Reviewed on 7/19/2022

What Is Terazosin and How Does It Work?

Terazosin is a prescription drug used as an alpha-adrenergic blocker to treat high blood pressure and enlarged prostate.

  • Terazosin is available under the following different brand names: Hytrin.

What Are Side Effects Associated with Using Terazosin?

Side effects of terazosin include:

Seek medical care or call 911 at once if you have the following serious side effects:

  • Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
  • Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
  • Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheartedness, or passing out.

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.


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Dosages of Terazosin

Adult and Pediatric Dosages


  • 1 mg
  • 2 mg
  • 5 mg
  • 10 mg

Dosage Considerations – Should be Given as Follows:

Benign Prostate Hyperplasia (BPH)


  • Initial: 1 mg orally at bedtime; up to 20 mg/day beneficial for some
  • Dosing considerations
    • Give first dose and subsequent increases at bedtime to avoid fainting (syncope)
    • May take with food


Adult dosage:

  • Initial: 1 mg orally at bedtime
  • Maintenance: 1-5 mg/day or every 12 hours; may increase up to 20 mg/day
  • Dosing considerations
    • Give first dose and subsequent increases at bedtime to avoid fainting (syncope)
    • May take with food

Geriatric Dosage:

  • Initial: 0.5 mg orally at bedtime and titrate to response
  • Dosing considerations
  • Avoid use for hypertension; high risk of orthostatic hypotension (Beers criteria)
  • May cause significant orthostatic hypotension and fainting
  • Lower initial doses than those used for non-geriatric adults, as well as gradual adjustments, are recommended for hypertension
  • Give first dose and subsequent increases at bedtime to avoid fainting
  • Adverse effects such as the dry mouth and urinary complications can be bothersome in the elderly
  • May take with food.


  • 1 mg/day orally; increase the dose gradually as necessary; up to a maximum of 20 mg/day

Dosing Modifications

Hepatic impairment: use with caution

What Other Drugs Interact with Terazosin?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.


How to Lower Blood Pressure: Exercise Tips See Slideshow

What Are Warnings and Precautions for Terazosin?


  • This medication contains terazosin. Do not take Hytrin if you are allergic to terazosin or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Hypersensitivity to terazosin, other quinazolines.

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • This drug may make you dizzy or drowsy
  • Do not drive, use machinery, or do any activity that requires alertness until you are sure you can perform such activities 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
  • See "What Are Side Effects Associated with Using Terazosin?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Terazosin?"


  • Prostate carcinoma
  • Liver disease
  • May cause first-dose fainting/sudden loss of consciousness and dizziness upon standing; minimize the effect by using a small first dose at bedtime; increase dose slowly
  • Concomitant use of other antihypertensive (additive low blood pressure effects)
  • May exacerbate heart failure
  • Concomitant administration with DFE-5 inhibitor (sildenafil) can result in additive blood pressure-lowering effects and symptomatic low blood pressure (hypotension); initiate PDE-5 inhibitor therapy at the lowest dose
  • The risk of persistent and painful erection of the penis (priapism), is rare but needs medical attention

Pregnancy and Lactation

  • Use terazosin during pregnancy with caution if the benefits outweigh the risks
  • Animal studies show risk and human studies are not available, or neither animal nor human studies were done
  • It is unknown if terazosin is excreted into breast milk; use caution and consult your doctor before breastfeeding
Medscape. Terazosin.
RxList. Hytrin Monograph.

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