Dissolution Criteria Research Articles

Establishing Virtual Bioequivalence and Clinically Relevant Specifications for Omeprazole Enteric-Coated Capsules by Incorporating Dissolution Data in PBPK Modeling.

Currently, Biopharmaceutics Classification System (BCS) classes I and III are the only biological exemptions of immediate-release solid oral dosage forms eligible for regulatory approval. However, through virtual bioequivalence (VBE) studies, BCS class II drugs may qualify for biological exemptions if reliable and validated modeling is used. Here, we sought to establish physiologically based pharmacokinetic (PBPK) models, in vitro-in vivo relationship (IVIVR), and VBE models for enteric-coated omeprazole capsules, to establish a clinically-relevant dissolution specification (CRDS) for screening BE and non-BE batches, and to ultimately develop evaluation criteria for generic omeprazole enteric-coated capsules. To establish omeprazole's IVIVR based on the PBPK model, we explored its in vitro dissolution conditions and then combined in vitro dissolution profile studies with in vivo clinical trials. The predicted omeprazole pharmacokinetics (PK) profiles and parameters closely matched the observed PK data. Based on the VBE results, the bioequivalence study of omeprazole enteric-coated capsules required at least 48 healthy Chinese subjects. Based on the CRDS, the capsules' in vitro dissolution should not be < 28%-54%, < 52%, or < 80% after two, three, and six hours, respectively. Failure to meet these dissolution criteria may result in non-bioequivalence. Here, PBPK modeling and IVIVR methods were used to bridge the in vitro dissolution of the drug with in vivo PK to establish the BE safety space of omeprazole enteric-coated capsules. The strategy used in this study can be applied in BE studies of other BCS II generics to obtain biological exemptions and accelerate drug development.

Predicting mini-tablet dissolution performance utilizing X-ray computed tomography

Mini-tablets (MTs) have been utilized as an alternative to monolithic tablets due to their ease of use for pediatric populations, dose flexibility and tailoring of drug release profiles. Similar to monolithic tablets, MTs can develop film coat and internal core defects during manufacturing processes that may adversely affect their dissolution performance. The use of x-ray computed microtomography (XRCT) is well documented for monolithic tablets as a means of identifying internal defects, but applications to MTs have not been well studied. In this study, we have developed a workflow that analyzes reconstructed XRCT images of enteric-coated mini-tablets using deep learning convolutional neural networks. This algorithm was utilized to extract key physical features of individual MTs, such as micro-crack volume and enteric coat thickness. By performing dissolution studies on individual MTs, correlations were established based on the physical parameters obtained by XRCT and the dissolution performance, enabling prediction of dissolution performance utilizing non-destructive imaging data. This workflow provides insight into the physical variability of MT populations that are generated during manufacturing, enabling optimization of critical tableting and coating parameters to achieve the target dissolution criteria. Through this mechanistic understanding, quality is built into the final drug product through rational development of formulation and process parameters.

Utility of Physiologically Based Biopharmaceutics Modeling (PBBM) in Regulatory Perspective: Application to Supersede f2, Enabling Biowaivers & Creation of Dissolution Safe Space

Product DRL is a generic IR tablet formulation with BCS Class-III API, available in two strengths: 50mg & 100mg. The reference and test formulations have salt-A & salt-B of API but both products were bioequivalent based on the in vivo bioequivalence study conducted for higher strength 100mg. While leveraging the generic product to different market, the reference product from other market showed slower release than generic formulation resulting in f2<50 in pH 6.8 for both 50mg and 100mg, because of which waiver for BE study couldn't be granted. To support f2 mismatch at 100mg, 50mg and to facilitate biowaiver of 50mg, a Gastroplus® PBBM model was developed & validated. Virtual bioequivalence trials were performed using the slower dissolution profile of other market reference. It was demonstrated that despite slower dissolution, bioequivalence was achieved for test product against other market reference for 50mg & 100mg strengths. Additionally, dissolution safe space was created using virtual dissolution profiles, which indicated that when >85% released up to 60 min there is no impact on bioequivalence. Overall, for molecules with permeability controlled absorption (i.e. BCS-III), very rapid dissolution criteria can be relaxed by defining dissolution safe space thereby enabling more waivers in future.

Pharmacokinetics of a new fixed-dose combination of candesartan cilexetil, hydrochlorothiazide, and rosuvastatin in healthy adult subjects.

