Bioavailability of phenytoin. A comparison of two preparations

Abstract

Plasma phenytoin levels were measured in 60 patients under steady-state conditions for a period of six weeks. During the trial, the preparation of phenytoin was changed from Phenytoin BP (Regent) to Epanutin Infatabs. A significant increase in plasma phenytoin levels following the change of tablet was matched by a decrease in the number of seizures.

Recommendations of the Italian League Against Epilepsy Working Group on Generic Products of Antiepileptic Drugs

“…In contrast to the lack of controlled studies, there are several published reports of loss or worsening of seizure control (Koch and Allen, 1978;Pedersen and Dam, 1985;McDonald, 1987;Wyllie et al, 1987;Sachdeo and Belendiuk, 1987;Hartley et al, 1990;Welty et al, 1992;Jain, 1993;Meyer and Straughn, 1993;Guberman and Corman, 2000;Burkhardt et al, 2004;Wilner, 2004;Haskins et al, 2005) or appearance of adverse events (Finestone and Williams, 1985;Gilman et al, 1993;Brown et al, 1998;Guberman and Corman, 2000;Wilner, 2004;Haskins et al, 2005) following substitution of a brand AED with a generic. Many of these reports date back several years, when regulatory requirements for the approval of generics were not as stringent as those currently in force in major industrialized countries (Richens, 1997;American Medical Association, 2006) and therefore some products of inadequate quality found their way into the market (Bochner et al, 1972;Sansom et al, 1975;Manson et al, 1975;Stewart et al, 1975;Tammisto et al, 1976;Hodges et al,1986;Mikati et al, 1992;Soryal and Richens, 1992;Meyer et al, 1992;Rosenbaum et al, 1994). In 1988, the U.S. Food and Drug Administration (FDA) set up a special committee to investigate these issues.…”

“…Many of these reports date back several years, when regulatory requirements for the approval of generics were not as stringent as those currently in force in major industrialized countries (Richens, 1997;American Medical Association, 2006) and therefore some products of inadequate quality found their way into the market (Bochner et al, 1972;Sansom et al, 1975;Manson et al, 1975;Stewart et al, 1975;Tammisto et al, 1976;Hodges et al,1986;Mikati et al, 1992;Soryal and Richens, 1992;Meyer et al, 1992;Rosenbaum et al, 1994). In 1988, the U.S. Food and Drug Administration (FDA) set up a special committee to investigate these issues.…”

Phenytoin: Basic and clinical pharmacology

“…The occurance of peripheral neuropathy has a higher incidence in the age group [40][41][42][43][44][45][46][47][48][49][50] years and is better correlated with the duration of the therapy than dosage. Clinical signs of peripheral neuropathy are quite minimal, consisting of absent knee and ankle reflexes without indications of weakness.,19 The sensory deficit, particularly to vibration perception, is relatively mild.…”

A comparison of the bioavailability of two brands of phenytoin.

“…Although the bioavailability of different brands of phenytoin available in the United Kingdom has not been widely studied, there have been some suggestions (Richens, 1976;Stewart et al, 1975) that different preparations could produce different steady-state plasma concentrations. In this study tablets obtained from Boots and capsules from ParkeDavis have been compared.…”