For decades, the condom has been the only temporary contraceptive easily available to men, but now a gel designed to limit the production of sperm is about to be trialled.

The gel, called NES/T, is designed to work by blocking the natural production of testosterone in the testes, therefore reducing sperm production. The gel is designed to be rubbed on to a man’s back and shoulders, so get your minds out of the gutter. 

If the trial goes to plan, the gel could finally ease the burden of contraception on women, while giving men more control around their fertility. About time, too. 

The trial will be conducted by the National Institutes of Health in America and will involve 420 couples. Researched are currently recruiting volunteers.

 The gel contains two key hormones, the progestin compound segesterone acetate (brand name Nestorone), in combination with testosterone. Applied to the back and shoulders, it is absorbed through the skin.

The progestin blocks natural testosterone production in the testes, reducing sperm production to low or nonexistent levels. The replacement testosterone should maintain normal sex drive and other functions that are dependent on the hormone.

Male volunteers 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 do not decline quickly, they will continue to use the formulation for up to 16 weeks. Once their sperm levels have declined to a threshold sufficient for contraception, the couples will rely on the male partner’s application of the gel as the sole method of contraception for 52 weeks. 

“Many women cannot use hormonal contraception and male contraceptive methods are limited to vasectomy and condoms,” said study investigator Diana Blithe, PhD. “A safe, highly effective and reversible method of male contraception would fill an important public health need.”