Sildenafil shows some promise for the treatment of pulmonary
hypertension
Sildenafil (Viagra) could be used to treat pulmonary
hypertension caused by hypoxia, say researchers from Hammersmith Hospital,
London.
In research funded by the British Heart Foundation,
Dr Lan Zhao and colleagues studied 10 healthy male volunteers who were
given either 100mg sildenafil or placebo one hour before breathing a low
oxygen atmosphere to induce pulmonary hypertension.
After taking placebo, breathing 11 per cent oxygen
for 30 minutes led to a fall in arterial oxygen saturation and a 56 per
cent rise in mean pulmonary artery pressure (increase from 16.0±2.1 to
25.0±4.8 mmHg).
The researchers observed that this increase was
almost abolished when the volunteers received sildenafil before inducing
hypoxia (increase from 16.0±2.1 to 18.0±3.6 mmHg). They add that sildenafil
had no significant effect on systemic blood pressure. The researchers
comment that hypoxia plays a significant role in the pulmonary hypertension
that accompanies chronic obstructive airways disease, and add that apart
from continuous oxygen administration, there is currently no satisfactory
treatment for the condition.
“Sildenafil may be a useful orally active treatment
for pulmonary hypertension secondary to hypoxia, but the safety and efficacy
of chronic administration in humans need to be subjected to controlled
clinical trials before it can be recommended for routine use,” they conclude.
A spokeswoman for Pfizer, the manufacturer of Viagra,
told The Journal earlier this week that the study was encouraging.
She added that Pfizer was currently researching into this area and hoped
that it would lead to benefits for patients with pulmonary hypertension.
Sildenafil is a selective phosphodiesterase-5 (PDE-5)
inhibitor used to treat erectile dysfunction. Levels of pulmonary vascular
cyclic GMP, which mediate the vasorelaxant actions of nitric oxide, are
elevated by PDE-5 inhibition.
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