a pharmaceutically equivalent and bioequivalent product, design of a consistent manufacturing process and conduct of the pivotal bioequivalence study. There are several areas of opportunity where scientific progress could accelerate the development and approval of generic products and expand the range of products for which generic versions are available, while maintaining high standards for quality, safety, and efficacy. These areas include the use of quality by design to develop bioequivalent products, more efficient bioequivalence methods for systemically acting drugs (expansion of BCS waivers, highly variable drugs), and development of new bioequivalence methods for locally acting drugs.
bioequivalence; critical path initiative; generic drugs
Quality by design (QbD) has recently been introduced in pharmaceutical product development in a regulatory context and the process of implementing such concepts in the drug approval process is presently on-going. This has the potential to allow for a more flexible regulatory approach based on understanding and optimisation of how design of a product and its manufacturing process may affect product quality. Thus, adding restrictions to manufacturing beyond what can be motivated by clinical quality brings no benefits but only additional costs. This leads to a challenge for biopharmaceutical scientists to link clinical product performance to critical manufacturing attributes. In vitro dissolution testing is clearly a key tool for this purpose and the present bioequivalence guidelines and biopharmaceutical classification system (BCS) provides a platform for regulatory applications of in vitro dissolution as a marker for consistency in clinical outcomes. However, the application of these concepts might need to be further developed in the context of QbD to take advantage of the higher level of understanding that is implied and displayed in regulatory documentation utilising QbD concepts. Aspects that should be considered include identification of rate limiting steps in the absorption process that can be linked to pharmacokinetic variables and used for prediction of bioavailability variables, in vivo relevance of in vitro dissolution test conditions and performance/interpretation of specific bioavailability studies on critical formulation/process variables. This article will give some examples and suggestions how clinical relevance of dissolution testing can be achieved in the context of QbD derived from a specific case study for a BCS II compound.
bioequivalence; biopharmaceutics classification system (BCS); biowaiver; in vitro dissolution; in vitro in vivo correlation (IVIVC); quality by design (QbD)
Lipid-based formulations encompass a diverse group of formulations with very different physical appearance, ranging from simple triglyceride vehicles to more sophisticated formulations such as self-emulsifying drug delivery systems (SEDDS). Lipid-based drug delivery systems may contain a broad range of oils, surfactants, and co-solvents. They represent one of the most popular approaches to overcome the absorption barriers and to improve the bioavailability of poorly water-soluble drugs. Diversity and versatility of pharmaceutical grade lipid excipients and drug formulations as well as their compatibility with liquid, semi-solid and solid dosage forms make lipid systems most complex. Digestion of triglyceride lipids, physicochemical characteristics and solubilisation of lipid digestion products as well as intestinal permeability are some of the variable parameters of such formulations. Furthermore, among the factors affecting the bioavailability of the drug from lipid-based formulations are the digestion of lipid, the mean emulsion droplet diameter, the lipophilicity of the drug and the type of lipids. The solubility of the Active Pharmaceutical Ingredient in the Lipid System, the desorption/sorption isotherm and the digestibility of lipid vehicle are important issues to be considered for formulations of isotropic lipid formulations. This review also describes the fate of lipid formulations in the gut and the factors influencing the bioavailability from lipid-based formulations. Novel formulation systems and currently marketed products conclude this review.
Lipids; Lipid digestion; Mean emulsion droplet diameter; Self-emulsifying drug delivery system; Isotropic lipid solutions
The WHO biowaiver procedure for BCS Class II weak acids was evaluated by running two multisource IR ibuprofen drug products (Ibuprofen, 200 mg tablets, Tatchempharmpreparaty, Russia and Ibuprofen, 200 mg tablets, Biosintez, Russia) with current Marketing Authorizations (i.e. in vivo bioequivalent) through that procedure. Risks associated with excipients interaction and therapeutic index were considered to be not critical. In vitro dissolution kinetic studies were carried out according WHO Guidance (WHO Technical Report Series, No. 937, Annexes 7 and 8) using USP Apparatus II (paddle method) at 75 rpm. Dissolution profiles of test and reference ibuprofen tablets were considered equivalent in pH 4.5 using factors f1 (13) and f2 (72) and not equivalent in pH 6.8 (factor f1 was 26 and f2 was 24). Drug release of ibuprofen at pH 1.2 was negligible due to its weak acid properties. Therefore, two in vivo bioequivalent tablets were declared bioinequivalent by this procedure, indicating that procedure seems to be over-discriminatory.
