Quantification of Adverse Drug Reactions Related to Drug Switches in The Netherlands

Interchangeability of generic drugs for subpopulations: Bioequivalence simulation from a nonparametric PK model of gabapentin generic drugs

Patients are often switched between generic formulations of the same drug, but in some cases generic interchangeability is questioned. For generic drugs to be approved, bioequivalence with the innovator drug should be demonstrated, but evidence of bioequivalence is not required in the intended patient population or relative to other approved generics.

AIM

We aim to identify pathophysiological pharmacokinetic subpopulations for whom there is a difference in comparative bioavailability compared to a healthy population.

METHODS

We used simulated exposures from a nonparametric model of multiple generics and the originator gabapentin. Exposure was simulated for virtual populations with pharmacokinetic characteristics beyond those of healthy subjects with regard to rate of absorption, volume of distribution and reduced renal function. Virtual parallel design bioequivalence studies were performed using a random sample of 24 simulated subjects, with standard acceptance criteria.

RESULTS

Results indicated increased pharmacokinetic variability for patient populations with a lower rate of absorption or a reduced renal function, but no change in the average comparable bioavailability ratio. This increased variability results in a reduced likelihood of demonstrating bioequivalence. Observations were similar for comparisons between all different formulations, as well as between subjects who received the identical formulation in a repeated fashion. No relevant effect was observed for simulations with increased volume of distribution.

CONCLUSION

Our simulations indicate that the reduced likelihood of demonstrating bioequivalence for subjects with altered pharmacokinetics is not influenced by a formulation switch, nor does the average comparable bioavailability ratio change, therefore these results support generic interchangeability and current approval requirements for generics.

Using death scene and toxicology evidence to define involvement of heroin, pharmaceutical morphine, illicitly manufactured fentanyl and pharmaceutical fentanyl in opioid overdose deaths, 38 states and the District of Columbia, January 2018-December 2019

BACKGROUND AND AIMS

Tracking specific drugs contributing to drug overdose deaths is limited when relying on death certificate (DC) data alone. This study aimed to determine whether integrating DC data with medical examiner/coroner reports, including postmortem toxicology and death investigation findings, would enhance identification of (1) heroin and pharmaceutical morphine involvement in overdose deaths and (2) fentanyl source (illicitly manufactured versus pharmaceutical).

DESIGN

Retrospective analysis of heroin, pharmaceutical morphine, illicitly manufactured fentanyl (IMF) and pharmaceutical fentanyl involvement in fatal overdoses. DC and toxicology data were compared with enhanced definitions integrating overdose scene, witness and toxicology evidence.

SETTING

United States: 38 states and the District of Columbia, participating in Centers for Disease Control and Prevention (CDC)-funded opioid overdose death surveillance.

CASES

Opioid overdose decedents from funded jurisdictions; deaths during 1 January 2018-31 December 2019.

MEASUREMENTS

Using medical examiner/coroner report data, deaths with 6-acetylmorphine and/or morphine detected by postmortem toxicology were defined as confirmed, probable or suspected heroin deaths, or probable pharmaceutical morphine deaths. Fentanyl was defined as probable or suspected IMF or probable pharmaceutical fentanyl.

FINDINGS

The enhanced definition defined 18 393 deaths as confirmed, probable, or suspected heroin deaths (including 2678 with morphine listed as cause of death on the DC) and 404 as probable pharmaceutical morphine deaths. Among deaths with fentanyl detected, 89.3% were defined as probable or suspected IMF and 1.0% as probable pharmaceutical fentanyl. Fentanyl source could not be determined for 9.7% of deaths.

CONCLUSIONS

Integrating drug overdose scene, witness and toxicology findings can improve identification of specific drugs contributing to overdose deaths and enhance overdose intervention targeting.

Pharmacokinetics and Generic Drug Switching: A Regulator's View

There appears to be a mismatch between the assumed therapeutic equivalence of generic drugs, their interchangeability, and reported clinical discomfort following generic drug use and drug switches. In this article, we describe why we are of the opinion that the current regulatory approach to the evaluation of generic drugs based on average bioequivalence is sufficient to expect therapeutic equivalence in the clinical setting. This has often been debated, specifically as adverse drug reactions related to generic drug switches are regularly reported. We agree that clinical discomfort during a bioequivalent drug switch may indeed be caused by different exposures to the active substance. However, this difference in exposure is not a result of the characteristics or quality of generic drugs; it is caused by the pharmacokinetic within-subject variability of the active substance, i.e., the variability on the bioavailability of the active substance, when comparing two occasions of administration of the same drug product, to the same patient. Therefore, reported clinical discomfort following generic drug use and drug switches does not warrant a change in the regulatory approach to the evaluation of the bioequivalence of generic drugs. Switching from a brand-name drug to currently approved generic drugs, or between different generic drugs, will in principle result in comparable exposure, within boundaries determined by the within-subject variability of the pharmacokinetics of the active substance involved.