A new method of male contraception that is as effective as a vasectomy, but will be entirely reversible and has little or no side-effects, is expected to become available within the next two years.

"If successful, this will drastically change the field of contraception," said Stellenbosch University (SU) urologist, Dr Amir Zarrabi, of a new male contraceptive that is currently showing promising results in human trials.

"It will give couples a lot of flexibility. They will have a safe and reliable form of contraception – with no hormonal effects or other side effects – that can be reversed when they want to start a family," he said ahead of the Western Cape Sterilisation Week marked from 23 to 27 July.

The new contraceptive, Vasalgel, which is currently being tested by the American Parsemus Foundation, is a type of "no-scalpel vasectomy". Like a vasectomy, it also blocks the flow of sperm from the testicles to the penis, but instead of severing the tube that carries sperm (called the vas deferens) a gel is injected into the tube forming a barrier that blocks sperm, but allows other fluids to pass through.

"Vasalgel does not require any surgery. Although a vasectomy is a small procedure, it does carry some risks, like bleeding or infection, and there is also a small chance that a man might experience post-vasectomy pain due to pressure build-up in the testicles. Vasalgel does not carry any of these risks," explained Zarrabi, a specialist in male fertility and microsurgery at the Division of Urology at SU's Faculty of Medicine and Health Sciences.

Another major advantage of Vasalgel is that it is reversible and can be used as a short- or long-term form of contraception. When a couple wants to conceive the Vasalgel can be flushed from the vas deferens with an injection of a sodium bicarbonate solution.

Although Vasalgel is already being tested in humans, reversal has only been attempted in animal studies where it showed rapid restoration of sperm flow.

Zarrabi warns that although Vasalgel blocks the flow of sperm, it does not offer any protection against the transmission of sexually transmitted infections such as HIV.

Previous efforts to develop a male contraceptive focused on hormonal manipulation, which is how the contraceptive "pill" for women works.

"The male hormone testosterone is linked to sperm production and by lowering the testosterone level in a man's testicles you can prevent the production of sperm," Zarrabi explained.

"It sounds counter-intuitive, but to lower testosterone in the testicles, you have to increase testosterone levels in die blood. But study after study showed that there were too many unpleasant side-effects," said Zarrabi. Side-effects of increased testosterone levels in the blood include aggression, depression, fatigue, low libido, high blood pressure and an increase in cholesterol levels.

"Researchers tried to tweak the method by adding other hormones, like the female hormone progesterone, but at the end of the day it still had too many side effects and wasn't effective enough. The idea of the 'male pill' was abandoned a couple of years ago and most new research has been focusing on intra-vas devices like the Vasagel," said Zarrabi.