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.     

浅谈世界卫生组织的药品生物等效性豁免

介绍世界卫生组织(WHO)有关药品生物等效性实验豁免(以下简称生物豁免)的政策指南,使国内制药行业对其有所了解。就WHO的生物豁免政策而言,更多的药品可以避免进行体内生物等效性研究,这对于以仿制药为主的药品研发更具节约时间和开发成本的效益,也为国内的有关生物等效性豁免提供借鉴。     

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.