[Primidone kinetics and analysis of its interactions with the major antiepileptic drugs]

In 5 volunteers, after single oral administration of 10 mg/Kg of primidone (PRM) plasmatic concentration of the drug has been monitored during 24 hours. PRM plasma half life was found longer than in previous reports. It was however confirmed that its metabolite phenobarbital (PB) is not present in the blood for at least 48 hours. Moreover 166 patients under long term PRM treatment were investigated as to the influence of phenytoin (DPH) and carbamazepine (CBZ) on the PB serum levels. It was found that patients in therapy with PRM + DPH showed a better relationship between PRM oral dose and PB plasma level and also between oral dose and plasma level of DPH than in patients in monotherapy with PRM or DPH, whereas these effects were not evident in patients taking PB + DPH.