Controlled-release morphine tablets. A double-blind trial in dental surgery patients.

We report a randomized double-blind comparison of controlled-release morphine tablets (MST-1; 2 x 10 mg) and oral morphine sulphate in solution (20 mg) in 28 patients (20 females) who had undergone removal of impacted lower third molars or a dental clearance under general anaesthetic. The response in both groups was very poor: eight of 15 patients in MST-1 group and six of 13 patients in the standard group required "rescue" analgesics and were withdrawn from the study within the first 2h. No threshold plasma concentration of morphine corresponding to a particular analgesic effect was apparent. MST-1 produced significantly greater plasma concentrations at 8h compared with the standard preparation. Controlled-release morphine, or any oral formulation of morphine, may not be suitable for the treatment of acute pain after operation.