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What is terazosin?

Terazosin is an alpha-adrenergic blocker that helps relax muscles in the veins and arteries. It is only available with a prescription.

Alpha-adrenergic blockers work by blocking norepinephrine, a hormone responsible for tightening muscles surrounding the blood vessels. This leads to improved blood flow and lowered blood pressure.

When the drug is prescribed to treat an enlarged prostate, it relaxes the bladder and prostate muscles and relieves urinary tract obstruction.

What is terazosin used to treat?

The US Food and Drug Administration (FDA) first approved terazosin in 1987 for the treatment of high blood pressure (hypertension).¹

Hypertension increases the workload on the heart and blood vessels. Untreated, it can damage the blood vessels, heart, brain, kidneys, and other organs, leading to complications such as heart failure, stroke, and kidney failure.

Terazosin blocks the hormone norepinephrine, causing the muscles in the veins and arteries to relax, improving blood flow. The drug may be used alone or in combination with other medication.²

Since its initial approval, the drug’s applications have been expanded to other medical conditions, including the treatment of symptoms associated with benign prostatic hyperplasia (BPH).

A man’s risk of developing BPH increases with age. An enlarged prostate causes symptoms such as difficulty urinating, urinary urgency, and painful urination. As the prostate enlarges, it puts increasing pressure on the bladder and urethra.

Terazosin is prescribed to help relax the prostate and bladder muscles and relieve some of the symptoms of BPH. However, it does not shrink the enlarging prostate, and surgery may still be necessary.

Other off-label applications for terazosin are being actively studied with a focus on potentially treating conditions such as hyperhidrosis, distal ureteral calculi, chronic prostatitis, hyperlipidemia, idiopathic oligozoospermia, and urethritis.³

Dosage forms and strengths

Terazosin is available as a capsule, which is taken orally. It’s usually taken once per day or according to the prescriber’s instructions.

The drug is available in strengths of 1mg, 2mg, 5mg, and 10mg.

Dosing information

Terazosin administration varies depending on your condition and age. The initial dosage may be low (1mg, for example) and then increased gradually depending on how it affects your symptoms. Most people respond to a 10mg daily dose.⁴

The recommended dosing for adults is as follows:⁵

  • Hypertension: 1–10mg daily, taken as one dose at bedtime or divided and taken twice daily (the maximum dose is 20mg daily)

  • Benign prostatic hyperplasia: 1–10mg daily at bedtime (the maximum dose is 20mg daily)

The recommended dosing for people under 18 years of age hasn’t yet been established.

How do you take terazosin?

Terazosin is administered daily. You can take it with or without food. Due to side effects like dizziness or fainting, it’s recommended to take it at bedtime.

You should stick to the prescribed dosage and only increase it as your doctor recommends.

If you stop taking the medication for a while, you should consult your doctor in case your dose needs to be changed. Restarting the prescription may require you to start at a lower dosage if it had previously been increased.

Seeing results

Terazosin’s effectiveness depends on the severity of your condition. It should work quickly when used to treat hypertension. If you are taking it for BPH, it can take 4–6 weeks before you start feeling symptom relief.

Remember, this drug is given to improve the symptoms of these conditions — not to cure them.

Who should not take terazosin?

Terazosin may not be recommended for people with certain conditions. Talk to your doctor if you:⁶

  • Are allergic to terazosin or similar medications, such as alfuzosin, prazosin, or doxazosin

  • Are younger than 18 years old

  • Have ever had prostate cancer

  • Are scheduled for cataract surgery (terazosin affects the pupils)

  • Are pregnant or breastfeeding

  • Have low blood pressure (hypotension) or a history of fainting

Terazosin may be given with caution or not recommended for older adults. In this case, the doctor may decide to monitor the patient closely or prescribe an alternative medication.⁷

Potential side effects of terazosin

Taking terazosin is usually safe if you don’t have any of the conditions mentioned above. But some side effects have been reported while using the drug.⁸

Common side effects include the following:

  • Dizziness, vertigo

  • Weakness

  • Tiredness

  • Fainting upon standing 

  • Headache

  • Nausea 

  • Blurred vision

  • Nasal congestion or runny nose

  • Swelling in the hands, ankles, feet, or legs

  • Anxiety

Moderate to severe adverse effects include the following:

  • Hives

  • Erectile dysfunction

  • Shortness of breath

  • Irregular or rapid heartbeat

  • Tingling, pain, or burning in the feet and hands

  • Abnormal heart rhythms

  • Low blood pressure

  • Low platelet count

  • Loss of consciousness

Rare mild to severe side effects include the following:

  • Weight gain

  • Back pain

  • Priapism (prolonged, painful erection)

Inform your doctor or get immediate medical attention if you experience any severe side effects or if they’re mild but persistent.


Overdosing on terazosin is dangerous, and it can sometimes be unexpected. For instance, if you stop taking the medication for several days and then resume a high dosage, this could result in an overdose.

Symptoms of an overdose may include the following:

  • Fainting

  • Blurred vision

  • Extreme dizziness and lightheadedness

  • Very low blood pressure, shock

If you are experiencing toxic effects and suspect you have overdosed, seek medical attention immediately by calling 911 or visiting the nearest emergency department. 

