Friday August 17, 2007
Viagra in acute pulmonary hypertension

The treatment of pulmonary hypertension remains very challenging due to multifactorial and multidimensional nature of disease as well as the side effects of therapeutic agents.

Understanding the mechanism of action: The vascular endothelium produces nitric oxide that diffuses into the vascular smooth muscle cells, where it binds to and activates guanylate cyclase, causing smooth muscle relaxation. The action of cGMP is terminated by phosphodiesterase (PDE), which converts cGMP to the inactive 5-GMP. It is postulated that PDE inhibitors such as milrinone should be capable of affecting vasodilatation by prolonging the action of cGMP.

Why Sildenafil (Viagra): At least 11 isoenzymes of PDE have been identified. The specificity of sildenafil for PDE type 5 is known to produce vasodilatation in the penile corpus cavernosum (for which it is well known). Because PDE type 5 is also found in high concentrations in the lung, sildenafil is also postulated as a treatment for pulmonary hypertension by causing pulmonary vasodilatation. Sildenafil is also said to ameliorates effects of inhaled nitric oxide withdrawal.

Note: Viagra is marketed with name "Revatio" to avoid possible embarrassment for patients with pulmnary hypertension at pharmacy counter.


references: click to get abstract/article

1. Sildenafil for Pulmonary Hypertension - The Annals of Pharmacotherapy: Vol. 39, No. 5, pp. 869-884

2. Sildenafil—a possible treatment for acute pulmonary hypertension during cardiac surgery - Proc (Bayl Univ Med Cent). 2002 January; 15(1): 13–15

3. Sildenafil in primary pulmonary hypertension. N Engl J Med. 2000;343:1342

4. Therapy of pulmonary hypertension: targeting pathogenic mechanisms with selective treatment delivery -Crit Care Med. 2001;29:1086–1087