Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Isavuconazonium Sulfate

A Biopharmaceutics Classification System (BCS)-based biowaiver monograph is presented for isavuconazonium sulfate. A BCS-based biowaiver is a regulatory option to substitute appropriate in vitro data for in vivo bioequivalence studies. Isavuconazonium sulfate is the prodrug of isavuconazole, a broad-spectrum azole antifungal indicated for invasive fungal infections. While the prodrug can be classified as a BCS Class III drug with high solubility but low permeability, the parent drug can be classified as a BCS Class II drug with low solubility but high permeability. Interestingly, the in vivo behavior of both is additive and leads isavuconazonium sulfate to act like a BCS class I drug substance after oral administration. In this work, experimental solubility and dissolution data were evaluated and compared with available literature data to investigate whether it is feasible to approve immediate release solid oral dosage forms containing isavuconazonium sulfate according to official guidance from the FDA, EMA and/or ICH. The risks associated with waiving a prodrug according to the BCS-based biowaiver guidelines are reviewed and discussed, noting that current regulations are quite restrictive on this point. Further, results show high solubility but instability of isavuconazonium sulfate in aqueous media. Although experiments on the dissolution of the capsule contents confirmed 'very rapid' dissolution of the active pharmaceutical ingredient (API) isavuconazonium sulfate, its release from the commercial marketed capsule formulation Cresemba is limited by the choice of capsule shell material, providing an additional impediment to approval of generic versions via the BCS-Biowaiver approach.

Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS)-Based Biowaivers: A workshop Summary Report

The workshop "Drug Permeability - Best Practices for Biopharmaceutics Classification System (BCS) Based Biowaivers" was held virtually on December 6, 2021, organized by the University of Maryland Center of Excellence in Regulatory Science and Innovation (M-CERSI), and the Food and Drug Administration (FDA). The workshop focused on the industrial, academic, and regulatory experiences in generating and evaluating permeability data, with the aim to further facilitate implementation of the BCS and efficient development of high-quality drug products globally. As the first international permeability workshop since the BCS based biowaivers was finalized as the ICH M9 guideline, the workshop included lectures, panel discussions, and breakout sessions. Lecture and panel discussion topics covered case studies at IND, NDA, and ANDA stages, typical deficiencies relating to permeability assessment supporting BCS biowaiver, types of evidence that are available to demonstrate high permeability, method suitability of a permeability assay, impact of excipients, importance of global acceptance of permeability methods, opportunities to expand the use of biowaivers (e.g. non-Caco-2 cell lines, totality-of-evidence approach to demonstrate high permeability) and future of permeability testing. Breakout sessions focused on 1) in vitro and in silico intestinal permeability methods; 2) potential excipient effects on permeability and; 3) use of label and literature data to designate permeability class.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Levocetirizine Dihydrochloride

Levocetirizine, a histamine H1-receptor antagonist, is prescribed to treat uncomplicated skin rashes associated with chronic idiopathic urticaria as well as the symptoms of both seasonal and continual allergic rhinitis. In this monograph, the practicality of using Biopharmaceutics Classification System (BCS) based methodologies as a substitute for pharmacokinetic studies in human volunteers to appraise the bioequivalence of immediate-release (IR) oral, solid dosage forms containing levocetirizine dihydrochloride was investigated, using data from the literature and in-house testing. Levocetirizine's solubility and permeability properties, as well as its dissolution from commercial products, its therapeutic uses, therapeutic index, pharmacokinetics and pharmacodynamic traits, were reviewed in accordance with the BCS, along with any reports in the literature about failure to meet bioequivalence (BE) requirements, bioavailability issues, drug-excipient interactions as well as other relevant information. The data presented in this monograph unequivocally point to classification of levocetirizine in BCS Class 1. For products that are somewhat supra-equivalent or somewhat sub-equivalent, clinical risks are expected to be insignificant in light of levocetirizine's wide therapeutic index and unlikelihood of severe adverse effects. After careful consideration of all the information available, it was concluded that the BCS-based biowaiver can be implemented for products which contain levocetirizine dihydrochloride, provided (a) the test product comprises excipients that are typically found in IR oral, solid drug products that have been approved by a country belonging to or associated with ICH and are used in quantities that are typical for such products, (b) data supporting the BCS-based biowaiver are gathered using ICH-recommended methods, and (c) all in vitro dissolution requirements specified in the ICH guidance are met by both the test and comparator products (in this case, the comparator is the innovator product).

