Phenobarbital interaction with chloramphenicol

Another study eonfirmed that this interaction occurred in 20 neonates, but no statistically significant effect was found in 40 infants. Decreased chloramphenicol levels have been described in a single case report of a child who was also being treated with phenytoin and phenobarbital. The serum chloramphenicol levels were 35.1 micrograms/mL prior to the antiepileptics, 19.1 micrograms/mL after 2 days of phenytoin and 13.2 micrograms/mL a month after the addition of phenobarbital. For more information on the interaetion of ehloramphenieol with phenytoin see Phenytoin + Chloramphenieol , p.555. 

Koup JR, Gibaldi M, McNamara P, HilUgoss DM, Colburn WA, Bruck E. Interaction of chloramphenicol with phen3(toin and phenobarbital. Case report. Clin Pharmacol Ther (1978) 24, 571-5. 

This interaction appears to be established. The documentation is limited but what happened is consistent with the recognised enzyme-inducing actions of phenobarbital and the inhibitory actions of chloramphenicol. Concurrent use should be well monitored to ensure that chloramphenicol serum levels are adequate, and that phenobarbital levels do not become too high. Make appropriate dosage adjustments as necessary. 

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