Opioid antagonists, partial agonists, and agonists/antagonists: The role of office-based detoxification

Abstract

Background:: The opioid receptor antagonists naloxone and naltrexone are competitive antagonists at the mu, kappa, and sigma receptors with a higher affinity for the mu receptor and lacking any mu receptor efficacy. Buprenorphine is classified as a partial agonist. It has a high affinity, but low efficacy at the mu receptor where it yields a partial effect upon binding. It also, however, possesses kappa receptor antagonist activity making it useful not only as an analgesic, but also in opioid abuse deterrence, detoxification, and maintenance therapies. Naloxone is added to sublingual buprenorphine (Suboxone®) to prevent the intravenous abuse of buprenorphine. The same product (sublingual buprenorphine) when used alone (i.e. without naloxone) is marketed as Subutex®. Objective: To evaluate and update the available evidence regarding the use of agonist/antagonists to provide office-based opioid treatment for addiction. Methods: A review using databases of EMBASE and MEDLINE (1992 to December 2007). These included systematic reviews, narrative reviews, prospective and retrospective studies, as well as cross-references from other articles. Outcome Measures: The primary outcome measure was treatment retention. Other outcome measures included opioid-free urine drug testing, opioid craving, intensity of withdrawal, pain reduction, adverse effects, addiction severity index, and HIV risk behavior. Results: The results found 17 studies, 1 systematic review, 12 RCTs, and 4 observational series, which document the efficacy and safety of buprenorphine alone and in combination with naloxone in detoxifying and maintaining abstinence from illicit drugs in patients with opioid addiction. Conclusion: Based on the present evaluation, it appears that opioid antagonists, partial agonists, and antagonists are useful in office-based opioid treatment for addiction.