Biowaiver Monograph for Immediate-Release Dosage Forms: Levamisole Hydrochloride

This work describes the potential applicability of the BCS-based Biowaiver to oral solid dosage forms containing Levamisole hydrochloride, an anthelmintic drug on the WHO List of Essential Medicines. Solubility and permeability data of levamisole hydrochloride were searched in the literature and/or measured experimentally. Levamisole hydrochloride is a highly soluble drug, but there is no clear evidence of high permeability in humans, indicating that it should provisionally be assigned to BCS class III. The biowaiver procedure would thus be applicable for solid oral dosage forms containing levamisole hydrochloride as the only active ingredient. Due to the lack of data in the literature regarding excipient effects on the bioequivalence of products containing levamisole, it is currently recommended that the products comply with the ICH and WHO guidelines: the test formulation should have the same qualitative composition as the comparator, contain very similar quantities of those excipients, and be very rapidly dissolving at pH 1.2, 4.5, and 6.8. However, for certain well-studied excipients, there appears to be opportunity for additional regulatory relief in future versions of the ICH BCS Guidance M9, such as not requiring that the quantities of these common excipients in the test and comparator be the same.

Donepezil Hydrochloride BCS Class Ambiguity: Relevant Aspects to be Considered in Drug Classification

Donepezil hydrochloride (DH) is the most used anti-Alzheimer's disease drug, however, its classification according to the Biopharmaceutics Classification System (BCS) is not clear in the literature. BCS is one of the accepted criteria used to grant biowaiver (waiver of in vivo bioequivalence studies) of new drug products. So, the purpose of this work was to elucidate the BCS classification of DH and to raise the discussion about the possibility of biowaiver for new medicines containing it. The polymorphic form was previously identified as form III of DH. The drug showed high solubility in the entire pH range evaluated (1.2 to 6.8, at 37 °C) with a pH-dependent solubility profile. The effective permeability (P_eff) values obtained with different DH concentrations, using in situ closed-loop perfusion model were statistically similar (p > 0.05), even when compared to high permeability control used (ketoprofen), demonstrating that DH has high permeability which, associated with its high solubility, allows to classify DH as BCS class 1. Relevant data to evaluate for granting a biowaiver for new medicines were also reviewed from the literature. Based on information reunited new immediate-release drug products containing DH should be eligible for BCS-based biowaiver.

Advances in in-vitro bioequivalence testing methods for complex ophthalmic generic products

The United States Food and Drug Administration (USFDA) demands that the generic industry prove topical ocular products' pharmaceutical and bioequivalence (BE). In contrast to generic oral drugs, topical ocular product BE testing has proved difficult. New generic versions are compared to an authorized drug product known as a Reference Listed Drug (RLD) to demonstrate their bioequivalence. If the excellent in-vitro results may support the presumption of equivalence in-vivo performance and the only clinically significant difference between the generic and RLD is in its physicochemical qualities and drug release rate, then in-vivo BE studies may be waived. Proving BE through dissolution tests is a golden standard for most conventional dosage forms. However, due to the limited number of biorelevant in-vitro drug release testing (IVRT) approaches capable of differentiating their performance based on product quality and physicochemical properties, the development of generic ophthalmic products has been slow and time-consuming. Often, BE of topical ophthalmic formulations cannot be proved using a single in-vitro test; therefore, an elaborated discussion on various IVRT methods performed to demonstrate bioequivalence of complex generis like ophthalmic emulsions, suspensions, ointments, and gels is necessary. This manuscript aims to review the status of biowaiver criteria for complex ophthalmic products concerning the product-specific FDA guidance to the generic industry.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Sitagliptin Phosphate Monohydrate

