Novel depots of buprenorphine have a long-acting effect for the management of physical dependence to morphine

Buprenorphine is a promising new pharmacotherapy for the management of physical dependence to opioids. The aim of the study was to evaluate the duration of action of several novel depots of buprenorphine in the treatment of physical dependence to morphine in mice. Following intramuscular injection, the duration of action of several novel oil‐based depots of buprenorphine base in morphine‐dependent mice were evaluated. The traditional dosage form of buprenorphine hydrochloride in saline was used as control. We found that the depot of buprenorphine base in sesame oil produced a dose‐related long‐lasting effect. On an equimolar basis of 6 μmol kg−1, its effect was 5.7‐fold longer than that of buprenorphine hydrochloride in saline. When prepared in several other oleaginous vehicles (castor oil, cottonseed oil, peanut oil and soybean oil), buprenorphine base also produced a long‐lasting effect, which was similar to buprenorphine base in sesame oil. In conclusion, buprenorphine base, when prepared in oleaginous vehicles and injected intramuscularly in mice, produced a long‐lasting effect on physical dependence to morphine.