Justification of metformin hydrochloride biowaiver criteria based on bioequivalence study

The Biopharmaceutics Classification System (BCS) represents the framework for predicting the intestinal drug absorption based on its solubility and intestinal permeability. Recent research has lead to the use of in vitro tests to waive additional in vivo bioequivalence studies for some pharmaceutical products (i.e., biowaiver). The current regulations permit waivers for BCS Class I (highly soluble/highly permeable) drug substances, which represent up to 25% of the drugs. Efforts in both the science and regulatory bodies are being made to extend biowaivers to certain Class II and III products, which would represent more than 50% of all drugs coming to the market. The aim of this study was to investigate the influence of experimental conditions on metformin hydrochloride (CAS 1115-70-4) release from two immediate-release tablet formulations with proven bioequivalence and justify the biowaiver request for dissolution profile similarity in three pH media. The results obtained indicate that differences in drug dissolution observed in vitro were not reflected in vivo. Such data support the existing idea that BCS Class III drugs are eligible biowaiver candidates, even if a very rapid dissolution criterion is not fulfilled.     

Solubilized formulation of olmesartan medoxomil for enhancing oral bioavailability

Olmesartan medoxomil (OLM) is an antihypertensive angiotensin II receptor blocker. OLM has a low bioavailability (BA), approximately 26% in humans, due to its low water solubility and efflux by drug resistance pumps in the gastrointestinal tract. Self-microemulsifying drug delivery system (SMEDDS), which is easily emulsified in aqueous media under gentle agitation and digestive motility, was formulated to increase the oral BA of OLM. Among the surfactants and oils studied, Capryol 90, Tween 20, and Tetraglycol were chosen and combined at a volume ratio of 1:6:3 on the basis of equilibrium solubility and phase diagram experiments. The mean droplet size of SMEDDS was 15 nm. In an oral absorption study in rats, SMEDDS formulation brought faster absorption compared to suspension, showing a T _max value of 0.2 hr. The C _max and AUC values of SMEDDS formulation were significantly higher than those of suspension, revealing a relative BA of about 170%. Our study demonstrated the potential usefulness of SMEDDS for the oral delivery of poorly absorbable compounds, including OLM.     

Classification of torasemide based on the Biopharmaceutics Classification System and evaluation of the FDA biowaiver provision for generic products of CLASS I drugs

The biopharmaceutical properties of an in-house developed new crystal modification of torasemide (Torasemide N) were investigated in comparison with the most well known crystal modification form of torasemide (Torasemide I) in order to classify the drug according to the Biopharmaceutics Classification System (BCS), and to evaluate the data in line with current US Food and Drug Administration (FDA) guidance (with biowaiver provision for Class I drugs) to determine if the biowaiver provision could be improved. The solubility profiles of Torasemide I and Torasemide N were determined, and tablets prepared from both forms of the drug were studied for in-vitro release characteristics in media recommended by the current FDA guidance for biowaiver of generic products, and in other media considered more appropriate for the purpose than the ones recommended by the FDA. Two separate bioequivalence studies in healthy humans (following oral administration) were performed with two test products (both prepared from Torasemide I) against a single reference product (prepared from Torasemide N). The absorption profiles of the drug from the tablets were determined by deconvolution for comparison with the in-vitro release profiles to determine the appropriateness of some dissolution media for predicting in-vivo performance and to determine the comparative rate and extent of absorption. The drug was absorbed from the tested products quickly and almost completely (about 95% within 3.5 h of administration). However, one test product failed to meet the bioequivalence criteria and had a significant initial lower absorption rate profile compared with the reference product (P< or =0.05), whereas the other product was bioequivalent and had a similar absorption profile to the reference product. A dissolution medium at pH 5.0, in which torasemide has minimum solubility, was found to be more discriminatory than the media recommended by the FDA. Torasemide has been classified as a Class I drug according to the BCS up to a maximum dose of 40 mg and the data suggest that the current FDA guidance could be improved by giving more emphasis to selection of appropriate dissolution media than is given in its current form for approving biowaiver to generic products of Class I drugs.     