Sitagliptin is an antihyperglycemic drug used in adults for the treatment of diabetes Type 2. Literature data and in-house experiments were applied in this monograph to assess whether methods based on the Biopharmaceutics Classification System (BCS) could be used to assess the bioequivalence of solid immediate-release (IR) oral dosage forms containing sitagliptin phosphate monohydrate, as an alternative to a pharmacokinetic study in human volunteers. The solubility and permeability characteristics of sitagliptin were reviewed according to the BCS, along with dissolution, therapeutic index, therapeutic applications, pharmacokinetics, pharmacodynamic characteristics, reports of bioequivalence (BE) / bioavailability problems, data on interactions between the drug and excipients and other data germane to the subject. All data reviewed in this monograph unambiguously support classification of sitagliptin as a BCS Class 1 drug. In light of its broad therapeutic index and lack of severe adverse effects, the clinical risks associated with moderately supraoptimal doses were deemed inconsequential, as were the risks associated with moderately suboptimal doses. Taking all evidence into consideration, it was concluded that the BCS-based biowaiver can be implemented for solid IR oral drug products containing sitagliptin phosphate monohydrate, provided (a) the test product is formulated solely with excipients commonly present in solid IR oral drug products approved in ICH or associated countries and used in amounts commonly applied in this type of product, (b) data in support of the BCS-based biowaiver are obtained using the methods recommended by the WHO, FDA, EMA or ICH and (c) the test product and the comparator product (which is the innovator product in this case) meet all in vitro dissolution specifications provided in the WHO, FDA, EMA or ICH guidance.

An Assessment of Occasional Bio-Inequivalence for BCS1 and BCS3 Drugs: What are the Underlying Reasons?

Despite having adequate solubility properties, bioequivalence (BE) studies performed on immediate release formulations containing BCS1/3 drugs occasionally fail. By systematically evaluating a set of 17 soluble drugs where unexpected BE failures have been reported and comparing to a set of 29 drugs where no such reports have been documented, a broad assessment of the risk factors leading to BE failure was performed. BE failures for BCS1/3 drugs were predominantly related to changes in C_max rather than AUC. C_max changes were typically modest, with minimal clinical significance for most drugs. Overall, drugs with a sharp plasma peak were identified as a key factor in BE failure risk. A new pharmacokinetic term (t½C_max) is proposed to identify drugs at higher risk due to their peak plasma profile shape. In addition, the analysis revealed that weak acids, and drugs with particularly high gastric solubility are potentially more vulnerable to BE failure, particularly when these features are combined with a sharp C_max peak. BCS3 drugs, which are often characterised as being more vulnerable to BE failure due to their potential for permeation and transit to be altered, particularly by excipient change, were not in general at greater risk of BE failures. These findings will help to inform how biowaivers may be optimally applied in the future.

Pharmacokinetics and Bioequivalence of Two Amoxicillin 500 mg Products: Effect of Food on Absorption and Supporting Scientific Justification for Biowaiver

PURPOSE

Aims of this study were to compare the bioequivalence of two formulations of amoxicillin 500 mg capsules under fasted and fed conditions in the same set of healthy volunteers, compare pharmacokinetics of amoxicillin under the two conditions and to assess the possibility of predicting in vivo bioequivalence of the two formulations using in vitro dissolution data.

METHOD

The innovator product of amoxicillin was used as the reference formulation and a test product, which showed in vitro equivalence after a biowaiver study with the same reference product was used in the bioequivalence study. Altogether 16 subjects were randomized to the reference and test products in the fasted study and 12 of them participated in the fed study. Plasma concentration of amoxicillin was analyzed by a validated Liquid chromatography coupled with two mass spectrometry (LC-MS/MS) method. Noncompartmental analysis was used to determine the pharmacokinetic parameters. Average bioequivalence method was used to evaluate the bioequivalence of the two formulations and statistical significance of the pharmacokinetic parameters were tested to study the effect of food on amoxicillin absorption.

