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Terazosin Side Effects

In Summary

Commonly reported side effects of terazosin include: dizziness. Other side effects include: asthenia, headache, and peripheral edema. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to terazosin: oral capsule, oral capsule liquid filled, oral tablet

As well as its needed effects, terazosin may cause unwanted side effects that require medical attention.

Severity: Moderate

If any of the following side effects occur while taking terazosin, check with your doctor or nurse as soon as possible:

More common:
  • Dizziness
Less common:
  • Chest pain
  • 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
  • Weight gain

Minor Side Effects

Some terazosin side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common:
  • Headache
  • unusual tiredness or weakness
Less common:
  • Back or joint pain
  • blurred vision
  • drowsiness
  • nausea and vomiting
  • stuffy nose

For Healthcare Professionals

Applies to terazosin: oral capsule, oral tablet


Syncope has occurred in less than 1% of patients. Palpitations have been reported in 5% of patients, but are much less likely than with some other alpha-adrenergic blockers. Peripheral edema, cold extremities, and chest pain have been reported in up to 6%, 12%, and 5% of patients, respectively. Atrial fibrillation has been reported (incidence not given).[Ref]

Cardiovascular side effects have included orthostatic hypotension, which generally occurs within 30 to 60 minutes after the first dose. For this reason, it is recommended that the first dose be administered at bedtime. Other symptoms of hypotension, such as mild to moderate dizziness, lightheadedness, palpitations and weakness have occurred in 1% to 30% of patients. Some cardiovascular side effects, particularly dizziness, have been more prevalent among persons greater than 65 years old.[Ref]


Ocular side effects including Intraoperative Floppy Iris Syndrome (IFIS) have been observed in some patients undergoing phacoemulsification cataract surgery while being treated with alpha-1 blockers.

Most reports were in patients treated with an alpha-1 blocker at the time IFIS occurred, but in some instances the alpha-1 blocker had been stopped prior to surgery. The manufacturer recommends that patients be questioned to determine whether or not they have taken alpha-1 blockers prior to being considered for cataract surgery. If it is determined that the patient has taken an alpha-1 blocker, the patient's ophthalmologist should be prepared for possible modifications to their surgical technique that may be necessary should IFIS be observed during the procedure.

Nervous system

Nervous system side effects, such as dizziness (5% to 30% of patients) and blurred vision (2% of patients) may be related to hypotension. Headaches (2% to 10%), asthenia (8%), and somnolence (6%) have occurred following long-term use.[Ref]


Metabolic side effects have included decreases in serum triglycerides and VLDL cholesterol, and increases in HDL cholesterol. Terazosin may counterbalance deleterious effects on the lipid profile associated with thiazide diuretics, making it a reasonable drug to use in combination with these agents.[Ref]


Musculoskeletal complaints of pain or cold extremities have been reported in up to 17% and 12% of patients, respectively.[Ref]


Nasal congestion and symptoms of sinusitis or dyspnea may be due to alpha-adrenergic blockade.[Ref]

Respiratory system side effects have been limited to nasal congestion in 2% to 12% of patients.[Ref]


Gastrointestinal problems have been limited mainly to nausea in 5% of patients.[Ref]

Only 4% of 354 patients from a multicenter trial complained of general abdominal pain or diarrhea within the first 90 days of therapy.[Ref]


Genitourinary complaints have rarely included impotence and priapism.[Ref]


In a study of 226 patients on terazosin for up to 2 years, only 2 discontinued therapy due to rash.[Ref]

Hypersensitivity reactions have been reported, including anaphylaxis and rashes.[Ref]


Dermatologic side effects of skin rash have been reported rarely. Lichenoid drug eruption has been associated with terazosin therapy.[Ref]

A 56-year-old white male developed a generalized scaling erythematous rash on the third day after starting terazosin 2 mg daily for benign prostatic hypertrophy. The rash was accompanied by mild fever, asthenia, and intense pruritus. The patient was on no other medications. Hematologic and histopathologic studies suggested a drug reaction. Terazosin was discontinued. Two weeks following oral methylprednisolone (40 mg daily) and emollients, symptoms had resolved completely.[Ref]


Hematologic side effects have included thrombocytopenia.[Ref]


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2. Shionoiri H, Gotoh E, Ito T, Hata T, Iwatsubo H, Takegawa K, Ogihara T, Mikami H, Ikegami H, Otsuka A, Katahira K, Kawaguchi Y "Long-term therapy with terazosin may improve glucose and lipid metabolism in hypertensives - a multicenter prospective study." Am J Med Sci 307 (1994): s91-5

3. Hosmane BS, Maurath CJ, Jordan DC, Laddu A "Effect of age and dose on the incidence of adverse events in the treatment of hypertension in patients receiving terazosin." J Clin Pharmacol 32 (1992): 434-43

4. "Product Information. Hytrin (terazosin)." Abbott Pharmaceutical, Abbott Park, IL.

5. Mersey JH "Long-term experience with terazosin for treatment of mild to moderate hypertension." Am J Med 80 (1986): 68-72

6. Lepor H, Jones K, Williford W "The mechanism of adverse events associated with terazosin: An analysis of the Veterans Affairs cooperative study." J Urol 163 (2000): 1134-7

7. Deger G "Comparison of the safety and efficacy of once-daily terazosin versus twice-daily prazosin for the treatment of mild to moderate hypertension." Am J Med 80 (1986): 62-7

8. Lowe FC "Safety assessment of terazosin in the treatment of patients with symptomatic benign prostatic hyperplasia - a combined analysis." Urology 44 (1994): 46-51

9. Cohen J "Long-term efficacy and safety of terazosin." J Clin Pharmacol 33 (1993): 272-8

10. Itskovitz HD "Alpha-1-blockade for the treatment of hypertension - a megastudy of terazosin in 2214 clinical practice settings." Clin Ther 16 (1994): 490-504

11. Hernandez RH, Angeligreaves M, Carvajal AR, Pajuelo JG, Padilla MCA, Armashernandez MJ "Terazosin: ex vivo and in vitro platelet aggregation effects in patients with arterial hypertension." Am J Hypertens 9 (1996): 437-44

12. Saunders E "The safety and efficacy of terazosin in the treatment of essential hypertension in blacks." Am Heart J 122 (1991): 936-42

13. Cohen J "Long-term efficacy and safety of terazosin alone and in combination with other antihypertensive agents." Am Heart J 122 (1991): 919-25

14. Sperzel WD, Glassman HN, Jordan DC, Luther RR "Overall safety of terazosin as an antihypertensive agent." Am J Med 80 (1986): 77-81

15. Lepor H "Long-term efficacy and safety of terazosin in patients with benign prostatic hyperplasia." Urology 45 (1995): 406-13

16. "Terazosin for hypertension." Med Lett Drugs Ther 29 (1987): 112-3

17. Guthrie R "Terazosin in the treatment of hypertension and symptomatic benign prostatic hyperplasia - a primary care trial." J Fam Pract 39 (1994): 129-33

18. Achari R, Laddu A "Terazosin: a new alpha adrenoceptor blocking drug." J Clin Pharmacol 32 (1992): 520-3

19. HernandezCano N, Herranz P, Lazaro TE, Mayor M, Casado M "Severe cutaneous reaction due to terazosin." Lancet 352 (1998): 202-3

20. Koh MJ, Seah PP, Tay YK, Mancer K "Lichenoid drug eruption to terazosin." Br J Dermatol 158 (2007): 426-7

It is possible that some side effects of terazosin may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.