In the U.S.—

In Canada—

• Antihypertensive, (pulmonary)
• Endothelin receptor antagonist

Bosentan (BOH-sen-tan) is used to treat the symptoms of pulmonary arterial hypertension. This is the high blood pressure that occurs in the main artery that carries blood from the right side of the heart (the ventricle) to the lungs. When the smaller blood vessels in the lungs become more resistant to blood flow, the right ventricle must work harder to pump enough blood through the lungs. Bosentan works by blocking a hormone (a naturally occurring substance), that is found in the blood and lungs in large quantities of the people with pulmonary arterial hypertension. Bosentan helps by increasing the supply of blood to the lungs and reducing the workload of the heart.

This medicine is available only with your doctor's prescription, in the following dosage forms:

Oral
• Tablets (U.S. and Canada)

In deciding to use a medicine, the risks of using the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For bosentan, the following should be considered:

Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to bosentan. Also tell your doctor and pharmacist if you are allergic to any other substances, such as foods, preservatives, or dyes.

Pregnancy—Bosentan is not recommended during pregnancy. It has been shown to cause serious birth defects or other problems in animals. Be sure you have discussed this with your doctor.

Monthly pregnancy tests are needed, and a gynecologist should help to decide what contraceptives should be used. Your doctor should be notified immediately if there is any delay in the start of your menstrual cycle, and any other reason to think that you may be pregnant.

Breast-feeding—It is not known whether bosentan passes into breast milk. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are using this medicine and who wish to breast-feed should discuss this with their doctor.

Children—Studies on this medicine have been done only in adult patients, and there is no specific information comparing use of bosentan in children with use in other age groups.

Older adults—Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information comparing use of bosentan in the elderly with use in other age groups.

Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine. When you are taking bosentan, it is especially important that your doctor and pharmacist know if you are taking any of the following:

• Cyclosporin A (e.g., Neoral) orUse of this medicine with bosentan can cause both medicines to not work properly

• Cytochrome P450 inhibitors (e.g., Ketoconazole) —These medicines may increase the effects of bosentan

• Hormonal Contraceptives that are implantable (e.g., NuvaRing), injectable (e.g., Lunelle), or oral (e.g., Triphasil)—Bosentan may prevent contraceptives from working properly and may result in an unplanned pregnancy

• Hypoglycemic agents, oral (e.g., Glyburide) —Use of this medicine with bosentan can cause both medicines to not work properly

• Statins, such as: Atorvastatin (e.g. Lipitor) orLovastatin (e.g., Mevacor) orSimvastatin (e.g. Zocor) —bosentan may decrease the effects of these medicines

• Liver disease—bosentan may make make these conditions worse in patients who have moderate or severe liver disease

Dosing—

The dose of will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of bosentan. If your dose is different, do not change it unless your doctor tells you to do so.

The number of tablets that you take depends on the strength of the medicine. Also,

• For oral dosage form (tablets):
  • • Adults—62.5 milligrams twice daily for 4 weeks, then increased to 125 milligrams twice a day. For patients who weigh less than 40 kilograms (88 pounds) and who are over 12 years of age, the dose is 62.5 milligrams twice a day.

Missed dose—

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.

Storage—

To store this medicine:

• Keep out of the reach of children.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Ask your health care professional how you should dispose of any medicine you do not use. Be sure that any discarded medicine is out of the reach of children.

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly and to check for unwanted effects.

In addition, check with your doctor immediately if you experience dark urine, light colored stools, loss of appetite, nausea and vomiting, unusual tiredness, yellow eyes or skin, fever with or without chills, or stomach pain.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• More common
  • Blurred vision;  confusion;  dizziness;  dark urine;  faintness or lightheadedness when getting up from a lying or sitting position;  fever with or without chills ;  light-colored stools;  loss of appetite;  nausea and vomiting;  stomach pain;  sudden sweating;  unusual tiredness or weakness;  yellow eyes or skin 
  
  

• Less common
  • swelling 
  
  

• Symptoms of Overdose

  Get emergency help immediately if any of the following symptoms of overdose occur

  • Blurred vision;  confusion;  dizziness ;  faintness or lightheadedness when getting up from a lying or sitting position ;  headache;  increased heart rate ;  nausea;  sudden sweating;  unusual tiredness or weakness;  vomiting 
  
  

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome.

• More common
  • Fast, irregular, pounding, or racing heartbeat or pulse;  feeling of warmth;  muscle aches;  redness of the face, neck, arms, and occasionally upper chest ;  stuffy or runny nose;  swelling of the legs;  sore throat;  unusual tiredness or weakness 
  
  

• Less Common
  • Acid or sour stomach;  belching ;  heartburn;  indigestion;  itching skin;  stomach discomfort, upset or pain 
  
  

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.