Bosentan

Conditions Treated

Bosentan is used to treat pulmonary arterial hypertension (PAH, high blood pressure in the vessels that carry blood to the lungs). Bosentan may improve the ability to exercise and slow the worsening of symptoms in patients with PAH. Bosentan is in a class of medications called endothelin receptor antagonists. It works by stopping the action of endothelin, a natural substance that causes blood vessels to narrow and prevents normal blood flow in people who have PAH.

Possible Side Effects

What Side Effects Can This Cause?

Bosentan may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• headache
• flushing
• itching
• runny nose, sore throat, and other cold symptoms
• heartburn

Some side effects can be serious. The following symptoms are uncommon, but if you experience any of them or those listed in the IMPORTANT WARNING section, call your doctor immediately:

• swelling of the arms, hands, feet, ankles, or lower legs
• sudden weight gain
• fast, pounding, or irregular heartbeat
• fainting
• dizziness
• blurred vision
• pale skin
• confusion
• shortness of breath
• weakness

Male laboratory animals who were given medications similar to bosentan developed problems with their testicles and produced fewer sperm (male reproductive cells) than normal. It is not known if bosentan will damage the testicles or decrease the number of sperm produced in men. Talk to your doctor about the risks of taking bosentan if you would like to have children in the future.Bosentan may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/Safety/MedWatch] or by phone [1-800-332-1088].

Usage Instructions

How Should This Medication Be Used

Bosentan comes as a tablet to take by mouth. It is usually taken with or without food twice a day in the morning and evening. To help you remember to take bosentan, take it at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take bosentan exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor. Your doctor will probably start you on a low dose of bosentan and increase your dose after 4 weeks. Bosentan controls the symptoms of PAH but does not cure it. It may take 1-2 months or longer before you feel the full benefit of bosentan. Continue to take bosentan even if you feel well. Do not stop taking bosentan without talking to your doctor. If you suddenly stop taking bosentan, your symptoms may get worse. Your doctor may decrease your dose gradually.

What Dietary Instructions Should I Follow

Talk to your doctor about drinking grapefruit juice while taking this medication.

Are There Any Special Instructions

Before taking bosentan, tell your doctor and pharmacist if you are allergic to bosentan, any other medications, or corn. do not take cyclosporine (Sandimmune, Neoral) or glyburide (DiaBeta, Glynase, Micronase, others) while taking bosentan. tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking. Be sure to mention any of the following: anticoagulants ('blood thinners') such as warfarin; cholesterol-lowering medications (statins) such as atorvastatin (Lipitor), fluvastatin (Lescol), lovastatin (Mevacor), pravastatin (Pravachol), and simvastatin (Zocor); hormonal contraceptives (birth control pills patches, rings, shots, implants, and intrauterine devices); ketoconazole (Nizoral); and medications for diabetes. Many other medications may also interact with bosentan, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects. tell your doctor if you have or have ever had anemia (condition in which red blood cells do not bring enough oxygen to the organs) or heart disease.