LACK of information left many researchers and doctors bemused last week after the British government issued a warning that seven brands of low-dose contraceptive pills increase women鈥檚 risk of thrombosis. Doctors complained that they were given too little information to advise patients properly. And researchers wondered how the government鈥檚 Committee on Safety of Medicines (CSM) had reached conclusions from one study when even the trial鈥檚 investigators could not decide how to interpret the results.
The government鈥檚 warning covers pills containing the newer progestogens gestodene and desogestrel. It was sent out on the advice of the CSM, which in turn reached its conclusions after reviewing results from three unpublished studies.
One of those studies, which covers five European countries, was the subject of a medical conference in Montreal last week. 鈥淣o consensus was reached at the Montreal meeting about what our data say,鈥� says Margaret Thorogood of the London School of Hygiene and Tropical Medicine, who is coordinating the British arm of the study. 鈥淲e all agreed that it was too soon to review the preliminary analyses, and that more analyses are needed.鈥�
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Thorogood says that even if the new analyses reveal that the suspect pills are linked to an increased risk of thrombosis, the researchers would still have to ensure that the pills have not been preferentially prescribed to women who already have a raised risk of thrombosis, such as smokers.
The second study scrutinised by the CSM began in 1989, involves 17 countries, and was coordinated by the WHO. The study apparently suggests that the risk for women taking pills containing gestodene and desogestrel is double that for women on older brands. But a WHO spokesman stressed that data from the trial are not publicly available because they have been submitted to a medical journal.
The third study is based on information from a database containing the records of 4 million British patients and was led by Hershel Jick, head of the Boston Collaborative Drug Surveillance Programme in Massachusetts. His research is also under wraps waiting to be published. 鈥淲e sent copies of our manuscripts to them in confidence,鈥� he says. 鈥淭hey do what they think is best.鈥� Jick describes as 鈥渦nfortunate鈥� the fact that doctors must now advise patients without the full facts.
James Drife, professor of obstetrics and gynaecology at the University of Leeds, wants the CSM to publish the data on which it based its warning. Without it, he says, the committee has left doctors 鈥渃arrying the can鈥�.