This common antidepressant helps people cut back on methamphetamine – new study

Methamphetamine – more commonly known as meth, crystal or ice – is a highly addictive, stimulant drug.

An estimated 7.4 million people in the world are dependent on it or “addicted” to it. They face multiple health risks including paranoia, feeling suicidal, heart problems, strokes, injuries from accidents, and a higher risk of early death.

But there are no medications approved anywhere in the world to treat meth dependence.

Now, a cheap, safe and readily available medicine that has been used to treat depression for years is showing promise. Our trial of mirtazapine, just published in JAMA Psychiatry, shows people who take it cut back their meth use.

Few other options

Australia has one of the highest number of people dependent on meth per capita worldwide.

As there are no medications approved for meth dependence anywhere in the world, we have few treatment options.

Currently available treatment options include counselling, detox or withdrawal and long-stay residential rehabilitation. However, access can be difficult and treatment dropout rates are high. Most people who go to rehab relapse.

More sophisticated treatments offered within the community such as contingency management, which involves setting targets and rewards for meeting them, are more effective but aren’t widely available.

Even though there are no approved medications for methamphetamine use, doctors sometimes prescribe existing medications that have shown promise in clinical trials.

Medications that are prescribed off label include prescription stimulants (methylphenidate, lisdexamfetamine, modafinil), the anti-smoking treatment bupropion, the opioid-blocking drug naltrexone (including in combination with bupropion) and antidepressants.

However, these drugs may not work and may cause unnecessary side effects or safety risks.

How about mirtazapine?

Studies in recent years suggest the antidepressant mirtazapine may provide some hope.

Two studies were conducted in the United States in an outpatient research clinic in San Francisco, California. Both trials found mirtazapine reduced meth use.

These initial trials were conducted a research clinic with a small group of patients (60 and 120 respectively) who were monitored closely. Patients were at risk of HIV: men and transgender women who had sex with men. Women and people with people with depression were excluded.

So our Australian team wanted to know if mirtazapine would have the same benefit if it was used by doctors in community clinics to treat a larger and more diverse group of patients.

What we did and what we found

The Tina Trial recruited a larger and more diverse sample of 339 people dependent on meth from six outpatient clinics in Australia.

At the start of the trial, participants had used meth an average of 22 days out of the previous 28.

Half were randomly assigned to either take home mirtazapine (a 30 milligram tablet daily), or a placebo, for 12 weeks. The researchers then tracked days when participants used meth across the 12-week period.

People who received mirtazapine reduced their meth use by more than people who received the placebo (an average reduction of seven out of 28 days compared with 4.8).

So the comparative advantage of mirtazapine was modest: 2.2 days in use out of 28 days.

This benefit was apparent regardless of whether people had depression at the start of the study.

Although this reduction is small, in the absence of any alternative medication this is an important step forward.

Our research team believes mirtazapine has a direct effect on meth dependence, distinct from its ability to reduce depression.

This implies mirtazapine is acting directly on brain systems involved in drug reward, and might restore function to pathways that long-term meth use can disrupt.

Our study found no unexpected safety issues when using mirtazapine to treat meth dependence. The most common side effects were drowsiness and weight gain.

This isn’t a ‘cure’

Mirtazapine is not an instant “cure” for meth dependence. But in the absence of any approved medications for methamphetamine use worldwide, it is a critical first step in providing a medications to reduce harms from methamphetamine.

Mirtazapine is cheap, safe and readily available. Many doctors are familiar with its use to treat depression.

It is a take-home medication, making it convenient for people to use. So there is no need for daily clinic visits or close medical monitoring.

It is also “off patent”, meaning there are inexpensive generic versions.

In order for mirtazapine to be routinely prescribed for meth dependence outside a clinical trial, regulators would need to approve it for this purpose. This requires research evidence, like that provided by the Tina Trial.

In the meantime, doctors can prescribe mirtazapine off label. Guidelines on the off label prescribing of medications are available from the Royal Australian New Zealand College of Psychiatrists.

Further information on the Tina Trial is available here.

If you have concerns about your own or someone else’s drug or alcohol use, call the National Alcohol and Other Drug Hotline on 1800 250 015. This 24/7 hotline provides free and confidential information and support.