Yes

Alpha₁ Blockers

Treatment of hypertension, severe congestive heart failure (in conjunction with diuretics and cardiac glycosides); reduce mortality in stable postmyocardial patients with left ventricular dysfunction (ejection fraction less than or equal to 40%)

C

Hypersensitivity to quinazolines (doxazosin, prazosin, terazosin) or any component

Can cause significant orthostatic hypotension and syncope, especially with first dose. Risk is increased at doses > 1 mg, hypovolemia, or in patients receiving concurrent beta-blocker therapy. Anticipate a similar effect if therapy is interrupted for a few days, if dosage is rapidly increased, or if another antihypertensive drug is introduced.

>10%: Central nervous system: Dizziness (10.3%)

1% to 10%:

Cardiovascular: Palpitations (5.3%), edema, orthostatic hypotension, syncope (1%)

Central nervous system: Headache (7.8%), drowsiness (7.6%), weakness (6.5%), vertigo, depression, nervousness

Dermatologic: Rash (1% to 4%)

Endocrine & metabolic: Decreased energy (6.9%)

Gastrointestinal: Nausea (4.9%), vomiting, diarrhea, constipation

Genitourinary: Urinary frequency (1% to 5%)

Ocular: Blurred vision, reddened sclera, xerostomia

Respiratory: Dyspnea, epistaxis, nasal congestion

<1% (Limited to important or life-threatening symptoms): Paresthesia, hallucinations, tachycardia, pruritus, alopecia, lichen planus, incontinence, impotence, priapism, abdominal discomfort, liver function abnormalities, pancreatitis, tinnitus, pigmentary mottling and serous retinopathy, cataracts (both development and disappearance have been reported), worsening of narcolepsy, angina, bradycardia, myocardial infarction

Case reports: Leukopenia, cataplexy, enuresis, systemic lupus erythematosus

Symptoms of overdose include hypotension, drowsiness

Hypotension usually responds to I.V. fluids, Trendelenburg positioning or vasoconstrictors; treatment is otherwise supportive and symptomatic

NSAIDs may reduce antihypertensive efficacy.

ACE inhibitors: Hypotensive effect may be increased.

Beta-blockers: Hypotensive effect may be increased.

Calcium channel blockers: Hypotensive effect may be increased.

Store in airtight container; protect from light

Competitively inhibits postsynaptic alpha-adrenergic receptors which results in vasodilation of veins and arterioles and a decrease in total peripheral resistance and blood pressure

Onset of hypotensive effect: Within 2 hours

Maximum decrease: 2-4 hours

Duration: 10-24 hours

Distribution: V_d: 0.5 L/kg (hypertensive adults)

Protein binding: 92% to 97%

Metabolism: Extensively in the liver

Bioavailability: Oral: 43% to 82%

Half-life: 2-4 hours; increased with congestive heart failure

Elimination: 6% to 10% excreted renally as unchanged drug

Oral:

Adults:

CHF, hypertension: Initial: 1 mg/dose 2-3 times/day; usual maintenance dose: 3-15 mg/day in divided doses 2-4 times/day; maximum daily dose: 20 mg

Hypertensive urgency: 10-20 mg once, may repeat in 30 minutes

Raynaud's: 0.5-3 mg twice daily

Benign prostatic hypertrophy: 2 mg twice daily

Alcohol: Avoid use

Blood pressure, standing and sitting/supine

Increased urinary UMA 17%, norepinephrine metabolite 42%

Prazosin can be used alone or in combination with other antihypertensive agents. Patients with BPH may derive benefit from therapy. Orthostatic hypotension, compared to newer alpha-blockers, is more of a concern.

Dizziness is common; may cause drowsiness or nervousness; may rarely cause nightmares

Concurrent use with low potency antipsychotics and TCAs may increase risk of postural hypotension

No information available to require special precautions

Significant orthostatic hypotension a possibility; monitor patient when getting out of dental chair; significant dry mouth in up to 10% of patients

Take as directed (first dose at bedtime). Do not skip dose or discontinue without consulting prescriber. Follow recommended diet and exercise program. Do not use alcohol or OTC medications which may affect blood pressure (eg, cough or cold remedies, diet pills, stay-awake medications) without consulting physician. You may experience drowsiness, dizziness, or impaired judgment (use caution when driving or engaging in tasks that require alertness until response to drug is known); postural hypotension (use caution when rising from sitting or lying position or when climbing stairs); dry mouth or nausea (frequent mouth care or sucking lozenges may help); or urinary incontinence (void before taking medication). Report altered CNS status (eg, fatigue, lethargy, confusion, nervousness); sudden weight gain (weigh yourself in the same clothes at the same time of day once a week); unusual or persistent swelling of ankles, feet, or extremities; palpitations or rapid heartbeat; difficulty breathing; or other persistent side effects. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to be pregnant - contraceptive use may be recommended. Consult prescriber if breast-feeding.

Syncope may occur (usually within 90 minutes of the initial dose)

Capsule, as hydrochloride: 1 mg, 2 mg, 5 mg

Friedman WF and George BL, "New Concepts and Drugs in the Treatment of Congestive Heart Failure," Pediatr Clin North Am, 1984, 31(6):1197-227.

Lenz K, Druml W, Kleinberger G, et al, "Acute Intoxication With Prazosin: Case Report," Hum Toxicol, 1985, 4(1):53-6.

McClean WJ, "Prazosin Overdose," Med J Aust, 1976, 1(16):592.

Rubin PC, Scott PJ, and Reid JL, "Prazosin Disposition in Young and Elderly Subjects," Br J Clin Pharmacol, 1981, 12(3):401-4.

Rygnestad TK and Dale O, "Self-Poisoning With Prazosin," Acta Med Scand, 1983, 213(2):157-8.

Sinaiko AR, "Pharmacologic Management of Childhood Hypertension," Pediatr Clin North Am, 1993, 40(1):195-212.

Vincent J, Meredith PA, Reid JL, et al, "Clinical Pharmacokinetics of Prazosin -- 1985," Clin Pharmacokinet, 1985, 10(2):144-54.