Cimetidine-benzodiazepine drug interaction.

The effect of cimetidine on the metabolism of benzodiazepines is discussed. Studies of cimetidine's inhibition of benzodiazepine metabolism by liver microsomal enzyme pathways are described. Cimetidine is known to have this effect on the metabolism of diazepam and chlordiazepoxide, and because chlorazepate and prazepam are similarly metabolized, cimetidine is likely to have the same effect on the metabolism of these drugs. Oxazepam and lorazepam are two benzodiazepines not metabolized by liver microsomal enzymes, but are thought to be glucuronidated in peripheral tissue by glucuronyl transferase. Cimetidine has been shown not to alter the pharmacokinetics of lorazepam or oxazepam when administered concurrently with either of these benzodiazepines. When it is necessary to treat a patients receiving cimetidine with a benzodiazepine, oxazepam or lorazepam may be the drug of choice.