Innovative approaches for demonstration of bioequivalence: the US FDA perspective

Integrating Quantitative Methods & Modeling and Analytical Techniques in Reverse Engineering; A Cutting-Edge Strategy in Complex Generic Development

Generic drugs are crucial for healthcare, offering affordable alternatives to brand-name drugs. Complex generics, with intricate ingredients, are gaining increasing importance in managing chronic conditions. However, prior to the regulatory market approval, they must demonstrate similarity in active ingredients, formulations, strength, and administration routes to ensure bioequivalence. The primary constraint lies in demonstrating bioequivalence with the innovator drug using traditional methods includes a lack of advanced technologies, and standardized protocols for analysing complex products. Given the multifaceted nature of these products, a single methodology may not suffice to establish in vitro/in vivo bioequivalence. Recognizing this, the USFDA conducts several workshops aiming advancement of complex generic drug product development. Notably, these efforts highlight the need to use Quantitative Methods and Modeling (QMM) approaches to support generic product development. QMM is a scientific approach used to analyze data and simulate drug development processes, ensuring safe, effective, and similar formulations of generic drugs using mathematical, statistical, and computational tools. QMM facilitates the design of formulations and processes, establishes a framework for in vivo BE studies, and suggests alternative ways to demonstrate BE. Appropriate utilization of the QMM approach can reduce the need for unwanted in vivo studies and bolster in vitro approaches for generic product development. Furthermore, use of orthogonal analytical techniques to characterize and decode innovator drugs can provide valuable insights into product attributes. Integrating this data into QMM enables the assessment of critical material attributes, or critical process parameters, thus demonstrating sameness. The combined application of QMM and analytical techniques not only supports regulatory decisions but also enhances the success rate of complex generic drug products.

Impact of active pharmaceutical ingredient variables and oleaginous base on the in vitro drug release from ophthalmic ointments: An investigation using dexamethasone as a model drug

The present study systematically investigates the impact of active pharmaceutical ingredient (API) variables and oleaginous base characteristics on the in vitro release (IVR) performance of ophthalmic ointments, utilizing dexamethasone as a model drug. The interplay between selected attributes (i.e., particle size distribution, crystallinity, and polymorphic form for API, and rheological factors for compendial-grade white petrolatum) and IVR performance was investigated. APIs from different vendors exhibited variations in crystallinity and polymorphism. Ointments containing amorphous dexamethasone presented higher release amounts/rates compared to crystalline counterparts, emphasizing the role of physical state in release kinetics. Variations in particle size of this lipophilic API (5.4 - 21.2 µm) did not appear to impact IVR performance significantly. In contrast, white petrolatum's rheological attributes, which varied substantially within USP-grade petrolatum, were found to critically affect the drug release rate and extent of the ointment. The study's comprehensive analysis establishes a coherent connection between the quality attributes of both API and petrolatum and IVR, delineating their intricate interdependent effects on ophthalmic ointment performance. These findings provide reference to formulation design, quality control, and regulatory considerations within the pharmaceutical industry, fostering a robust foundational understanding of commonly overlooked quality attributes in ophthalmic ointments.

Impact of Apparatus and Adapter on In vitro Drug Release of Ophthalmic Semisolid Drug Products

PURPOSE

In vitro release testing (IVRT) is a widely used tool for evaluating the quality and performance of drug products. However, standardized sample adaptors or drug release apparatus setups for IVRT studies are still lacking for ophthalmic ointments. The aim of this study was to provide a better understanding of the impact of apparatus and sample adaptor setups on IVRT of ophthalmic ointments.

METHODS

Dexamethasone (DEX), a steroidal ingredient commonly used in ophthalmic drug products, was selected as a model drug. Ointments were prepared by mixing DEX in white petrolatum using a high shear mixer. A novel two-sided adapter was developed to increase the drug release surface area. DEX ointment was placed in one-sided or two-sided release adaptors coupled with 1.2 μm polyethersulfone membrane, and the drug release was studied in different USP apparatuses (I, II, and IV).

