Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release solid oral dosage forms containing mefloquine hydrochloride as the only active pharmaceutical ingredient (API) are reviewed. The solubility and permeability data of mefloquine hydrochloride as well as its therapeutic use and therapeutic index, its pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability studies were taken into consideration. Mefloquine hydrochloride is not a highly soluble API. Since no data on permeability are available, it cannot be classified according to the Biopharmaceutics Classification System with certainty. Additionally, several studies in the literature failed to demonstrate BE of existing products. For these reasons, the biowaiver cannot be justified for the approval of new multisource drug products containing mefloquine hydrochloride. However, scale-up and postapproval changes (HHS-FDA SUPAC) levels 1 and 2 and most EU type I variations may be approvable without in vivo BE, using the dissolution tests described in these regulatory documents.

Literature and new 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 furosemide are reviewed. The available data on solubility, oral absorption, and permeability are sufficiently conclusive to classify furosemide into Class IV of the Biopharmaceutics Classification System (BCS). Furosemide's therapeutic use and therapeutic index, its pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability (BA) problems are also taken into consideration. In view of the data available, it is concluded that the biowaiver procedure cannot be justified for either the registration of new multisource drug products or major postapproval changes (variations) to existing drug products.(c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci.

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 doxycycline hyclate are reviewed. According to the Biopharmaceutics Classification System (BCS), doxycycline hyclate can be assigned to BCS Class I. No problems with BE of IR doxycycline formulations containing different excipients and produced by different manufacturing methods have been reported and hence the risk of bioinequivalence caused by these factors appears to be low. Doxycycline has a wide therapeutic index. Further, BCS-based dissolution methods have been shown to be capable of identifying formulations which may dissolve too slowly to generate therapeutic levels. It is concluded that a biowaiver is appropriate for IR solid oral dosage forms containing doxycycline hyclate as the single Active Pharmaceutical Ingredient (API) provided that (a) the test product contains only excipients present in doxycycline hyclate IR solid oral drug products approved in the International Conference on Harmonization (ICH) or associated countries; and (b) the comparator and the test products comply with the BCS criteria for "very rapidly dissolving" or, alternatively, when similarity of the dissolution profiles can be demonstrated and the two products are "rapidly dissolving.".

The solubility and dissolution rate of active ingredients are of major importance in preformulation studies of pharmaceutical dosage forms. In the present study passively absorbed drugs are classified based on their intrinsic dissolution rate (IDR) and their intestinal permeabilities. Intrinsic dissolution rate was determined by measuring the dissolution of a non-disintegrating disk of drug and effective intestinal permeability of tested drugs in rat jejunum was determined using single perfusion technique. The obtained intrinsic dissolution rate values were in the range of 0.035-56.8 mg cm(-2) min(-1) for tested drugs. The minimum and maximum intestinal permeabilities in rat intestine were determined to be 1.6x10(-5) and 2x10(-4) cm/sec respectively. Four classes of drugs were defined, i.e. Category I: P(eff,rat)> 5x 10(-5)(cm/sec) or P(eff,human)> 4.7x 10(-5)(cm/sec), IDR > 1(mg/min/cm(2)), Category II: P(eff,rat)> 5x 10(-5)(cm/sec) or P(eff,human)> 4.7x 10(-5)(cm/sec), IDR < 1(mg/min/cm(2)), Category III: P(eff,rat)< 5x 10(-5)(cm/sec) or P(eff,human)< 4.7x 10(-5)(cm/sec), IDR > 1(mg/min/cm(2)) and Category IV: P(eff,rat)< 5x 10(-5)(cm/sec) or P(eff,human)< 4.7x 10(-5)(cm/sec), IDR < 1(mg/min/cm(2)). According the obtained results and proposed classification for drugs, it is concluded that drugs could be categorized correctly based on their intrinsic dissolution rate and intestinal permeability values.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing rifampicin as the only Active Pharmaceutical Ingredient (API) are reviewed. Rifampicin's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. Solubility and absolute BA data indicate that rifampicin is a BCS Class II drug. Of special concern for biowaiving is that many reports of failure of IR solid oral dosage forms of rifampicin to meet BE have been published and the reasons for these failures are yet insufficiently understood. Moreover, no reports were identified in which in vitro dissolution was shown to be predictive of nonequivalence among products. Therefore, a biowaiver based approval of rifampicin containing IR solid oral dosage forms cannot be recommended for either new multisource drug products or for major scale-up and postapproval changes (variations) to existing drug products.

