Riociguat: what it treats, how to take it, and side effects
Last updated September 7, 2026.
**Riociguat, sold as Adempas, is a prescription tablet for two types of pulmonary hypertension, and it belongs to a drug class called soluble guanylate cyclase stimulators.** It switches on an enzyme in the walls of your lung arteries that raises a signaling molecule called cGMP, which relaxes and widens those arteries so blood moves through your lungs at lower pressure and your right heart works less hard. Because that same pathway is used by nitrates and by erectile dysfunction drugs such as sildenafil and tadalafil, combining riociguat with them can drop your blood pressure to a dangerous level and is never allowed. Riociguat also causes serious harm to a developing fetus, so it carries a boxed warning against use in pregnancy and is dispensed to people who can become pregnant only through a restricted program with monthly pregnancy testing.
What does it treat?
Riociguat is approved for chronic thromboembolic pulmonary hypertension (CTEPH, WHO Group 4) that persists or comes back after surgery to remove clot from the lung arteries, or that cannot be operated on, and for pulmonary arterial hypertension (PAH, WHO Group 1), including the idiopathic, inherited, and connective tissue disease forms such as scleroderma. In both conditions the small arteries in your lungs are narrowed or scarred, and the pattern people describe is breathlessness that shows up with stairs, hills, or carrying groceries, unusual fatigue, lightheadedness or near fainting with exertion, chest pressure, and swelling in the ankles or belly from strain on the right side of the heart. In studies it improved how far people could walk in six minutes and delayed clinical worsening in PAH. Riociguat comes only as a single ingredient tablet, with no combination products, but pulmonary hypertension specialists often pair it with drugs from other classes such as ambrisentan, bosentan, macitentan, or a prostacyclin. It is never paired with a PDE-5 inhibitor.
How do you take it?
Riociguat is a film coated tablet in 0.5, 1, 1.5, 2, and 2.5 mg strengths, taken three times a day roughly 6 to 8 hours apart. The usual adult start is 1 mg three times a day, or 0.5 mg three times a day if you tend to run a low blood pressure. Your prescriber then raises the dose by 0.5 mg per dose no sooner than every 2 weeks, as long as your systolic blood pressure stays above 95 and you have no symptoms of low pressure, up to the maximum of 2.5 mg three times a day, which is 7.5 mg in 24 hours. If your systolic pressure falls below 95 with dizziness or faintness, the dose is reduced by 0.5 mg. You can take it with or without food, and taking it with food may help if your blood pressure drops easily; if you cannot swallow tablets whole, they can be crushed and mixed with water or soft food right before you take them. Keep antacids containing aluminum or magnesium at least 1 hour away from your dose, since they block absorption. If you miss a dose, skip it and take the next scheduled dose, and never double up. Call your prescriber before restarting if you have gone 3 days or more without it, because you have to begin the titration again at 1 mg three times a day, and call the same day if you faint, cough up blood, or notice your breathing getting worse.
Side effects to know
- Common: The effects people most often notice are headache, dizziness, indigestion or stomach upset, nausea, diarrhea, vomiting, constipation, and low blood pressure, and these are most common during the weeks when the dose is being raised.
- Serious: Stop and get help for fainting or near fainting with a systolic blood pressure under 95, and for coughing up blood or any airway bleeding, which can be serious or life threatening in these conditions. Also get urgent care for sudden worsening shortness of breath, especially early in treatment, since it can signal pulmonary edema from an underlying vein blockage that makes riociguat unsafe to continue.
Who should not take it?
Do not take riociguat with any nitrate or nitric oxide donor, including nitroglycerin tablets, patches, or spray, isosorbide, and amyl nitrite poppers, and do not take it with PDE-5 inhibitors such as sildenafil, tadalafil, or vardenafil, or with nonspecific PDE inhibitors such as dipyridamole and theophylline. It is also contraindicated in pulmonary hypertension caused by idiopathic interstitial pneumonias. It must not be used in pregnancy because it causes fetal harm, so people who can become pregnant need a negative pregnancy test before starting, monthly tests during treatment and one month after stopping, and reliable contraception, and access runs through a restricted riociguat program; do not breastfeed while taking it. Tell your clinician before starting if you have severe liver disease (Child-Pugh C) or kidney function with a creatinine clearance under 15 or you are on dialysis, since riociguat is not recommended in those situations, and if you have low blood pressure or are on blood pressure medicines or diuretics. Strong inhibitors like ketoconazole, itraconazole, and ritonavir raise riociguat levels and usually call for a 0.5 mg starting dose, while rifampin, phenytoin, carbamazepine, phenobarbital, and St. John's wort lower levels and may make it stop working. Tell your prescriber if you smoke or quit smoking, because smoking cuts blood levels by about half and quitting can push levels up. Alcohol lowers blood pressure on its own, so keep it minimal and avoid it entirely while your dose is being raised.
