Prazosin

Prazosin hydrochloride is indicated for the treatment of hypertension, to lower blood pressure. Lowering blood pressure reduces the risk of fatal and nonfatal cardiovascular events, primarily strokes and myocardial infarctions. These benefits have been seen in controlled trials of antihypertensive drugs from a wide variety of pharmacologic classes, including this drug. Control of high blood pressure should be part of comprehensive cardiovascular risk management, including, as appropriate, lipid control, diabetes management, antithrombotic therapy, smoking cessation, exercise, and limited sodium intake. Many patients will require more than one drug to achieve blood pressure goals. …

• The dose of Prazosin Hydrochloride Capsules, USP should be adjusted according to the patient's individual blood pressure response
• The following is a guide to its administration: Initial Dose 1 mg two or three times a day (see WARNINGS .) Maintenance Dose Dosage may be slowly increased to a total daily dose of 20 mg given in divided doses
• The therapeutic dosages most commonly employed have ranged from 6 mg to 15 mg daily given in divided doses
• Doses higher than 20 mg usually do not increase efficacy, however a few patients may benefit from further increases up to a daily dose of 40 mg given in divided doses
• After initial titration some patients can be maintained adequately on a twice daily dosage regimen
• Use With Other Drugs When adding a diuretic or other antihypertensive agent, the dose of prazosin hydrochloride should be reduced to 1 mg or 2 mg three times a day and retitration then carried out
• Concomitant administration of prazosin hydrochloride with a PDE-5 inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension; therefore, PDE-5 inhibitor therapy should be initiated at the lowest dose in patients taking prazosin hydrochloride

Usage in Children: Safety and effectiveness in children have not been established.

• Dizziness or drowsiness may occur after the first dose of this medicine
• Avoid driving or performing hazardous tasks for the first 24 hours after taking this medicine or when the dose is increased
• Dizziness, lightheadedness, or fainting may occur, especially when rising from a lying or sitting position
• Getting up slowly may help lessen the problem
• These effects may also occur if you drink alcohol, stand for long periods of time, exercise, or if the weather is hot
• While taking prazosin hydrochloride, be careful in the amount of alcohol you drink
• Also, use extra care during exercise or hot weather, or if standing for long periods
• Check with your physician if you have any questions

Prazosin hydrochloride is contraindicated in patients with known sensitivity to quinazolines, prazosin, or any of the inert ingredients.

Prazosin hydrochloride has been administered without any adverse drug interaction in limited clinical experience to date with the following: (1) cardiac glycosides– digitalis and digoxin; (2) hypoglycemics–insulin, chlorpropamide, phenformin, tolazamide, and tolbutamide; (3) tranquilizers and sedatives–chlordiazepoxide, diazepam, and phenobarbital; (4) antigout– allopurinol, colchicine, and probenecid; (5) antiarrhythmics–procainamide, propranolol (see WARNINGS however), and quinidine; and (6) analgesics, antipyretics and anti-inflammatories– propoxyphene, aspirin, indomethacin, and phenylbutazone. …

As with all alpha-blockers, prazosin hydrochloride may cause syncope with sudden loss of consciousness. In most cases, this is believed to be due to an excessive postural hypotensive effect, although occasionally the syncopal episode has been preceded by a bout of severe tachycardia with heart rates of 120–160 beats per minute. Syncopal episodes have usually occurred within 30 to 90 minutes of the initial dose of the drug; occasionally, they have been reported in association with rapid dosage increases or the introduction of another antihypertensive drug into the regimen of a patient taking high doses of prazosin hydrochloride. …

Clinical trials were conducted on more than 900 patients. During these trials and subsequent marketing experience, the most frequent reactions associated with prazosin hydrochloride therapy are: dizziness 10.3%, headache 7.8%, drowsiness 7.6%, lack of energy 6.9%, weakness 6.5%, palpitations 5.3%, and nausea 4.9%. In most instances, side effects have disappeared with continued therapy or have been tolerated with no decrease in dose of drug. Less frequent adverse reactions which are reported to occur in 1–4% of patients are: Gastrointestinal: vomiting, diarrhea, constipation. Cardiovascular: edema, orthostatic hypotension, dyspnea, syncope. …

Usage in Pregnancy: Prazosin hydrochloride has been shown to be associated with decreased litter size at birth, 1, 4, and 21 days of age in rats when given doses more than 225 times the usual maximum recommended human dose. No evidence of drug-related external, visceral, or skeletal fetal abnormalities were observed. …

Accidental ingestion of at least 50 mg of prazosin hydrochloride in a two year old child resulted in profound drowsiness and depressed reflexes. No decrease in blood pressure was noted. Recovery was uneventful. Should overdosage lead to hypotension, support of the cardiovascular system is of first importance. Restoration of blood pressure and normalization of heart rate may be accomplished by keeping the patient in the supine position. If this measure is inadequate, shock should first be treated with volume expanders. If necessary, vasopressors should then be used. …

Tome assim que lembrar, a menos que esteja quase na hora da próxima dose. Nesse caso, pule a dose esquecida. Nunca tome duas doses de uma vez para compensar. Confira a bula, pois alguns medicamentos são diferentes.