CHLORAMPHENICOL AND PHENOBARBITAL

Studies in children show that phenobarbital can markedly reduce chloramphenicol levels. An isolated case describes markedly increased phenobarbital levels in an adult caused by the use of chloramphenicol. Note that primidone is metabolised to phenobarbital and therefore may interact similarly.
Concurrent use should be well monitored to ensure that chloramphenicol serum levels are adequate. Make appropriate dosage adjustments as necessary. The case of raised phenobarbital levels is of uncertain importance.