Efficacy of lofexidine for mitigating opioid withdrawal symptoms: results from two randomized, placebo-controlled trials.

Fear of opioid withdrawal syndrome (OWS) often dissuades opioid discontinuation. Lofexidine is an FDA-approved, alpha-adrenergic receptor agonist for treatment of OWS. Pivotal trial results from the per-protocol statistical analyses have been published. However, the FDA prescribing information presents these efficacy results using a different, standardized statistical approach that does not transform data or impute missing values. This analysis is easier to interpret and allows comparison across studies. This reanalysis is presented here. Studies were double-blind, placebo-controlled for 7 days in Study 1 and 5 days in Study 2. Opioid-dependent adults received placebo or lofexidine; efficacy was assessed using the Short Opioid Withdrawal Scale of Gossop (SOWS-G) daily. Study 1 ( = 602) mean SOWS-G scores were 6.1 (SE: 0.35), 6.5 (SE: 0.34), and 8.8 (SE: 0.47) over Days 1-7 for lofexidine 2.88 mg/day, 2.16 mg/day, and placebo, respectively (for 2.88,  < .0001; for 2.16 mg,  < .0001). Study 2 ( = 264) mean SOWS-G scores were 7.0 (SE: 0.44) and 8.9 (SE: 0.48) over Days 1-5 for lofexidine 2.16 mg/day and placebo, respectively ( = .0037). Median time to treatment discontinuation was approximately 2 days later with lofexidine treatment than with placebo and significantly more lofexidine-treated subjects completed the studies. Hypotension and bradycardia were more common with lofexidine. More placebo subjects withdrew prematurely for lack of efficacy. This simplified analysis confirmed previous per-protocol results, that lofexidine better reduces OWS severity and increases retention compared with placebo in opioid-dependent adults. These results are robust and comparable across studies using various methods of analysis. : Study 1, NCT01863186; Study 2 NCT00235729. URL: https://clinicaltrials.gov/.