VIAGRA, the wonder drug that has revolutionised life for many older men, has a new use. It has been used successfully to improve the uterine circulation to pregnant women starting to develop placental insufficiency. As a pregnancy continues into the later months so there are many cases in which the placental circulation is no longer adequate to keep the developing baby fully nourished. Recent research suggests that Viagra can improve placental blood supply.

Viagra has also been in the news because of its possible link with sudden failure of the blood supply to the optic nerve. This is nothing to do with the firmly held belief that masturbatory sex blinded Victorian youths and blighted their potential imperial career before it had started. Nor is it related to the very genuine, but always slightly physiologically puzzling, comparatively common prevalence of orgasmic headaches.

Viagra, together with Levitra and Cialis — the other two drugs with similar, but not identical, action to Viagra — are phosphodiesterase 5 inhibitors. They inhibit the PDE5 enzyme that breaks down another chemical, cGMP, and this has an effect on arterial blood supply. Viagra was the first of the PDE5 inhibitors and is not quite as specific to the pelvic arteries as is Levitra.

The common manifestation of an improvement to the blood supply to the eyes’ arteries is that men who have taken Viagra may view the world as if through blood-red tinted spectacles. The PDE5 inhibitors may cause headaches; they can dilate the body’s blood vessels so that the patient feels dizzy or faint.

There is always a close association between pelvic and nasal-blood supply. Many women have nasal congestion in pregnancy or even before a period. Likewise, Viagra may cause nasal congestion. Levitra is more pelvic arterial specific than Viagra, although some men may still suffer headaches.

The main difference between Levitra and Viagra is speed of action. Levitra can be effective in anything from as little as 15 minutes, yet may still be active five hours after the dose. Nor is its action so likely to be influenced by food and drink. Cialis has the advantage of working for a long time — up to 36 hours. It adds 21st-century significance to the chemist’s old question “And something for the weekend, sir?” Unfortunately, just as its benefits last longer, so do any side-effects. Patients taking Viagra, or the other anti-impotence drugs, should not be alarmed by this research on the eyes’ blood supply. From the many millions of people who take Viagra, only a very few cases who have suffered have so far been identified.