A fixed-dose combination (FDC) of candesartan cilexetil, hydrochlorothiazide and rosuvastatin (CC/HCTZ/RSV) has been developed to enhance patient compliance in the primary prevention of cardiovascular diseases. To evaluate if the combination of the product components in the new FDC capsule formulation affects their respective pharmacokinetic and in vitro dissolution patterns. In vitro dissolution profiles were compared in USP-43 and in biorelevant dissolution media. In vivo comparisons were obtained in a randomized, open-label, single-dose, two-treatment, two-way crossover study in 24 healthy subjects. During each treatment period, subjects received the test formulation (FDC hard capsule containing CC/HCTZ/RSV) or the reference formulation (co-administration of a FDC CC/HCTZ tablet and a RSV tablet). Plasma samples were collected periodically over 48 hours post-dose. Safety and tolerability were assessed. Dissolution profiles of all active drugs in the Test (capsule) and Reference Products (as tablets) were within the tolerance dissolution criteria of USP-43 conditions. HCTZ dissolution profiles were closely similar whereas those for RSV and CC did not match at specific pHs. In the pharmacokinetic study, the 90% confidence intervals (CIs) for the geometric least-square mean ratios of Cmax, AUC0-last, and AUC0-inf were 0.95-1.18, 0.95-1.15 and 0.95-1.13 (CC); 0.91-1.10, 0.96-1.08, and 0.96-1.09 (HCTZ) and 0.82-1.23, 0.81-1.13, and 0.82-1.12 (RSV), respectively. All adverse events were mild. The new FDC product (Sinlip Prevent), a stable FDC hard capsule, was bioequivalent (similar pharmacokinetics) when compared to the co-administration of the components and may be considered as a suitable and simplified medication for cardiovascular disease management.

Physiologically relevant dissolution conditions towards improved in vitro - in vivo relationship – A case study with enteric coated pantoprazole tablets

There are many hurdles in the development of generic formulations. In vitro biopredictive dissolution conditions together with alternative in vitro - in vivo relationship (IVIVR) approaches can be a powerful tool to support the development of such formulations. In this study, we hypothesized that the release profile of enteric coated (EC) formulations of pantoprazole in physiologically relevant bicarbonate buffer (BCB) would detect possible performance differences between test and reference formulations resulting in more accurate IVIVR results and predictability when compared to a pharmacopeial dissolution test. We correlated the in vitro performance of test and reference formulations (both in BCB and pharmacopeial phosphate buffer) with the in vivo data from a failed bioequivalence study. Test and reference formulations of EC pantoprazole tablets passed the USP dissolution criteria. However, they failed statistical similarity in vitro both in compendial and BCB. Bicarbonate buffer was additionally more discriminative while being more physiologically relevant. Having BCB as an additional test to evaluate EC products in vitro might improve the comparison of formulations. This can de-risk the development of generic EC formulations.

Quality of Glucosamine Products: Is it a Potential Reason for Inconsistent Clinical Outcomes in Osteoarthritis?

Clinical studies have reported inconsistent outcomes of glucosamine therapy in osteoarthritis patients. One possible reason could be the use of glucosamine products of varying quality. Hence, this study aimed to assess the quality of glucosamine products marketed in Australia and India. This is the first study to investigate both the content and dissolution profiles of glucosamine products. The content and dissolution analysis of Australian (n = 25 brands) and Indian (n = 21 brands) glucosamine products was performed according to the criteria specified in the United States Pharmacopoeia (USP). The quality analysis revealed that 16% and 18% of Australian brands, as well as 24% and 19% of Indian brands, did not fulfil the USP content and dissolution criteria, respectively. In approximately half of these cases, the glucosamine content was only slightly below (<3%) that specified by the USP and dissolution was achieved within 15 min after the duration specified by the USP. The majority of the brands did meet both the content and dissolution analysis criteria of the USP. The extent of deviation from the specified criteria for the other brands was probably insufficient to account for the significant variability in clinical effects. Hence, the study proposed that inter-patient pharmacokinetic variations in glucosamine could be another potential reason for inconsistent therapeutic effects.

Evaluation of impurities and dissolution profiles of illegal antimicrobial drugs encountered in Belgium.