RESULTS

The Geometric Mean Ratio (GMR) for the test/reference product for the maximum drug concentrations (C_max) was 102.77% and 97.38% in fasted and fed conditions respectively which was within 80.00-125.00% range required to demonstrate bioequivalence. The GMR for test/reference products for the area under the curve (AUC_0-8,) was 100.05% and 96.91% in fasted and fed conditions respectively meeting the bioequivalence criteria. For the reference product, the C_max was 9.38 and 7.61 µg x mL^-1(p =0.0224), time to reach maximum concentration (T_max) was 1.73 and 3.02 h (p=0.0005) and AUC_0-8 was 26.02 and 25.54 µg/h^-1 mL^-1p = 0.672) under fasted and fed conditions respectively.

CONCLUSION

The test and the reference formulations were bioequivalent under both fasted and fed conditions. Although the C_max was significantly lower and T_max was significantly delayed under fed conditions, it did not affect the AUC. Therefore, being a time dependent antibiotic, clinically significant effect of food on efficacy of amoxicillin is unlikely. As the selected products were equivalent in vitro, these findings support scientific justification for conducting in vitro dissolution studies for solid oral amoxicillin products as a surrogate for in vivo bioequivalence studies.

Prediction of plasma concentrations using in silico modelling and simulation approach: Case of Acebutolol

PURPOSE

The aim of this study was to predict the plasma concentrations of acebutolol tablets with different dissolution profiles using computer modelling and evaluating whether they are bioequivalent using simulated population studies.

METHODS

The dissolution behaviour of acebutolol was studied in the USP Apparatus-II using different dissolution media for pH 1.2, 4.5, and 6.8 at 37±0.5°C. The obtained dissolution data, as well as plasma concentration-time data of the reference product from the literature were used as inputs to build pharmacokinetic model of acebutolol within GastroPlus™ software (version 9.7, Simulations Plus Inc., Lancaster, CA, USA) to simulate the in vivo profiles of the drug.

RESULTS

The dissolution profiles of the reference product Sectral® 400mg tablets and a locally produced generic product were>85% in 15min in three dissolution media. Simulation results demonstrated that the brand and generic products would show the same in vivo performance. Population simulation results of the ln-transformed 90% confidence interval for the ratio of C_max, AUC_0-t and AUC_0-inf values for the two products were within the 80-125% interval, showing to be bioequivalent.

CONCLUSION

Based on the in vitro results combined with in silico simulations using GastroPlus™, a biowaiver for immediate release acebutolol tablets is justified. Furthermore, computer modelling has shown to be a very intersting tool to prove the bioequivalence for these products.

Biowaiver Monograph for Immediate-Release Solid Oral Dosage Forms: Carbamazepine

Literature relevant to assessing whether BCS-based biowaivers can be applied to immediate release (IR) solid oral dosage forms containing carbamazepine as the single active pharmaceutical ingredient are reviewed. Carbamazepine, which is used for the prophylactic therapy of epilepsy, is a non-ionizable drug that cannot be considered "highly soluble" across the range of pH values usually encountered in the upper gastrointestinal tract. Furthermore, evidence in the open literature suggests that carbamazepine is a BCS Class 2 drug. Nevertheless, the oral absolute bioavailability of carbamazepine lies between 70 and 78% and both in vivo and in vitro data support the classification of carbamazepine as a highly permeable drug. Since the therapeutic and toxic plasma level ranges overlap, carbamazepine is considered to have a narrow therapeutic index. For these reasons, a BCS based biowaiver for IR tablets of carbamazepine cannot be recommended. Interestingly, in nine out of ten studies, USP dissolution conditions (900 mL water with 1% SLS, paddle, 75 rpm) appropriately discriminated among bioinequivalent products and this may be a way forward to predicting whether a given formulation will be bioequivalent to the comparator product.

