Phenobarbital is a barbiturate.
You should not use this medicine if you have had an allergic reaction to phenobarbital or other barbiturate drugs, such as pentobarbital, amobarbital, or secobarbital. You should not use if you are pregnant or breastfeeding, if you have porphyria, or if you have severe lung or liver disease. It is best to take this medicine on an empty stomach. Store at room temperature, away from heat, direct light, and moisture. Keep all medicine away from children.