Allergy information

Taking terazosin may cause allergic reactions in some people, such as:

  • Swelling of the tongue, lips, and throat

  • Hives and itching

  • Trouble breathing

  • Difficulty breathing

  • Vomiting

  • Loss of consciousness

Seek medical attention immediately if you react to the medication. You should also avoid using the drug if you have had any previous allergic reactions to it or a similar medication.

Long-term use of terazosin

Studies have shown that terazosin is well tolerated when treating benign prostatic hyperplasia and hypertension over long periods. However, unmonitored long-term administration can lead to complications, such as low blood pressure and low platelet counts.⁹ ¹⁰

Once you are taking this medication, your doctor will regularly monitor your blood pressure and platelet count through blood tests.

It’s safe to continue taking this medication as your doctor has prescribed, but you should seek immediate medical attention whenever you experience severe or prolonged side effects.

Pregnancy category

Terazosin falls under US FDA pregnancy category C.¹¹

Terazosin and pregnancy

The risks of taking terazosin while pregnant have not been established. There are no adequate studies with pregnant women. However, animal studies have demonstrated potential risks to the fetus.

The drug should not be used in pregnancy unless the benefit outweighs the risk it poses to the fetus. If you discover you are pregnant while taking the drug, you should inform your doctor immediately.

Terazosin and breastfeeding

There are no studies to show whether terazosin passes into breast milk. If you’re breastfeeding, your doctor will only prescribe this medicine if they believe it’s safe for your specific situation.

Missed doses

If you miss your regularly scheduled dose, take it as soon as you remember. However, if you’re more than halfway to the next dose, skip the missed one and return to the regular schedule for the next dose.

You should not make up for missed medication by doubling the dose.

Drug interactions

Terazosin can interact with other medications. Inform your doctor if you take any medicines, herbal supplements, or vitamins. You should also tell them if you take any over-the-counter medicines or other drugs on occasion.

Examples of medications that are contraindicated for people taking terazosin include other alpha-1 blockers and the following:

  • Erectile dysfunction drugs (Viagra, Cialis)

  • Aripiprazole lauroxil (Aristada)

  • Lofexidine (Lucemyra)

Patients taking this drug should be monitored closely if they take any of the following:

  • Anti-inflammatories like aspirin, ibuprofen (Motrin, Advil), ketorolac (Toradol), and meloxicam (Mobic)

  • Albuterol

  • Amoxapine (Ascendin)

  • Steroids such as betamethasone and cortisone

  • Alpha-agonists like clonidine (Catapres, Kapvay) and guanfacine (Intuniv, Tenex)

  • Medications to treat high blood pressure, such as beta-blockers (Tenormin, Lopressor) and calcium-channel blockers (Catalan, Cardizem)

  • Nerve pain medications like desipramine (Norpramin), doxepin (Sinequan), duloxetine (Cymbalta), and imipramine (Tofranil)

  • Migraine medications like erenumab (Aimovig) and naratriptan (Amerge)

  • Hormone therapies like estradiol

  • Opiates like hydrocodone and morphine

  • Benzodiazepines like midazolam (Versed)

This is not a complete list of potential drug interactions. Always consult with your doctor when starting a new medication and seek medical help if you notice any adverse effects.

Can I drink alcohol while taking terazosin?

Alcohol has an intoxicating effect on the brain and body. Drinking alcohol while taking terazosin may increase the risk of drowsiness and dizziness. It should therefore be avoided.

What to discuss with your doctor before starting terazosin

Before your doctor prescribes terazosin, they will ask about your medical history to assess your suitability for the treatment.

Some of the things you need to tell your doctor include the following:

  • If you’re allergic to terazosin or other related medications, such as prazosin and doxazosin

  • Any prescription or non-prescription medicines, supplements, or vitamins you are taking regularly or occasionally

  • If you’re pregnant, planning a pregnancy, or breastfeeding

  • If you have ever had prostate cancer

  • If you are being treated for erectile dysfunction

  • Any medical conditions you have, such as high blood pressure, diabetes, liver disease, or low platelet count

  • If you’ve ever had fainting episodes or low blood pressure

  • If you’re scheduled for surgery (particularly eye surgery) or any other medical or dental procedures

Stopping terazosin

Don’t stop taking terazosin unless the doctor tells you to do so. Stopping the medication can worsen the symptoms you are managing.

It is risky to resume taking the same dosage after skipping the medication for several days. If you miss the dose for several days, talk to your doctor, as they may need to taper the prescription.

Drug approval history

Terazosin was proven effective as a treatment for hypertension and was approved by the FDA in 1987.

In 1993, it was approved to treat benign prostatic hyperplasia symptoms.

Tips for taking terazosin

  • Avoid driving or doing activities that require your full attention until you know how the drug affects you.

  • If you have a balance problem or a condition like osteoporosis, weakness, instability, or difficulty walking, take terazosin just before bedtime to reduce your risk of falling.

  • When you stand up after lying down or sitting, move slowly and hold on to something to avoid falling or fainting.

  • Inform the medical team that you are taking terazosin before undergoing any surgery or medical/dental procedures.

  • Do not take terazosin if you are allergic to any of its ingredients.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.

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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.