Terazosin is used alone or with other drugs to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. This medication works by relaxing blood vessels so blood can flow more easily.

Terazosin is also used in men to treat the symptoms of an enlarged prostate (benign prostatic hyperplasia-BPH). It does not shrink the prostate, but it works by relaxing the muscles in the prostate and part of the bladder. This helps to relieve symptoms of BPH such as difficulty in beginning the flow of urine, weak stream, and the need to urinate often or urgently (including during the middle of the night).

Terazosin belongs to a class of drugs known as alpha blockers.

This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This drug may also be used to help your body "pass," or get rid of, kidney stones through urination. It may also be used for bladder problems in women.

Read the Patient Information Leaflet if available from your pharmacist before you start taking terazosin and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually once daily at bedtime.

If you are taking this drug for the first time, do not take more than 1 milligram to start. Terazosin may cause a sudden drop in your blood pressure, which could lead to dizziness or fainting. This risk is higher when taking your first dose. To avoid injury related to dizziness or fainting, take your first dose of terazosin at bedtime.

Your doctor will start this medication at a low dose and gradually increase your dose. Any time your dose is increased or if you restart treatment after you have stopped it, take your first dose at bedtime unless otherwise directed to lessen the risk of injury related to dizziness or fainting. Also during these times, avoid situations where you may be injured if you faint.

The dosage is based on your medical condition and response to treatment.

Take this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. If you miss taking terazosin for a few days, you may need to restart treatment at the low dose and gradually increase your dose again. Consult your doctor for more details.

If you are taking this medication for high blood pressure, keep taking this medication even if you feel well. Most people with high blood pressure do not feel sick.

If you are taking this drug for an enlarged prostate, it may take 2 to 4 weeks to see an improvement in your symptoms, and up to 6 weeks before you see the full benefit of this drug.

Tell your doctor if your condition does not get better or if it gets worse (for example, your blood pressure readings remain high or increase).

Dizziness, lightheadedness, tiredness, nausea, drowsiness, blurred vision, headache, or stuffy nose may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• fainting
• fast/irregular heartbeat
• burning/tingling in the hands/feet
• sexual function problems
• swelling of the ankles/hands/feet
• unexpected weight gain

Rarely, males may have a painful or prolonged erection lasting 4 or more hours. If this occurs, stop using this drug and get medical help right away, or permanent problems could occur.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking terazosin, tell your doctor or pharmacist if you are allergic to it; or to other alpha blockers such as doxazosin or prazosin; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• low blood pressure/fainting
• certain eye problems (cataracts, glaucoma)

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. You should avoid driving or hazardous tasks for 12 hours after the first dose, after your dose is increased, and when this medication is restarted after it has been stopped. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery (including cataract/glaucoma eye surgery), tell your doctor or dentist if you are taking or have ever taken this medication, and about all the other products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially dizziness, fainting, and low blood pressure when getting up from a sitting or lying position. These side effects can increase the risk of falling.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this drug passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• other alpha blocker drugs (such as prazosin, tamsulosin)

If you are also taking a drug to treat erectile dysfunction-ED or pulmonary hypertension (such as sildenafil, tadalafil), your blood pressure may get too low which can lead to dizziness or fainting. Your doctor may need to adjust your medications to minimize this risk.

Some products have ingredients that could raise your blood pressure. Tell your pharmacist what products you are using, and ask how to use them safely (especially cough-and-cold products, diet aids, or NSAIDs such as ibuprofen/naproxen).

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, fainting.

Do not share this medication with others.

If you have high blood pressure, lifestyle changes that may help this medication work better include exercising, stopping smoking, and eating a low-cholesterol/low-fat diet. Consult your doctor for more details.

Have your blood pressure checked regularly while taking this medication. Learn how to monitor your own blood pressure at home, and share the results with your doctor.

Lab and/or medical tests (such as prostate exams, blood pressure) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up. See also How to Use section.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.