When is it an emergency?
Call 911 in the US if you collapse or pass out, if you have trouble breathing or sudden severe shortness of breath at rest, if you cough up more than a streak of blood, or if you have signs of an allergic reaction such as swelling of the lips, tongue, or throat, hives with wheezing, or throat tightness. Taking too much riociguat mainly causes a dangerous drop in blood pressure, which shows up as severe dizziness, cold and clammy skin, confusion, blurred vision, a racing pulse, or fainting; for a suspected overdose or an accidental dose by a child, call Poison Control at 1-800-222-1222 right away, and call 911 instead if the person is unresponsive or not breathing normally. If you accidentally took a nitrate or an erectile dysfunction drug along with riociguat, treat it as an emergency even if you feel fine at first. If you are pregnant or think you might be, stop riociguat and contact your prescriber the same day.
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Common questions
What is the maximum dose of riociguat?
The ceiling is 2.5 mg three times a day, which is 7.5 mg in 24 hours. You get there in steps: most adults start at 1 mg three times a day, and the dose goes up by 0.5 mg per dose no sooner than every 2 weeks, only if your systolic blood pressure stays above 95 and you have no dizziness or faintness. People who tend toward low blood pressure start at 0.5 mg three times a day. One exception runs the other way: current smokers clear the drug faster, so a specialist may go above 2.5 mg per dose, and that dose has to come back down if you quit.
Can I drink alcohol on riociguat?
There is no specific alcohol interaction on the label, but alcohol lowers blood pressure and so does riociguat, so the two stack. Skip alcohol entirely during the weeks your dose is being raised, since that is when dizziness and fainting are most likely. Once you are on a steady dose and your pressure is stable, an occasional single drink with food is usually workable, and standing up slowly helps. If a drink leaves you lightheaded, dizzy, or unsteady, tell your prescriber, because it usually means your dose is at the edge of what your blood pressure can support.
Can I take riociguat while pregnant or breastfeeding?
No. Riociguat carries a boxed warning for fetal harm and is contraindicated in pregnancy based on animal data showing birth defects and pregnancy loss. If you can become pregnant, you need a negative pregnancy test before your first dose, a test every month during treatment, and one more test a month after you stop, plus reliable contraception the whole time, and the drug is dispensed through a restricted program for that reason. If you become pregnant or miss a period, stop the drug and call your prescriber the same day. Do not breastfeed while taking riociguat, since there are no data and the risk to a nursing infant is unknown.
Do I take riociguat with food, and what about antacids?
You can take it with or without food, so pick whichever pattern you can repeat three times a day at roughly 6 to 8 hour intervals. If your blood pressure runs low or you get lightheaded after doses, taking it with food is a reasonable adjustment. Antacids containing aluminum or magnesium hydroxide cut how much riociguat you absorb, so keep them at least 1 hour away from your doses. If you cannot swallow the tablet, it can be crushed and mixed with water or a soft food such as applesauce and taken immediately.
What are the signs of a riociguat overdose?
An overdose mainly shows up as a steep drop in blood pressure. Watch for severe dizziness, feeling like you are about to pass out, actually fainting, blurred vision, confusion, a fast or pounding pulse, and cold clammy skin. There is no specific antidote, so treatment is supportive, and riociguat is not removed effectively by dialysis. Call Poison Control at 1-800-222-1222 for a suspected overdose or an accidental dose by a child, and call 911 if the person collapses, is unresponsive, or is having trouble breathing.
Which medicines interact with riociguat?
The absolute ones are nitrates and nitric oxide donors, including nitroglycerin in any form, isosorbide, and amyl nitrite poppers, and PDE inhibitors including sildenafil, tadalafil, vardenafil, dipyridamole, and theophylline; combining any of these with riociguat can cause a dangerous fall in blood pressure. Strong inhibitors of the enzymes and transporters that clear riociguat, such as ketoconazole, itraconazole, and ritonavir, push levels up, so a 0.5 mg starting dose and closer blood pressure monitoring are typical. Strong inducers such as rifampin, phenytoin, carbamazepine, phenobarbital, and St. John's wort drop levels enough that the drug may stop working. Blood pressure medicines and diuretics add to the low pressure effect, and antacids reduce absorption. Give your prescriber a full list including supplements before you start.