How does this medication work? What will it do for me?

Bosentan belongs to a class of medications called endothelin receptor antagonists. Bosentan is used to treat pulmonary arterial hypertension, which is high blood pressure of the blood vessels between the heart and lungs.

Bosentan works to block the effect of a natural compound called endothelin, which is something the body makes to tighten blood vessels. Blocking the effect of endothelin allows the blood vessels to relax, thereby decreasing the blood pressure between the heart and lungs.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

62.5 mg
Each orange-white, round, coated tablet, embossed with "B" on one side and "62.5"on the other, contains bosentan monohydrate 62.5 mg. Nonmedicinal ingredients: magnesium stearate, povidone, pregelatinized starch, and sodium starch glycolate; film coating: hydroxypropyl methylcellulose, iron oxide red, iron oxide yellow, titanium dioxide, and triacetin.

125 mg
Each orange-white, ovaloid, coated tablet, debossed with "B" on one side and "125" on the other, contains bosentan monohydrate 125 mg. Nonmedicinal ingredients: magnesium stearate, povidone, pregelatinized starch, and sodium starch glycolate; film coating: hydroxypropyl methylcellulose, iron oxide red, iron oxide yellow, titanium dioxide, and triacetin.

How should I use this medication?

The recommended starting dose is 62.5 mg twice daily (once in the morning and once in the evening) for 4 weeks. After 4 weeks, the dose is increased to the recommended maintenance dose of 125 mg twice daily. Bosentan can be taken with or without food. It should be taken consistently.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take bosentan if you:

  • are allergic to bosentan or to any of the ingredients of the medication
  • are pregnant, planning to become pregnant, or may become pregnant (unless using adequate contraception)
  • are taking a medication called cyclosporine A
  • are taking a medication called glyburide
  • have moderately to severely reduced liver function

What side effects are possible with this medication?

Many medications can cause side-effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects

  • blurred vision
  • dry mouth
  • fatigue
  • flu-like symptoms (e.g., fever, cough, sore throat, runny nose, headache)
  • flushing
  • headache
  • heartburn
  • inflammation of the throat and nasal passages
  • irregular heartbeat
  • itching
  • joint pain
  • low blood pressure
  • skin rash
  • stomach upset
  • symptoms of anemia (e.g., fatigue, shortness of breath)

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:

  • abdominal pain
  • chest pain
  • swelling of the ankles and legs
  • swelling in other parts of the body (severe)
  • symptoms of liver problems (e.g., yellowing of the skin or eyes, nausea, vomiting, fever, abdominal pain, or unusual tiredness)
  • wheezing

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • signs of a serious allergic reaction (e.g., swelling of face or throat, hives, or difficulty breathing)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medication conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Anemia: Bosentan can reduce the number of red blood cells, which carry oxygen throughout your body, and make you feel tired. Your doctor will periodically do blood work to monitor your red blood cell levels to ensure that this does not happen.

Heart failure: People with severe chronic heart failure may see a worsening of their condition when they first start bosentan. This may be due to fluid retention, which is one of the side effects of bosentan. If you have severe chronic heart failure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver problems: Bosentan can affect your liver. Your doctor will perform regular blood tests to make sure your liver is functioning properly. Bosentan should not be used by people who have moderately to severely reduced liver function.

Low blood pressure: If you have low blood pressure, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Stopping medication: Suddenly stopping bosentan may worsen your symptoms. Do not stop taking this medication unless directed by your doctor. If you are stopping treatment, your doctor will monitor you and reduce the dose over a period of time before stopping the medication completely.

Pregnancy: The medication should not be used during pregnancy, as it can cause serious harm to the fetus. Your doctor should perform a pregnancy test before you start this medication, and monthly thereafter while you are taking this medication. Since bosentan decreases the effectiveness of hormonal birth control, you should use more than one form of contraception (e.g., a non-hormonal forms such as condoms) while taking this medication. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if bosentan passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication in children are not well established. Your doctor will determine if the benefits of the medication outweigh the risks for your child.

What other drugs could interact with this medication?

There may be an interaction between bosentan and any of the following:

  • antifungal medications (e.g., fluconazole, itraconazole, ketoconazole, voriconazole)
  • atazanivir
  • carbamazepine
  • clarithromycin
  • cyclosporine A
  • glyburide
  • hormonal birth control (e.g., tablets, injections, patches, implants)
  • imatinib
  • lopinavir
  • maraviroc
  • nevirapine
  • phenobarbital
  • phenytoin
  • quinidine
  • rifampicin
  • ritonavir
  • sirolimus
  • St. John's wort
  • statins (e.g., simvastatin, atorvastatin)
  • tacrolimus
  • warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.