Literature data are reviewed relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing quinidine sulfate. Quinidine sulfate's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. The available data are not fully conclusive, but do suggest that quinidine sulfate is highly soluble and moderately to highly permeable and would likely be assigned to BCS Class I (or at worst BCS III). In view of the inconclusiveness of the data and, more important, quinidine's narrow therapeutic window and critical indication, a biowaiver based approval of quinidine containing dosage forms cannot be recommended for either new multisource drug products or for major postapproval changes (variations) to existing drug products.

Literature data are reviewed regarding the scientific advisability of allowing a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing either diclofenac potassium and diclofenac sodium. Within the biopharmaceutics classification system (BCS), diclofenac potassium and diclofenac sodium are each BCS class II active pharmaceutical ingredients (APIs). However, a biowaiver can be recommended for IR drug products of each salt form, due to their therapeutic use, therapeutic index, pharmacokinetic properties, potential for excipient interactions, and performance in reported BE/bioavailability (BA) studies, provided:(a) test and comparator contain the same diclofenac salt;(b) the dosage form of the test and comparator is identical;(c) the test product contains only excipients present in diclofenac drug products approved in ICH or associated countries in the same dosage form, for instance as presented in this paper;(d) test drug product and comparator dissolve 85% in 30 min or less in 900 mL buffer pH 6.8, using the paddle apparatus at 75 rpm or the basket apparatus at 100 rpm; and (e) test product and comparator show dissolution profile similarity in pH 1.2, 4.5, and 6.8.

Ranitidine hydrochloride is a H(2) receptor blocker used in the treatment of gastric ulcers. Pharmacological factors, in addition to the dosage regimen, favor development of a sustained-release system for ranitidine especially in the therapeutic condition of erosive esophagitis. This investigation delves into the development of bioadhesive type of gastroretentive formulation (tablets) of ranitidine. The effect of mucoadhesive polymers such as Carbopol, hydroxypropyl methyl cellulose, and dextrose were studied. Mucoadhesion, in vitro drug release profile, water uptake, and swelling of the tablet were evaluated. Alkalizing agents were incorporated in an attempt to maintain an alkaline microenvironment within the tablet and improve the stability of the drug in acidic medium. The stability was evaluated using dye test and degradation studies. The drug release profiles were fit into various kinetic models.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing (biowaiver) for the approval of immediate release (IR) solid oral dosage forms containing aciclovir are reviewed. Aciclovir therapeutic use and therapeutic index, pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability (BA) studies were also taken into consideration in order to ascertain whether a biowaiver can be recommended. According to the Biopharmaceutics Classification System (BCS) and considering tablet strengths up to 400 mg, aciclovir would be BCS Class III. However, in some countries also 800 mg tablets are available which fall just within BCS Class IV. Aciclovir seems not to be critical with respect to a risk for bioinequivalence, as no examples of bioinequivalence have been identified. It has a wide therapeutic index and is not used for critical indications. Hence, if:(a) the test product contains only excipients present in aciclovir solid oral IR drug products approved in ICH or associated countries, for instance as presented in this article; and (b) the comparator and the test product both are very rapidly dissolving, a biowaiver for IR aciclovir solid oral drug products is considered justified for all tablet strengths.