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Metformin Hydrochloride

Data are examined regarding possible waiver of in vivo bioequivalence testing (i.e. biowaiver) for approval of metformin hydrochloride (metformin) immediate-release solid oral dosage forms. Data include metformin's Biopharmaceutics Classification System (BCS) properties, including potential excipient interactions. Metformin is a prototypical transporter-mediated drug and is highly soluble, but only 50% of an orally administered dose is absorbed from the gut. Therefore, metformin is a BCS Class III substance. A BCS-based approval approach for major changes to marketed products and new generics is admissible if test and reference dosage forms have the identical active pharmaceutical ingredient and if in vitro dissolution from both are very rapid (i.e. at least 85% within 15 min at pH 1.2, 4.5, and 6.8). Recent International Council for Harmonisation BCS guidance indicates all excipients for Class III biowaivers are recommended to be qualitatively the same and quantitatively similar (except for preservatives, flavor agents, colorant, or capsule shell or film coating excipients). However, despite metformin being a prototypical transporter-mediated drug, there is no evidence that commonly used excipients impact metformin absorption, such that this restriction on excipients for BCS III drugs merits regulatory relief. Commonly used excipients in usual amounts are not likely to impact metformin absorption.

Policy of Multisource Drug Products in Latin America: Opportunities and Challenges on the Application of Bioequivalence In Vitro Assays

BACKGROUND

The replacement of traditional in vivo bioequivalence studies by in vitro dissolution assays, based on the biopharmaceutical classification system (BCS), has emerged as an important tool for demonstrating the interchangeability of multisource products. This paper summarizes the current implementation of the BCS-based biowaiver for the development of multisource products in Latin America, and identifies several challenges and opportunities for greater convergence and application of BCS regulatory requirements.

METHODS

Differences and similarities between the current BCS-based biowaivers' guidelines proposed by two relevant regulatory agencies for the Latin American region (FDA and WHO) and the new ICH harmonization guideline were identified and compared. An update of the BCS-based biowaiver guideline for Latin American countries was also considered, based on the respective regulatory information on bioequivalence studies, which is publicly available.

RESULTS

About 50% of the Latin American countries analyzed have no information on the implementation of any bioequivalence standards, while in the countries where bioequivalence studies are considered, the acceptance and application of BCS-based biowaiver requirements is quite heterogeneous. This situation contrasts with the international trend of global harmonization for BCS-based biowaiver guidance, suggesting the need in Latin America to identify opportunities and overcome challenges to improve the development of BCS-based biowaivers to avoid costly and time-consuming in vivo bioequivalence studies.

CONCLUSIONS

The study shows that the region is in a position to improve access to safe and effective medicines at a reasonable cost by applying BCS-based biowaiver guidance.

Relationship between rheological properties, in vitro release and in vivo equivalency of topical formulations of diclofenac

Determination of bioequivalence remains a challenge in generic topical drug development. To support pharmacokinetic studies, strategies to demonstrate microstructure sameness of the products being compared include in vitro evaluations, such as the comparison of rheological properties, droplet size and in vitro release rates. Nevertheless, defining the appropriate acceptance range to consider equivalence between test and reference formulation is complex. To shed more light into this issue, in vitro release and rheological properties were compared to in vivo bioequivalence data (systemic blood measurements within a clinical trial) after topical application of a single dose. Test and reference formulations of diclofenac diethylamine emulgels were evaluated. While the test formulation met the requirements for equivalence in both the in vivo bioequivalence and in vitro release study, the rheological properties were considered equivalent depending on the criteria used. The 90% confidence interval of the ratios between geometric mean values of both formulations were within the limits of 75-133%, but outside the 90-111% limit under discussion in the scientific community. Altogether these data indicate that differences beyond ±10% between rheological parameters of test and reference formulation might not translate into meaningful release nor bioavailability divergence.

Regulatory requirements for the registration of generic medicines and format of drug dossiers: procedures in Sri Lanka in comparison with selected regulatory authorities

BACKGROUND

The regulatory requirements for approval of generic medicines and the format of compiling drug dossiers vary among regulatory authorities. The variation is particularly wide between High-income countries (HIC) and lower and middle-income countries (LMIC) with different regulatory frameworks. In this study, document requirements for approval of generic products, approval timelines, and consideration of bioequivalence and/or biowaiver data by Regulatory Authorities (RAs) of 10 selected jurisdictions was studied.