Substandard and falsified (SF) antimicrobials are gaining popularity in both developing and developed countries, posing a growing threat to public health. In general, the evaluation of SF antimicrobial drugs mainly focuses on the identification and quantification of the pharmaceutical active ingredients, ignoring other parameters of drug quality control. This study performed an in-depth characterization and hazard identification of suspected SF antimicrobial medicinal products encountered in Belgium. In this comprehensive evaluation, impurity tests and dissolution studies were carried out. The dissolution profiles of illegal SF antimicrobials were mathematically compared to their genuine counterparts using the f1 and f2 -factor. The results indicated that 17 out of 57 illegal samples contained higher than permitted amounts of impurities and clearly demonstrated low equivalences of dissolution profiles between SF antimicrobials and genuine products. The variations between tablets at the different time points of the dissolution curves were also higher for the SF medicines. Moreover, 11 out of 19 illegal samples failed to meet the dissolution criteria prescribed by the United States Pharmacopeia. As impurities may induce adverse reactions and improper dissolution patterns may be the cause of insufficient drug efficacy, aggravation of illness and even promotion of antimicrobial resistance can be expected.

A reaction limited in vivo dissolution model for the study of drug absorption: Towards a new paradigm for the biopharmaceutic classification of drugs

The aim of this work is to develop a gastrointestinal (GI) drug absorption model based on a reaction limited model of dissolution and consider its impact on the biopharmaceutic classification of drugs. Estimates for the fraction of dose absorbed as a function of dose, solubility, reaction/dissolution rate constant and the stoichiometry of drug-GI fluids reaction/dissolution were derived by numerical solution of the model equations. The undissolved drug dose and the reaction/dissolution rate constant drive the dissolution rate and determine the extent of absorption when high-constant drug permeability throughout the gastrointestinal tract is assumed. Dose is an important element of drug-GI fluids reaction/dissolution while solubility exclusively acts as an upper limit for drug concentrations in the lumen. The 3D plots of fraction of dose absorbed as a function of dose and reaction/dissolution rate constant for highly soluble and low soluble drugs for different “stoichiometries” (0.7, 1.0, 2.0) of the drug-reaction/dissolution with the GI fluids revealed that high extent of absorption was found assuming high drug- reaction/dissolution rate constant and high drug solubility. The model equations were used to simulate in vivo supersaturation and precipitation phenomena. The model developed provides the theoretical basis for the interpretation of the extent of drug's absorption on the basis of the parameters associated with the drug-GI fluids reaction/dissolution. A new paradigm emerges for the biopharmaceutic classification of drugs, namely, a model independent biopharmaceutic classification scheme of four drug categories based on either the fulfillment or not of the current dissolution criteria and the high or low % drug metabolism.

Numerical analysis of the dissolution of uranium dioxide by molten zircaloy using MPS method

Dissolution of uranium dioxide by molten zircaloy at high temperatures is an important chemical process affecting the fuel melting during nuclear reactor severe accidents. In this study, the dissolution model, based on the mass transfer model and the dissolution criteria, was developed and incorporated into the Moving Particle Semi-implicit (MPS) method. To verify the dissolution model, the one-dimensional mass transfer between two semi-infinite materials was simulated by the improved MPS code. The sensitivity analyses of the particle size have been conducted since particle size determines the simulation accuracy. Then analyses on dissolution of UO2 by molten zircaloy were performed according to results by the improved MPS code. In this study, two series of experiments on dissolution of UO2 by molten zircaloy conducted by Kim and Olander were simulated respectively. The first series of experiments focuses on mass transfer. The corresponding simulation results of MPS show that the dissolution kinetics of UO2 by molten zircaloy follows the parabolic law, and the penetration depths of chemical elements (U, O, Zr) were limited by time. The second series of experiments concerns on natural convection. The simulation results show that the natural convection of melting process has a significant influence on the dissolution behavior. The results indicate that the dissolution of UO2 by molten zircaloy fits the parabolic law before the concentration of UO2 in the liquid reaches the saturation point. After the concentration of UO2 reaches the saturation point, the dissolution of UO2 by molten zircaloy also obeys the parabolic law. The difference between the two parabolic laws is the dissolution rate. The dissolution rate decreases after the UO2 is saturated in the liquid. For natural convection, the penetration depths of chemical elements (U and O) become deeper, which could accelerate the progress of dissolution.