RESULTS

The sample adaptor setups had a minimal impact on cumulative drug release amount per area or release rate while USP IV apparatus with agitated flow enhanced drug release rates. The USP apparatus I with a two-sided semisolid adapter, which uses membranes on both sides, showed dramatically higher cumulative drug release and discriminative release profiles when evaluating ophthalmic formulations.

CONCLUSIONS

USP apparatuses and sample adaptors are critical considerations for IVRT. Two-sided semisolid adapter provides higher cumulative release, facilitating the discrimination between low drug content ophthalmic ointment formulations with good sensitivity and repeatability without affecting the drug release rate.

Computational Model of In Vivo Corneal Pharmacokinetics and Pharmacodynamics of Topically Administered Ophthalmic Drug Products

INTRODUCTION

Although the eye is directly accessible on the surface of the human body, drug delivery can be extremely challenging due to the presence of multiple protective barriers in eye tissues. Researchers have developed complex formulation strategies to overcome these barriers to ophthalmic drug delivery. Current development strategies rely heavily on in vitro experiments and animal testing to predict human pharmacokinetics (PK) and pharmacodynamics (PD).

OBJECTIVE

The primary objective of the study was to develop a high-fidelity PK/PD model of the anterior eye for topical application of ophthalmic drug products.

METHODS

Here, we present a physiologically-based in silico approach to predicting PK and PD in rabbits after topical administration of ophthalmic products. A first-principles based approach was used to describe timolol dissolution, transport, and distribution, including consideration of ionized transport, following topical instillation of a timolol suspension.

RESULTS

Using literature transport and response parameters, the computational model described well the concentration-time and response-time profiles in rabbit. Comparison of validated rabbit model results and extrapolated human model results demonstrate observable differences in the distribution of timolol at multiple time points.

CONCLUSION

This modeling framework provides a tool for model-based prediction of PK in eye tissues and PD after topical ophthalmic drug administration to the eyes.

Generic lamotrigine extended-release tablets are bioequivalent to innovator drug in fully replicated crossover bioequivalence study

OBJECTIVE

Lamotrigine is a commonly prescribed antiepileptic drug. U.S. Food and Drug Administration (FDA)-funded clinical studies have demonstrated bioequivalence (BE) for generic lamotrigine immediate-release (IR) products in epilepsy patients with generic substitution. To address the potential concerns about the risk of generic-brand substitution of lamotrigine extended-release (ER) products, considering the complexity of controlled release systems and pharmacokinetic variations associated with possible within-subject variability (WSV), this prospective study assessed (1) BE of generic and brand lamotrigine ER products in a fully replicated BE study design in healthy subjects and (2) whether such fully replicated study design and WSV data can better support the approval of generic lamotrigine ER products.

METHODS

This open-label, single-dose, two-treatment, four-period, two-sequence, fully replicated crossover BE study compared generic lamotrigine ER tablet to brand Lamictal XR (200 mg) in 30 healthy subjects under fed conditions. Pharmacokinetics (PK) profiles were generated based on intensive blood sampling up to 144 h.

RESULTS

The two products showed comparable peak plasma concentration (C_max ), area under the concentration-time curve (AUC) from time zero to the last measurable time point (AUC_0-t ) and AUC extrapolated to infinity (AUC_0-inf ), whereas median time to C_max (T_max ) values differed, that is, 10 h for generic and 22 h for brand products, respectively. WSVs for PK metrics were small (~8% of C_max and ~6% of AUC) and similar between these two products. PK simulation predicted equivalent PK measurements of both products at steady state and after brand-to-generic switch, except the first day upon switching. No serious adverse events were reported.

SIGNIFICANCE

The generic lamotrigine ER tablet product demonstrates BE to the brand product in a fully replicated BE study design with healthy subjects, supporting the adequacy of the two-way crossover study design to demonstrate BE and generic-brand substitution of lamotrigine ER products.

