Generic and therapeutic substitutions: are they always ethical in their own terms?

Prescription switching: Rationales and risks

BACKGROUND

Therapeutic drug switching is commonplace across a broad range of indications and, within a drug class, is often facilitated by the availability of multiple drugs considered equivalent. Such treatment changes are often considered to improve outcomes via better efficacy or fewer side effects, or to be more cost-effective. Drug switching can be both appropriate and beneficial for several reasons; however, switching can also be associated with negative consequences.

AIM

To consider the impact of switching in two situations: the use of statins as a well-studied example of within-class drug switching, and gonadotropin-releasing hormone (GnRH)-targeting drug switching as an example of cross-class switching.

RESULTS

With the example of statins, within-class switching may be justified to reduce side effects, although the decision to switch is often also driven by the lower cost of generic formulations. With the example of GnRH agonists/antagonists, switching often occurs without the realisation that these drugs belong to different classes, with potential clinical implications.

CONCLUSION

Lessons emerging from these examples will help inform healthcare practitioners who may be considering switching drug prescriptions.

Deficiencies of the FDA in evaluating generic formulations: addressing narrow therapeutic index drugs

Generic drugs represent a significant portion of the medical arsenal in treating disease. As copies of originator drugs, these drugs have been permitted abbreviated approval under the Hatch-Waxman Act. Yet with the current cost focus upon generic formulations, potential safety issues with generics have arisen. Although there is an established criterion of "bioequivalence" that generic formulations must demonstrate, narrow-therapeutic index drugs for sensitive clinical circumstances such as epilepsy, antiplatelet therapies, and mental health treatments may require different regulatory treatment than other generic drugs. Further, in these circumstances, differences in generic formulations may lead to adverse clinical outcomes due to less stringent bioequivalence tolerances. Yet there is no mandate for comparison between different generic formulations. Countries outside the United States advocate for narrowing tolerance ranges for these high risk health situations and the drugs for their treatment. We argue in this paper that additional patient safety matters must be taken into account for narrow therapeutic disease drugs, and regulatory bodies should emphasize greater tightness in bioequivalence before these narrow-therapeutic drug generic formulations are approved.

The differences between the branded and generic medicines using solid dosage forms: In-vitro dissolution testing

INTRODUCTION

Dissolution is the amount of substance that goes into solution per unit time under standardised conditions of liquid/solid interface, solvent composition and temperature. Dissolution is one of the most important tools to predict the in-vivo bioavailability and in some cases to determine bioequivalence and assure interchangeability.

AIM

To compare the differences in dissolution behaviour of solid dosage forms between innovators (reference products) and their generic counterparts (tested products).

METHODS

Four replicates for each batch of 37 tested medicines was carried out using A PT-DT70 dissolution tester from Pharma Test. A total of 13 branded medicines and 24 generic counterparts were obtained locally and internationally to detect any differences in their dissolution behaviour. They were tested according to the British Pharmacopeia, European Pharmacopeia and the US Pharmacopeia with the rate of dissolution determined by ultra-violet Spectrophotometery.

RESULTS

Most tested medicines complied with the pharmacopoeial specifications and achieved 85% dissolution in 60 min. However, some generic medicines showed significant differences in dissolution rate at 60 and 120 min. Many generic medicines showed a slower dissolution rate than their branded counterparts such as the generic forms of omeprazole 20 mg. Some showed an incomplete dissolution such as the generic form of nifedipine 10 mg. Other generics showed faster dissolution rate than their branded counterpart such as the generic forms of meloxicam 15 mg. Moreover, some generics from different batches of the same manufacturer showed significant differences in their dissolution rate such as the generic forms of meloxicam 7.5 mg. Nevertheless, some generic medicines violated the EMA and the FDA guidelines for industry when they failed to achieve 85% dissolution at 60 min, such as the generic form of diclofenac sodium 50 mg.

CONCLUSION

Most medicines in this study complied with the pharmacopeial limits. However, some generics dissolved differently than their branded counterparts. This can clearly question the interchangeability between the branded and its generic counterpart or even among generics.