Numerical investigation on the dissolution kinetics of ZrO2 by molten zircaloy using MPS method

During the postulated core meltdown accident of the nuclear reactor which employs the dispersion plate-type fuel, the UO2 microspheres would be dissolved by the molten zirconium, and the dissolution process is accelerated by the mass diffusion phenomenon. In this study, the dissolution model, based on the Fick’s second law and the dissolution criteria, was developed and incorporated into the Moving Particle Semi-implicit (MPS) method. To validate the dissolution model, the one-dimensional mass diffusion problem was simulated by the improved MPS code. The study of numerical convergence was also performed based on the sensitivity analysis of the particle size. The distribution of the oxygen predicted by the improved MPS agreed well with the analytical solution for the particle size of 0.5mm. Then the improved MPS was adopted to analyze the dissolution kinetics of the three-dimensional ZrO2-Zr system in this study. The oxygen concentration and the interface displacement of the ZrO2-Zr system were considered, and the simulation results indicate that the behavior of ZrO2 dissolution caused by molten zircaloy follows the parabolic law. The improved MPS method is proved to be capable of simulating the dissolution process and the induced phase change.

Application of the BCS biowaiver approach to assessing bioequivalence of orally disintegrating tablets with immediate release formulations

The aim of this study was to compare the dissolution profiles of oral disintegrating tablets (ODTs) and immediate release (IR) formulations in order to experimentally validate the regulatory biowaiver scheme (BWS) for biopharmaceutical classification system (BCS) class III drugs. We examined six drugs that show clinical bioequivalence between the ODTs and IR formulations: taltirelin, olopatadine, droxidopa, famotidine, fexofenadine, and hydrochlorothiazide. The dissolution profiles of these drugs were evaluated using the compendium paddle apparatus at pH 1.2 and 6.8. Taltirelin and olopatadine showed very rapid dissolution and met the dissolution criteria in the BWS, whereas droxidopa, famotidine, fexofenadine, and hydrochlorothiazide did not. Furthermore, in the case of famotidine, fexofenadine, and hydrochlorothiazide, the ODTs and IR formulations showed dissimilar dissolution profiles. The dose-to-solubility ratio (D:S) of these drugs was larger than that of the other drugs. The results of this study suggest that extension of the BCS-BWS to ODTs and IR formulations of BCS class III drugs is appropriate. Furthermore, for BCS class III drugs with relatively high D:S, clinical bioequivalence would be achievable even when two formulations showed different dissolution profiles in vitro.

Pharmacokinetic simulations to explore dissolution criteria of BCS I and III biowaivers with and without MDR-1 efflux transporter

In this study, a pharmacokinetic simulation model was used to explore the dissolution acceptance criteria for BCS I and III biowaivers and to examine the risk of MDR-1 efflux transporter on bioequivalence of substrates. The compartmental absorption and transit (CAT) model with one- or two systemic compartments was used. The parameter values used in the simulations were based on the pharmacokinetics of existing 70 BCS I and III drugs. Based on the simulations BCS I drug products with Tmax of >0.9h, both dissolution criteria “very rapid” and “rapid and similar” were acceptable. For rapidly absorbed and distributed BCS I drug products with Tmax of 0.6–0.9h, the dissolution criterion “very rapid” is preferred. If Tmax is less than 0.6h there is a risk of bioinequivalence for the BCS I drug products regardless of the dissolution criteria. Based on the simulations, all BCS III drug products were good biowaiver candidates with both dissolution criteria. Almost all the BCS III drug products (>89%) and many BCS I products (9–57%) showed risks of bioinequivalence, if an excipient in either product inhibits MDR1-efflux transport of the drug. To eliminate these risks excipients with prior use in bioequivalent products should be used for MDR-1 efflux substrates.

Progressive Applications of Dissolution, Its Impact, and Implications in the Pharmaceutical World

Progressive Applications of Dissolution, Its Impact, and Implications in the Pharmaceutical World

Comparative in vitro dissolution study of carbamazepine immediate-release products using the USP paddles method and the flow-through cell system

Dissolution profiles of four carbamazepine immediate-release generic products (200mg tablets) and the reference product Tegretol® were evaluated using the USP paddles method and an alternative method with the flow-through cell system, USP Apparatus 4. Under official conditions all products met the Q specification, dissolution profiles of generic products were similar to the dissolution profile of the reference product (f2>50) and model-independent parameters showed non significant differences to the reference product except mean dissolution time for product A (p<0.05). On the other hand, when the flow-through cell system was used, none of the products met the pharmacopeial specification at 15min and product A did not reach dissolution criteria at 60min, dissolution profiles of all generic products were not similar to the reference product profile (f2<50) and all model-independent parameters showed significant differences compared to the reference product (p<0.05). Weibull’s model was more useful for adjusting the dissolution data of all products in both USP apparatuses and Td values showed significant differences compared to the reference product (p<0.05) when USP Apparatus 4 was used. These results indicate that the proposed method, using the flow-through cell system, is more discriminative in evaluating both, rate and extent of carbamazepine dissolution process from immediate-release generic products.

