By Christian Duffin
GPs have been given the go-ahead to prescribe almost all classes of antibiotics to women who take the contraceptive pill, in a major change to current practice prompted by new evidence on the interactions between the drugs.
Current standard practice is to recommend to women on the contraceptive pill that they do not take antibiotics at the same time, and that they or their partner use other methods of contraception instead.
But the Royal College of Obstetricians and Gynaecologists has issued updated guidance stating that ‘additional precautions’ are no longer necessary, as the latest evidence suggests antibiotics do not reduce the effectiveness of the pill – provided that women are taking the antibiotics for less than three weeks.
The updated recommendations were prompted by an examination of research evidence on drug interactions with hormonal contraception, published last month, which brings the UK recommendations in line with those issued last year by both the World Health Organization.
The guidance, produced by the clinical effectiveness unit of the College’s Faculty of Sexual and Reproductive Healthcare, states: ‘Overall, the evidence does not support reduced combined oral contraception efficacy with non-enzyme-inducing antibiotics. Additional contraceptive precautions are not required during or after courses of antibiotics that do not induce enzymes.’
Rrifampicin and rifabutin are the only enzyme-inducing antibiotics that are excluded from the guidance, and are used rarely for the treatment of tuberculosis. But women using these drugs long-term should be advised to switch to a method that is unaffected by enzyme-inducing drugs.
Women who do not wish to change from their contraceptive method while on short-term treatment with an enzyme-inducing drug can be advised to continue using a combined oral contraceptive containing at least 30?g ethinylestradiol, the patch or ring along with additional contraception, with a hormone-free interval of four days. Additional contraception should be continued for 28 days after stopping the enzyme-inducing drug.
Dr Rachel Brown, a GP in Bristol with an interest in women’s health and contraception, welcomed the clarification. She said: ‘The GP population has been taking a belt and braces approach and advising people to use condoms while they are taking antibiotics and for a week after. The evidence has been vague for some years, but things will be easier now.’
Dr Imogen Shaw, a GP from Essex with a special interest in gynaecology, said: ‘GPs have probably been over cautious in their advice about the length of time to use condoms. Anything that makes pill taking easier and more straightforward, and helps women worry less about it has to be a good thing.’
Other changes have been made in the updated guidance, including an interaction between the pill and lamotrigine. The guidance rules out prescribing combined hormonal contraception to women with epilepsy taking lamotrigine monotherapy, ‘due to the risk of reduced seizure control, and the potential for toxicity in the contraceptive-free week.’
The proton-pump inhibitior lansoprazole is no longer listed as an enzyme-inducing drug, because there is ‘good evidence’ that it does not induce or inhibit the enzymes involved in the metabolism of contraceptive hormones.
Faculty of Sexual & Reproductive Healthcare Clinical Guidance GPs can now prescribe most antibiotics to women on combined hormonal contraceptives