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Concept: Bioequivalence

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Fesoterodine is a non-selective muscarinic-receptor antagonist, used in the treatment of overactive bladder syndrome. A highly sensitive, selective and rapid method has been developed for the simultaneous determination of fesoterodine and its active metabolite, 5-hydroxymethyl tolterodine (5-HMT) in human plasma by liquid chromatography-tandem mass spectrometry (LC-ESI-MS/MS). Due to rapid conversion of parent drug to 5-HMT, ex vivo stability of fesoterodine in human plasma was extensively studied to optimize the extraction protocol. The analytes and their deuterated analogs were quantitatively extracted from 100μL human plasma by liquid-liquid extraction in methyl tert-butyl ether: n-hexane. The chromatographic separation of analytes was achieved on a Kromasil C18 (100mm×4.6mm, 5μm) column under isocratic conditions. The method was validated over a dynamic concentration range of 0.01-10ng/mL for both the analytes. Ion-suppression effects were investigated by post-column infusion of analytes. The precision (% CV) values for the calculated slopes of calibration curves, which would reflect the relative matrix effect, were less than 1.5% for both the analytes. The intra-batch and inter-batch precision (% CV) across quality control levels varied from 1.82 to 3.73% and the mean extraction recovery was >96% for both the analytes. The method was successfully applied to a bioequivalence study of 8mg fesoterodine tablet formulation (test and reference) in 12 healthy Indian subjects under fasted and fed condition. The assay reproducibility estimated by reanalysis of incurred samples showed a change of ±12.0%.

Concepts: Scientific method, Mass spectrometry, Urology, Sociology, Chromatography, Overactive bladder, Liquid chromatography-mass spectrometry, Bioequivalence

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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.

Concepts: Pharmacology, Pharmaceutical industry, Drug development, Generic drug, Bioequivalence, Food and Drug Administration, Drug Price Competition and Patent Term Restoration Act, Abbreviated New Drug Application

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PURPOSE: The objective of the study was to investigate the relative bioavailability between the generic tacrolimus products that are presently authorized in Spain by adjusted indirect comparison. This was based on demonstration of bioequivalence with the reference product (Prograf, Astellas Pharma), which makes these generic tacrolimus products prescribable, switchable and therapeutically equivalent to the reference product; yet, according to Spanish legislation, only prescribers can switch tacrolimus-containing products. METHODS: Data from independent bioequivalence studies that compare each generic product with the reference product were combined by adjusted indirect comparisons to investigate the relative bioavailability between generic drug products, since there is no direct bioequivalence study comparing generics to each other. RESULTS: Eight generic tacrolimus products in the form of capsules are presently authorized in Spain, but only five are marketed. These eight products represent only three different generic product developments. One product is authorized with four different names/companies, while another is authorized under three different names/companies. The adjusted indirect comparisons between generic products show bioequivalence within the conventional 80-125 % confidence interval acceptance criteria for area under the curve (AUC) and maximum concentration (Cmax). CONCLUSION: Not only are the generic products bioequivalent with the reference product, but also with each other.

Concepts: Comparison, Generic drug, Comparisons, Marketing, Bioavailability, Bioequivalence, Tacrolimus, Astellas Pharma

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The purpose of this review is to discuss the process of genericisation of medications in the US and Europe with a focus on ophthalmic drugs. Regulatory guidelines of the US Food and Drug Administration and the European Medicines Agency will be discussed, and the advantages and concerns of genericisation will be explored. We will look at various studies concerning the safety and efficacy of generic drugs compared to their branded counterparts. In particular, the challenges of assuring bioequivalence and therapeutic equivalence in topical ophthalmic drugs will be examined.

