Riociguat is a new medication for the treatment of pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH). It is indicated for use in adults in World Health Organization (WHO) Functional Class II, III, or IV. Riociguat is the first medication approved for the treatment of CTEPH that is inoperable, or persists or recurs after surgery. For patients with PAH, riociguat may be used as monotherapy or in combination with other approved PAH therapies such as endothelin receptor antagonists or prostanoids.

Riociguat is a stimulator of soluble guanylate cyclase (sGC); an essential enzyme in the nitric oxide (NO) signalling pathway. Activation of sGC causes a cascade of events that leads to vasodilation and reduced pulmonary artery pressure. Smooth muscle proliferation, platelet aggregation, and vascular remodelling are also inhibited. A double-blind randomised clinical trial demonstrated significant improvements in exercise tolerance, pulmonary vascular resistance, and time to clinical worsening for riociguat compared to placebo.

Systemic hypotension is a potentially serious adverse effect of riociguat. This effect may be potentiated by nitrates, nitric acid donors, and phosphodiesterase inhibitors. The concomitant use of these medications is, therefore, contraindicated. Caution should be exercised when coadministered with antihypertensives or strong inhibitors of cytochrome P450 or P-glycoprotein, such as itraconazole, ciclosporin, and HIV-protease inhibitors. It should also be noted that riociguat is contraindicated in patients with pulmonary hypertension associated with idiopathic interstitial pneumonias.

References:

  1. Adempas® (riociguat) Australian approved product information. Pymble: Bayer Australia. Approved July 2016.
  2. Ghofrani HA, D’Armini AM, Grimminger F, Hoeper MM, Jansa P, Kim NH, et al. Riociguat for the treatment of chronic thromboembolic pulmonary hypertension. N Engl J Med. 2013; 369: 319-29.
  3. Ghofrani HA, Galiè N, Grimminger F, Grünig E, Humbert M, Jing ZC, et al. Riociguat for the treatment of pulmonary arterial hypertension. N Engl J Med. 2013; 369: 330-40.

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