Anti-addiction drugs face more than medical issues
16:15 25 July 2011 by Ferris Jabr
Should drug addicts be vaccinated to help them recover? Some authorities, such as bioethicist Arthur Caplan of the University of Pennsylvania, Philadelphia, have suggested coercing addicts into taking drugs like naltrexone, which curb the highs they crave.
The recent death of singer Amy Winehouse, who had well-documented problems with drugs and alcohol, and the publication last week of research on a heroin vaccine and an anti-cocaine drug, have again raised the question.
Kim Janda of the Scripps Research Institute in La Jolla, California, and his colleagues have created a vaccine cocktail that consists of a heroin-like hapten – a molecule that provokes the immune system – bound to a carrier protein and mixed with alum, an adjuvant that further stimulates the immune system.
The vaccine trains the immune system to swarm heroin molecules with antibodies, as though the drug were an invasive organism, thereby sequestering the drug in the bloodstream before it can reach the brain.
Janda's team fitted rats with catheters that delivered a dose of heroin straight into the bloodstream whenever the rodents pushed a lever. All the unvaccinated rats pushed the heroin lever frequently and eagerly, whereas only three of the seven vaccinated rats dosed themselves like addicts (Journal of Medicinal Chemistry, DOI: 10.1021/jm200461m).
Zheng-Xiong Xi of the National Institute on Drug Abuse in Baltimore, Maryland, and his colleagues studied mice that, like the rats, were implanted with a catheter that delivered cocaine when they pushed a lever. Xi gave the rodent addicts a drug that binds the CB-2 cannabinoid receptors in the brain, inhibiting dopamine activity and thereby blunting the cocaine high.
Mice who received the anti-cocaine drug pushed the cocaine lever less frequently and did not scurry around as much as their high peers (Nature Neuroscience, DOI: 10.1038/nn.2874).
If they were successfully adapted for people, both treatments would be very useful for addicts in therapy, to prevent slip-ups from becoming full-blown relapses. The vaccines against cocaine and nicotine that have been tested in clinical trials so far have failed to match the success of animal studies, only generating sufficient antibody levels in about one-third of the recipients.
But researchers remain invested in anti-addiction vaccines because unlike pharmaceuticals that act on the central nervous system, vaccines should produce fewer side effects and longer-lasting benefits.
One serious concern is that addicts will overdose in an attempt to overcome the blunting effect, or turn to other dangerous drugs. In one study, some cocaine addicts that received an experimental vaccine wound up with 10 times as much cocaine in their blood than usual in an attempt to get high. Such compensation is especially likely if the vaccine is implemented through legal coercion, which gives an addict the choice between jail or vaccine therapy.
"Before any vaccine is put on the market we need to get these ethical considerations worked out," says Kathleen Kantak of Boston University. "It should always be the individual's choice to be immunised. The treatments will only be successful if the individual is motivated to quit, otherwise they will find ways to get around it."
Wayne Hall at the University of Queensland in Brisbane, Australia, raises several ethical concerns about vaccines and pharmaceuticals aimed at addictive drugs. Although the antibodies that vaccines generate dwindle a few months after an injection, they never disappear completely. Potential employers could unfairly discriminate against past addicts if they detect such antibodies in a blood test.
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