A couple from Edinburgh are among the first people in the world to use a male hormonal contraceptive.
James Owers, 29, and Diana Bardsley, 27, are part of a University of Edinburgh study involving 450 couples who are relying on a hormone gel as their sole form of contraceptive for the next 12 months.
The gel is a mixture of progesterone and testosterone. The progesterone switches off sperm production in the testes and the testosterone compensates for the drop in testosterone that this causes.
The hope is that couples in long-term relationships could eventually use the gel as an alternative to the female contraceptive pill.
'Taking the burden off women'
Speaking to BBC Radio 5 Live Breakfast, James explained: "I squeeze a 50p-piece-size out of the dispenser - the dispenser is a bit like one of those posh toothpaste tubes. It's got the consistency of hand sanitiser.
"I rub it into my shoulder and pectoral area and that dries in three to four seconds. I do that to the other shoulder and then I get dressed and go about my day as normal."
James has been using the gel since February but only started to use it as the sole form of contraception a week ago. "One of the side-effects has been an increased sex drive," he said, but any negative side-effects have been minimal.
"I have experienced no change in mood, I've got a few small spots on my back but they are already clearing up. I've put on maybe 1kg [in weight] but that's probably due to the beer, if I'm quite honest!"
He said the benefits of being involved in the trial were more than just medical.
"The most positive thing for me has been I've got to experience a change in discourse about contraception. My friends and colleagues at work have been coming up to me and asking about it, asking when it's available, asking all sorts of stuff.
"I'm feeling very, very positive that either this contraceptive or other contraceptives for men will become available."
However, this could be some years away, according to Dr Cheryl Fitzgerald, a consultant in reproductive medicine at Manchester University NHS Foundation Trust.
"This trial is looking at hundreds of men and looking at them quite closely to check that it's safe and effective and tolerated well. After that there would be a much bigger trial so we are certainly looking at 10-plus years," she said.
The trial has brought benefits for James's partner, Diana. She said: "One of the fantastic things for me is that I have been on hormonal contraception since I was 16 and this has now allowed me to have a break for the next year.
"By giving men more choice we are taking some of the burden off women and allowing men to have more freedom over their own contraceptive method."