Generic drug products in paediatrics: Where are the data?

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.

Pediatric Oral formulations: Why don't our kids have the medicines they need?

Medication use in children represents between 15-20% of total drug sales. More than 50% of children receive at least one prescription medication a year. Despite this, few drugs have a pediatric formulation available. Furthermore, 80% of pediatric prescriptions are considered off-label. Off-label use is defined as the use of products that differ in dose, indication or route from the one established in the summary of product characteristics. ^[1] Off-label use is associated with an increased risk of adverse drug reactions including therapeutic failure. The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have made changes to regulations to incentivize the development of pediatric formulations. Novel pediatric formulations can ease drug administration, reducing medication errors, increasing dosing acceptability, medication adherence and improve safety. Two routes for pediatric drug approval are available, the traditional requiring clinical trials, and the formulation bridging path where these formulations need to demonstrate equivalence with the existing adult formulations. New formulations seeking regulatory approval require bioequivalence studies , but the regulatory framework which states bioequivalence data is obtained from adults and then extrapolated to children may be disregarding important physiological differences between these two populations of patients. It is important to ensure that drugs for children have been appropriately studied and are properly manufactured for them. Adequately designed studies will provide data that will improve our understanding of how drug disposition differs between adults and children and will pave the way for children to get the best possible treatment.

Treatment optimization of maintenance immunosuppressive agents in pediatric renal transplant recipients

Introduction: Graft survival in pediatric kidney transplant patients has increased significantly within the last three decades, correlating with the discovery and utilization of new immunosuppressants as well as improvements in patient care. Despite these developments in graft survival for patients, there is still improvement needed, particularly in long-term care in pediatric patients receiving grafts from deceased donor patients. Maintenance immunosuppressive therapies have narrow therapeutic indices and are associated with high inter-individual and intra-individual variability.Areas covered: In this review, we examine the impact of pharmacokinetic variability on renal transplantation and its association with age, genetic polymorphisms, drug-drug interactions, drug-disease interactions, renal insufficiency, route of administration, and branded versus generic drug formulation. Pharmacodynamics are outlined in terms of the mechanism of action for each immunosuppressant, potential adverse effects, and the utility of pharmacodynamic biomarkers.Expert opinion: Acquiring abetter quantitative understanding of immunosuppressant pharmacokinetics and pharmacodynamic components should help clinicians implement treatment regimens to maintain the balance between therapeutic efficacy and drug-related toxicity.