Sildenafil (CTD-Associated PAH / Raynaud's)

How it works

By inhibiting PDE5 it raises cyclic GMP in vascular smooth muscle, producing pulmonary and peripheral vasodilatation that lowers pulmonary arterial pressure and improves digital perfusion.

Prescribing in practice

• It is contraindicated with nitrates and nicorandil because of the risk of profound, potentially life-threatening hypotension — this is the critical interaction to exclude.
• Avoid combining with other potent vasodilators and use caution with alpha-blockers and antihypertensives owing to additive blood-pressure lowering, and the PAH dose differs from that used for erectile dysfunction.
• Seek urgent advice for sudden visual or hearing loss or for priapism.

Monitoring

Monitor blood pressure and symptomatic response, and in pulmonary hypertension assess functional capacity within specialist follow-up.

Counselling the patient

• Never take it with nitrate medicines such as GTN.
• Report sudden changes in vision or hearing promptly.
• It may cause headache, flushing or dizziness, especially when standing.

Evidence & guidelines

Benefit in pulmonary arterial hypertension is established by randomised trials, while Raynaud's use is supported by smaller studies and is generally off-label in the UK.