Very rapid dissolution is not needed to guarantee bioequivalence for biopharmaceutics classification system (BCS) I drugs

Currently, the EMEA, FDA, and WHO as regulatory authorities accept rapidly dissolving (>85% dissolved in 30 min) biopharmaceutics classification system (BCS) I drug products for biowaiver candidates. In the draft EMEA guideline the requirement has been set tighter, that is, the drug product should be very rapidly dissolving (>85% dissolved in 15 min) to be eligible for a biowaiver. Pharmacokinetic modeling of 32 BCS I drugs was performed to demonstrate that very rapid dissolution is not necessary to guarantee bioequivalence for them. Rapid dissolution and similar dissolution profiles are sufficient criteria for all BCS I drugs. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:621–625, 2010     

Biowaiver monographs for immediate-release solid oral dosage forms: Ketoprofen

Literature and experimental 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 ketoprofen are reviewed. Ketoprofen's solubility and permeability, its therapeutic use and therapeutic index, pharmacokinetic properties, data related to the possibility of excipient interactions, and reported BE/bioavailability (BA)/dissolution data were taken into consideration. The available data suggest that according to the current Biopharmaceutics Classification System (BCS) and all current guidances, ketoprofen is a weak acid that would be assigned to BCS Class II. The extent of ketoprofen absorption seems not to depend on formulation or excipients, so the risk of bioinequivalence in terms of area under the curve is very low, but the rate of absorption (i.e., BE in terms of peak plasma concentration, C_max) can be altered by formulation. Current in vitro dissolution methods may not always reflect differences in terms of C_max for BCS Class II weak acids; however, such differences in absorption rate are acceptable for ketoprofen with respect to patient risks. As ketoprofen products may be taken before or after meals, the rate of absorption cannot be considered crucial to drug action. Therefore, a biowaiver for IR ketoprofen solid oral dosage form is considered feasible, provided that (a) the test product contains only excipients present also in IR solid oral drug products containing ketoprofen, which are approved in International Conference on Harmonisation or associated countries, for instance, as presented in this paper; (b) both the test drug product and the comparator dissolve 85% in 30 min or less in pH 6.8 buffer; and (c) test product and comparator show dissolution profile similarity in pH 1.2, 4.5, and 6.8. When one or more of these conditions are not fulfilled, BE should be established in vivo.     

一致性评价中部分品种BCS分类不明确问题的解决方案

基于生物药剂学分类系统（BCS）的生物等效性豁免旨在减少对体内生物等效性研究的需求,即可以提供一种体内生物等效性的替代方法。基于BCS分类的生物等效性豁免需提供药物的溶解性、渗透性和体外溶出数据。主要论述药物溶解性、渗透性和体外溶出度测定的方法,希望建立药物相关特性的标准化、规范化测定流程,以保证企业在申报生物等效性豁免时,所提供的数据是准确、可靠的。     

Biowaiver Monographs for Immediate Release Solid Oral Dosage Forms: Piroxicam

Literature and experimental 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 piroxicam in the free acid form are reviewed. Piroxicam solubility and permeability, its therapeutic use and therapeutic index, pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability (BA), and corresponding dissolution data are taken into consideration. The available data suggest that according to the current biopharmaceutics classification system (BCS) and all current guidances, piroxicam would be assigned to BCS Class II. The extent of piroxicam absorption seems not to depend on manufacturing conditions or excipients, so the risk of bioinequivalence in terms of area under the curve (AUC) is very low, but the rate of absorption (i.e., BE in terms of C_max) can be affected by the formulation. Current in vitro dissolution methods may not always reflect differences in terms of C_max for BCS Class II weak acids; however, minor differences in absorption rate of piroxicam would not subject the patient to unacceptable risks: as piroxicam products may be taken before or after meals, the rate of absorption cannot be considered crucial to drug action. Therefore, a biowaiver for IR piroxicam solid oral dosage form is considered feasible, provided that (a) the test product contains only excipients, which are also present in IR solid oral drug products containing piroxicam, which have been approved in ICH or associated countries, for instance, those presented in Table 3 of this paper; (b) both the test and comparator drug products dissolve 85% in 30 min or less at pH 1.2, 4.5, and 6.8; and (c) the test product and comparator show dissolution profile similarity in pH 1.2, 4.5, and 6.8. When not all of these conditions can be fulfilled, BE of the products should be established in vivo.     