A randomized, cross-over trial of metoprolol succinate formulations to evaluate PK and PD end points for therapeutic equivalence

There are limited comparison data throughout the dosing interval for generic versus brand metoprolol extended-release (ER) tablets. We compared the pharmacokinetics (PKs) and pharmacodynamics of brand name versus two generic formulations (drugs 1 and 2) of metoprolol ER tablets with different time to maximum concentration (T_max ) in adults with hypertension. Participants were randomized to equal drug doses (50-150 mg/day) administered in one of two sequences (brand-drug1-brand-drug2 or brand-drug2-brand-drug1) and completed 24-h PK, digital heart rate (HR), ambulatory blood pressure (BP), and HR studies after taking each formulation for greater than or equal to 7 days. Metoprolol concentrations were determined by liquid chromatography tandem mass spectrometry, with noncompartmental analysis performed to obtain PK parameters in Phoenix WinNonlin. Heart rate variability (HRV) low-to-high frequency ratio was determined per quartile over the 24-h period. Thirty-six participants completed studies with the brand name and at least one generic product. Among 30 participants on the 50 mg dose, the primary PK end points of area under the concentration-time curve and C_max were similar between products; T_max was 6.1 ± 3.6 for the brand versus 3.5 ± 4.9 for drug 1 (p = 0.019) and 9.6 ± 3.2 for drug 2 (p < 0.001). Among all 36 participants, 24-h BPs and HRs were similar between products. Mean 24-h HRV low-to-high ratio was also similar for drug 1 (2.04 ± 1.35), drug 2 (1.86 ± 1.35), and brand (2.04 ± 1.77), but was more sustained over time for the brand versus drug 1 (drug × quartile interaction p = 0.017). Differences in T_max between metoprolol ER products following repeated doses may have implications for drug effects on autonomic balance over the dosing interval.

Nanoliposomes as drug delivery systems: safety concerns

The review highlights the safety issues of drug delivery systems based on liposomes. Due to their small sizes (about 80-120 nm, sometimes even smaller), phospholipid nanoparticles interact intensively with living systems during parenteral administration. This interaction significantly affects both their transport role and safety; therefore, special attention is paid to these issues. The review summarises the data on the basic factors affecting the safety of nanoliposomes: composition, size, surface charge, stability, the release of an incorporated drug, penetration into tissues, interaction with the complement system. Attention is paid to the authors' own research of unique phospholipid nanoparticles with a diameter of 20-30 nm. The influence of technological processes of nanoliposome production on their properties is considered. The article also discusses the modern safety assessment criteria contained in the preliminary regulatory documents of the manufacturing countries for new nanoliposome-based drugs being developed or used in the clinic.

Influence of in vitro release methods on assessment of tobramycin ophthalmic ointments

The current investigation was carried out to identify appropriate parameters for measuring the in vitro release of tobramycin (TOB) ophthalmic ointments and to evaluate the feasibility of in vitro release testing methods to assess the product performance. Drug release was assessed using USP dissolution apparatus IV and a modified USP dissolution apparatus I with simulated tear solution (STS) as the dissolution medium. The study variables included temperature, membrane material, source and pore size. The results demonstrated a significant influence of the membrane source and pore size on the release of TOB from the ointments. A dissolution medium temperature of 40 °C was found to be appropriate for the release studies. Both of the apparatuses were able to discriminate between the release profiles of ointments with different physicochemical/rheological properties. Maximum release rate of TOB was observed in the first hour which followed a logarithmic time dependent release. The correlation between the release rates/amounts and yield stress of the ointments was observed in both the dissolution apparatuses. These results support a rational approach to guide the in vitro release testing of TOB ophthalmic ointments.

Old active ingredients in new medicinal products: is the regulatory path coherent with patients' expectations?

The rising costs of new medicinal products are a challenge to the economic sustainability of national healthcare systems in ensuring patients' access to therapies. European Union (EU) and US legislators have provided regulatory pathways aimed at simplifying Marketing Authorization (MA) applications for new medicinal products in cases when safety and efficacy profiles can be derived from the data of already-marketed products. In this review, we discuss the different regulatory pathways towards the MA of new medicinal products containing old drug substances and intended to improve the therapeutic value of a treatment, to obtain a new therapeutic indication (drug repositioning), or to ensure the same therapeutic value of a reference product at lower costs.

