Antidepressant shows promise for meth addicts

The antidepressant mirtazapine may help some methamphetamine addicts curb their use of the drug -- at least in the short term, a small trial suggests.

Right now, no medication is approved for treating dependence on methamphetamine, a highly addictive stimulant that can be snorted, smoked, injected or swallowed.

That's in contrast to other abused substances, like heroin and alcohol, for which there are medications that can help addicts cut down.

"Drug counselling is the standard treatment for methamphetamine dependence," said Dr Grant N. Colfax of the San Francisco Department of Public Health. "But it's not nearly as successful as we'd like it to be. There's still a lot of room for improvement."

For their study, funded by the National Institute on Drug Abuse, Colfax and his colleagues looked at the effectiveness of mirtazapine (Remeron) among 60 gay or bisexual men who wanted treatment for meth dependence.

Methamphetamine abuse is considered a particular problem among men who have sex with men, because among the drug's effects are "disinhibition" and sexual risk-taking. And meth use among gay and bisexual men has been linked to an increased risk of contracting HIV.

Reduced meth use

Colfax's team randomly assigned their patients to either 12 weeks of drug counselling alone or counselling plus mirtazapine. By the end of the study, those on the antidepressant were less likely to test positive for recent meth use.

After 12 weeks, 44% of those taking mirtazapine had a positive urine drug test, versus 73% at the study's start. In contrast, almost no change was seen in the counselling-only group: 63% had a positive test after 12 weeks, versus 67% at the outset.

"We're cautiously optimistic," Colfax said, noting that the study was small and needs to be followed up by larger and longer-term research.

One big question remaining is how long any benefits of mirtazapine may last.

"Do people have to stay on the medication in order to stay off of methamphetamines?" Colfax said. "We don't know because we studied them while they were on the medication."

An encouraging finding, according to Colfax, was that men on the antidepressant also cut down on their risky sexual behaviour.

Among mirtazapine patients, the number of male sex partners in the past month declined from an average of almost 12 to three by the study's end. The men also reported fewer instances of unprotected sex.

Different antidepressants

A number of studies have tested different antidepressants for treating meth dependence, since the medications act on some of the same brain chemicals that meth does to produce its "high." But so far, none have panned out.

Colfax said his team chose to study mirtazapine because it acts on more than one brain chemical implicated in methamphetamine's effects. "Mirtazapine works on both dopamine and serotonin," he noted. "We know both of those (brain) pathways become disrupted in methamphetamine dependence."

Like all antidepressants, mirtazapine can also have side effects. One of the main ones is weight gain -- and the risk is higher compared with some of the more popular serotonin-targeting antidepressants, like fluoxetine (Prozac) and sertraline (Zoloft).

In this study, three of the 30 men assigned to the medication gained a substantial amount of weight: anywhere from 4 to 12 kilos But none of the three stopped taking the antidepressant, Colfax noted.

Drowsiness and increased appetite, which are known potential side effects of the drug, were also reported by some of the participants.

Future studies, according to Colfax's team, need to look not only at the long-term effects of using mirtazapine to treat meth addiction – but also whether any successes translate into a lower risk of HIV infection.

Figuring out how long people need to stay on the antidepressant to stay off of meth is also important as far as determining treatment costs. The average monthly price of mirtazapine ranges from about R370.00 to almost R1600.00, depending on the dose and whether you use the brand-name or generic.

(Reuters Health, Amy Norton, November 2011)

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