Phosphodiesterase 5 (sildenafil) inhibitors for pulmonary hypertension

Pulmonary hypertension (PH) is high blood pressure in the lung circulation. It can occur without a known cause, or it can be caused by another lung disease or be secondary to abnormalities in the left side of the heart. The review sought to determine whether there was evidence that sildenafil (also known as Viagra), a drug which opens up the arteries and increases the flow of blood, could decrease pulmonary artery blood pressure and alleviate symptoms of PH. A limited number of studies of short term i duration indicated that the drug can open up the arteries. One small longer-term study found some favourable effects in terms of symptoms, but in the absence of longer term outcomes, we could not establish whether this meant that the people given the drug felt that their levels of daily activity were better. Future studies should be longer in duration, and should measure the impact of treatment on daily activities, mortality, quality of life and exercise capacity.

Authors' conclusions: 

The validity of the observed effects is undermined by small participant numbers and inadequate exploration of the different disease etiologies. The effects on long term outcome such as NYHA functional class, symptoms, mortality and exercise capacity require further validation. More studies of adequate size are required before the long term effects of sildenafil on clinically important outcomes can be established.

Read the full abstract...

Pulmonary Hypertension (PH) can be either of unknown aetiology (primary pulmonary hypertension (PPH)) or due to a known underlying cause (secondary pulmonary hypertension (SPH). Pulmonary arteriolar vasoconstriction is considered to be an important characteristic of PH. Therapies which aim to vasodilate are used to treat pulmonary hypertension.


To determine the clinical efficacy of sildenafil, a vasodilator which works through inhibition of the enzyme phosphodiesterase type V (PDE5I), administered via any route to people with pulmonary hypertension in primary or secondary forms.

Search strategy: 

MEDLINE, EMBASE and CENTRAL were searched with pre-defined search terms. Searches were current as of October 2006.

Selection criteria: 

Randomised controlled trials were considered for inclusion in the review. We included studies which assessed the effects of sildenafil in participants with PPH and SPH.

Data collection and analysis: 

Two reviewers independently assessed and extracted data from clinical trials. Data were entered in RevMan Analyses 1.0.2. Continuous data were pooled with an estimate on either WMD (weighted mean difference) or SMD (standardised mean difference) scales. Dichotomous data were pooled and a RR (relative risk) was calculated.

Main results: 

Four studies recruiting 77 participants met the inclusion criteria of the review. Two studies assessed the acute effects of sildenafil. Two small crossover study assessed the effects of long term administration. The 'acute effect' studies indicated that sildenafil has a pulmonary vasodilatory effect. The two crossover studies showed improvement in symptoms. One study showed improvement in fatigue domains from a validated health status questionnaire. Both crossover studies reported that the drug was well tolerated.