Dosing & Uses
Dosage Forms & Strengths
capsule
- 1mg
- 2mg
- 5mg
- 10mg
Benign Prostate Hyperplasia
Initial: 1 mg PO qHS
May gradually increase to 5 mg PO qHS; up to 20 mg/day beneficial for some
Dosing considerations
- Give first dose and subsequent increases at bedtime to avoid syncope
- May take with food
Hypertension
Initial: 1 mg PO qHS
Maintenance: 1-5 mg/day or q12hr; may increase to ≤20 mg/day
Dosing considerations
- Give first dose and subsequent increases at bedtime to avoid syncope
- May take with food
Dosing Modifications
Hepatic impairment: Use with caution
Dosage Forms & Strengths
capsule
- 1mg
- 2mg
- 5mg
- 10mg
Hypertension (Off-label)
1 mg/day PO; increase dose gradually as necessary; up to maximum of 20 mg/day
Hypertension
Initial: 0.5 mg PO qHS and titrate to response
Dosing considerations
Avoid use for hypertension; high risk of orthostatic hypotension (Beers criteria)
May cause significant orthostatic hypotension and syncope
Lower initial doses than those used for nongeriatric adults, as well as gradual adjustments, are recommended for hypertension
Give first dose and subsequent increases at bedtime to avoid syncope
Adverse effects such as dry mouth and urinary complications can be bothersome in the elderly
May take with food
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Adverse Effects
>10%
Dizziness (10-20%)
Asthenia (2-13%)
1-10%
Hypotension (3-7%)
Rhinitis/nasal congestion (2-6%)
Lightheadedness (3-5%)
Somnolence (3-5%)
Palpitation (4%)
Nausea (2-4%)
Edema (3%)
Sinusitis (3%)
Dyspnea (2-3%)
Fatigue (2.5%)
Headache (2.5%)
Back pain (2.4%)
Flulike syndrome (2.4%)
Tachycardia (2%)
Amblyopia (1-2%)
Blurred vision (1-2%)
Impotence (1-2%)
Syncope (1%)
Warnings
Contraindications
Hypersensitivity to terazosin, other quinazolines
Cautions
Carcinoma of the prostate and BPH cause many of the same symptoms; these two diseases frequently co-exist; patients thought to have BPH should be examined prior to starting therapy to rule out presence of carcinoma of the prostate
Therapy can cause marked lowering of blood pressure, especially postural hypotension, and syncope in association with first dose or first few days of therapy; a similar effect can be anticipated if therapy is interrupted for several days and then restarted; to decrease likelihood of syncope or excessive hypotension, treatment should always be initiated at a low dose (1 mg) and increased slowly; additional antihypertensive agents should be added with caution; patient should be cautioned to avoid situations, such as driving or hazardous tasks, where injury could result should syncope occur during initiation of therapy
If syncope occurs, the patient should be placed in a recumbent position and treated supportively as necessary; there is evidence that orthostatic effect is greater, even in chronic use, shortly after dosing; the risk of the events is greatest during initial seven days of treatment, but continues at all time intervals
While syncope is the most severe orthostatic effect, other symptoms of lowered blood pressure, such as dizziness, lightheadedness and palpitations, are more common; patients with occupations in which such events represent potential problems should be treated with particular caution
May cause CNS depression, which may impair physical or mental abilities; use caution when performing tasks that may require mental alertness, including driving or operating heavy machinery
May exacerbate heart failure
Concomitant administration with PDE-5 inhibitor (eg, sildenafil) can result in additive blood pressure-lowering effects and symptomatic hypotension; initiate PDE-5 inhibitor therapy at lowest dose
Risk of priapism (rare); because this condition can lead to permanent impotence if not promptly treated, patients must be advised about seriousness of the condition
Pregnancy & Lactation
Pregnancy category: C
Lactation: Not known if excreted into breast milk; use caution
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Blocks postsynaptic alpha-1 receptor; alpha blockade causes arterial and venous dilation
Selective agents cause less tachycardia than do nonselective agents
Absorption
Bioavailability: 90%
Onset (hypertension): 3 hr
Onset (benign prostate hyperplasia): 2 weeks
Duration: 24 hr
Peak response (benign prostate hyperplasia): 4-6 weeks
Peak plasma time: 1 hr
Distribution
Protein bound: 90-94%
Vd: 25-30 L
Metabolism
Metabolized extensively via hydrolysis, O-demethylation, and N-dealkylation in liver
Metabolites: 6- and 7-O-demethyl terazosin, piperazine derivative, diamine metabolite
Elimination
Half-life: 9-12 hr
Renal clearance: 9-12.5 mL/min
Excretion: Feces (55-60%); urine (40%)
Images
Patient Handout
Formulary
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