riociguat + sildenafil

**Riociguat + sildenafil** is a non-standard, non-approved combination of two distinct pulmonary hypertension treatments: riociguat—a soluble guanylate cyclase stimulator—and sildenafil—a phosphodiesterase type 5 inhibitor. Both drugs act on the *nitric oxide–cGMP pathway* to induce vasodilation in the pulmonary vasculature: riociguat directly stimulates soluble guanylate cyclase, increasing cGMP both in an NO-dependent and independent manner; sildenafil inhibits the breakdown of cGMP via phosphodiesterase type 5 inhibition. This leads to relaxation and widening of pulmonary arteries, reduction of pulmonary arterial pressure, and improvement of right heart function. **However, concomitant administration of riociguat and sildenafil is contraindicated due to a significantly increased risk of systemic hypotension, as clinical studies found no positive benefit:risk ratio for the combination. There is no approved clinical indication for co-administration, and switching protocols recommend wash-out periods between these drugs rather than overlap**[1]. Riociguat is developed and manufactured by Bayer, while sildenafil is developed by Pfizer, with generic options available for sildenafil. Both are oral small molecule therapies.

Other names

riociguat + sildenafil