Investigation to Explain Bioequivalence Failure in Pravastatin Immediate-Release Products

The purpose of this work is to explore the predictive ability of the biopharmaceutics classification system (BCS) biowaiver based on the dissolution methods for two pravastatin test products, where one of them showed bioequivalence (BE) while the other test failed (non-bioequivalence, or NBE), and to explore the reasons for the BE failure. Experimental solubility and permeability data confirmed that pravastatin is a BCS class III compound. The permeability experiments confirmed that the NBE formulation significantly increased pravastatin permeability, and could explain its higher absorption rate and higher C_max. This finding highlights the relevance of requiring similar excipients for BCS class III drugs. The BCS-based biowaiver dissolution tests at pH 1.2, 4.5, and 6.8, with the paddle apparatus at 50 rpm in 900 mL media, were not able to detect differences in pravastatin products, although the NBE formulation exhibited a more rapid dissolution at earlier sampling times. Dissolution tests conducted in 500 mL did not achieve complete dissolution, and both formulations were dissimilar because the amount dissolved at 15 min was less than 85%. The difference was less than 10% at pH 1.2 and 4.5, while at pH 6.8 f₂, results reflected the C_max rank order.

Generics in transplantation medicine: Randomized comparison of innovator and substitution products containing mycophenolate mofetil

Objective: Mycophenolate mofetil (MMF) is widely used as an immunosuppressant for the prophylaxis of acute organ rejection in recipients of solid organ transplants. Materials and methods: We have compared, in healthy subjects, the pharmacokinetics of mycophenolic acid when MMF was administered in the form of the innovator product CellCept (F. Hoffmann-La Roche Ltd.) or one of three commercially available generics, Renodapt (Biocon Ltd.), Mycept (Panacea Biotec), or Cellmune (Cipla Ltd.). The study was powered to detect a 20% difference in mean formulation performance measures, but not to formally evaluate bioequivalence. Geometric mean ratios of maximum concentrations (C_max) and areas under plasma concentration-time curves were calculated. Results: Comparing generics against each other, the differences in point estimates of the geometric mean ratios of C_max of two of the comparisons were either borderline within (Renodapt/Cellmune) or clearly outside (Mycept/Cellmune) a region of 80 – 125% around the reference mean, indicating that bioequivalence between these generics may be difficult to show. Conclusion: Physicians in the field of transplantation should be aware of the potential risk of altering the therapeutic outcome when switching from one preparation of MMF to another. ClinicalTrials.gov identifier: NCT02981290.

Evaluating the Clinical Impact of Formulation Variability: A Metoprolol Extended-Release Case Study

The objective of this research was to evaluate the impact of changes in the formulation of metoprolol extended-release (ER) tablets on dissolution, pharmacokinetic, and exercise-induced heart rate (EIHR) using a combined physiologically based absorption pharmacokinetic, and population pharmacokinetic/pharmacodynamic modeling and simulation approach. Using a previously developed physiologically based absorption pharmacokinetic model in DDDPlus and GastroPlus, we simulated the changes in drug release and exposure as the result of quantitative changes in the release-controlling excipient, hydroxylpropylmethylcellulose, for 50 and 200 mg. The similarity of dissolution profiles was assessed using the f₂ test, and bioequivalence was tested on the simulated pharmacokinetic profiles. We used the simulated concentration-time profiles following formulation changes as pharmacokinetic input into a population pharmacokinetic/pharmacodynamic model newly developed in NONMEM to determine if changes in pharmacokinetics lead to clinically significant changes in pharmacodynamics. Pharmacodynamic assessment was based on the percentage reduction in the EIHR from baseline. Therapeutic effect was considered similar when the model-predicted EIHR was within 50% to 85% of the average maximum EIHR of healthy 30-year-old subjects. A 40% or more increase in the release rate constant resulted in dissimilarity in dissolution profiles and bioINequivalence in pharmacokinetics for both 50 and 200 mg. Formulation-related differences in drug release of metoprolol ER tablets can lead to differences in pharmacokinetics. However, the evaluated pharmacokinetic differences do not lead to clinically meaningful differences in EIHR, suggesting that EIHR may not be sensitive enough to detect changes in pharmacokinetics of metoprolol ER products.

