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Prazosin hydrochloride
Prazosin hydrochloride (Minipress)
Prazosin hydrochloride
(
PRAY-zoh-sin)
Pregnancy Category: C
Alti-Prazosin
Apo-Prazo
Minipress
Novo-Prazin
Nu-Prazo
Rho-Prazosin
(Rx)
Classification:
Antihypertensive, alpha-1-adrenergic blocking agent
See Also:
See also
Alpha-1-Adrenergic Blocking Agents
[ and
Antihypertensive Agents
][.
]
Action/Kinetics:
Produces selective blockade of postsynaptic alpha-1-adrenergic receptors. Dilates arterioles and veins, thereby decreasing total peripheral resistance and decreasing DBP more than SBP. CO, HR, and renal blood flow are not affected. Can be used to initiate antihypertensive therapy; most effective when used with other agents (e.g., diuretics, beta-adrenergic blocking agents).
Onset: 2 hr. Absorption not affected by food.
Maximum effect: 2-3 hr;
duration: 6-12 hr.
t
1/2: 2-3 hr. Full therapeutic effect: 4-6 weeks. Metabolized extensively; excreted primarily in feces.
Uses:
Mild to moderate hypertension alone or in combination with other antihypertensive drugs.
Investigational: CHF refractory to other treatment. Raynaud's disease, BPH.
Special Concerns:
Safe use in children has not been established. Use with caution during lactation. Geriatric clients may be more sensitive to the hypotensive and hypothermic effects; may be necessary to decrease the dose in these clients due to age-related decreases in renal function.
Side Effects:
First-dose effect:
Marked hypotension and syncope 30-90 min after administration of initial dose (usually 2 or more mg), increase of dosage, or addition of other antihypertensive agent.
CNS: Dizziness, drowsiness, headache, fatigue, paresthesias, depression, vertigo, nervousness, hallucinations.
CV: Palpitations, syncope, tachycardia, orthostatic hypotension, aggravation of angina.
GI: N&V, diarrhea or constipation, dry mouth, abdominal pain, pancreatitis.
GU: Urinary frequency or incontinence, impotence, priapism.
Respiratory: Dyspnea, nasal congestion, epistaxis.
Dermatologic: Pruritus, rash, sweating, alopecia, lichen planus.
Miscellaneous: Asthenia, edema, symptoms of lupus erythematosus, blurred vision, tinnitus, arthralgia, myalgia, reddening of sclera, eye pain, conjunctivitis, edema, fever.
Laboratory Test Alterations:
 Urinary metabolites of norepinephrine, VMA.
Overdose Management:
Symptoms: Hypotension,
shock.
Treatment: Keep client supine to restore BP and HR. If shock is manifested, use volume expanders and vasopressors; maintain renal function.
Drug Interactions:
-
Antihypertensives (other) /
Antihypertensive effect
-
Beta-adrenergic blocking agents / Enhanced acute postural hypotension after first dose of prazosin
-
Clonidine /
 Antihypertensive effect
-
Diuretics /
Antihypertensive effect
-
Indomethacin /
Effect of prazosin
-
Nifedipine /
Hypotensive effect
-
Propranolol / Especially pronounced additive hypotensive effect
-
Verapamil /
Hypotensive effect;
sensitivity to prazosin-induced postural hypotension
How Supplied:
Capsule: 1 mg, 2 mg, 5 mg
Dosage
?Capsules
Hypertension.
Individualized: Initial 1 mg b.i.d.-t.i.d.;
maintenance: if necessary, increase gradually to 6-15 mg/day in two to three divided doses. Do not exceed 20 mg/day, although some clients have benefitted from doses of 40 mg daily. If used with diuretics or other antihypertensives, reduce dose to 1-2 mg t.i.d.
Pediatric, less than 7 years of age, initial: 0.25 mg b.i.d.-t.i.d. adjusted according to response.
Pediatric, 7-12 years of age, initial: 0.5 mg b.i.d.-t.i.d. adjusted according to response. |
