Naltrexone

Abstract

Naltrexone is a long acting competitive antagonist at opioid receptors which blocks the subjective and objective responses produced by intravenous opioid challenge. It is suitable for oral administration, and has been studied as an adjunct for use in opioid addiction management programmes. In non-comparative clinical trials involving detoxified patients, oral naltrexone reduced heroin craving and between 23 and 62% of patients remained in treatment after 3 to 4 weeks. However, in two studies 32 to 58% of patients who continued in treatment were opioid-free between 6 and 12 months after stopping naltrexone. As might be expected studies involving highly motivated patients have shown this type of patient group to achieve greater treatment success rates during naltrexone therapy, and remain opioid-free longer than other groups of apparently less motivated patients. In addition, when naltrexone is combined with family support, psychotherapy and counselling, patients are more likely to remain opioid-free. Naltrexone produces a low incidence of side effects, with gastrointestinal effects being the most commonly reported symptoms. Thus, despite the overall high attrition rates from trials, in selected patient groups and in combination with appropriate support mechanisms and psychotherapy, naltrexone represents a useful adjunct for the maintenance of abstinence in the detoxified opioid addict.

Extended release naltrexone injection is performed in the majority of opioid dependent patients receiving outpatient induction: A very low dose naltrexone and buprenorphine open label trial

“…Among available interventions, outpatient detoxification has had very low success rates (Kleber, 2007) and though inpatient treatment is accessible to insured patients, the coverage often falls short of providing the 7 to 10 opioid-free days necessary to eliminate physiological dependence (Gonzalez and Brogden, 1988; Kleber, 2007) and avoid precipitated withdrawal with the first dose XR-NTX (Vivitrol®, 2013). These issues may lessen the interest of patients and physicians, and are a barrier to initiating XR-NTX treatment.…”

Opioid Detoxification and Naltrexone Induction Strategies: Recommendations for Clinical Practice

“…Naltrexone and its active metabolite 6-β-naltrexol are competitive antagonists at μ- and κ-opioid receptors and, to a lesser extent, at δ-opioid receptors (6). When taken regularly in sufficient doses, naltrexone blocks the reinforcing effects of opioids, is not associated with tolerance, withdrawal, or abuse potential, and decreases the likelihood of relapse to opioid use (7–9). Additionally, because it is not a controlled substance, it can be prescribed flexibly in a wide range of treatment settings (10–15).…”

Sulfation of opioid drugs by human cytosolic sulfotransferases: Metabolic labeling study and enzymatic analysis

“…The tissue distributions of those enzymes are in line with stronger sulfating activity toward hydromorphone in small intestine and stronger sulfating activity toward oxymorphone, butorphanol, nalbuphine, and naltrexone in liver, among the four human organs tested. It is noteworthy that these opioid drugs tested may be administered through various routes including oral, intravenous, and intramuscular (Fudala and Johnson, 2006; Gonzalez and Brogden, 1988; Krenzischek et al, 2008; Prommer, 2005; Sarhill et al, 2001; Smith, 2011). It is possible that the administration route may influence the metabolic pattern of opioid drugs.…”