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Efavirenz

Literature data pertaining to the decision to allow a waiver of in vivo bioequivalence testing for the approval of immediate-release (IR) solid oral dosage forms containing efavirenz as the only active pharmaceutical ingredient (API) are reviewed. Because of lack of conclusive data about efavirenz's permeability and its failure to comply with the "high solubility" criteria according to the Biopharmaceutics Classification System (BCS), the API can be classified as BCS Class II/IV. In line with the solubility characteristics, the innovator product does not meet the dissolution criteria for a "rapidly dissolving product." Furthermore, product variations containing commonly used excipients or in the manufacturing process have been reported to impact the rate and extent of efavirenz absorption. Despite its wide therapeutic index, subtherapeutic levels of efavirenz can lead to treatment failure and also facilitate the emergence of efavirenz-resistant mutants. For all these reasons, a biowaiver for IR solid oral dosage forms containing efavirenz as the sole API is not scientifically justified for reformulated or multisource drug products.

Biowaiver Monographs for Immediate-Release Solid Oral Dosage Forms: Primaquine Phosphate

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate-release (IR) solid oral dosage forms containing the antimalarial drug primaquine phosphate as the only active pharmaceutical ingredient (API) are reviewed. On the basis of permeability data and solubility studies, primaquine phosphate was found to be "highly soluble" and "highly permeable" API, thus conforming to Class I of the Biopharmaceutical Classification System (BCS). It has a wide therapeutic index. BCS-conform dissolution studies showed the products to be rapidly dissolving. No data pertaining to BE or bioinequivalence of IR primaquine phosphate products could be located in open literature. On the basis of the available data, a biowaiver-procedure-based approval can be recommended for IR solid oral dosage forms of primaquine phosphate, provided the generic product contains excipients present in products already approved by the International Conference on Harmonisation or associated countries in similar amounts and the test and reference products meet the dissolution criteria for "rapidly dissolving" (>85% drug release in 30 min in standard media at pH 1.2, 4.5, and 6.8; similarity factor (f(2)) > 50) or "very rapidly dissolving" products (>85% drug release in 15 min in standard media at pH 1.2, 4.5, and 6.8).

Comparative Bioavailability of Two Oral L-Thyroxine Formulations after Multiple Dose Administration in Patients with Hypothyroidism and its Relation with Therapeutic Endpoints and Dissolution Profiles

The aim of the present study was to evaluate the bioequivalence and therapeutic equivalence of the two most commonly prescribed L-thyroxine (monsodium L-thyroxine hydrate, CAS 25416-65-3) formulations in Brazil in patients treated for hypothyroidism. Twenty-four patients received 100 micrograms L-thyroxine daily of either Puran T4 (test) or the Brazilian reference formulation (reference) during 42 days, in a two-period crossover design. Serum samples obtained over a 24-h interval were analyzed for their total T4 concentration by a chemiluminescent immunoassay. Content and uniformity of the tablets and dissolution studies were also assessed according to USP 24 monograph using an isocratic HPLC-UV system and a rotating-paddle method. The mean pharmacokinetic parameters for total T4, expressed as geometric means (CV), for the test and reference were, respectively: Cmax (microgram/dl) 9.8 (14.3%) and 10.8 (14.9%); AUC0-24 h (microgram/dl.h) 206.8 (13.9%) and 230.4 (14.9%). Median values (90% CI) for Tmax (h) were 3 (2-3) and 2 (2-4) for the test and reference, respectively. 90% CI for ratios of LogCmax and LogAUC0-24 h were 86.6-94.9 and 86.3-93.4, respectively. Although the test exhibited values of Cmax and AUC0-24 h around 10% lower than the reference, these formulations must be considered bioequivalent since the 90% CI for both Cmax and AUC0-24 h mean ratio were within the 80-125% interval as proposed by the US Food and Drug Administration and the Brazilian legislation. TSH dosages within the normal range further support therapeutic equivalence between the two formulations. Dissolution data were roughly in agreement with in vivo results since both formulations comply with the USP dissolution criteria although the test tablets had a slower dissolution rate than the reference tablets. As a conclusion, the two oral formulations of L-thyroxine are both bioequivalent and therapeutically equivalent although presenting a small difference in their extent of absorption. Noteworthy, the dissolution profiles of the tablets correlate well with their bioavailability in the present experimental conditions.

