Cytochrome P450(CYP)3A4 is one of the CYP enzymes catalyzing oxidative metabolism, and involved in the metabolism of many drugs. Among benzodiazepines, alprazolam, triazolam, brotizolam and midazolam are mainly metabolished by CYP3A4, and quazepam, diazepam and flunitrazepam are partly metabolised by this enzyme. Azole antifungals, macrolide antibiotics, calcium antagonists and grapefruit juice inhibit CYP3A4 activity, while antiepileptics and rifampicin induce the activity. The drugs affecting CYP3A4 activity inhibit or induce the metabolism of the benzodiazepines metabolised by this enzyme, and induce side effects or reduce therapeutic effects of these drugs. Therefore, the combination of the two groups of drugs should be avoided, and if it is unavoidable the dose of benzodiazepines should be adjusted.