METHODS

The guidelines and procedures from 5 purposively chosen RA of HIC and4 regional RAs relevant for Sri Lanka were compared with the Sri Lankan National Medicines Regulatory Authority (NMRA). Information available in the official websites of the selected RAs, published journal articles and via personal communication was collected in2016. Drug approval timelines achieved in Sri Lanka was obtained from data available from another study.

RESULTS

Common technical dossier (CTD) format of the International Council on Harmonization (ICH) for registration of pharmaceuticals (ICH:CTD) or the Association of South East Asian Nations (ASEAN) CTD format (ACTD) was used by all RAs studied except Sri Lanka which use its own dossier format. Nine out of ten RAs studied request BE data or justification for not submitting BE data for generic medicines. Sri Lanka requested BE studies only for antimicrobials, antiepileptic drugs and narrow therapeutic index drugs. Biowaivers are allowed for Biopharmaceutics Classification System (BCS)-based Class 1drugs in Singapore and India. USA, EMA, Canada and South Korea allowed biowaiver for BCS Class1and Class 3drugs but Sri Lanka does not accept BW at present. Nine NMRAs out of the ten studied reported legislated timelines for approval of generic pharmaceuticals except Sri Lanka.

CONCLUSIONS

Streamlining the drug regulatory systems in LMIC such as Sri Lanka with that of HIC would facilitate an effective drug regulatory system based on reliance on decisions made by stringent regulatory authorities. Findings of this study encourage Sri Lanka to adopt a CTD format for regulatory submission of drug dossiers. Expanding the BE requirement drug list and accepting BCS-based biowaivers for BSC class 1 and 3 drugs during registration of generic drugs when it is scientifically justified is also recommended for Sri Lanka.

The Gradually Expanding Scope for Biowaivers of Oral Products: An Overview

The regulatory paradigm is relaxing gradually without compromising the safety, efficacy and the quality of the drug product and, most importantly, a perceptible scientific consensus is maturing towards the need of affordable medicines. The establishment of bioequivalence (BE) is no longer being considered to be accomplished only by in vivo studies in oral drug products. The potential use of in vitro dissolution testing in lieu of BE studies has now been regulatory adopted and is commonly referred to as "biowaiver". Further, the advent of biopharmaceutics classification system (BCS) and in vitro-in vivo correlation (IVIVC) proves to be sound milestones and signifies that we are incessantly forwarding towards a scenario that would reduce regulatory burden, save time and make the drug products more affordable while ensuring their quality. This review outlines, the current and pertinent regulatory environment for biowaiver based on in vitro drug dissolution, primarily as per the FDA perspective. The rationale used for qualification of biowaiver for different strengths, post-approval changes and multi-source products are discussed along with the role of BCS and IVIVC.

Commonality between BCS and TCS

Both biopharmaceutics classification system (BCS) and topical drug classification system (TCS) are based on sound scientific principles with the aim of providing biowaiver and reducing regulatory burden without lowering the quality requirements and standards of approval for the drug products. BCS is based on the solubility and permeability properties of the active pharmaceutical ingredient (API, or drug substance) whereas the TCS is based on the qualitative and quantitative composition of the dosage form and the in vitro release rate of the active ingredient as key decision tools. Both BCS and TCS take drug release and dissolution as their guiding principle for providing biowaiver, increasing the availability and affordability of safe and effective medicines to the consumers and at the same time maintaining the drug product quality.

A science based approach to topical drug classification system (TCS)

The Biopharmaceutics Classification System (BCS) for oral immediate release solid drug products has been very successful; its implementation in drug industry and regulatory approval has shown significant progress. This has been the case primarily because BCS was developed using sound scientific judgment. Following the success of BCS, we have considered the topical drug products for similar classification system based on sound scientific principles. In USA, most of the generic topical drug products have qualitatively (Q1) and quantitatively (Q2) same excipients as the reference listed drug (RLD). The applications of in vitro release (IVR) and in vitro characterization are considered for a range of dosage forms (suspensions, creams, ointments and gels) of differing strengths. We advance a Topical Drug Classification System (TCS) based on a consideration of Q1, Q2 as well as the arrangement of matter and microstructure of topical formulations (Q3). Four distinct classes are presented for the various scenarios that may arise and depending on whether biowaiver can be granted or not.

