Doctors are looking for couples to try a male birth control gel that is rubbed into the shoulder.

University of Kansas researchers have promised to pay couples who take part more than $4,000 (£3,063) in compensation.

Each man will need to apply the clear gel to their arm or shoulder every day for two years and be having regular sex with his partner.

The gel is absorbed into the skin and reduces the amount of sperm a man produces.

Couples must be willing to have a baby in case the gel fails – but it is expected to be more effective than condoms.

A new method of birth control for men is being tested by couples in the US in the form of a contraceptive gel that is applied to a man's arm or shoulder (stock photo)

The Kansas trial is part of ongoing research whereby 420 couples across the world will test the gel over three years.

So far, research at other universities has indicated the gel, called NES/T, can cause side effects of weight gain, muscle gain and acne.

Currently, men who want to control their fertility have limited options – condoms or vasectomies, surgical procedures to block sperm.

There are myriad forms of birth control for women, which come with complicated and disruptive side effects.

If the gel proves safe and effective, it would be the first new birth control for men since the condom was introduced in the 1800s.

It could reduce the number of unplanned pregnancies, lead investigator of the Kansas trial Dr Ajay Nangia said.

'Men only have a vasectomy and condoms. The world has changed,' said Dr Nangia said.

The gel has been in development over the past decade by The Population Council, a non-profit organisation, in collaboration with The National Institutes of Health (NIH).

The NIH-funded trial is recruiting 420 couples to test the gel, including in Edinburgh, Manchester, Los Angeles, Washington, Italy and Sweden.

Now, KU Medical Centre, part of University of Kansas, are inviting couples in the area to join the trial at no cost to them, CBS Detroit reports.

They must have been in a relationship for at least a year to take part, and be open to the possibility of having a child.

HOW DOES THE GEL WORK? The contraceptive gel contains the hormones progesterone and testosterone. The progesterone essentially sends a signal to the brain's pituitary gland to shut down the production of sperm in the testicles, one researcher involved in the trial at Edinburgh University, Dr Cheryl Fitzgerald, told Sky News. It takes between six and 12 weeks for the man's sperm count to drop to make him clinically infertile, meaning he can't get a woman pregnant. But because the testicles also produce most of the body's testosterone, a side effect of the gel is that the men's level of their sex hormone also drops. Low testosterone can cause weight gain, low sex drive, mood changes and erection problems. To counteract this, the gel also contains testosterone which can be absorbed by the skin and boost the man's levels back up to normal. The researchers say a man's fertility should return to normal within months after stopping using the gel. Advertisement

Men will be paid $2,985 (£2,286) to turn up at the clinic 31 times over two years, while their partners will receive $1,140 (£873) for visiting ten times.

At first, the couple can use other forms of contraceptive. Then, when the man's sperm is measured to at a low level, they will trial the gel exclusively for around one year.

NES/T contains two hormones - progestin and testosterone - that are absorbed through the skin when the gel is rubbed onto a man's back and shoulders.

Progestin - found in most hormonal female birth controls - naturally blocks the action of testosterone, keeping the testes from producing sperm.

But testosterone is also key to male physical features and sex drive, so the gel also delivers a dose of replacement hormone.

The gel is anticipated to be more than 90 per cent effective, making it roughly three per cent more reliable than condoms.

The effects are reversible within three to four months of use, bringing sperm production to the man's normal level.

Scientists say the gel will not reduce sex drive, which can be a problem for women using contraceptives.

Emerging evidence from trials elsewhere in the US indicate some possible side effects of the gel.

In an earlier trial of the gel, some men gained weight, although mostly in muscle, and other men who had trouble with acne as a teen had recurrences.

Despite this, Dr William Bremner, of the University of Washington – one of the universities involved in the study - said, 'the potential of this new gel is huge'.

If the trials are successful, the substance may become available to couples within 10 years after relying on women's options such as the Pill for decades.

The first oral contraceptive, Enovid, was approved by the US Food and Drug Administration (FDA) as contraception in the 1960.