Biowaiver; dissolution test; ibuprofen; interchangeability
The purpose of this investigation is to evaluate the scientific benefits of a novel approach in using stable isotopes to reduce the number of subjects needed to perform relative bioavailability and bioequivalence pharmacokinetic studies for formulations that are qualitatively and quantitatively the same and quality by design (QbD) pharmacokinetic studies. The stable isotope approach was investigated using simulations to determine the impact this approach would have on the estimation of variability and, subsequently, the sample size for a bioequivalence study. A biostudy was conducted in dogs in a two period crossover to explore the viability of the stable isotope approach. For a drug product with within-subject variability (CVw) of 50% and assuming a correlation of 0.95 between the enriched and non-enriched pharmacokinetics (PK), simulations showed that the variability can be reduced by 70% and the required sample size can be reduced by 90% while maintaining 90% power to demonstrate bioequivalence. The dog study showed a strong correlation (R2, > 0.99) between the enriched and non-enriched area under the curve and maximum observed concentration, and a significant reduction in the variability (reduction in % coefficient of variation from 79.9% to 6.3%). Utilization of a stable isotope approach can markedly improve the efficiency and accuracy of bioavailability and bioequivalence studies particularly for highly variable drugs in formulations that are qualitatively and quantitatively the same and for studies designed for QbD investigations.
bioequivalence; biopharmaceutics; quality by design; relative bioavailability; stable isotope
Crystal form can be crucial to the performance of a dosage form. This is especially true for compounds that have intrinsic barriers to drug delivery, such as low aqueous solubility, slow dissolution in gastrointestinal media, low permeability and first-pass metabolism. The nature of the physical form and formulation tends to exhibit the greatest effect on bioavailability parameters of water insoluble compounds that need to be given orally in high doses. An alternative approach available for the enhancement of drug solubility, dissolution and bioavailability is through the application of crystal engineering of co-crystals. The physicochemical properties of the active pharmaceutical ingredients and the bulk material properties can be modified, whilst maintaining the intrinsic activity of the drug molecule. This article covers the advantages of co-crystals over salts, solvates (hydrates), solid dispersions and polymorphs, mechanism of formation of co-crystals, methods of preparation of co-crystals and application of co-crystals to modify physicochemical characteristics of active pharmaceutical ingredients along with the case studies. The intellectual property implications of creating co-crystals are also highly relevant.
Crystal form; bioavailability; drug solubility; dissolution; physicochemical property
Under the Abbreviated New Drug Application pathway, a proposed generic salmon calcitonin nasal spray is required to demonstrate pharmaceutical equivalence and bioequivalence to the brand-name counterpart or the reference listed drug. This review discusses two important aspects of pharmaceutical equivalence for this synthetic peptide nasal spray product. The first aspect is drug substance sameness, in which a proposed generic salmon calcitonin product is required to demonstrate that it contains the same active ingredient as that in the brand-name counterpart. The second aspect is comparability in product- and process-related factors that may influence immunogenicity (i.e., peptide-related impurities, aggregates, formulation, and leachates from the container/closure system). The comparability of these factors helps to ensure the product safety, particularly with respect to immunogenicity. This review also highlights the key features of in vitro and/or in vivo studies for establishing bioequivalence for a solution nasal spray containing a systemically acting salmon calcitonin.
bioequivalence; generic; immunogenicity; nasal spray; pharmaceutical equivalence; salmon calcitonin
Rifampicin (RIF) is a major component in fixed dose combination therapy for the treatment of tuberculosis. RIF has low solubility and high permeability with high dose and hence it is classified as class II drug in Biopharmaceutical Classification System (BCS). RIF has poor and variable bioavailability because of its poor solubility, acid decomposition and, drug and food interaction. The present investigation was aimed to develop RIF loaded porous microspheres as a controlled release dosage form. Eudragit based porous microspheres of RIF were prepared by emulsion solvent diffusion method. Prepared porous microspheres were evaluated for its entrapment efficacy, morphology, thermal behavior, crystalline nature, in-vitro drug release and stability in simulated gastric fluid. The entrapment efficacy of drug loaded microspheres was found to be in the range of 19.04–74.57%. Surface morphology revealed the porous and spherical structure of microspheres. Differential scanning calorimetric studies confirmed that formulation process altered the crystalline nature of RIF. In vitro drug release studies indicated that drug to polymer ratio of 2:1 showed more than 85% drug release over the period of 3 h. Stability studies in simulated gastric fluid (SGF) indicated that low relative decomposition of 18.5% was achieved with high drug to low polymer ratio of 1:4. The results obtained from the present investigation concluded that RIF loaded porous microspheres are suitable for developing oral controlled release dosage form of RIF that can prevent acid decomposition and provide better biopharmaceutical properties. Further more the microspheres can be evaluated for preventing the interaction with isoniazid, other drugs and foodstuffs.
Tuberculosis; Rifampicin; Porous micro-spheres; Biopharmaceutics