Hulse 2009: naltrexone implant vs daily tablets for heroin dependence

What they tested

Of 129 eligible people, 70 (54%) agreed to take part. One group got daily naltrexone tablets (50 mg a day) for 6 months plus a placebo implant. The other got a single 2.3 g naltrexone implant plus placebo tablets. This double-placebo setup meant nobody knew which treatment was real.

The researchers tracked blood naltrexone levels, return to regular heroin use (4 or more days a week), other drug use, overdoses needing hospital care and side effects.

What they found

More people on tablets had blood naltrexone levels below 2 ng/mL in month 1 (P < .001) and month 2 (P = .01). More people on tablets had returned to regular heroin use by 6 months (P = .003), and they got there sooner: a median of 115 days versus 158 days.

There were 10 trial-related, unexpected adverse events. One was serious: a wound hematoma, a collection of blood under the skin, from the implant surgery.

Among men, implants kept naltrexone above 1 ng/mL for 101 days and above 2 ng/mL for 56 days. Among women, the figures were 124 days and 43 days.

Limits

• It was small (70 people) and took place in one city.
• Follow-up was 6 months, so it doesn't show what happens after that.
• Blood levels above 2 ng/mL lasted well under the full 6 months, so the implant's protection may wane before the follow-up ends.

What it means if you're considering naltrexone

For people with heroin dependence, the main problem with naltrexone tablets is that people stop taking them. This trial found that an implant, which doesn't depend on daily pill-taking, led to less relapse to regular heroin use than tablets over 6 months.

No naltrexone implant is FDA-approved. The long-acting form approved in the US is Vivitrol, a monthly shot.