Study rats showed better performance for Allergan’s rapstinel than ketamine.
Standard of care for treatment of opioid addiction involves management of withdrawal symptoms using a less powerful opioid and then medication-assisted treatment (MAT) using methadone, buprenorphine or naltrexone. This approach is less than ideal because these drugs can have dangerous side effects, and relapse before treatment is ended is common because the brain chemistry associated with addiction is maintained.
The pharma industry is seeking non-opioid alternatives. The ketamine-based drug Spravato is one that has received approval from the U.S. Food and Drug Administration (FDA). Ketamine has its own issues, however; it induces a trance-like state and can cause hallucinations.
Allergan is hoping that is failed antidepressant drug rapastinel will offer a better option. Rapastinel binds to the same receptor as ketamine but at a different site, where it confers a milder effect.
Early results of a study in rats are promising. Following induction of opioid dependence in male and female Sprague–Dawley rats, the animals were injected with naloxone, and their withdrawal symptoms measured. Some of the rats were then given ketamine injections twice a day, others were injected with rapastinel every other day and saline injections were administered to a control group. On the ninth day, the rats were again given a naloxone injection and their withdrawal signs measured. It was found that the rats treated with rapastinel exhibited significantly fewer withdrawal signs than those given ketamine.
The fact that the rats treated with rapastinel appeared to experience safer withdrawal without serious side effects suggests that the drug may lead to lower risks for opioid relapse during treatment. Further studies are planned in rodents only, but clinical trials in humans could take place if the results continue to be positive.