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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

Along with its needed effects, terazosin 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 while taking terazosin:

More Common

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

Some side effects of terazosin 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

Less Common

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]


1. Elhilali MM, Ramsey EW, Barkin J, Casey RW, Boake RC, Beland G, Fradet Y, Trachtenberg J, Orovan WL, Schick E, Klotz LH "A multicenter, randomized, double-blind, placebo-controlled study to evaluate the safety and efficacy of terazosin in the treatment of benign prostatic hyperplasia." Urology 47 (1996): 335-42

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

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

6. 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

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

8. 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

9. 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

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

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

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

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

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

15. 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

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

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

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.