Pharmacokinetic simulation of biowaiver criteria: the effects of gastric emptying, dissolution, absorption and elimination rates.

In vitro dissolution tests can be used to waive in vivo bioequivalency studies (biowaiver), if drug has high solubility and high permeability according to biopharmaceutics classification system (BCS I). Then absorption of BCS I drugs is not dependent on drug dissolution or gastrointestinal transit time and the solid dosage form behaves like oral solution. Currently biowaivers are determined based on solubility, permeability and dissolution, but the factors related to the gastrointestinal tract and the dynamic nature of drug dissolution and systemic pharmacokinetics are not taken into account. We utilized pharmacokinetic simulation model to study effects of formulation types, and different rates of dissolution and gastric emptying on drug concentrations in plasma. Simulated maximum concentration in plasma (C(max)) and area under the curve (AUC) values of solid dosage forms were compared to the simulations of oral solution. Based on simulations about half of BCS I drugs have higher risk to fail in bioequivalency (BE) study than BCS III drugs. For these BCS I compounds 10-25% differences of C(max) were observed. Rest of the BCS I drugs and all BCS III drugs have lower risk to fail in BE study since less than 10% difference in C(max) and AUC were observed. Pharmacokinetic simulation model was valuable tool to evaluate biowaiver criteria and to study the effects of drug and physiology gastrointestinal related factors on C(max) and AUC.     

BCS Biowaivers: Similarities and Differences Among EMA,FDA, and WHO Requirements

The Biopharmaceutics Classification System (BCS), based on aqueous solubility and intestinal permeability, has enjoyed wide use since 1995 as a mechanism for waiving in vivo bioavailability and bioequivalence studies. In 2000, the US-FDA was the first regulatory agency to publish guidance for industry describing how to meet criteria for requesting a waiver of in vivo bioavailability and bioequivalence studies for highly soluble, highly permeable (BCS Class I) drugs. Subsequently, the World Health Organization (WHO) and European Medicines Agency (EMA) published guidelines recommending how to obtain BCS biowaivers for BCS Class III drugs (high solubility, low permeability), in addition to Class I drugs. In 2015, the US-FDA became better harmonized with the EMA and WHO following publication of two guidances for industry outlining criteria for obtaining BCS biowaivers for both Class I and Class III drugs. A detailed review and comparison of the BCS Class I and Class III criteria currently recommended by the US-FDA, EMA, and WHO revealed good convergence of the three agencies with respect to BCS biowaiver criteria. The comparison also suggested that, by applying the most conservative of the three jurisdictional approaches, it should be possible for a sponsor to design the same set of BCS biowaiver studies in preparing a submission for worldwide filing to satisfy US, European, and emerging market regulators. It is hoped that the availability of BCS Class I and Class III biowaivers in multiple jurisdictions will encourage more sponsors to request waivers of in vivo bioavailability/bioequivalence testing using the BCS approach.     

Effect of Gastric Fluid Volume on the <Emphasis Type="Italic">In Vitro</Emphasis> Dissolution and <Emphasis Type="Italic">In Vivo</Emphasis> Absorption of BCS Class II Drugs: a Case Study with Nifedipine

Nifedipine is a BCS Class II drug used for treatment of hypertension and preterm labor. Large inter-patient variability in nifedipine absorption results in variable exposure among different patients. We conducted in vitro dissolution studies to compare nifedipine dissolution from immediate release (IR) capsules with different volumes of dissolution media. Results from dissolution studies were used to design a crossover study in healthy volunteers to evaluate the effect of coadministered water volume with nifedipine 10 mg IR capsules on nifedipine pharmacokinetics, especially absorption (C _max, t _max, and AUC_0-6). Dissolution studies demonstrated that larger gastric fluid volumes result in enhanced nifedipine dissolution from 10 mg IR cosolvent capsules (73 vs. 17% in 200 and 100 mL simulated gastric fluid, respectively, at 30 min). The pharmacokinetic crossover study in healthy volunteers (N?=?6) did not show a significant effect of the water volume administered with the capsule (50 vs. 250 mL) on C _max, t _max, or AUC_0-6 of orally administered nifedipine IR capsules (10 mg). However, administration of large water volumes resulted in lower variability in nifedipine C _max (47 vs. 70% for 250 and 50 mL, respectively). Administration of large water volumes with nifedipine 10 mg IR cosolvent capsules may reduce inter-individual variability in plasma exposure. Evaluation of similar effects in other BCS Class II drugs is recommended.     

