Hypersensitivity to barbiturates or any part of the formulation; ; background of manifest or latent porphyria butabarbital will decrease the extent or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. butabarbital will reduce the extent or result of levoketoconazole by influencing hepatic/intestinal enzyme CYP3A4 metabolism. Slight/Importance Unfamiliar... https://philj197vcj4.wikicorrespondence.com/user