Concepts: Pharmacology, Medicine, Drug, Pharmaceutical industry, Pharmaceutical drug, Generic drug, Bioequivalence, Food and Drug Administration

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The objective of this article is to discuss the similarities and differences among bioequivalence approaches used by international regulatory authorities when reviewing applications for marketing new generic drug products which are systemically active and intended for oral administration. We focused on the 13 jurisdictions and organizations participating in the International Generic Drug Regulators Pilot. These are Australia, Brazil, Canada, China, Chinese Taipei, the European Medicines Association, Japan, Mexico, Singapore, South Korea, Switzerland, the USA, and the World Health Organization. We began with a comparison of how the various jurisdictions and organizations define a generic product and its corresponding reference product. We then compared the following bioequivalence approaches: recommended bioequivalence study designs, method of pharmacokinetic calculations and bioequivalence acceptance limits, recommendations for modifying bioequivalence study designs and limits for highly variable drugs and narrow therapeutic index drugs, provisions for waiving bioequivalence study requirements (granting biowaivers), and implementation of the Biopharmaceutics Classification System. We observed that, overall, there are more similarities than differences in bioequivalence approaches among the regulatory authorities surveyed.

Concepts: Pharmacology, Generic drug, Marketing, World Health Organization, Bioavailability, Bioequivalence, Republic of China, Therapeutic index

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Many antihypertensive drugs are now available in generic formulations at fractions of the cost of their branded counterparts. In the United States, marketing approval for generic medications is usually granted by the Food and Drug Administration on the basis of two simple studies involving dissolution rates and bioavailability in 24 - 36 healthy people, without data regarding antihypertensive efficacy, safety, or long-term outcomes. This process leaves many true disciples of “Evidence-Based Medicine” in a quandary: prescribe only brand-name medications that have been demonstrated in clinical trials to both lower blood pressure and prevent cardiovascular events, or instead recommend lower-priced generic agents that are usually supported by no such data. This review summarizes the current evidence that generic antihypertensive drugs are likely to be safe and effective, may increase the probability of medication availability and adherence for many patients, but, by law, must have a different physical appearance than the original product.

Concepts: Pharmacology, The Canon of Medicine, Blood pressure, Pharmaceutical industry, Pharmaceutical drug, Generic drug, Bioequivalence, Food and Drug Administration

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Objective: To determine the oral bioavailability of a pregabalin capsule relative to a pregabalin solution. Methods: This was an open-label, randomized, crossover study in 12 healthy volunteers. Pharmacokinetics were compared for a 100-mg capsule and a 100- mg capsule dissolved in water, administered fasted. Results: Mean Cmax and AUC0-∞ for the capsule were within 2% of those for the solution (3.8 vs. 3.7 μg/ml and 26.7 vs. 27.0 μg×h/ml, respectively). The 90% confidence intervals for the ratios of Cmax and AUC0-∞ fell fully within 80 - 125%. Conclusions: A 100-mg pregabalin capsule is bioequivalent to a pregabalin solution (100-mg capsule dissolved in water).

Concepts: Pharmacology, Statistics, Crossover study, Clinical research, Confidence interval, Pharmacokinetics, Bioavailability, Bioequivalence

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Biowaivers are recommended for immediate-release solid oral dosage forms using dissolution testing as a surrogate for in vivo bioequivalence studies. Several guidance are currently available (the World Health Organization (WHO), the US FDA, and the EMEA) where the conditions are described. In this study, definitions, criteria, and methodologies according to the WHO have been applied. The dissolution performances of immediate-release metronidazole, zidovudine, and amoxicillin products purchased in South African and Indian markets were compared to the relevant comparator pharmaceutical product (CPP)/reference product. The dissolution performances were studied using US Pharmacopeia (USP) apparatus 2 (paddle) set at 75 rpm in each of three dissolution media (pH1.2, 4.5, and 6.8). Concentrations of metronidazole, zidovudine, and amoxicillin in each dissolution media were determined by HPLC. Of the 11 metronidazole products tested, only 8 could be considered as very rapidly dissolving products as defined by the WHO, whereas 2 of those products could be considered as rapidly dissolving products but did not comply with the f 2 acceptance criteria in pH 6.8. All 11 zidovudine products were very rapidly dissolving, whereas in the case of the 14 amoxicillin products tested, none of those products met any of the WHO criteria. This study indicates that not all generic products containing the same biopharmaceutics classification system (BCS) I drug and in similar strength and dosage form are necessarily in vitro equivalent. Hence, there is a need for ongoing market surveillance to determine whether marketed generic products containing BCS I drugs meet the release requirements to confirm their in vitro bioequivalence to the respective reference product.

