What is the appropriate dosing, side effect profile, contraindications, and monitoring for terazosin in adults with hypertension or benign prostatic hyperplasia?

Terazosin for Hypertension and Benign Prostatic Hyperplasia

Dosing

Terazosin requires mandatory dose titration starting at 1 mg at bedtime to minimize severe hypotensive responses, with gradual escalation to therapeutic doses of 5-10 mg daily for BPH or 1-5 mg daily for hypertension. 1

For Benign Prostatic Hyperplasia:

• Start at 1 mg at bedtime (this initial dose must not be exceeded) 1
• Titrate stepwise to 2 mg, then 5 mg, then 10 mg once daily based on symptom improvement and flow rates 1
• 10 mg daily is generally required for clinical response, requiring 4-6 weeks at this dose to assess efficacy 1
• Maximum studied dose is 20 mg daily, though insufficient data support routine use above 10 mg 1
• If therapy is discontinued for several days, restart at 1 mg and retitrate 1

For Hypertension:

• Start at 1 mg at bedtime 1
• Usual therapeutic range is 1-5 mg once daily, though some patients benefit from up to 20 mg daily 1
• Doses above 20 mg provide no additional blood pressure benefit 1
• Monitor blood pressure at end of dosing interval and 2-3 hours post-dose to assess peak effects 1

Dual Indication (BPH + Hypertension):

• Terazosin effectively treats both conditions simultaneously with a single daily dose 2
• In 1,483 patients with symptomatic BPH and hypertension, terazosin produced 55% reduction in BPH symptoms while controlling blood pressure 2

Side Effect Profile

Terazosin causes orthostatic hypotension more frequently than other alpha-blockers but has lower rates of ejaculatory dysfunction compared to tamsulosin. 3

Cardiovascular Effects:

• Orthostatic hypotension is the primary concern, especially with first dose and during titration 1, 4
• Only 4 of 163 patients (2.5%) developed clinically significant orthostatic hypotension in controlled trials 4
• Blood pressure reductions in normotensive patients are statistically significant but clinically minimal 2
• Dizziness and palpitations may occur from excessive hypotensive response 1

Sexual Function:

• Lower incidence of ejaculatory dysfunction compared to tamsulosin 3
• No cases of erectile dysfunction reported in clinical trials 5

Other Common Effects:

• Asthenia (tiredness/weakness) in 1-2% of patients 6
• Nasal congestion and rhinitis from alpha-receptor blockade 6
• Overall adverse events are mild and reversible 4

Ophthalmologic:

• Associated with intraoperative floppy iris syndrome (IFIS) during cataract or glaucoma surgery 6

Contraindications and Precautions

Patients planning cataract or glaucoma surgery must inform their ophthalmologist about terazosin use, and initiation should be avoided in those with scheduled eye surgery. 6

Relative Contraindications:

• Baseline hypotension or severe orthostatic hypotension 6
• High risk for falls, particularly in elderly patients 6
• Scheduled cataract or glaucoma surgery 6

Drug Interactions Requiring Caution:

• Calcium channel blockers (especially verapamil): Risk of significant hypotension; may require dose reduction of either agent 1
• PDE-5 inhibitors: Hypotension reported with concomitant use 1
• Other antihypertensives: Additive hypotensive effects; consider dose reduction and retitration 1
• Beta-blockers: When combined with agents like carvedilol, start lowest doses and monitor blood pressure supine and standing 6

Special Populations:

• Older adults: Higher risk of orthostatic hypotension, though terazosin demonstrates lower probability than doxazosin or prazosin 6
• Hypertensive patients with cardiac risk factors: Alpha-blocker monotherapy should not be assumed optimal for hypertension management; separate antihypertensive therapy may be needed 6

Monitoring

Monitor blood pressure in both supine and standing positions, particularly after dose changes and 2-3 hours post-dose when peak effects occur. 6, 1

Initial Monitoring:

• Close observation during initial administration to detect severe hypotensive response 1
• Blood pressure at end of dosing interval (24 hours) to ensure control throughout 1
• Blood pressure 2-3 hours post-dose to assess maximum response and symptoms like dizziness 1

Ongoing Monitoring:

• Assess for symptoms of hypoperfusion: fatigue, weakness, syncope 6
• For BPH: Symptom scores, peak urinary flow rates (Qmax), post-void residual urine 7, 4
• Expected improvements: 50% increase in peak flow rate, 54-67% reduction in symptom scores 4
• Clinical response assessment requires minimum 4-6 weeks at therapeutic dose (10 mg) 1

Efficacy Timeline:

• Significant symptom improvement by 3 months, maintained at 6 and 9 months 7, 5
• Mean obstructive symptom improvement: 67%; irritative symptoms: 35% 4
• Average peak flow increase: 2 ml/s above baseline 7

Critical Pitfalls to Avoid

• Never exceed 1 mg as initial dose regardless of indication—this is the most common prescribing error 1
• Do not restart at previous dose after therapy interruption; always reinitiate at 1 mg and retitrate 1
• Avoid rapid titration; stepwise escalation minimizes hypotensive complications 1
• Screen for planned eye surgery before initiating therapy due to IFIS risk 6
• Do not assume blood pressure control equals optimal hypertension management in cardiac risk patients; consider dedicated antihypertensive therapy 6