8 Adempas (Riociguat) Interactions: Paxlovid, Smoking, Viagra, and More

If you're living with pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH), you may be prescribed Adempas (riociguat). Adempas works by relaxing blood vessels in your lungs, which can help improve your symptoms. But Adempas also has a few important interactions to know about.

Some medications can be dangerous to combine with Adempas. The interaction can lead to very low blood pressure. Other interactions can be managed with dosage adjustments and monitoring. Here's what you should know about eight Adempas interactions.

1. Nitrates

Adempas improves PAH and CTEPH symptoms by relaxing blood vessels in your lungs. But it can also relax blood vessels in other parts of your body, causing low blood pressure (hypotension). Because of this, Adempas can interact with medications that also relax blood vessels, such as nitrates.

If you combine Adempas and nitrates, your blood pressure could drop dangerously low. For this reason, you shouldn't take these medications together.

2. PDE5 inhibitors like sildenafil

Phosphodiesterase 5 (PDE5) inhibitors are often used to treat erectile dysfunction. But certain PDE5 inhibitors, such as sildenafil (Revatio) and tadalafil (Adcirca), are used for PAH. They work on the same pathway in the body as Adempas to relax blood vessels in your lungs - just at a different step in the process.

Adempas can be a good option for people who don't respond well to PDE5 inhibitors. But they shouldn't be taken together. Don't combine Adempas and a PDE5 inhibitor due to the risk of severe hypotension.

3. Azole antifungals

Azole antifungals, such as ketoconazole and itraconazole (Sporanox), can interfere with how Adempas is broken down in your body. This can result in higher Adempas levels and increase the risk of side effects, including hypotension. Your prescriber may need to lower your Adempas dose if you're taking these antifungals.

If you need to take an azole antifungal with Adempas, your healthcare team may advise you to monitor your blood pressure. Watch out for symptoms such as dizziness, lightheadedness, or blurry vision. These can be signs of low blood pressure. It's best to go to the ER if you have these symptoms.

4. Ritonavir

Ritonavir (Norvir) is an antiviral that can increase Adempas levels in the body. This can raise the risk of side effects, such as hypotension. If you need to take ritonavir with Adempas, your healthcare team may lower your Adempas dose.

Ritonavir is available on its own. But it's also found in combination antiviral medications. Examples of these include Kaletra (lopinavir / ritonavir) and Paxlovid (nirmatrelvir / ritonavir).

To minimize your risk of this interaction, tell your healthcare team if you plan to start one of these medications while you're taking Adempas.

5. St. John's wort

Adempas can also interact with over-the-counter (OTC) herbal supplements like St. John's wort.

St. John's wort can interfere with how Adempas is broken down in the body. And this interaction can lower Adempas levels, making it less effective.

Sometimes these types of interactions can be missed if you don't include supplements on your current medication list. Make sure your healthcare team has an up-to-date list of everything you take, including supplements. And let them know if you're thinking about starting or stopping any OTC products or herbal supplements. They can determine the best way to manage these interactions.

6. Certain seizure medications

Certain seizure medications can interact with Adempas. Examples include carbamazepine (Tegretol), phenobarbital (Luminal), and phenytoin (Dilantin). These medications can lower Adempas levels in the body, making it less effective.

The manufacturer doesn't list specific dosage adjustments for dealing with these interactions. But if your current Adempas dose isn't helping with your symptoms, your prescriber may increase it. Be sure to notify them if you plan to start or stop one of these medications.

7. Antacids

Before you grab an OTC antacid for heartburn, chat with your pharmacist. Adempas can interact with antacids that contain aluminum hydroxide or magnesium hydroxide.

If they're taken together, these antacids can prevent your body from properly absorbing Adempas. And if you don't absorb Adempas, it won't work as intended.

If you need to take an antacid, take it at least one hour before or one hour after your Adempas dose. You can also ask your prescriber or pharmacist about alternative options for heartburn relief.

8. Smoking

If you smoke, Adempas may not work as well as expected. This is because smoking can interfere with how your body breaks down Adempas, resulting in lower levels. What's more, smoking can worsen PAH symptoms.

To manage this interaction, your prescriber will likely have you take a higher Adempas dose if you smoke. So be sure to tell them if you start smoking or plan to quit.