PHENOBARBITAL AND PHENYTOIN
The concurrent use of phenytoin and phenobarbital is normally uneventful. However, changes in phenytoin levels (often decreases but sometimes increases) can occur if phenobarbital is added, but seizure control is not usually affected by this pharmacokinetic interaction. Phenytoin toxicity following barbiturate withdrawal has been seen. Increased phenobarbital levels and possibly toxicity may occur as a result of the addition of phenytoin to phenobarbital. Similar interaction may occur with primidone and fosphenytoin.
Given the unpredictable outcome of concurrent use it would seem prudent to monitor levels if one drug is added to the other or if a dose is changed. Indicators of phenobarbital toxicity include drowsiness, ataxia or dysarthria.
Given the unpredictable outcome of concurrent use it would seem prudent to monitor levels if one drug is added to the other or if a dose is changed. Indicators of phenobarbital toxicity include drowsiness, ataxia or dysarthria.