The first large-scale clinical trial of a cheap drug used to treat high blood pressure has found that it could help thousands of women who suffer from persistent acne.

A team of researchers led by the Southampton Clinical Trials Unit found that the drug, spironolactone, could change the way acne in women is routinely treated and reduce the number of antibiotics prescribed for the condition.

Acne is common in adolescence but almost a third of women who have it when young continue to be affected in their adult life, relying on creams and gels and antibiotics prescribed by a GP if these do not work.

The team recruited more than 400 women, aged over 18, with acne that had persisted for more than six months and where oral antibiotics would have normally been the next treatment.

For the study funded by the National Institute for Health and Care Research (NIHR), half of the participants were randomly allocated to take spironolactone, while the other half were given a placebo, or dummy pill.

Professor Miriam Santer, GP and co-lead of the trial, said: “The results showed that the women taking spironolactone saw a significant improvement in their acne after 12 and 24 weeks compared to those on the placebo.

“A significantly higher proportion of people also reported that they felt satisfied that their skin had been helped compared with those receiving placebo, and any side effects were uncommon and very minor.

“These results show that spironolactone could offer an alternative to antibiotics for many women with persistent acne to use alongside topical acne treatments.”

She added: “We hope the publication of these results will mean more GPs and dermatologists feel confident to prescribe spironolactone as a treatment for acne.

“The drug is already included in treatment guidelines for persistent acne in the US and Europe, and we hope this trial will lead to a change in the UK guidelines.”

Kelly Cornick, 39, from Dorset, said that she had been prescribed various creams as well as the contraceptive pill to try to control her “horrible” acne.

The mother of three said: “It was embarrassing. People would stare and you almost feel that they’re looking at you like you’re dirty and don’t wash properly.

“I think the worst thing for me was when one of my nieces said: ‘Have you got chicken pox?’”

Speaking of the impact of using spironolactone, she said: “Initially I started on the lower dose and there was an improvement. I then went on to the higher dose and within about three months everything was gone, all the spots had disappeared.

“Knowing how much it’s helped me, I hope that other people will now be given this treatment as an option instead of just trying the antibiotics. I want people to be able to experience it, because everyone should feel confident and happy, and not have spots.”