Researchers from University of Adelaide in the Discipline of Pharmacology have found a genetic key for improving treatment success rates of heroin addicts around the world. They have discovered a gene that helps determining the optimum methadone dosage levels for heroin addicts.
The study reveals why people are either less efficient or more effective in distributing drugs throughout their body to the central nervous system. It will allow people undergoing methadone treatment programs to be tested for the genetic variation to determine optimal treatment doses. The study results were published in journal Clinical Pharmacology and Therapeutics.When the heroin addicts were tested, it was found that 25% of the people with a mutation of the gene can cope on lower doses of methadone. But the majority without the mutation process faster methadone, need almost double the amount to stave off heroin withdrawal.
It was also found that about 62% of drug addicts dropped out of methadone programs because of severe withdrawal symptoms.
Lead researcher and pharmacologist, Dr Janet Coller said "Individualised dosing may decrease the incidence of withdrawal symptoms in some people and therefore encourage them to continue with the methadone treatment" and added that “Accurate determination of methadone doses was essential to successfully treat users.”
This research is the first of its kind to investigate the problem of inaccurate dosing, which sees almost two out of every three of Australia's methadone users drop out of programs prematurely. Most fail in the first four weeks of the treatment, when the withdrawal effects are most severe. "It's entirely possible that the people who are failing are doing so because their genotype is such that they need more methadone than they're getting," says Dr Janet Coller. Dr Coller and her team tested 60 heroin addicts for the gene, called abcb1, and worked out whether they were getting the right dose, usually between 50 and 110 milligrams a day. Currently, dosing is decided using weight and drug use history.
The clinical services director of Drug and Alcohol Services SA, Associate Professor Robert Ali, said the methadone program had proven to be the most successful treatment. "However, they don't suit everyone but this kind of leading-edge research will help us tailor treatment for individuals, which is an important milestone," he added.
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