Literature data are reviewed relevant to the decision for a biowaiver of immediate release (IR) solid oral dosage forms containing metoclopramide hydrochloride. In addition, new solubility data, obtained under Biopharmaceutics Classification System (BCS) conditions are presented. Metoclopramide HCl is conservatively assigned to BCS Class III. Taken also into consideration excipient interactions reported in metoclopramide drug products, its pharmacokinetic properties and therapeutic use and therapeutic index, a biowaiver can be recommended when:(a) the test product contains only excipients present also in metoclopramide HCl containing IR solid oral drug products approved in ICH or associated countries, for instance as presented in this paper,(b) in amounts in normal use in IR solid oral dosage forms, and (c) the test product and the comparator both comply with the criteria for very rapidly dissolving.

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.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing ciprofloxacin hydrochloride as the only active pharmaceutical ingredient (API) are reviewed. Ciprofloxacin hydrochloride's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. Solubility and BA data indicate that ciprofloxacin hydrochloride is a BCS Class IV drug. Therefore, a biowaiver based approval of ciprofloxacin hydrochloride containing IR solid oral dosage forms cannot be recommended for either new multisource drug products or for major scale-up and postapproval changes (variations) to existing drug products.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release solid oral dosage forms containing mefloquine hydrochloride as the only active pharmaceutical ingredient (API) are reviewed. The solubility and permeability data of mefloquine hydrochloride as well as its therapeutic use and therapeutic index, its pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability studies were taken into consideration. Mefloquine hydrochloride is not a highly soluble API. Since no data on permeability are available, it cannot be classified according to the Biopharmaceutics Classification System with certainty. Additionally, several studies in the literature failed to demonstrate BE of existing products. For these reasons, the biowaiver cannot be justified for the approval of new multisource drug products containing mefloquine hydrochloride. However, scale-up and postapproval changes (HHS-FDA SUPAC) levels 1 and 2 and most EU type I variations may be approvable without in vivo BE, using the dissolution tests described in these regulatory documents.

Literature and new 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 furosemide are reviewed. The available data on solubility, oral absorption, and permeability are sufficiently conclusive to classify furosemide into Class IV of the Biopharmaceutics Classification System (BCS). Furosemide's therapeutic use and therapeutic index, its pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability (BA) problems are also taken into consideration. In view of the data available, it is concluded that the biowaiver procedure cannot be justified for either the registration of new multisource drug products or major postapproval changes (variations) to existing drug products.(c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci.

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 doxycycline hyclate are reviewed. According to the Biopharmaceutics Classification System (BCS), doxycycline hyclate can be assigned to BCS Class I. No problems with BE of IR doxycycline formulations containing different excipients and produced by different manufacturing methods have been reported and hence the risk of bioinequivalence caused by these factors appears to be low. Doxycycline has a wide therapeutic index. Further, BCS-based dissolution methods have been shown to be capable of identifying formulations which may dissolve too slowly to generate therapeutic levels. It is concluded that a biowaiver is appropriate for IR solid oral dosage forms containing doxycycline hyclate as the single Active Pharmaceutical Ingredient (API) provided that (a) the test product contains only excipients present in doxycycline hyclate IR solid oral drug products approved in the International Conference on Harmonization (ICH) or associated countries; and (b) the comparator and the test products comply with the BCS criteria for "very rapidly dissolving" or, alternatively, when similarity of the dissolution profiles can be demonstrated and the two products are "rapidly dissolving.".

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing rifampicin as the only Active Pharmaceutical Ingredient (API) are reviewed. Rifampicin's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. Solubility and absolute BA data indicate that rifampicin is a BCS Class II drug. Of special concern for biowaiving is that many reports of failure of IR solid oral dosage forms of rifampicin to meet BE have been published and the reasons for these failures are yet insufficiently understood. Moreover, no reports were identified in which in vitro dissolution was shown to be predictive of nonequivalence among products. Therefore, a biowaiver based approval of rifampicin containing IR solid oral dosage forms cannot be recommended for either new multisource drug products or for major scale-up and postapproval changes (variations) to existing drug products.