Formulation characteristics and in vitro release testing of cyclosporine ophthalmic ointments

The aim of the present study was to investigate the relationship between formulation/process variables versus the critical quality attributes (CQAs) of cyclosporine ophthalmic ointments and to explore the feasibility of using an in vitro approach to assess product sameness. A definitive screening design (DSD) was used to evaluate the impact of formulation and process variables. The formulation variables included drug percentage, percentage of corn oil and lanolin alcohol. The process variables studied were mixing temperature, mixing time and the method of mixing. The quality and performance attributes examined included drug assay, content uniformity, image analysis, rheology (storage modulus, shear viscosity) and in vitro drug release. Of the formulation variables evaluated, the percentage of the drug substance and the percentage of corn oil in the matrix were the most influential factors with respect to in vitro drug release. Conversely, the process parameters tested were observed to have minimal impact. An evaluation of the release mechanism of cyclosporine from the ointment revealed an interplay between formulation (e.g. physicochemical properties of the drug and ointment matrix type) and the release medium. These data provide a scientific basis to guide method development for in vitro drug release testing of ointment dosage forms. These results demonstrate that the in vitro methods used in this investigation were fit-for-purpose for detecting formulation and process changes and therefore amenable to assessment of product sameness.

Complexity of intravenous iron nanoparticle formulations: implications for bioequivalence evaluation

Intravenous iron formulations are a class of complex drugs that are commonly used to treat a wide variety of disease states associated with iron deficiency and anemia. Venofer® (iron-sucrose) is one of the most frequently used formulations, with more than 90% of dialysis patients in the United States receiving this formulation. Emerging data from global markets outside the United States, where many iron-sucrose similars or copies are available, have shown that these formulations may have safety and efficacy profiles that differ from the reference listed drug. This may be attributable to uncharacterized differences in physicochemical characteristics and/or differences in labile iron release. As bioequivalence evaluation guidance evolves, clinicians should be educated on these potential clinical issues before a switch to the generic formulation is made in the clinical setting.

A New Level A Type IVIVC for the Rational Design of Clinical Trials Toward Regulatory Approval of Generic Polymeric Long-Acting Injectables

Chronic neuropsychiatric disorders and diabetes mellitus affect millions of patients and require long-term supervision and expensive medical care. Although repeated drug administration can help manage these diseases, relapses and re-hospitalization owing to patient non-adherence and reduced therapeutic efficacy remain challenging. In response, long-acting injectables, which provide sustained drug release over longer periods at concentrations close to therapeutic ranges, have been proposed. Recent advancements include polymeric long-acting injectables (pLAIs), in which the active pharmaceutical ingredient (API) is encapsulated within U.S. Food and Drug Administration (FDA)-approved biocompatible polymers, such as poly(lactic-co-glycolic acid), or PLGA. Despite significant progress and development in the global pLAI market, FDA guidance for the approval of complex drug products, such as generic pLAIs, is not clearly defined. Although in vitro to in vivo correlation (IVIVC) can facilitate the identification of critical quality attributes (CQAs), drug formulations, and in vitro test platforms for evaluating drug performance in vivo, the application of IVIVC in order to shortlist time- and resource-intensive clinical trials for generic pLAIs has not been reported. Here, we propose a new Level A Type IVIVC that directly correlates the in vitro outcomes, such as drug dissolution, of candidate generic formulations with the clinical characteristics, such as drug absorption, of a reference listed drug (RLD), to help identify the specific generic pLAI formulations with clinical absorptions that are likely to be similar to that of the RLD, thereby reducing the number of clinical trials required for evaluation of clinical bioequivalence (BE). Therefore, the scope of the proposed method is intended only for the rational design of clinical trials, i.e., to shortlist the specific pLAI generic formulations for clinical BE evaluation, and not necessarily to analyze drug performances (i.e., drug safety and effectiveness) in the shortlisted clinical trials or post-approval. Once validated, this method will be of great value to developers of generic pLAIs and regulatory bodies to accelerate their approval of these generic pLAIs.