In-situ intestinal rat perfusions for human Fabs prediction and BCS permeability class determination: Investigation of the single-pass vs. the Doluisio experimental approaches

Intestinal drug permeability has been recognized as a critical determinant of the fraction dose absorbed, with direct influence on bioavailability, bioequivalence and biowaiver. The purpose of this research was to compare intestinal permeability values obtained by two different intestinal rat perfusion methods: the single-pass intestinal perfusion (SPIP) model and the Doluisio (closed-loop) rat perfusion method. A list of 15 model drugs with different permeability characteristics (low, moderate, and high, as well as passively and actively absorbed) was constructed. We assessed the rat intestinal permeability of these 15 model drugs in both SPIP and the Doluisio methods, and evaluated the correlation between them. We then evaluated the ability of each of these methods to predict the fraction dose absorbed (Fabs) in humans, and to assign the correct BCS permeability class membership. Excellent correlation was obtained between the two experimental methods (r(2)=0.93). An excellent correlation was also shown between literature Fabs values and the predictions made by both rat perfusion techniques. Similar BCS permeability class membership was designated by literature data and by both SPIP and Doluisio methods for all compounds. In conclusion, the SPIP model and the Doluisio (closed-loop) rat perfusion method are both equally useful for obtaining intestinal permeability values that can be used for Fabs prediction and BCS classification.

Novel insights into excipient effects on the biopharmaceutics of APIs from different BCS classes: Lactose in solid oral dosage forms

Excipients encompass a wide range of properties that are of importance for the resulting drug product. Regulatory guidelines on biowaivers for immediate release formulations require an in depth understanding of the biopharmaceutic effects of excipients in order to establish bioequivalence between two different products carrying the same API based on dissolution tests alone. This paper describes a new approach in evaluating biopharmaceutic excipient effects. Actually used quantities of a model excipient, lactose, formulated in combination with APIs from different BCS classes were evaluated. The results suggest that companies use different (relative) amounts depending on the characteristics of the API. The probability of bioinequivalence due to a difference in lactose content between test and reference products was classified as low for BCS class I APIs and medium for BCS class II and III APIs, whereas a high probability was assigned to the combination of lactose and BCS class IV APIs. If repeated for other excipients, this retrospective, top-down approach may lead to a new database and more widespread applications of the biowaiver approach.

The complexity of intestinal permeability: Assigning the correct BCS classification through careful data interpretation

While the solubility parameter is fairly straightforward when assigning BCS classification, the intestinal permeability (Peff) is more complex than generally recognized. In this paper we emphasize this complexity through the analysis of codeine, a commonly used antitussive/analgesic drug. Codeine was previously classified as a low-permeability compound, based on its lower LogP compared to metoprolol, a marker for the low-high permeability class boundary. In contrast, high fraction of dose absorbed (Fabs) was reported for codeine, which challenges the generally recognized Peff-Fabs correlation. The purpose of this study was to clarify this ambiguity through elucidation of codeine's BCS solubility/permeability class membership. Codeine's BCS solubility class was determined, and its intestinal permeability throughout the small intestine was investigated, both in vitro and in vivo in rats. Codeine was found to be unequivocally a high-solubility compound. All in vitro studies indicated that codeine's permeability is higher than metoprolol's. In vivo studies in rats showed similar permeability for both drugs throughout the entire small-intestine. In conclusion, codeine was found to be a BCS Class I compound. No Peff-Fabs discrepancy is involved in its absorption; rather, it reflects the risk of assigning BCS classification based on merely limited physicochemical characteristics. A thorough investigation using multiple experimental methods is prudent before assigning a BCS classification, to avoid misjudgment in various settings, e.g., drug discovery, formulation design, drug development and regulation.

Interchangeability evaluation of multisource Ibuprofen drug products using biowaiver procedure

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 f(1) (13) and f(2) (72) and not equivalent in pH 6.8 (factor f(1) was 26 and f(2) 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.