A man who has abused oxazepam (Sobril) 90 mg per day for 15 to 17 years is also being treated with

Fråga: A man who has abused oxazepam (Sobril) 90 mg per day for 15 to 17 years is also being treated with cimetidine (Tagamet) 1500 mg daily for several years. The indication for cimetidine treatment is apparently gastritis though it has not been possible to prove if this is the case. The doctor wishes to stop the cimetidine treatment though the questioner is uncertain what scheme to follow. The reason for this uncertainty is a suspicion that there may be a metabolic interaction between oxazepam and cimetidine.

Sammanfattning: On theoretical grounds, there are no reasons to suspect an interaction between cimetidine and oxazepam. We have not found any case reports in the literature on interactions between these two compounds. Hence, the working hypothesis must be that the two drugs act independent of one another.

Svar: Cimetidine is well-known for causing an interaction with several different compounds both at the renal excretion level as well as at the level of hepatic metabolism (1). However, oxazepam is being eliminated through a conjugation reaction, and the conjugate, which is pharmacologically inactive, is being renally excreted (1). Because cimetidine is mainly affecting cytochrome P450-system, it is unlikely that an interaction between these two compounds would take place. In the present case this means that tapering can probably proceed without any special precautions being made with respect to the oxazepam therapy. It should, however, be pointed out that the elimination of other bensodiazepines such as diazepam and chlordiazepoxide are being affected by cimetidine treatment.