Halonal is a phenobarbital inductor of the monooxygenase system.

Experiments on rats demonstrated induction of the hepatic monooxygenase system with halonal. The effects of halonal and phenobarbital on the contents of cytochrome P-450 and its isoform P-450b+e and on the rate of substrate metabolism were similar. This suggests that enzyme-inducing activity of halonal is determined by the effect of its major metabolite. It cannot be excluded that halonal molecules possess intrinsic enzyme-inducing activity.