Efficacy and Safety of Glaucoma Patients' Switch from a 2% Dorzolamide/0.5% Timolol Fixed-Combination Brand-Name Drug to Its Generic Counterpart

Topical carbonic anhydrase inhibitors and glaucoma in 2021: where do we stand?

Carbonic anhydrase inhibitors (CAIs) have been used for many decades in the treatment of glaucoma. Systemic CAIs were an early treatment option to lower intraocular pressure by reducing aqueous humour production; however, frequent side effects including polyuria and paresthesia contributed to the eventual development of topical CAIs. As topical drug development evolved over time, prostaglandin analogues and beta-blockers have become the gold standard of glaucoma therapies. Although prescribed less often than other classes of topical glaucoma therapies, topical CAIs continue to be used in combination therapies with beta-blockers and alpha agonists. Topical CAIs have also been demonstrated to alter biomarkers of ocular haemodynamics, which have relevance in glaucoma. The purpose of this review is to review and summarise the current state of topical CAI prescribing trends, known efficacy and suggested mechanisms and potential influence on ocular haemodynamics for the future of glaucoma management.

Acceptability of generic versus innovator oral medicines: not only a matter of taste

Optimum use of generic products would require equivalence, not only in terms of quality, safety, and efficacy in clinical studies, but also patient acceptability to not jeopardize treatment success because of non-adherence which would de facto limit the potential cost saving anticipated by their use. Although acceptability is a requirement for the authorization of pediatric innovator products, a survey of European Union (EU) regulatory authorities showed that few have a formal process for assessing patient acceptability of generic products during the registration processes. The current International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) focus on unifying guidance for the development and scrutiny of generics but should include acceptability alongside the other factors being considered for harmonization.

North American cost analysis of brand name versus generic drugs for the treatment of glaucoma

Background

According to the World Health Organization, glaucoma is a leading cause of irreversible blindness worldwide. By 2020, 80 million people will be affected by glaucoma in the world, which represents a significant financial burden to society. Glaucoma medications alone make up 38-52% of the total direct cost. The purpose of this research is to conduct a cost-minimization analysis to evaluate brand-name medications versus generic medications for treating glaucoma patients.

Methods

The per-bottle cost (in Canadian dollars) of brand-name drugs for glaucoma was obtained from the wholesaler, McKesson Canada, and, for generic drugs, from the Ontario Drug Benefit (ODB) Formulary. Further, a wastage adjustment fee, a pharmacy mark-up, and an ODB dispensing fee ($CAD) was added to the cost of both brand and generic. Previously published frequencies of medication prescription were utilized to calculate the average annual cost for each class of brand and generic. For each medication class and for mono-, bi-, and tri-drug therapy, the cost differential between brands and generics over a six-year period was computed and analyzed from third-party payer perspective.

Results

In descending order, the average annual government-funded health care system costs were: combination drugs such as Cosopt^® ($748.23) were the most expensive, followed by prostaglandin analogs ($246.36), carbonic anhydrase inhibitors (CAIs) ($45.04), α-agonist ($30.34), β-blockers ($29.29), and cholinergic agonists ($16.51). Brand-name mono-drugs are 34% more expensive compared to generics. Brand-generic percentage cost differential for various medication classes over a six-year period was the highest for prostaglandin analogous (44%), followed by β-blockers (35%), α-agonist (31%), cholinergic agonists (22%), combination drugs (10%), and CAIs (1%).

Conclusion

Brand-name drugs are relatively more expensive than their generic counterparts, with variable cost differentials depending on drug class.

Comparison of Generic-to-Brand Switchback Rates Between Generic and Authorized Generic Drugs

STUDY OBJECTIVE

Generic drugs contain identical active ingredients as their corresponding brand drugs and are pharmaceutically equivalent and bioequivalent, whereas authorized generic drugs (AGs) contain both identical active and inactive ingredients as their corresponding brand drugs but are marketed as generics. This study compares generic-to-brand switchback rates between generic and AGs.

DESIGN

Retrospective cohort study.

DATA SOURCE

Claims and electronic health record data from a regional U.S. health care system.

PATIENTS

The full cohort consisted of 5542 unique patients who received select branded drugs during the 6 months prior to their generic drug market availability (between 1999 and 2014) and then were switched to an AG or generic drug within 30 months of generic drug entry. For these patients, 5929 unique patient-drug combinations (867 with AGs and 5062 with generic drugs) were evaluated.

MEASUREMENTS AND MAIN RESULTS

Ten drugs with AGs and generics marketed between 1999 and 2014 were evaluated. The date of the first generic prescription was considered the index date for each drug, and it marked the beginning of follow-up to evaluate the occurrence of generic-to-brand switchback patterns over the subsequent 30 months. Switchback rates were compared between patients receiving AGs versus those receiving generics using multivariable Cox proportional hazards models, controlling for individual drug effects, age, sex, Charlson Comorbidity Score, pre-index drug use characteristics, and pre-index health care utilization. Among the 5542 unique patients who switched from brand to generic or brand to AG, 264 (4.8%) switched back to the brand drug. Overall switchback rates were similar for AGs compared with generics (hazard ratio [HR] 0.86, 95% confidence interval [CI] 0.65-1.15). The likelihood of switchback was higher for alendronate (HR 1.64, 95% CI 1.20-2.23) and simvastatin (HR 1.81, 95% CI 1.30-2.54) and lower for amlodipine (HR 0.27, 95% CI 0.17-0.42) compared with the other drugs evaluated.

CONCLUSION

Overall switchback rates were similar between AG and generic drug users, indirectly supporting similar efficacy and tolerability profiles for brand and generic drugs. Reasons for differences in switchback rates among specific products need to be explored further.

Pediatric Glaucoma: Pharmacotherapeutic Options

Childhood glaucoma is a major therapeutic challenge for pediatric ophthalmologists and glaucoma specialists worldwide. Management depends on the etiology and age at presentation. A variety of drugs are available for the control of intraocular pressure in children; however, none of these drugs have been licensed by the regulatory agencies for use in children. Furthermore, evidence gained from randomized controlled trials in the pediatric population is sparse, and little is known regarding the use of newer anti-glaucoma preparations. This evidence-based review aims to discuss the available pharmacotherapeutic options for glaucoma in children. Topical adrenoceptor blockers, topical and systemic carbonic anhydrase inhibitors, prostaglandin (PG) analogs, adrenoceptor agonists, parasympathomimetics, and combined preparations are available for use in children, but usually as an off-label indication. Therefore, it is important to recognize that serious side effects have been reported, even with topical drops, and measures to reduce systemic absorption should be taken. Most drugs have been shown to have comparable ocular hypotensive effects, with the lowest occurrence of systemic side effects with PG analogs. Whereas a newly introduced prostaglandin analog, tafluprost, and some other preservative-free preparations have shown promising results in adult glaucoma patients, no pediatric reports are available as yet. Future studies may describe their role in treating pediatric glaucoma. This review also shares some suggested treatment pathways for primary congenital glaucoma (PCG), juvenile open angle glaucoma (JOAG), developmental glaucoma, aphakic/pseudophakic glaucoma, and uveitic glaucoma.