Prazosin is used to treat hypertension (high blood pressure). Lowering blood pressure may lower your risk of a stroke or heart attack.

Prazosin may also be used for other purposes not listed in this medication guide.

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

Prazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it, or whenever your dose is changed. You may feel very dizzy when you first wake up.

Your blood pressure will need to be checked often.

Swallow the capsule whole and do not crush, chew, break, or open it.

Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.

Prazosin is only part of a complete treatment program that may also include diet, exercise, weight control, and special medical care. Follow your doctor's instructions very closely.

Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, or heavy sweating. Call your doctor if you are sick with vomiting or diarrhea.

Store at room temperature away from moisture and heat.

Usual Adult Dose for Hypertension:

Initial dose: 1 mg orally 2 or 3 times a day
Maintenance dose: 1 to 20 mg orally per day in divided doses

Comments:
-Titrate slowly as determined by blood pressure response.
-Therapeutic dosages usually range from 6 to 15 mg per day in divided doses.
-Total daily doses greater than 20 mg usually do not increase efficacy, but some patients may benefit from daily doses up to 40 mg per day in divided doses.

You should not use prazosin if you are allergic to it.

Tell your doctor if you have ever had:

• low blood pressure, especially if caused by taking medications.

Prazosin can affect your pupils. If you have cataract surgery, tell your surgeon ahead of time that you use prazosin.

Tell your doctor if you are pregnant or plan to become pregnant. It is not known whether prazosin will harm an unborn baby. However, having high blood pressure during pregnancy may cause complications such as diabetes or eclampsia (dangerously high blood pressure that can lead to medical problems in both mother and baby). The benefit of treating hypertension may outweigh any risks to the baby.

It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.

Prazosin is not approved for use by anyone younger than 18 years old.

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include extreme drowsiness or underactive reflexes.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

Follow your doctor's directions for your meals, including advice for a reduced salt (sodium) diet.

Avoid driving or hazardous activity until you know how prazosin will affect you. Your reactions could be impaired.

Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.

Drinking alcohol with this medicine can cause side effects.

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

Prazosin may cause serious side effects. Call your doctor at once if you have:

• a light-headed feeling, like you might pass out;

• pounding heartbeats or fluttering in your chest;

• new or worsening chest pain; or

• upper stomach pain, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Call your doctor or seek emergency medical attention if your erection is painful or lasts longer than 4 hours. A prolonged erection (priapism) can damage the penis.

Common side effects of prazosin may include:

• dizziness, drowsiness;

• headache;

• feeling weak or tired; or

• nausea.

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.

Tell your doctor about all your other medicines, especially:

• propranolol;

• any other blood pressure medication;

• a diuretic or "water pill"; or

• sildenafil (Viagra) and other erectile dysfunction medicines.

This list is not complete. Other drugs may affect prazosin, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Keep all appointments with your doctor and the laboratory. Your blood pressure should be checked regularly to determine your response to prazosin.

Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking prazosin.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.