Real-time predictions of drug release and end point detection of a coating operation by in-line near infrared measurements

The aim of this work was to carry out real-time near infrared (NIR) predictions of drug release from sustained release coated tablets and to determine end point of coating operation.In-line measurements were ensured by implementation of a NIR probe inside a pan coater. Tablets were coated using a functional aqueous dispersion of ethylcellulose blended with PVA–PEG graft copolymer to obtain a controlled drug release dosage form over 16h. Samples were collected at regular intervals and subjected to a standardized curing step. Percentages of released drug at 4h, 8h and 12h were selected to describe the controlled drug release of cured tablets. These dissolution criteria were used as reference values to calibrate NIR spectral information and to develop three partial least squares regressions.Low predictive errors of 1.7%, 1.9% and 1.5%, respectively, were obtained. The coating operation was stopped while desired dissolution criteria were achieved, corresponding to a coating level around 10%.The present study demonstrated that real-time NIR measurements could be performed on non-finished drug products to predict dissolution properties of cured coated tablets. This novel and innovative approach fulfils the expectations of ICH Q8 guideline on pharmaceutical development, in terms of process understanding and process analytical technology (PAT) control strategy. This approach should be however adapted to curing operation to allow a real-time release testing.

COMMENTARY: Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Lamivudine

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing lamivudine as the only active pharmaceutical ingredient were reviewed. The solubility and permeability data of lamivudine as well as its therapeutic index, its pharmacokinetic properties, data indicating excipient interactions, and reported BE/bioavailability (BA) studies were taken into consideration. Lamivudine is highly soluble, but its permeability characteristics are not well-defined. Reported BA values in adults ranged from 82% to 88%. Therefore, lamivudine is assigned to the biopharmaceutics classification system (BCS) class III, noting that its permeability characteristics are near the border of BCS class I. Lamivudine is not a narrow therapeutic index drug. Provided that (a) the test product contains only excipients present in lamivudine IR solid oral drug products approved in the International Conference on Harmonization or associated countries in usual amounts and (b) the test product as well as the comparator product fulfills the BCS dissolution criteria for very rapidly dissolving; a biowaiver can be recommended for new lamivudine multisource IR products and major post-approval changes of marketed drug products.

The Biowaiver Extension for BCS Class III Drugs: The Effect of Dissolution Rate on the Bioequivalence of BCS Class III Immediate-Release Drugs Predicted by Computer Simulation

The Biopharmaceutical Classification System (BCS) guidance issued by the FDA allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release (IR) solid oral dosage forms only for BCS class I drugs. However, a number of drugs within BCS class III have been proposed to be eligible for biowaivers. The World Health Organization (WHO) has shortened the requisite dissolution time of BCS class III drugs on their Essential Medicine List (EML) from 30 to 15 min for extended biowaivers; however, the impact of the shorter dissolution time on AUC(0-inf) and C(max) is unknown. The objectives of this investigation were to assess the ability of gastrointestinal simulation software to predict the oral absorption of the BCS class I drugs propranolol and metoprolol and the BCS class III drugs cimetidine, atenolol, and amoxicillin, and to perform in silico bioequivalence studies to assess the feasibility of extending biowaivers to BCS class III drugs. The drug absorption from the gastrointestinal tract was predicted using physicochemical and pharmacokinetic properties of test drugs provided by GastroPlus (version 6.0). Virtual trials with a 200 mL dose volume at different drug release rates (T(85%) = 15 to 180 min) were performed to predict the oral absorption (C(max) and AUC(0-inf)) of the above drugs. Both BCS class I drugs satisfied bioequivalence with regard to the release rates up to 120 min. The results with BCS class III drugs demonstrated bioequivalence using the prolonged release rate, T(85%) = 45 or 60 min, indicating that the dissolution standard for bioequivalence is dependent on the intestinal membrane permeability and permeability profile throughout the gastrointestinal tract. The results of GastroPlus simulations indicate that the dissolution rate of BCS class III drugs could be prolonged to the point where dissolution, rather than permeability, would control the overall absorption. For BCS class III drugs with intestinal absorption patterns similar to those of cimetidine, atenolol or amoxicillin, the dissolution criteria for extension of biowaivers to BCS class III drugs warrants further investigation.