Regulatory framework on bioequivalence criteria for locally acting gastrointestinal drugs: the case for oral modified release mesalamine formulations

Bioequivalence testing for locally acting gastrointestinal drugs is a challenging issue for both regulatory authorities and pharmaceutical industries. The international regulatory framework has been characterized by the lack of specific bioequivalence tests that has generated a negative impact on the market competition and drug use in clinical practice. Areas covered: This review article provides an overview of the European Union and United States regulatory frameworks on bioequivalence criteria for locally acting gastrointestinal drugs, also discussing the most prominent scientific issues and advances that has been made in this field. A focus on oral modified release mesalamine formulations will be also provided, with practical examples of the regulatory pathways followed by pharmaceutical companies to determine bioequivalence. Expert commentary: The development of a scientific rationale to demonstrate bioequivalence in this field has been complex and often associated with uncertainties related to scientific and regulatory aspects. Only in recent years, thanks to advanced knowledge in this field, the criteria for bioequivalence assessment are undergoing substantial changes. This new scenario will likely result in a significant impact on pharmaceutical companies, promoting more competition through a clearer regulatory approach, conceived for streamlining the demonstration of therapeutic equivalence for locally acting gastrointestinal drugs.

Bioequivalence Between Generic and Branded Lamotrigine in People With Epilepsy: The EQUIGEN Randomized Clinical Trial

Importance

Switching between generic antiepileptic drugs is a highly debated issue that affects both clinical care and overall health care costs.

Objective

To evaluate the single-dose pharmacokinetic bioequivalence of 3 (1 branded and 2 generic drugs) on-market, immediate-release lamotrigine drug products.

Design, Setting, and Participants

The Equivalence Among Antiepileptic Drug Generic and Brand Products in People With Epilepsy (EQUIGEN) single-dose study is a crossover, prospective, sequence-randomized, replicate pharmacokinetic study conducted at 5 US academic epilepsy centers. Fifty adults (≥18 years) with epilepsy who were taking concomitant antiepileptic drugs and not currently receiving lamotrigine were enrolled between July 18, 2013, and January 19, 2015. Every participant was randomly assigned to 1 of 3 equivalent sequences, each comprising 6 study periods, during which they had blood draws before and after medication administration. Forty-nine participants were included in intention-to-treat analyses.

Interventions

Participants received a single 25-mg dose of immediate-release lamotrigine at the start of each period, with the branded and the 2 most disparate generic products each studied twice. Lamotrigine was selected as the antiepileptic drug of interest because of its wide use, publications indicating problems with generic switches, and complaints to the US Food and Drug Administration regarding generic products. Both participants and study personnel were blinded to the specific generic products selected.

Main Outcomes and Measures

The primary outcome was bioequivalence between products. Maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) were compared, and average bioequivalence (ABE) was established if the 90% CIs of the ratios of the 2 products were within equivalence limits (80%-125%).

Results

Of the 50 randomized participants, 49 (98%) received all 3 lamotrigine products and completed at least 3 pharmacokinetic assessments and 46 (92%) completed all 6 pharmacokinetic assessments. Among the 49 participants, 28 (57%) were men and 21 (43%) were women, 42 (86%) self-identified as white, and 46 (16) years was the mean (SD) age. The 3 drug products were considered bioequivalent because the 90% CIs were within equivalence limits (lowest and highest CI limits for Cmax, 92.6% and 110.4%; for AUC0-96, 96.9% and 101.9%). Replicate testing demonstrated no significant differences in within-subject variability across the 3 products (likelihood ratios, χ22 for log-transformed variables: AUC0-96, 2.58; Cmax, 0.64; and AUC0-∞, 4.05; P ≥ .13) and that the 3 products were also bioequivalent according to scaled ABE and individual bioequivalence criteria with no subject × formulation interaction (Cmax, 0.00; AUC0-96, 0.54; and AUC0-∞, 0.36; P ≥ .76).

Conclusions and Relevance

This study provides evidence that the disparate lamotrigine products studied are bioequivalent when tested in people with epilepsy taking concomitant antiepileptic drugs.

Trial Registration

clinicaltrials.gov Identifier: NCT01733394.

