Medical Editor: John P. Cunha, DO, FACOEP Last updated on RxList: 11/5/2021
Opsumit Side Effects Center

What Is Opsumit?

Opsumit (macitentan) is an endothelin receptor antagonist used to treat pulmonary arterial hypertension (PAH, WHO Group I) to delay disease progression.

What Are Side Effects of Opsumit?

Common side effects of Opsumit include:

Dosage for Opsumit

The recommended dosage of Opsumit is 10 mg once daily for oral administration.

What Drugs, Substances, or Supplements Interact with Opsumit?

Opsumit may interact with rifampin, ketoconazole, and ritonavir. Tell your doctor all medications and supplements you use. Opsumit is not recommended for use during pregnancy. It may harm a fetus.

Opsumit During Pregnancy and Breastfeeding

Women can receive the drug only through the Opsumit Risk Evaluation and Mitigation Strategy (REMS) Program and must comply with applicable pregnancy testing and contraception requirements before initiating treatment; consult your doctor. Consult your doctor before breastfeeding.

Additional Information

Our Opsumit (macitentan) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


COPD Foods to Boost Your Health - COPD Diet Tips See Slideshow
Opsumit Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using macitentan and call your doctor at once if you have:

  • pain or burning when you urinate;
  • swelling, rapid weight gain;
  • liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or
  • new lung problems--anxiety, sweating, pale skin, severe shortness of breath, wheezing, gasping for breath, cough with foamy mucus, chest pain, fast or uneven heart rate.

Common side effects may include:

  • stuffy nose, sinus pain, sore throat;
  • a bladder infection;
  • headache; or
  • flu symptoms (fever, chills, body aches).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Opsumit (Macitentan Tablets)


COPD (chronic obstructive pulmonary disease) is the same as adult-onset asthma. See Answer
Opsumit Professional Information


Clinically significant adverse reactions that appear in other sections of the labeling include:

  • Embryo-fetal Toxicity [see WARNINGS AND PRECAUTIONS]
  • Hepatotoxicity [see WARNINGS AND PRECAUTIONS]
  • Fluid Retention [see WARNINGS AND PRECAUTIONS]
  • Decrease in Hemoglobin [see WARNINGS AND PRECAUTIONS]

Clinical Trial Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.

Safety data for OPSUMIT were obtained primarily from one placebo-controlled clinical study in 742 patients with PAH (SERAPHIN study) [see Clinical Studies].

The exposure to OPSUMIT in this trial was up to 3.6 years with a median exposure of about 2 years (N=542 for 1 year; N=429 for 2 years; and N=98 for more than 3 years). The overall incidence of treatment discontinuations because of adverse events was similar across OPSUMIT 10 mg and placebo treatment groups (approximately 11%).

Table 2 presents adverse reactions more frequent on OPSUMIT than on placebo by ≥3%.

Table 2: Adverse Reactions

Adverse Reaction OPSUMIT 10 mg
(N=242) (%)
(N=249) (%)
Anemia 13 3
Nasopharyngitis/pharyngitis 20 13
Bronchitis 12 6
Headache 14 9
Influenza 6 2
Urinary tract infection 9 6

Postmarketing Experience

The following adverse reactions have been identified during post-approval use of OPSUMIT. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Immune system disorders: hypersensitivity reactions (angioedema, pruritus and rash)

Respiratory, thoracic and mediastinal disorders: nasal congestion

Gastrointestinal disorders: Elevations of liver aminotransferases (ALT, AST) and liver injury have been reported with OPSUMIT use; in most cases alternative causes could be identified (heart failure, hepatic congestion, autoimmune hepatitis). Endothelin receptor antagonists have been associated with elevations of aminotransferases, hepatotoxicity, and cases of liver failure [see WARNINGS AND PRECAUTIONS].

General disorders and administration site conditions: edema/fluid retention. Cases of edema and fluid retention occurred within weeks of starting OPSUMIT, some requiring intervention with a diuretic, fluid management or hospitalization for decompensated heart failure. [see WARNINGS AND PRECAUTIONS]

Cardiac disorders: symptomatic hypotension


Strong CYP3A4 Inducers

Strong inducers of CYP3A4 such as rifampin significantly reduce macitentan exposure. Concomitant use of OPSUMIT with strong CYP3A4 inducers should be avoided [see CLINICAL PHARMACOLOGY].

Strong CYP3A4 Inhibitors

Concomitant use of strong CYP3A4 inhibitors like ketoconazole approximately double macitentan exposure. Many HIV drugs like ritonavir are strong inhibitors of CYP3A4. Avoid concomitant use of OPSUMIT with strong CYP3A4 inhibitors [see CLINICAL PHARMACOLOGY]. Use other PAH treatment options when strong CYP3A4 inhibitors are needed as part of HIV treatment [see CLINICAL PHARMACOLOGY].

Moderate Dual Or Combined CYP3A4 And CYP2C9 Inhibitors

Concomitant use of moderate dual inhibitors of CYP3A4 and CYP2C9 such as fluconazole is predicted to increase macitentan exposure approximately 4-fold based on physiologically based pharmacokinetic (PBPK) modelling. Avoid concomitant use of OPSUMIT with moderate dual inhibitors of CYP3A4 and CYP2C9 (such as fluconazole and amiodarone) [see CLINICAL PHARMACOLOGY].

Concomitant treatment of both a moderate CYP3A4 inhibitor and moderate CYP2C9 inhibitor with OPSUMIT should also be avoided [see CLINICAL PHARMACOLOGY].

Read the entire FDA prescribing information for Opsumit (Macitentan Tablets)

© Opsumit Patient Information is supplied by Cerner Multum, Inc. and Opsumit Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

Health Solutions From Our Sponsors