Suivi d'une cohorte de patients après substitution de la phénytoïne pour de la phénytoïne sodique dans un centre de lutte contre l'épilepsie

In March 2012, the French Health Products Safety Agency interrupted the commercialization of di-hydan (phenytoin). It was replaced by diphantoïne (phenytoin sodium) and prescribers were informed that posology was equivalent for both products. We conducted a retrospective study of phenytoinemia and clinical effects comparatively for these two drugs in a population of adult patients with epilepsy admitted in La TEPPE. Forty-four patients were included. Mean age was 47.6 years. Phenytoinemia significantly decreased after substitution (17.14 mg/L with di-hydan versus 12.17 mg/L with diphantoïne, P < 8 10−6). Moreover an increase in post substitution posology of diphantoïne was noticed (264.77 mg/L with di-hydan versus 274.73 mg/L with diphantoïne), although not significant (P = 0.11). Increase of seizures was non-significant (P = 0.09). The decrease of phenytoinemia was probably due to the difference of composition between the drugs: a 100 mg di-hydan tablet contains 100 mg of phenytoin whereas a 100 mg diphantoïne tablet contains 92 mg. The specific non-linear kinetics of phenytoin reinforces this difference. A prospective study could better evaluate the risk of substituting di-hydan with diphantoïne.