PHENOBARBITAL

Studies in man and animals clearly show that the barbiturates are potent liver enzyme inducers. The most commonly used barbiturate is phenobarbital, which is known to induce CYP3A4, amongst other isoenzymes. Most of the interaction information concerns phenobarbital, but all barbiturates would be expected to share its inter- actions to a greater or lesser extent. Note that primidone is metabolised to phenobarbital, and so would therefore also be expected to share many of its interactions.