Bioequivalence of generic alendronate sodium tablets (70 mg) to Fosamax® tablets (70 mg) in fasting, healthy volunteers: a randomized, open-label, three-way, reference-replicated crossover study

PURPOSE

The aim of this study was to evaluate the bioequivalence of a generic product 70 mg alendronate sodium tablets with the reference product Fosamax^® 70 mg tablet.

MATERIALS AND METHODS

A single-center, open-label, randomized, three-period, three-sequence, reference-replicated crossover study was performed in 36 healthy Chinese male volunteers under fasting conditions. In each study period, the volunteers received a single oral dose of the generic or reference product (70 mg). Blood samples were collected at pre-dose and up to 8 h after administration. The bioequivalence of the generic product to the reference product was assessed using the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) reference-scaled average bioequivalence (RSABE) methods.

RESULTS

The average maximum concentrations (C_max) of alendronic acid were 64.78±43.76, 56.62±31.95, and 60.15±37.12 ng/mL after the single dose of the generic product and the first and second doses of the reference product, respectively. The areas under the plasma concentration-time curves from time 0 to the last timepoint (AUC_0-t ) were 150.36±82.90, 148.15±85.97, and 167.11±110.87 h⋅ng/mL, respectively. Reference scaling was used because the within-subject standard deviations of the reference product (s_WR ) for C_max and AUC_0-t were all higher than the cutoff value of 0.294. The 95% upper confidence bounds were -0.16 and -0.17 for C_max and AUC_0-t , respectively, and the point estimates for the generic/reference product ratio were 1.08 and 1.00, which satisfied the RSABE acceptance criteria of the FDA. The 90% CIs for C_max and AUC_0-t were 90.35%-129.04% and 85.31%-117.15%, respectively, which were within the limits of the EMA for the bioequivalence of 69.84%-143.19% and 80.00%-125.00%.

CONCLUSION

The generic product was bioequivalent to the reference product in terms of the rate and extent of alendronate absorption after a single 70 mg oral dose under fasting conditions.

Complement activation as a bioequivalence issue relevant to the development of generic liposomes and other nanoparticulate drugs

Liposomes are known to activate the complement (C) system, which can lead in vivo to a hypersensitivity syndrome called C activation-related pseudoallergy (CARPA). CARPA has been getting increasing attention as a safety risk of i.v. therapy with liposomes, whose testing is now recommended in bioequivalence evaluations of generic liposomal drug candidates. This review highlights the adverse consequences of C activation, the unique symptoms of CARPA triggered by essentially all i.v. administered liposomal drugs, and the various features of vesicles influencing this adverse immune effect. For the case of Doxil, we also address the mechanism of C activation and the opsonization vs. long circulation (stealth) paradox. In reviewing the methods of assessing C activation and CARPA, we delineate the most sensitive porcine model and an algorithm for stepwise evaluation of the CARPA risk of i.v. liposomes, which are proposed for standardization for preclinical toxicology evaluation of liposomal and other nanoparticulate drug candidates.

An Evaluation of Health Service Impacts Consequent to Switching from Brand to Generic Venlafaxine in New Zealand under Conditions of Price Neutrality

OBJECTIVE

To study the health impact on adult New Zealand patients who switch from originator brand to generic venlafaxine.

METHODS

The national pharmacy database was used to select patients using venlafaxine for at least 6 months. Switchers and nonswitchers were identified, and switch behavior was compared for a 12-month follow-up period. Change in health service use following switching was also compared between switchers and nonswitchers including use of the emergency department, hospital, and specialist outpatient services over the same period.

RESULTS

Approximately 12% of all originator brand users switched to generic venlafaxine, at least half of whom continued to use the generic throughout the follow-up period to August 1, 2012. Almost 60% of new users of the generic venlafaxine, however, switched to using the originator brand. Aside from a slight reduction in the use of outpatient services among switchers, there were no significant differences in health services use between switchers and nonswitchers for either existing or new venlafaxine users.

CONCLUSIONS

Although both products remain fully subsidized and available, there is little incentive for prescribers, pharmacists, or patients to switch to the less expensive generic brand. If savings to the national New Zealand budget are to be realized, additional policy measures should be implemented to minimize incentives for multiple and reverse switching, and prescribers, as key opinion leaders, could take the lead in promoting generics to their patients.

Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide

PURPOSE

The therapeutic index (TI) is the range of doses at which a medication is effective without unacceptable adverse events. Drugs with a narrow TI (NTIDs) have a narrow window between their effective doses and those at which they produce adverse toxic effects. Generic drugs may be substituted for brand-name drugs provided that they meet the recommended bioequivalence (BE) limits. However, an appropriate range of BE for NTIDs is essential to define due to the potential for ineffectiveness or adverse events. Flecainide is an antiarrhythmic agent that has the potential to be considered an NTID. This review aims to evaluate the literature surrounding guidelines on generic substitution for NTIDs and to evaluate the evidence for flecainide to be considered an NTID.

METHODS

A review of recommendations from various regulatory authorities regarding BE and NTIDs, and publications regarding the NTID characteristics of flecainide, was carried out.

RESULTS

Regulatory authorities generally recommend reduced BE limits for NTIDs. Some, but not all, regulatory authorities specify flecainide as an NTID. The literature review demonstrated that flecainide displays NTID characteristics including a steep drug dose-response relationship for safety and efficacy, a need for therapeutic drug monitoring of pharmacokinetic (PK) or pharmacodynamics measures and intra-subject variability in its PK properties.

CONCLUSIONS

There is much evidence for flecainide to be considered an NTID based on both preclinical and clinical data. A clear understanding of the potential of proarrhythmic effects or lack of efficacy, careful patient selection and regular monitoring are essential for the safe and rational administration of flecainide.

A Bioequivalence Approach for Generic Narrow Therapeutic Index Drugs: Evaluation of the Reference-Scaled Approach and Variability Comparison Criterion

Various health communities have expressed concerns regarding whether average bioequivalence (BE) limits (80.00-125.00%) for the 90% confidence interval of the test-to-reference geometric mean ratio are sufficient to ensure therapeutic equivalence between a generic narrow therapeutic index (NTI) drug and its reference listed drug (RLD). Simulations were conducted to investigate the impact of different BE approaches for NTI drugs on study power, including (1) direct tightening of average BE limits and (2) a scaled average BE approach where BE limits are tightened based on the RLD's within-subject variability. Addition of a variability comparison (using a one-tailed F test) increased the difficulty for generic NTIs more variable than their corresponding RLDs to demonstrate bioequivalence. Based on these results, the authors evaluate the fully replicated, 2-sequence, 2-treatment, 4-period crossover study design for NTI drugs where the test product demonstrates BE based on a scaled average bioequivalence criterion and a within-subject variability comparison criterion.

The impact on health outcomes and healthcare utilisation of switching to generic medicines consequent to reference pricing: the case of lamotrigine in New Zealand

BACKGROUND

Many countries have implemented generic reference pricing and substitution as methods of containing pharmaceutical expenditure. However, resistance to switching between medicines is apparent, especially in the case of anti-epileptic medicines.

OBJECTIVES

This study sought to exploit a nation-wide policy intervention on generic reference pricing in New Zealand to evaluate the health outcomes of patients switching from originator to generic lamotrigine, an anti-epileptic medicine.

METHODS

A retrospective study using the national health collections and prescription records was conducted comparing patients who switched from originator brand to generic lamotrigine with patients who remained on the originator brand. Primary outcome measures included switch behaviour, changes in utilisation of healthcare services at emergency departments, hospitalisations and use of specialist services, and mortality.

RESULTS

Approximately one-quarter of all patients using the originator brand of lamotrigine switched to generic lamotrigine, half of whom made the switch within 60 days of the policy implementation. Multiple switches (three or more) between generic and brand products were evident for around 10% of switchers. Switch-back rates of 3% were apparent within 30 days post-switch. No difference in heath outcome measures was associated with switching from originator lamotrigine to a generic equivalent and hence no increased costs could be found for switchers.

CONCLUSIONS

Switching from brand to generic lamotrigine is largely devoid of adverse health outcomes; however, creating an incentive to ensure a greater proportion of patients switch to generic lamotrigine is required to achieve maximal financial savings from a policy of generic reference pricing.