The New Straits Times, October 4, 1996
Of late, there have been several news reports about the use or naltrexone in the treatment of drug addiction. How can this drug be used for treating addiction? Is it safe?
Drugs like naltrexone can be categorised as 'narcotic antagonists'. They are so called because they can counteract the actions and effects of the drugs of dependence belonging to the class of narcotics, for example, heroin and morphine.
Consequently, the-effects of addiction can be gradually weaned off since 'narcotic antagonists' themselves are not addictive and does not have the properties of the narcotics. Thus by itself, naltrexone has no effect as such. Naloxone is another example of a narcotic antagonist.
Naltrexone exert its action by binding on special sites called 'opiate receptors' that are found in the brain and thought to be involved causing addiction.
These are the same receptors that narcotics like heroin and morphine act upon to give all the central effects associated with their use. Thus by competing for the same receptors, naltrexone is able to prevent the narcotic drugs from exerting any effect on the brain.
Naltrexone can also reverse the actions of the narcotics to precipitate symptoms similar to 'drug withdrawal'. This mode of action, which is generally called 'competitive inhibition' makes drugs like naltrexone especially suitable for use in treating narcotic addicts.
Nevertheless, the use of naltrexone (and other narcotic antagonists) is not without its own dangers and precautions. Some of the more common side-effects include:
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headache, anxiety, sleep disorders, nightmares
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nausea, vomiting, diarrhoea, constipation, abdominal cramps
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palpitations, increase in blood pressure and heart rate
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urinary discomfort, changes in interest in sex
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nasal congestion, cough, sneezing, sore throat, shortness of breath
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skin rash, acne, loss of hair
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tremors, muscle twitches, pain in legs, knees or shoulders
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blurred vision, liver damage and so on.
Safety during use in pregnancy and lactation and in children under 18 years of age has not been established.
Naltrexone is particularly dangerous when used by those who are still using narcotics. It can cause withdrawal within minutes and may last for up to 48 hours. The symptoms can be severe and fatal. The user should therefore be opiate free for at least seven to 10 days before beginning naltrexone therapy.
The inhibition caused by naltrexone can be overcome by taking large amounts of narcotics. This can cause disastrous results.