Literature data are reviewed relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing quinidine sulfate. Quinidine sulfate's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. The available data are not fully conclusive, but do suggest that quinidine sulfate is highly soluble and moderately to highly permeable and would likely be assigned to BCS Class I (or at worst BCS III). In view of the inconclusiveness of the data and, more important, quinidine's narrow therapeutic window and critical indication, a biowaiver based approval of quinidine containing dosage forms cannot be recommended for either new multisource drug products or for major postapproval changes (variations) to existing drug products.

Literature data are reviewed regarding the scientific advisability of allowing a waiver of in vivo bioequivalence (BE) testing for the approval of immediate release (IR) solid oral dosage forms containing either diclofenac potassium and diclofenac sodium. Within the biopharmaceutics classification system (BCS), diclofenac potassium and diclofenac sodium are each BCS class II active pharmaceutical ingredients (APIs). However, a biowaiver can be recommended for IR drug products of each salt form, due to their therapeutic use, therapeutic index, pharmacokinetic properties, potential for excipient interactions, and performance in reported BE/bioavailability (BA) studies, provided:(a) test and comparator contain the same diclofenac salt;(b) the dosage form of the test and comparator is identical;(c) the test product contains only excipients present in diclofenac drug products approved in ICH or associated countries in the same dosage form, for instance as presented in this paper;(d) test drug product and comparator dissolve 85% in 30 min or less in 900 mL buffer pH 6.8, using the paddle apparatus at 75 rpm or the basket apparatus at 100 rpm; and (e) test product and comparator show dissolution profile similarity in pH 1.2, 4.5, and 6.8.

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing (biowaiver) for the approval of immediate release (IR) solid oral dosage forms containing aciclovir are reviewed. Aciclovir therapeutic use and therapeutic index, pharmacokinetic properties, data related to the possibility of excipient interactions and reported BE/bioavailability (BA) studies were also taken into consideration in order to ascertain whether a biowaiver can be recommended. According to the Biopharmaceutics Classification System (BCS) and considering tablet strengths up to 400 mg, aciclovir would be BCS Class III. However, in some countries also 800 mg tablets are available which fall just within BCS Class IV. Aciclovir seems not to be critical with respect to a risk for bioinequivalence, as no examples of bioinequivalence have been identified. It has a wide therapeutic index and is not used for critical indications. Hence, if:(a) the test product contains only excipients present in aciclovir solid oral IR drug products approved in ICH or associated countries, for instance as presented in this article; and (b) the comparator and the test product both are very rapidly dissolving, a biowaiver for IR aciclovir solid oral drug products is considered justified for all tablet strengths.

Literature data are reviewed relevant to the decision for a biowaiver of immediate release (IR) solid oral dosage forms containing metoclopramide hydrochloride. In addition, new solubility data, obtained under Biopharmaceutics Classification System (BCS) conditions are presented. Metoclopramide HCl is conservatively assigned to BCS Class III. Taken also into consideration excipient interactions reported in metoclopramide drug products, its pharmacokinetic properties and therapeutic use and therapeutic index, a biowaiver can be recommended when:(a) the test product contains only excipients present also in metoclopramide HCl containing IR solid oral drug products approved in ICH or associated countries, for instance as presented in this paper,(b) in amounts in normal use in IR solid oral dosage forms, and (c) the test product and the comparator both comply with the criteria for very rapidly dissolving.