Biowaiver extension potential to BCS Class III high solubility-low permeability drugs: bridging evidence for metformin immediate-release tablet.

The biopharmaceutics classification system (BCS) allows biowaiver for rapid dissolving immediate-release (IR) products of Class I drugs (high solubility and high permeability). The possibility of extending biowaivers to Class III high solubility and low permeability drugs is currently under scrutiny. In vivo bioequivalence data of different formulations of Class III drugs would support such an extension. The objective of this work was to demonstrate the bioequivalence of two marketed IR tablet products of a Class III drug, metformin hydrochloride, that are rapidly dissolving and have similar in vitro dissolution profiles. The effect of race on the systemic exposure of metformin was also explored. A randomized, open-label, two-period crossover study was conducted in 12 healthy Chinese male volunteers. Each subject received a single-dose of 500 mg of each product after an overnight fasting. The plasma concentrations of metformin were followed for 24 h. No significant formulation effect was found for the bioequivalence metrics: areas under concentration-time curve (AUC0-t, AUC0-infinity) and maximal concentration (Cmax). The 90% confidence intervals for the ratio of means were found within the acceptance range of 80-125% for the log-transformed data. Based on these results, it was concluded that the two IR products are bioequivalent. The pharmacokinetic parameters of metformin in Chinese for both products were similar and were in good agreement with those reported for metformin IR tablets in other ethnic populations. This study serves as an example for supporting biowaiver for BCS Class III drugs.     

益血生胶囊联合多糖铁复合物治疗妊娠期缺铁性贫血的临床研究

目的 探讨益血生胶囊联合多糖铁复合物胶囊治疗妊娠期缺铁性贫血的临床疗效.方法 选取2018年8月—2020年8月在南阳市中心医院进行治疗的158例妊娠期缺铁性贫血患者为研究对象,根据用药差别分为对照组(79例)和治疗组(79例).对照组口服多糖铁复合物胶囊,0.3 g/次,1次/d;治疗组在对照组基础上口服益血生胶囊,...     

Using Physiologically Based Pharmacokinetic (PBPK) Modeling to Evaluate the Impact of Pharmaceutical Excipients on Oral Drug Absorption: Sensitivity Analyses

Drug solubility, effective permeability, and intestinal metabolism and transport are parameters that govern intestinal bioavailability and oral absorption. However, excipients may affect the systemic bioavailability of a drug by altering these parameters. Thus, parameter sensitivity analyses using physiologically based pharmacokinetic (PBPK) models were performed to examine the potential impact of excipients on oral drug absorption of different Biopharmaceutics Classification System (BCS) class drugs. The simulation results showed that changes in solubility had minimal impact on C_max and AUC_0-t of investigated BCS class 1 and 3 drugs. Changes in passive permeability altered C_max more than AUC_0-t for BCS class 1 drugs but were variable and drug-specific across different BCS class 2 and 3 drugs. Depending on the drug compounds for BCS class 1 and 2 drugs, changes in intestinal metabolic activity altered C_max and AUC_0-t. Reducing or increasing influx and efflux transporter activity might likely affect C_max and AUC_0-t of BCS class 2 and 3 drugs, but the magnitude may be drug dependent. Changes in passive permeability and/or transporter activity for BCS class 2 and 3 drugs might also have a significant impact on fraction absorbed and systemic bioavailability while changes in intestinal metabolic activity may have an impact on gut and systemic bioavailability. Overall, we demonstrate that PBPK modeling can be used routinely to examine sensitivity of bioavailability based on physiochemical and physiological factors and subsequently assess whether biowaiver requirements need consideration of excipient effects for immediate release oral solid dosage forms.     

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.     

Statistics on BCS Classification of Generic Drug Products Approved Between 2000 and 2011 in the USA

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.     

