Almost 90 per cent of patients prescribed Roaccutane (isotretinoin) pills show improvements to their skin, but by taking it they run a risk of developing high levels of triglycerides (fats) and cholesterol in the blood. Tests of liver function show the presence of enzymes that normally signal liver damage.

The patient leaflet for the drug, which is made by Roche, does give warning of possible adverse effects. It says that about a quarter of patients will sustain higher levels of triglycerides while taking the drug, and 15 per cent will develop higher liver enzyme levels.

Researchers believe that the figures may be even higher. A team led by Lee Zane, of the University of California in San Francisco, followed 13,772 patients aged between 13 and 50 who took Roaccutane — called Accutane in the US — between 1995 and 2002.

The patients were all members of Kaiser Permanente, a medical care organisation with 3.3 million members based in Oakland, California.

The researchers report in Archives of Dermatology that 44 per cent of patients who had normal levels of triglyceride before taking the drug developed high levels after taking it; 31 per cent developed high cholesterol and 11 per cent high liver enzymes.

When they stopped taking the drug their blood levels and liver enzymes mostly returned to normal. Not all were retested, but of those who were 90 per cent returned to an acceptable trigycleride level and all cholesterol tests were normal or only slightly elevated.

Acne is a disabling condition that can limit a sufferer’s social life and cause serious psychological symptoms if untreated. For most people it is transitory, but some need medical treatment. Antibiotics are often used, but in very difficult cases Roaccutane may be the only treatment that works.

Dermatologists who prescribe the drug are likely to conclude that short-term and reversible changes to blood and liver are prices worth paying when other drugs do not work.

In Britain, isotretinoin is more commonly given as a cream. There is no indication in the study that in this form it has the same effects.

The team points out that abnormalities in laboratory tests do not necessarily signify anything serious, but patients with large increases in triglyceride levels are, they say, at greater risk of future ill-health, which could include the set of symptoms known as the metabolic syndrome: obesity, high cholesterol, high blood pressure and insulin resistance, which can lead to type 2 diabetes. They plan further studies to examine whether Roaccutane patients are more prone to these symptoms.

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