Researchers plan to enrol approximately 420 couples in the clinical trial.

Hundreds of couples based in the UK have been recruited to take part in a groundbreaking trial of a male contraceptive gel that could allow men and women to balance the birth control responsibility in future. 

According to the Guardian, eighty men in Manchester and Edinburgh have been asked to use a daily gel containing hormones that “send the testes to sleep”, meaning the sperm count drops to zero.

The clinical trial will see all couples involved rely solely on the gel – called NES/T – as their contraceptive for a full year. The aim of the project is to see how effective it is at preventing pregnancy and whether the side-effects are acceptable.

According to Richard Anderson, a professor of clinical reproductive science at the University of Edinburgh, the method was expected to be more effective than condoms, which – according to Planned Parenthood – in real-life conditions are about 82% effective.

“We’re aiming to get it down to the sort of level you get with the pill which is a very small but not zero failure rate,” he said.

NES/T includes the progestin compound segesterone acetate (brand name Nestorone), in combination with testosterone.

Male volunteers will apply the gel-like formula to the back and shoulders where it will be absorbed through the skin.

The progestin blocks natural testosterone production in the testes, reducing sperm production to 'low or nonexistent levels'. It's believed that the replacement testosterone will maintain the volunteer's normal sex drive and other functions that are dependent on adequate blood levels of the hormone.

Men involved in the study will use the gel daily for four to 12 weeks to determine whether they tolerate the formulation and to ensure they do not experience unacceptable side effects.

If sperm levels have not adequately declined, they will continue to use the formulation for up to 16 weeks. 

Once a man’s sperm count has dropped to almost zero – which is expected to take a few months – couples will use the gel as their sole contraceptive and be followed for more than a year.

Should the trial reap success, it's likely that various pharmaceutical companies will develop the gel as a commercial product. This would be the first of its kind in the market.

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