Foy A, Sadler C, Taylor A. An open trial of naltrexone for opiate dependence. Drug Alcohol Rev 1998 17:167-174
This pilot study was performed on heroin addict volunteers in order to determine the safety and acceptability of naltrexone treatment in preparation for a larger controlled trial. The drug is still unregistered in Australia but is likely to come on the market later this year.
There were 43 patients (29 male, 14 female) prescribed naltrexone 50mg daily for six months following detoxification lasting from 5 to 10 days using clonidine. Of 32 who could be contacted at one year, 8 had ceased heroin use for virtually the whole period. A further 2 patients had patterns of remission and relapse which were confirmed by clear urine tests specific for morphine (heroin metabolite) for at least one full month.
Only two patients (5%) took naltrexone for the full six months yet retention was reported at 34%. By ten weeks, more than half the patients had stopped taking naltrexone and had dropped out of treatment.
Three patients ceased the drug due to side effects in the first two weeks. One had a seizure and two had symptoms associated with depression. There were 20 patients (47%) who developed headache in the first 3 days, but only one, with associated depression, had to stop the treatment.
There were weekly visits to the clinic with dosing apparently unsupervised.
Comment: This study results are consistent with the literature on the subject which shows little if any benefit in unselected addicts prescribed oral naltrexone. Rather than justifying a larger trial in such patients, more might be gained by examining groups which have already shown promising results such as professionals, prisoners and 'probationers' (not to mention alcoholics).
Compliance in methadone, buprenorphine and prescribed heroin trials is much higher than in this report. Twelve month retention is of the order of 50 to 80% and continued illicit drug use is consistently low. All of these treatments need better matching to appropriately diagnosed patients especially so as to determine who may be suitable for general practice management. Buprenorphine, a long acting opioid, has been prescribed widely in France recently by GPs with no regulatory framework in place and results have been gratifying thus far.