Concepts: Pharmacology, Drug, In vivo, In vitro, Pharmaceutical drug, Biopharmaceutics Classification System, Bioequivalence, Food and Drug Administration

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Purpose: To compare the pharmacokinetic profiles and to evaluate the bioequivalence of two commercial amoxicillin suspension formulations (500 mg/5 mL AMOXIL®, reference formulation and AMOXI-PED®, test formulation) in healthy Brazilian volunteers. Methods: Under fasting condition, 25 volunteers (13 males and 12 females) were included in this randomized, open-label, two-period crossover (1-week washout interval) bioequivalence study. Blood samples were collected at pre-dose (0 hour) and 0.5, 1, 1.33, 1.66, 2, 2.5, 3, 4, 6, 8, and 12 hours after drug ingestion. Pharmacokinetic parameters (Cmax, tmax, t1/2, AUC0-tlast, and AUC0-∞) were calculated from plasma concentrations for both formulations in each subject. Results: Arithmetic mean values of the pharmacokinetic parameters were: Cmax = 12.004 (± 2.824) μg×mL-1; tmax = 1.118 (± 0.396) h; t1/2 = 1.226 (± 0.179) h; AUC0-tlast = 29.297 (± 6.007) μg×h×mL-1; and AUC0-∞ = 29.299 (± 6.007) μg×h×mL-1 for reference formulation and Cmax = 11.456 (± 2.825) μg×mL-1; tmax = 1.331 (± 0.509) h; t1/2 = 1.141 (± 0.133) h; AUC0-tlast = 28.672 (± 5.778) μg×h×mL-1; and AUC0-∞ = 28.693 (± 5.796) μg×h×mL-1 for test formulation. The confidence intervals (90% CI) for reference and test formulations were, respectively, 90.74 - 100.46% for Cmax and 93.62 - 103.61% for AUC0-t. Conclusion: Based on the results, both formulations of amoxicillin evaluated in this study were considered bioequivalent according to FDA and ANVISA/Brazil criteria.

Concepts: Pharmacology, Sample size, Arithmetic mean, Mean, Confidence interval, Pharmacokinetics, Bioavailability, Bioequivalence

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The pharmacokinetics of 2 brands of pregabalin 300 mg capsules were compared in 23 healthy human volunteers after a single oral dose in a randomized cross-over study. The study protocol was prepared with relevance to the requirements set in the US FDA and the EMA guidances for conduction of bioequivalence studies. Reference (Lyrica®, Pfizer, France) and test (Neurexal, Pharmaline, Lebanon) products were administered to fasted volunteers. Blood samples were collected up to 48 h and assayed for pregabalin using a validated LC-MS/MS method. The pharmacokinetic parameters AUC0-t, AUC0-∞, Cmax, Tmax, T1/2 and elimination rate constant were determined from plasma concentration-time profile by non-compartmental analysis method using WinNonlin V5.2. The analysis of variance did not show any significant difference between the 2 formulations and 90% confidence intervals fell within the acceptable range for bioequivalence: 80-125%. It was concluded that the 2 brands exhibited comparable pharmacokinetic profiles and that Pharmaline’s Neurexal is bioequivalent to Lyrica® of Pfizer, France.

Concepts: Pharmacology, Confidence interval, Normal distribution, Generic drug, Pharmacokinetics, Analysis of variance, Bioavailability, Bioequivalence