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Alpha Blocker Terazosin: Side Effects and Dosage

Terazosin is a nonselective α₁-blocker with a long elimination half-life. Please see section general pharmacology of alpha blocker.

**Structural formula of terazosin**

Indications for Terazosin

Treatment of benign prostatic hyperplasia: Terazosin improves urinary flow and bladder emptying, relieves irritative and obstructive urinary symptoms (LUTS), reduces the risk of urinary retention, improves the success of a trial without a catheter after urinary retention, and is approved for long-term use.
Treatment of arterial hypertension as a second-line add-on in patients with insufficient effect of the first-line medication.
Off-label treatment of female LUTS due to neurogenic bladder neck obstruction.
Off-label treatment: improve the spontaneous passage of distal ureteral stones.

Pharmacokinetics of Terazosin

Well absorbed after oral administration,Bioavailability 90%
High protein binding, hepatic metabolism (CYP3A4), elimination half-life 10–18 hours
Time to steady-state 4–5 days.

Side Effects of Terazosin

Increased risk for cardiovascular side effects since terazosin is a nonselective α1 blocker.

The overall rate of side effects is 10–30%; selective alpha_1A-blocker have a reduced cardiovascular side effect rate.
Initial hypotension, orthostatic collapse, reflex tachycardia, usually transient.
Increased risk (HR 1,2) of cardiac failure in patients with cardial comorbidity (Lusty et al., 2021).
Stuffy nose
Retrograde ejaculation
Dizziness, weakness.
Rare side effects: priapism (alpha blocker inhibit sympathetic mechanisms for detumescence), intraoperative floppy iris syndrome during cataract surgery.

Contraindications of Terazosin

Urological Contraindications:

Conservative treatment of BPH with terazosin is not indicated, if surgical treatment is imperative: chronic urinary retention with renal failure, recurrent hematuria due to prostatic enlargement, recurrent urinary tract infections and bladder stones.

Cardiac Contraindications:

Hypotension, mechanical heart failure (valvular diseases, pulmonary embolism, pericarditis), congestive heart failure.

Other contraindications:

Terazosin should be paused perioperatively for cataract surgery to prevent an intraoperative floppy iris syndrome.

Drug interactions

Increased hypotensive effect with other antihypertensives or phosphodiesterase-5 inhibitors.
CYP3A4 inhibitors such as ketoconazole increase the terazosin plasma level and side effects.
Do not combine terazosin with another alpha blocker for better treatment effect.

Dosage of Terazosin

2–10 mg orally once daily, titrate dosage after effect and side-effects, first week 1 mg, second week 2 mg, third week 5 mg, if necessary and possible fourth week 10 mg. Terazosin should be given in the evening before bedtime to reduce side effects.

Alpha blocker

Index

Doxazosin

Index: 1–9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

References

Chapple 2004 CHAPPLE, C. R.: Pharmacological therapy of benign prostatic hyperplasia/lower urinary tract symptoms: an overview for the practising clinician.
In: BJU Int
94 (2004), Nr. 5, S. 738–44

Fusco et al., “Alpha-Blockers Improve Benign Prostatic Obstruction in Men with Lower Urinary Tract Symptoms: A Systematic Review and Meta-analysis of Urodynamic Studies.,” Eur Urol., vol. 69, no. 6, pp. 1091–1101, 2016, doi: 10.1016/j.eururo.2015.12.034.

C. de Mey, “alpha(1)-blockers for BPH: are there differences?,” Eur Urol, vol. 36 Suppl 3, pp. 52–63, 1999.

Deutsche Version: Terazosin