Predicting Pharmacokinetics of Multisource Acyclovir Oral Products Through Physiologically Based Biopharmaceutics Modeling

Highly variable disposition after oral ingestion of acyclovir has been reported, although little is known regarding the underlying mechanisms. Different studies using the same reference product (Zovirax ®) showed that C_max and AUC were respectively 44 and 35% lower in Saudi Arabians than Europeans, consistent with higher frequencies of reduced-activity polymorphs of the organic cation transporter (OCT1) in Europeans. In this study, the contribution of physiology (i.e., OCT1 activity) to the oral disposition of acyclovir immediate release (IR) tablets was hypothesized to be greater than dissolution. The potential role of OCT1 was studied in a validated physiologically-based biopharmaceutics model (PBBM), while dissolution of two Chilean generics (with demonstrated bioequivalence) and the reference product was assessed in vitro. The PBBM suggested that OCT1 activity could partially explain population-related pharmacokinetic differences. Further, dissolution of generics was slower than the regulatory criterion for BCS III IR products. Remarkably, virtual bioequivalence (incorporating in vitro dissolution into the PBBM) correctly and robustly predicted the bioequivalence of these products, showcasing its value in support of failed BCS biowaivers. These findings suggest that very-rapid dissolution for acyclovir IR products may not be critical for BCS biowaiver. They also endorse the relevance of cross-over designs in bioequivalence trials.     

Biowaiver approach for biopharmaceutics classification system class 3 compound metformin hydrochloride using in silico modeling

The dependency of metformin in vivo disposition on the rate and extent of dissolution was studied. The analysis includes the use of fundamental principles of drug input, permeability, and intestinal transit time within the framework of a compartmental absorption transit model to predict key pharmacokinetic (PK) parameters and then compare the results to clinical data. The simulations show that the maximum plasma concentration (C_max) and area under the curve (AUC) are not significantly affected when 100% of drug is released within 2 h of oral dosing, which was confirmed with corresponding human PK data. Furthermore, in vitro dissolution profiles measured in aqueous buffers at pH values of 1.2, 4.5, and 6.8 were slower than in vivo release profiles generated by deconvolution of metformin products that were bioequivalent. On the basis of this work, formulations of metformin that release 100% in vitro in a   time period equal to or less than two hours are indicated to be bioequivalent. The use of modeling offers a mechanistic-based approach for demonstrating acceptable bioperformance for metformin formulations without having to resort to in vivo bioequivalence studies and may be more robust than statistical comparison of in vitro release profiles. This work further provides a strategy for considering Biopharmaceutics Classification System (BCS) Class 3 compounds to be included under biowaiver guidelines as for BCS Class 1 compounds. © 2012Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 101:1773–1782, 2012     

An Investigation into the Importance of “Very Rapid Dissolution” Criteria for Drug Bioequivalence Demonstration using Gastrointestinal Simulation Technology

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).     

Biowaiver monographs for immediate release solid oral dosage forms: amitriptyline hydrochloride

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 amitriptyline hydrochloride are reviewed. Its therapeutic uses, its pharmacokinetic properties, the possibility of excipient interactions and reported BE/bioavailability (BA) problems are also taken into consideration. Literature data indicates that amitriptyline hydrochloride is a highly permeable active pharmaceutical ingredient (API). Data on the solubility according to the current Biopharmaceutics Classification System (BCS) were not fully available and consequently amitriptyline hydrochloride could not be definitively assigned to either BCS Class I or BCS Class II. But all evidence taken together, a biowaiver can currently be recommended provided that IR tablets are formulated with excipients used in existing approved products and that the dissolution meets the criteria defined in the Guidances.     

Biowaiver monographs for immediate release solid oral dosage forms: ibuprofen

Literature data are reviewed on the properties of ibuprofen related to the biopharmaceutics classification system (BCS). Ibuprofen was assessed to be a BCS class II drug. Differences in composition and/or manufacturing procedures were reported to have an effect on the rate, but not the extent of absorption; such differences are likely to be detectable by comparative in vitro dissolution tests. Also in view of its therapeutic use, its wide therapeutic index and uncomplicated pharmacokinetic properties, a biowaiver for immediate release (IR) ibuprofen solid oral drug products is scientifically justified, provided that the test product contains only those excipients reported in this paper in their usual amounts, the dosage form is rapidly dissolving (85% in 30 min or less) in buffer pH 6.8 and the test product also exhibits similar dissolution profiles to the reference product in buffer pH 1.2, 4.5, and 6.8.