Struggling to give up the drink? Gene therapy might be the answer. Rats bred to crave alcohol will drink 50 per cent less for more than a month after being injected with viruses engineered to disrupt the gene for a key enzyme involved in alcohol metabolism.

Many people in east Asia react badly to alcohol because of mutations in the gene for aldehyde dehydrogenase. But these mutations also reduce the risk of succumbing to alcoholism by two-thirds or more.

Aldehyde dehydrogenase is blocked by the drug disulfiram, also known as Antabuse, which is sometimes used to help alcoholics quit the habit. "But you have to take it every day, so there is a big problem with compliance," says Amalia Sapag at the University of Chile in Santiago.

To provide a longer-lasting effect, Sapag's team engineered adenoviruses to carry an "antisense" version of the aldehyde dehydrogenase gene. This produces RNA that binds to the original gene's messenger RNA, blocking enzyme production.

A single injection of viruses reduced the enzyme's activity in rats' livers by 80 per cent, Sapag revealed at the American Society of Gene Therapy meeting in Seattle earlier this month.