The present monograph reviews data relevant to applying the biowaiver procedure for the approval of immediate release (IR) multisource solid dosage forms containing amodiaquine hydrochloride (ADQ) as the single active pharmaceutical ingredient (API). Both biopharmaceutical and clinical data of ADQ were assessed. Solubility studies revealed that ADQ meets the "highly soluble" criteria according to World Health Organization (WHO) and European Medicines Agency (EMA) but fails to comply with the United States Food and Drug Administration (US FDA) specifications. Although metabolism hints at high permeability, available permeability data are too scanty to classify ADQ inequivocably as a Class I drug substance. According to WHO and EMA guidances, ADQ would be conservatively categorized as a Class III drug, whereas according to the US FDA specifications, it would fall into Class IV. ADQ has a wide therapeutic index. Furthermore, no cases of bioinequivalent products have been reported in the open literature. As risks associated with biowaiving appear minimal and requirements for "highly soluble" API are met in the WHO and EMA jurisdictions, the biowaiver procedure can be recommended for bioequivalence (BE) testing of multisource IR products containing ADQ as the only API, provided the test product contains excipients used in ADQ products approved in International Conference of Harmonisation and associated countries, and in similar amounts. Furthermore, both comparator and test should conform to "very rapidly dissolving" product criteria (≥85% dissolution of the API in 15 min at pH 1.2, 4.5, and 6.8) and the labeling should specify that the product not be coadministered with high-fat meals. If the comparator and/or test product fails to meet these criteria, BE needs to be established by pharmacokinetic studies in humans. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.

A biowaiver monograph for acetylsalicylic acid (ASA) is presented. Literature and experimental data indicate that ASA is a highly soluble and highly permeable drug, leading to assignment of this active pharmaceutical ingredient (API) to Class I of the Biopharmaceutics Classification System (BCS). Limited bioequivalence (BE) studies reported in the literature indicate that products that have been tested are bioequivalent. Most of the excipients used in products with a marketing authorization in Europe are not considered to have an impact on gastrointestinal motility or permeability. Furthermore, ASA has a wide therapeutic index. Thus, the risks to the patient that might occur if a nonbioequivalent product were to be incorrectly deemed bioequivalent according to the biowaiver procedure appear to be minimal. As a result, the BCS-based biowaiver procedure can be recommended for approval of new formulations of solid oral dosage forms containing ASA as the only API, including both multisource and reformulated products, under the following conditions:(1) excipients are chosen from those used in ASA products already registered in International Conference on Harmonization and associated countries and (2) the dissolution profiles of the test and the comparator products comply with the BE guidance. © 2012 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.

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).

The biowaiver approach permits evaluation of bioequivalence (BE) using a set of laboratory tests, obviating the need for expensive and time-consuming pharmacokinetic BE studies provided that both the active pharmaceutical ingredient and the formulations can meet the specified criteria. In the present monograph, the biowaiver-relevant data including solubility and permeability data, therapeutic use and therapeutic index, pharmacokinetic properties, reported excipient interactions, and BE/bioavailability studies of quinine sulfate are itemized and discussed. Quinine sulfate has borderline solubility characteristics and, on the whole, is highly permeable. Thus, depending on the jurisdiction, it is assigned to Biopharmaceutics Classification System class I or II. Although these characteristics would suggest a low risk of bioinequivalence among oral quinine products, a recent pharmacokinetic study showed bioinequivalence of two products. Even though quinine does not, strictly speaking, fit the definition of a narrow therapeutic index drug, it shows dose-related and, in some cases, irreversible side effects and toxicities at concentrations not far above the therapeutic concentration range. Taking all relevant aspects into consideration, a biowaiver cannot be recommended for new quinine immediate-release multisource products or major post-approval changes of already marketed quinine products, and in such cases, BE should be evaluated using an in vivo BE study.

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 stavudine (d4T) are reviewed. According to Biopharmaceutics Classification System (BCS), d4T can be assigned to BCS class I. No problems with BE of IR d4T formulations containing different excipients and produced by different manufacturing methods have been reported and, hence, the risk of bioinequivalence caused by these factors appears to be low. Furthermore, d4T has a wide therapeutic index. It is concluded that a biowaiver is appropriate for IR solid oral dosage forms containing d4T as the single active pharmaceutical ingredient (API) provided that (a) the test product contains only excipients present in the IR d4T drug products that have been approved in a number of countries for the same dosage form, and (b) both test product and its comparator are either "very rapidly dissolving" or "rapidly dissolving" with similarity of dissolution profiles demonstrated at pH 1.2, 4.5, and 6.8.

