Lofexidine, an α2-Receptor Agonist for Opioid Detoxification

Abstract

Objective: To review the pharmacology, toxicology, pharmacokinetics, efficacy, adverse effects, drug interactions, and dosage guidelines for lofexidine, an α2-agonist, for opioid detoxification. Data Sources: Primary literature was identified through a MEDLINE search (1950–September 2009), EMBASE (1988–Juty 2009), International Pharmaceutical Abstracts (1970–September 2009), and the Cochrane Library (1996–September 2009) using the key words lofexidine and opioid withdrawal. Abstracts were included in the absence of published results of studies. Study Selection and Data Extraction: Studies published in English-language literature reporting on animal and human pharmacology, toxicology, and pharmacokinetics were included in addition to clinical trials using lofexidine for opioid detoxification in comparison to placebo or active controls. Data Synthesis: Lofexidine is an α2-agonist structurally related to clonidine. It is not an effective antihypertensive agent; however, it decreases the sympathetic outflow responsible for many opioid withdrawal symptoms. Nine clinical studies were reviewed representing 354 patients receiving lofexidine including a recent Phase 3 clinical trial. Eight studies involved comparisons of lofexidine to an opioid receptor agonist or clonidine for opioid detoxification. In these trials, lofexidine dosing was titrated to a maximum of 1.6–3.2 mg/day in divided doses for a total of 5–18 days. The data suggest that lofexidine has positive efficacy in reducing opioid withdrawal symptoms and is at least as effective as the opioid receptor agonists utilized for detoxification. Not all withdrawal symptoms are alleviated by α2-agonists, with many patients complaining of insomnia and aching. The most common adverse event with lofexidine in the Phase 3 trial was insomnia. Hypotension was also reported; however, the studies comparing clonidine with lofexidine suggest decreased incidence and severity of adverse events with lofexidine. Conclusions: Lofexidine appears to be a promising agent for opioid detoxification. If approved, it would be the first nonopioid agent approved for this indication. Further large-scale controlled studies are needed to identify the safest, most effective dosage regimen required to achieve opioid detoxification.