Drug Interactions between chloramphenicol and fosphenytoin

GENERALLY AVOID: Chloramphenicol often markedly increases serum phenytoin levels. Toxicity has been reported. Also, phenytoin has been reported both to increase and to decrease serum chloramphenicol levels. Significant systemic absorption of otic or ophthalmic chloramphenicol products is unlikely. However, the clinician should be aware of the possibility of a drug interaction. Similar effects may occur with other hydantoins.

MANAGEMENT: This combination usually should be avoided if possible. Patients should be closely observed for signs of hydantoin toxicity if these drugs must be given concurrently and serum phenytoin concentrations should be monitored. Patients should be advised to notify their physician if they experience symptoms of toxicity, including drowsiness, visual disturbances, change in mental status, seizures, nausea, or ataxia. The hydantoin dose may need to be decreased.