Blocking the effects of heroin

June 9, 2012 - 06:33
Article from University of Oslo

The euphoric effects of heroin can be blocked using a drug called naltrexone.

(Illustration Photo: Colourbox)

Heroin without the high is possible, as long as the heroin users are willing to take the drug naltrexone.

Naltrexone binds to the most important opioid receptor without producing any stimulant or euphoric effects. Since naltrexone binds to the receptor first, it blocks any other substances trying to bind. The patients can take heroin, but will they experience any euphoric effects? None at all.

More bespoke

Previously, treatments for those addicted to opiates have been designed on a one size fits all basis. However, researchers now want to tailor treatments to suit different patients. Part of the solution is the drug naltrexone, which simply blocks the effects of heroin.

Why, then, is this method not in wider use? Postdoctoral fellow at the Norwegian Centre for Addiction Research, Nikolaj Kunøe, tries to explain:

"It is inherent in the nature of addiction that users prefer opiates," he says.

"If we take a somewhat pragmatic view of heroin addicts, we can imagine that they primarily want to stimulate their opioid receptors, to achieve a high, and that it is difficult to motivate them to move forward."

However, a number have wanted to undergo naltrexone treatment that fully blocks the opioid receptors, well aware that this means no stimulant effects. Therefore, researchers have also set themselves a goal of recruiting 220 patients over two years, and then following them up for one year to survey the effects of naltrexone treatment.

Subutex with a slight twist

Today, patients undergoing drug assisted rehabilitation receive either methadone or Subutex, opiates that sustain their addiction, but in a controlled manner.

The active ingredient in Subutex does not make heroin addicts sober. Instead, it replaces the euphoric effects of heroin with a controlled form of euphoria. However, you can get high on Subutex as well; the user just has to inject the drug instead of swallowing it. That is why patients undergoing drug assisted rehabilitation today are given Suboxone.

Suboxone is Subutex mixed with a small amount of another blocking drug called Naloxone. This drug is added to prevent patients saving their Suboxone and injecting it rather than swallowing it. If you inject Suboxone, the antidote Naloxone is faster than the Subutex and thus reaches the brain first. The result is withdrawal rather than a high.

One of the points is to keep patients away from the needle.

Researchers have experimented with naltrexone earlier, but in tablet form. Naltrexone only works for 24 hours at a time when taken as a tablet. Given that heroin addicts' lives are not exactly characterised by tranquillity and predictability, its short-term effect is a problem. Taking the tablet every day proved to be a problem, and things particularly went wrong at weekends.

If the tablet is not taken, the effect disappears and patients get just as high from heroin as they did before.

Depot medication

Naltrexone is now injected into a muscle. This results in it being released more slowly and, thus, its effects lasting longer.

"With an effect that lasts for 28 days instead of one day, the chance of problems occurring is minimised by a factor of 28, theoretically," says Kunøe.

"Naltrexone does not cause many or troublesome effects. It does block some of the body's own opioid system, since it is an opiate inhibitor, but it appears that the body adapts to this almost without problems," explains Kunøe.

"After initially peaking, the dosage drops to an appropriate level without producing any particular side effects," he says.

Front line research

The naltrexone project is unique. It is steered by neither commercial companies nor major institutions.

"It is a quite pioneering work," says associate professor Lars Tanum.

"Our study is now so formalistic and comprehensive, that on the whole it could only be matched by major institutions or companies."

Substance abuse research and treatment is a young field. The choice has often been between one or two drugs, unlike in the world of medicine in general where the focus is more on bespoke treatments for each patient.

Some of the patients will benefit from being sober. Those who want it will now receive a long-awaited offer through naltrexone depot injections. Those who must have opiates can get Suboxone.

"We are now seeing the contours of a more differentiated treatment system," says Tanum. A system that is more in line with other fields within medicine.

Rest of their lives?

Do naltrexone patients have to have depot injections of the blocking drug for the rest of their lives to stay sober? That depends.

"Patients are so different. If no changes or development takes place during the naltrexone treatment, they should definitely continue. The risks to health and of overdosing are large when a patient stops taking naltrexone.

Therefore, something more has to happen vis-à-vis the patient that makes him or her, and also others around them, confident that the desire to remain sober is stronger than the craving to get high," says Kunøe.

A successful naltrexone project could pave the way for a more wide-ranging offer for patients. Thus, the days of the idea that one pill fits all may be numbered.

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