Reversible chemical vasectomy

A new approach to contraception, this time for men, is being developed by researchers in China...

Oral contraceptives have been available to women since the early 1960s and are a very effective and widely used method of family planning. In contrast, the contraceptive choices for men are much more limited. These include using a condom, which some individuals find reduces the pleasure of sex, or having a vasectomy, which can be difficult to reverse. In a fair, egalitarian society it would be good to give men the opportunity to share the responsibility for contraception using a method that is as convenient as the female pill.

A male contraceptive must be safe, effective and reversible with minimal side effects. Various approaches have been explored, including the injection of synthetic versions of the male sex hormone testosterone. Unfortunately, there have been adverse side effects documented with this hormonal approach, including weight gain, acne, and an increase in the risk of strokes and prostate cancer. Thus, there is a need for a safe and reversible male contraceptive that does not rely on altering male hormones.

An alternative approach is to physically block the tube that allows sperm to leave the testes and thus prevent normal fertility. No sperm, no babies. One problem with this method, however, is that it is not easily reversible and would require an additional surgical procedure to remove the blockage.

Now, innovative work just published by scientists from Nanchang University in China describes a novel method to block the sperm exit tube but in such a way that the block can be reversed easily with a simple heat treatment. The block is inserted by a simple procedure to inject the components into one part of the sperm duct. The chemicals are added in a specific sequence, producing a series of layers rather like a fancy cocktail. One layer consists of a gel plug made from alginate, a substance derived from brown seaweed. This physically prevents sperm from moving along the tube. Three further layers above the gel plug form a "sandwich" containing a filling of a substance that can dissolve the alginate gel. Gold nanoparticles in the "bread" layers of the sandwich can absorb infrared radiation. This means that modest heat treatment can be used to melt the "bread" and release the filling to reverse the blockage and restore fertility.

Consequently, the approach described in the study is particularly appealing as it should be easily reversible. And in a group of rats on which the Chinese team tested the technique, it provided effective contraception over more than sixty days of testing.

One concern about the method, however, is that the low heat required to dissolve the blockage might be easily obtained by a hot bath – ironically meaning that individuals might have to have cold showers to maintain the effectiveness of this contraceptive method! In addition, the safety of the chemicals used in the blockage will have to be more carefully evaluated before this method can be tried in men, particularly when the chemicals might be left in place for many months or years. The prolonged affect of the chemicals on the tubes that carry the spem will therefore have to be evaluated. Consequently, it will be many years before this approach will ever be tested in men, but the study is encouraging in that research is progressing to develop non-hormonal methods of contraception in males.