Table 3.

Opioid antagonist

Pharmacological agents	Study design Sample characteristics	Outcomes	Results	Main limitations	References
Naltrexone (50 mg day−1)	12-week open clinical trial 20 amphetamine-dependent patients	Primary outcomesAdverse events Compliance to medication (assessed by by the presence of naltrexone's metabolite, 6-beta-naltrexol in urine) Tolerability: patient's self-report and observed adverse effects along with plasma markers of hepatotoxicity.	No serious adverse events Moderate rates of compliance Decrease of amphetamine use	Small sample size Open label design High attrition rate	[112]
Naltrexone (50 mg day−1)	Randomized double-blind placebo-controlled design. 20 abstinent amphetamine-dependent patients DSM-IV criteria for ADHD Drug-free from amphetamine for a minimum of 30 days Residence in Stockholm county.	Primary outcomeDifference in subjective measures of amphetamine effects (use of a Visual Analog Scale). Secondary outcomesEffects of naltrexone on physiological and biochemical responses to amphetamine, as measured by changes in blood pressure, heart rate, skin conductance and cortisol.	Significant decrease of the subjective effects produced by dexamphetamine Reduction in dexamphetamine craving No difference between the groups on the physiological measures.	Study was conducted in a small homogenous population of male amphetamine-dependent individuals. Small dexamphetamine dose	[113]
Naltrexone (50 mg day−1)	12-week double-blind, placebo-controlled clinical trial 80 treatment-seeking amphetamine-dependent individuals Amphetamine use on at least 12 days in the past 12 weeks.	Primary outcomeNumber of negative amphetamine urine samples during 12 weeks of treatment (of a total of 24 samples) Secondary outcomesTreatment retention Medication adherence Craving Pill count Adverse events	Decrease in amphetamine use High treatment retention and medication adherence Significant reduction in craving No serious adverse events	Sample selected for the study did not achieve an equal representation of the genders. Treatment outcomes assessed for 3 months Long-term effects in this population are unknown.	[114]