The ratio of AUC to the dose (AUC/dose) was previously found as a parameter that predicts a risk of bioinequivalence of oral drug products. On the basis of the combination of this parameter and the biopharmaceutics classification system (BCS), a perspective for biowaivers of human bioequivalence studies is discussed. Databases of bioequivalence studies using immediate-release solid oral dosage forms were disclosed by 6 Japanese generic pharmaceutical companies, and the number of subjects required for demonstrating bioequivalence between generic and reference products was plotted as a function of AUC/dose for each BCS category. A small variation in the number of subjects was constantly observed in bioequivalence studies using dosage forms containing an identical BCS class 1 or class 3 drug, even though formulations of the generic product differ between companies. The variation was extremely enlarged when the drugs were substituted with BCS class 2 drugs. Rate-determining steps in oral absorption of highly water-soluble BCS class 1 and class 3 drugs are independent of formulations when there is no significant difference in the in vitro dissolution profiles between formulations. The small variation observed for both BCS categories indicates that the number of subjects converges into one value for each drug. Our analysis indicates the appropriateness of biowaiver of bioequivalence studies for immediate-release solid oral dosage forms containing not only BCS class 1 drugs but also class 3 drugs.

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.

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 levofloxacin as the only active pharmaceutical ingredient (API) are reviewed. According to the current Biopharmaceutics Classification System, levofloxacin can be assigned to Class I. No problems with BE of IR levofloxacin formulations containing different excipients and produced by different manufacturing methods have been reported and hence the risk of bioinequivalence caused by these factors appears to be low. In addition, levofloxacin has a wide therapeutic index. On the basis of this evidence, a biowaiver is recommended for IR solid oral dosage forms containing levofloxacin as the single API provided that (a) the test product contains only excipients present in IR levofloxacin drug products that have been approved in International Conference on Harmonization (ICH) or associated countries and which have the same dosage form;(b) both the test and comparator dosage form are "very rapidly dissolving" or "rapidly dissolving" with similarity of the dissolution profiles demonstrated at pH 1.2, 4.5, and 6.8; and (c) if the test product contains polysorbates, it should be both qualitatively and quantitatively identical to its comparator in terms of polysorbate content.

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 metronidazole are reviewed. Metronidazole can be assigned to Biopharmaceutics Classification System Class I. Most BE studies that were identified reported the investigated formulations to be bioequivalent, indicating the risk of bioinequivalence to be low. Formulations showing differences in bioavailability showed dissimilarities in in vitro dissolution profiles. Furthermore, metronidazole has a wide therapeutic index. It is concluded that a biowaiver for solid IR formulations is justified, provided:(a) the test product and its comparator are both rapidly dissolving;(b) meet similarity of the dissolution profiles at pH 1.2, 4.5, and 6.8;(c) the test product contains only excipients present in IR drug products approved in International Conference on Harmonisation (ICH) or associated countries in the same dosage form; and (d) if the test product contains sorbitol, sodium laurilsulfate, or propylene glycol. The test product needs to be qualitatively and quantitatively identical to its comparator with respect to these excipients.

Although US Food and Drug Administration (FDA)-approved Biopharmaceutics Classification System (BCS) class 1 drugs are designated as high-permeability drugs, in fact, the criterion utilized is high extent of absorption. This ambiguity should be eliminated, and the FDA criterion should explicitly be stated as > or =90% absorption based on absolute bioavailability or mass balance. Maintaining confidentiality regarding the drugs for which the FDA has approved BCS waivers of in vivo bioequivalence studies is not good public policy and should be reversed.