The influence of phenobarbital on the pharmacokinetics of propranolol in pregnancy.

In 7 pregnant hypertensive patients the elimination half-life of propranolol was enhanced to 6.1 +/- 1.2 h in comparison to 4.4 +/- 0.4 in 9 nonpregnant females. In 8 out of 11 pregnant hypertensive patients in the 29th week of gestation treated with 90 mg phenobarbital daily for at least 7 days before starting propranolol therapy, the half-life of propranolol was 3.1 +/- 0.4 h only. This significant difference between pregnant women with and without phenobarbital pretreatment is discussed as enzyme induction by phenobarbital.