1. Terazosin oral capsule is available only as a generic drug.
  2. Terazosin comes only as a capsule you take by mouth.
  3. Terazosin oral capsule is used to improve urinary flow and other symptoms of benign prostatic hyperplasia (BPH) in men. It’s also used to treat high blood pressure in men and women.

  • Low blood pressure warning: Terazosin can cause a sudden drop in blood pressure. This typically occurs when you stand up after lying down or sitting. This is called orthostatic hypotension. You may feel dizzy, faint, or lightheaded. It can occur anytime while you are taking this drug. However, it is more likely to occur right after your first dose and during the first few days of treatment.
  • Painful erection warning: This drug may cause priapism, a painful erection of the penis that lasts for hours. If you have an abnormal erection, go to the nearest emergency room right away. If left untreated, this condition can lead to impotence (a permanent inability to have an erection).
  • Cataract surgery warning: If you’re going to have cataract surgery, be sure to tell your doctor that you are taking this drug. Intraoperative floppy iris syndrome (IFIS) can occur during this surgery in people taking terazosin. IFIS causes problems with the iris of the eye.

Terazosin is a prescription drug. It comes only as a capsule you take by mouth.

Terazosin oral capsule is only available as a generic drug. Generic drugs usually cost less than brand-name drugs.

Why it’s used

Terazosin is used to improve urinary flow and other symptoms of benign prostatic hyperplasia (BPH) in men. It is also used to treat high blood pressure in men and women.

Terazosin may be used as part of a combination therapy. That means you may need to take it with other drugs.

How it works

Terazosin belongs to a class of drugs called alpha-blockers. A class of drugs refers to a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Terazosin works by relaxing the muscles in your bladder and prostate to improve urine flow. It also widens blood vessels in your body so blood can flow through more easily. This helps lower your blood pressure.

Terazosin oral capsule can cause a sudden drop in blood pressure. This typically occurs when you stand after lying down or sitting. It’s called orthostatic hypotension. You may feel dizzy, faint, or lightheaded. It can occur anytime while you are taking this drug. However, it’s more likely to occur right after your first dose and during your first few days of treatment.

Terazosin can also cause other side effects.

More common side effects

The more common side effects that can occur with terazosin include:

  • weakness
  • low blood pressure
  • drowsiness
  • stuffy or runny nose
  • impotence (inability to have an erection)
  • blurred or hazy vision
  • nausea
  • swelling or puffiness in hands, feet, or lower legs
  • increased heart rate
  • urinary tract infection

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Allergic reaction. Symptoms can include:
    • rash
    • fever
    • shortness of breath
  • Priapism (painful erection of the penis that lasts for hours)
  • Thrombocytopenia (low blood platelet count)
  • Atrial fibrillation (irregular heartbeat)
  • Intraoperative floppy iris syndrome (IFIS). This condition can occur during cataract surgery. It causes problems with the iris of your eye. If you are going to have cataract surgery, tell your doctor that you are taking an alpha-blocker.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Terazosin oral capsule can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with terazosin are listed below.

Blood pressure drug

Taking verapamil with terazosin may cause very low blood pressure.

Erectile dysfunction (ED) drugs

When taken with terazosin, drugs to treat ED can cause very low blood pressure. Examples of these drugs include:

  • avanafil
  • tadalafil
  • vardenafil
  • sildenafil

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

Terazosin oral capsule comes with several warnings.

Allergy warning

This drug can cause a severe allergic reaction. Symptoms can include:

  • trouble breathing
  • swelling of your throat or tongue

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it or to any ingredient in the terazosin capsule. Taking it again could be fatal (cause death). If you have questions about your allergies and taking this drug, talk to your doctor or pharmacist.

Warnings for people with certain health conditions

For people with hypotension (low blood pressure): If you’re using this drug for benign prostatic hypertrophy and also have low blood pressure, terazosin may lower your blood pressure even more.

For people with thrombocytopenia (low platelet count): This drug has caused low platelet count in the blood of some people who take it. If you already have this condition, taking this drug could make it worse. While you are taking this drug, your doctor may monitor your platelet count through blood tests.

For people with risk of falls: If you are at risk of falls, the low blood pressure that can occur when taking this drug can increase your fall risk. Factors that put you at risk of falls include being a senior (ages 65 years and older), having osteoporosis, and having problems with balance.

To help reduce your fall risk, if you’re taking this drug once a day, take it at bedtime. Also, be sure to move slowly when standing after sitting or lying down.

Warnings for other groups

For pregnant women: Terazosin is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. This drug should only be used if the potential benefit justifies the potential risk to the fetus.

For women who are breastfeeding: It isn’t known if this drug passes into breast milk. Talk to your doctor about whether you should take this drug while breastfeeding.

