The most common side effects are:

• headache
• dizziness
• low blood pressure
• indigestion
• swelling of your hands, legs, feet, and ankles (peripheral edema)
• nausea and vomiting
• diarrhea

This medication has rarely caused serious bleeding. Contact your doctor right away if you notice:

• unusual bleeding from the vagina
• coughing up blood
• bleeding around catheter site
• signs of stomach/intestinal bleeding (such as black/bloody stools, vomit that contains blood or looks like coffee grounds)
• signs of bleeding in the brain (such as severe headache, weakness on one side of the body, vision problems, slurred speech, confusion)

Get medical help right away if you notice any symptoms of a serious allergic reaction, such as:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

Riociguat is a soluble guanylate cyclase (sGC) stimulator.   sGC is a chemical already found in the body that interacts with another chemical called nitric oxide (NO). Riociguat stimulates sGC to carry out these interactions with NO, which are important to helping more blood flow through the lung blood vessels. It relaxes and widens the blood vessels in the lungs and this decreases the pulmonary blood pressure to the heart and improves its function. 

Do not take riociguat if:

• you have severe liver disease
• severe kidney dysfunction or are on dialysis
• you are pregnant
• you are a smoker

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• smoking or history of smoking
• low or high blood pressure
• other lung conditions (such as pulmonary veno-occlusive disease, idiopathic interstitial pneumonia)
• a severe loss of body water (dehydration)
• a severe blockage of blood flow out of the heart

Drug interactions - Do not take riociguat if you:

• are taking certain drugs used to treat chest pain/angina or high blood pressure (nitrates such as nitroglycerin, isosorbide)
• are taking dipyridamole
• are taking drugs to treat erectile dysfunction-ED/pulmonary hypertension (such as sildenafil, tadalafil, vardenafil)
• are taking theophylline or aminophylline
• smoke cigarettes - it decreases blood levels of this medication.

Use in pregnancy: Riociguat may harm an unborn baby. It is important to prevent pregnancy while taking this medication and for 1 month after treatment. Therefore, female patients must use reliable birth control during treatment.

Use in breastfeeding: It is not known if riociguat passes into breast milk. Breastfeeding is not recommended.