Terazosin is a medication that’s typically used to treat difficulty urinating caused by an enlarged prostate (also known as benign prostatic hyperplasia or BPH). It can also be used to treat high blood pressure, but it’s not a first-choice option for this condition due to the risk of side effects, like feeling dizzy or weak, particularly for older adults. Terazosin is taken by mouth, typically once daily at bedtime. It’s only available as a lower-cost generic (former brand name Hytrin).
Difficulty urinating caused by an enlarged prostate (benign prostatic hyperplasia, BPH)
High blood pressure
Terazosin is an alpha-1 blocker. It treats BPH by relaxing certain muscles in the prostate and bladder, which allows urine to flow more easily.
Terazosin can also treat high blood pressure by relaxing your blood vessels. This helps blood flow smoothly through the body.
Source: DailyMed
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor as soon as possible if any of the following side effects occur:
More common
Dizziness
Less common
dizziness or lightheadedness when getting up from a lying or sitting position
fainting (sudden)
fast or irregular heartbeat
pounding heartbeat
shortness of breath
swelling of feet or lower legs
Rare
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Headache
unusual tiredness or weakness
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Available as a lower-cost generic medication
Taken once a day
Can be taken with or without food
Not a first-choice option for high blood pressure
Can cause dizziness, especially if you stand up quickly
If you miss your dose for many days, you may need to restart treatment at the starting dose
Terazosin can be taken with or without food, and it’s best to take it at bedtime.
Terazosin can make you feel dizzy or light-headed, especially when you start taking it for the first time and when your dose is raised. If you’ve been sitting or lying down, get up slowly to avoid the risk of falling.
Because terazosin can cause dizziness, avoid driving and doing things that may be dangerous until your body gets used to the medication.
Common side effects of terazosin include feeling more tired than usual or having a hard time standing up. If you feel dizzy or lightheaded, it may be helpful to tell your loved ones or caregiver since they might be able to help you stay steady.
Terazosin can raise your risk of falls since it causes dizziness. If you fall down and hit your head or are in pain after a fall, the safest choice is to seek medical care right away. This is because there could be bleeding inside the body, and it’s best to have your provider check for these injuries. This is particularly important if you’re taking blood thinners, which can raise your risk for bleeds that are difficult to stop.
If you miss taking your terazosin for 2 or more days in a row, talk to your provider about how to safely restart terazosin. You might need to start taking a lower dose to avoid side effects that could cause you to fall or faint, like dizziness and weakness.
Terazosin can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Risk factors: Age 65 years or older | Taking other blood pressure medications
Terazosin can cause you to feel dizzy or faint when you stand up after sitting or lying down. This is because your blood pressure may change quickly when you change positions (also known as orthostatic hypotension). The risk of this side effect is highest after your first dose. But it’s also more likely to happen during the first 7 days of taking terazosin and whenever your dose is raised. Typically, you tend to feel most dizzy within 90 minutes of taking a dose.
When you take terazosin for the first time or take a higher dose, avoid activities that could be dangerous for 12 hours after your dose. This includes driving, operating heavy machinery, and exercising. If you feel dizzy, lightheaded, or like your heart is pounding, make sure to stop doing anything that could be hazardous. If these symptoms are bothersome, let your healthcare provider know because they might need to change your dose.
In some rare cases, terazosin can cause a painful erection (also known as priapism) that continues for more than 4 hours. If this happens to you, contact your provider right away to avoid the risk of permanent erectile dysfunction.
Risk factors: Cataract surgery
If you take terazosin and plan to get cataract eye surgery, let your provider know. In some rare cases, this medication can cause changes to your iris, a condition called Intraoperative Floppy Iris Syndrome (IFIS). Keep in mind that terazosin is probably less likely to cause IFIS than other medications used to treat BPH, like tamsulosin. You don’t need to stop taking terazosin before the surgery, but your surgeon needs to adjust how they perform the operation. Letting your provider know ahead of time can help them prepare accordingly.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Difficulty urinating caused by an enlarged prostate (benign prostatic hyperplasia, BPH)
High blood pressure
Enlarged prostate (benign prostatic hyperplasia, BPH)
High blood pressure - immediate-release tablet only
Enlarged prostate (benign prostatic hyperplasia or BPH)
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Apnar Pharma LP. (2023). Terazosin hydrochloride capsule [package insert]. DailyMed.
Centers for Disease Control and Prevention. (2017). Postural hypotension: What it is and how to manage it.
Chang, D. F. (2009). Floppy iris syndrome: Why BPH treatment can complicate cataract surgery. American Family Physician.
Dong, Z., et al. (2009). Tamsulosin versus terazosin for benign prostatic hyperplasia: A systematic review. Systems Biology in Reproductive Medicine.
Saad, M., et al. (2022). Alpha blocker-associated intraoperative floppy iris syndrome. The Senior Care Pharmacist.
Sandhu, J. S., et al. (2023). Management of lower urinary tract symptoms attributed to benign prostatic hyperplasia (BPH): AUA Guideline amendment 2023. Journal of Urology.
Silberman, M., et al. (2023). Priapism. StatPearls.
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