For the first time, Britain has allowed an oral antibiotic used to treat chlamydia to be sold without prescription, the Medicines and Healthcare Products Regulatory Agency (MHRA) said on Wednesday.

People over 16 will be able to buy the azithromycin pill Clamelle, manufactured by Icelandic drugmaker Actavis, after testing positive for the infection. The drug will also be made available over-the-counter (OTC) for their sexual partners. The new regulation will come into effect later this year.

However, the person willing to buy the drug will have to show a letter giving the results of either a postal test kit or a test carried out in a surgery or clinic. The drug will still be available via prescription from a physician or a genito-urinary medicine clinic.

The government is encouraging OTC sales of drug to offer a more convenient alternative for some patients. Britain already allows OTC sales of cholesterol-lowering and migraine drugs, as well as antibiotic eye drops.

Chlamydia is a sexually transmitted infection (STI) caused by a tiny bacterium, Chlamydia trachomatis. Chlamydia is the most common STI in the U.K. It affects both sexes, although young women are more at risk.

The disease can be treated, but it often has no symptoms in either men or women, so it remains undetected. Serious long-term health complications include infertility and ectopic pregnancy.