For seniors: The lowered blood pressure that can occur with posture changes when taking this drug can increase your fall risk. To help reduce your risk of falls, take this drug at bedtime if you are taking it once a day. Also, be sure to move slowly when standing after sitting or lying down.

For children: This drug has not been established as safe or effective for use in children younger than 18 years.

If you’re taking this drug to treat BPH, you should see your symptoms start to improve within 2 to 4 weeks. If you’re taking it to treat high blood pressure, you should notice a change right away when you check your blood pressure.

This dosage information is for terazosin oral capsule. All possible dosages may not be included here. Your doctor will tell you what dosage is right for you. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Forms and strengths

Generic: Terazosin

  • Form: oral capsule
  • Strengths: 1 mg, 2 mg, 5 mg, 10 mg

Dosage for benign prostatic hyperplasia

Adult dosage (ages 18 years and older)

  • Typical starting dosage: 1 mg per day at bedtime.
  • Dosage increases: Your doctor may gradually increase your dosage to 2 mg, 5 mg, or 10 mg per day. Any increase in your dosage will depend on how your body responds to the medication.
    • If you’re at the 10 mg daily dose, your doctor will want to wait at least 4–6 weeks before increasing the dosage. This will help confirm whether the drug is working. After that time, the dosage can be increased to 20 mg per day if needed.
    • If you stop taking this drug for several days, be sure to restart the medication at 1 mg/day. Do not stop taking this drug without talking to your doctor first.
  • Maximum dosage: 20 mg per day.

Child dosage (ages 0–17 years)

Dosage for people younger than 18 years has not been established.

Dosage for hypertension (high blood pressure)

Adult dosage (ages 18 years and older)

  • Typical starting dosage: 1 mg once per day at bedtime.
  • Dosage increases: Your doctor may gradually increase your dosage. The usual recommended dosage range is 1 to 5 mg once daily. However, you may benefit from doses as high as 20 mg per day.
    • You can help determine whether changes to your dosage are needed. Do this by checking your blood pressure right before your next dose, and again 2–3 hours after that dose. Changes to your dosage could be a change in your dose amount, or a change from taking this drug once a day to twice a day.
    • If you stop taking this drug for several days, be sure to restart the medication at 1 mg/day. Do not stop taking this drug without talking to your doctor first.
  • Maximum dosage: 20 mg per day. Dosages over 20 mg per day do not lower blood pressure any further.

Child dosage (ages 0–17 years)

Dosage for people younger than 18 years has not been established.

Special dosage considerations

Taking terazosin at the same time as other medications that lower blood pressure can cause very low blood pressure. The dosage of either terazosin or any other drug you take for high blood pressure may need to be changed. Talk to your doctor for more information.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

Do not stop taking this drug without talking to your doctor first. Stopping this drug suddenly could result in a sudden and dangerous increase in blood pressure.

Terazosin oral capsule is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all:

  • If you’re taking this drug to treat BPH, your symptoms may worsen. These symptoms include an urgent need to urinate and a weak urine stream.
  • If you’re taking it to treat high blood pressure, your blood pressure may increase.

If you miss doses or don’t take the drug on schedule: Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much: You could have dangerous levels of the drug in your body, which could cause very low blood pressure. Symptoms of very low blood pressure can include:

  • feeling dizzy
  • feeling faint or lightheaded
  • passing out

If you think you’ve taken too much of this drug, call your doctor or seek guidance from the American Association of Poison Control Centers at 800-222-1222 or through their online tool. But if your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: Call your doctor for guidance on how you should restart this drug.

How to tell if the drug is working:

  • If you’re taking this drug to treat BPH, your urinary flow should improve.
  • If you’re taking it to treat high blood pressure, your blood pressure should go down. Your doctor can check your blood pressure, or you can do it using a home blood pressure monitor.

Keep these considerations in mind if your doctor prescribes terazosin oral capsule for you.

General

If you’re taking this medication once a day, take it at bedtime to avoid side effects such as a sudden drop in blood pressure.

Storage

  • Store terazosin at room temperature between 68°F (20°C) and 77°F (25°C).
  • Do not freeze this drug.
  • Keep this drug away from light.
  • Don’t store this medication in moist or damp areas such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport X-ray machines. They won’t damage your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

To make sure that terazosin is safe for you to take, your doctor may monitor the following before you begin treatment and regularly during treatment:

  • blood pressure
  • heart rate
  • blood cell counts
  • symptoms of BPH

When you have an enlarged prostate, you’re at risk of prostate cancer. Your doctor may also look at your levels of prostate-specific antigen (PSA) to check for prostate cancer.

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other options that may work for you.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.