Interactions
Other medications and dietary supplements, such as alcohol, barbiturates, benzodiazepines, cimetidine, MAO inhibitors, and warfarin, may interact with phenobarbital.
Alcohol and other drugs that depress the central nervous system shouldn't be combined with phenobarbital. These substances increase the likelihood of respiratory depression and potentiate the sedative effects of phenobarbital.
The blood concentrations of phenobarbital can rise when taking cimetidine. This could intensify phenobarbital's sedative effects and raise the possibility of negative side effects.
Phenobarbital and MAO inhibitors can interact, raising the possibility of adverse effects.
Blood thinner warfarin (Coumadin) and phenobarbital may interact. Warfarin levels in the blood can rise due to phenobarbital, which could lead to an increased risk of bleeding.