Furazosin

Furazosin - General Information

A selective adrenergic alpha-1 antagonist used in the treatment of heart failure, hypertension, pheochromocytoma, Raynaud&

Pharmacology of Furazosin

Furazosin is an alpha-adrenergic blocking agent used to treat hypertension and benign prostatic hyperplasia. Accordingly, Furazosin is a selective inhibitor of the alpha1 subtype of alpha adrenergic receptors. In the human prostate, Furazosin antagonizes phenylephrine (alpha1 agonist)-induced contractions, in vitro, and binds with high affinity to the alpha1c adrenoceptor, which is thought to be the predominant functional type in the prostate. Studies in normal human subjects have shown that Furazosin competitively antagonized the pressor effects of phenylephrine (an alpha1 agonist) and the systolic pressor effect of norepinephrine. The antihypertensive effect of Furazosin results from a decrease in systemic vascular resistance and the parent compound Furazosin is primarily responsible for the antihypertensive activity.

Furazosin for patients

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, light-headedness 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 HCl, 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.

Furazosin Interactions

Prazosin 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, and quinidine; and (6) analgesics, antipyretics and anti-inflammatories - propoxyphene, aspirin, indomethacin, and phenylbutazone.

Addition of a diuretic or other antihypertensive agent to prazosin HCl has been shown to cause an additive hypotensive effect. This effect can be minimized by reducing the prazosin dose to 1 to 2mg three times a day, by introducing additional antihypertensive drugs cautiously and then by retitrating prazosin based on clinical response.

Drug/Laboratory Test Interactions

In a study on five patients given from 12 to 24 mg of prazosin per day for 10 to 14 days, there was an average increase of 42% in the urinary metabolite of norepinephrine and an average increase in urinary VMA of 17%. Therefore, false positive results may occur in screening tests for pheochromocytoma in patients who are being treated with prazosin. If an elevated VMA is found, prazosin should be discontinued and the patient retested after a month.

Furazosin Contraindications

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

Additional information about Furazosin

Furazosin Indication: For treatment of hypertension and chronic heart failure.
Mechanism Of Action: Furazosin acts by inhibiting the postsynaptic alpha(1)-adrenoceptors on vascular smooth muscle. This inhibits the vasoconstrictor effect of circulating and locally released catecholamines (epinephrine and norepinephrine), resulting in peripheral vasodilation.
Drug Interactions: Acebutolol Risk of hypotension at the beginning of therapy
Atenolol Risk of hypotension at the beginning of therapy
Betaxolol Risk of hypotension at the beginning of therapy
Bevantolol Risk of hypotension at the beginning of therapy
Bisoprolol Risk of hypotension at the beginning of therapy
Carteolol Risk of hypotension at the beginning of therapy
Carvedilol Risk of hypotension at the beginning of therapy
Esmolol Risk of hypotension at the beginning of therapy
Labetalol Risk of hypotension at the beginning of therapy
Metoprolol Risk of hypotension at the beginning of therapy
Nadolol Risk of hypotension at the beginning of therapy
Oxprenolol Risk of hypotension at the beginning of therapy
Digoxin Furazosin increases the effect of digoxin
Penbutolol Risk of hypotension at the beginning of therapy
Pindolol Risk of hypotension at the beginning of therapy
Practolol Risk of hypotension at the beginning of therapy
Propranolol Risk of hypotension at the beginning of therapy
Sotalol Risk of hypotension at the beginning of therapy
Timolol Risk of hypotension at the beginning of therapy
Verapamil Risk of hypotension at the beginning of therapy
Tadalafil Risk of significant hypotension with this association
Food Interactions: Avoid alcohol.
Avoid natural licorice.
Generic Name: Prazosin
Synonyms: Prazocin; Prazosin HCl; Prazosin Hydrochloride; Prazosina [Inn-Spanish]; Prazosine [Inn-French]; Prazosinum [Inn-Latin]
Drug Category: Antihypertensive Agents; Alpha-adrenergic Blocking Agents
Drug Type: Small Molecule; Approved

Other Brand Names containing Prazosin: Furazosin; Lentopres; Minipress; Minipress Xl; Vasoflex;
Absorption: Well-absorbed from gastrointestinal tract; bioavailability is variable (50 to 85%).
Toxicity (Overdose): Not Available
Protein Binding: 97%
Biotransformation: Primarily hepatic. Several metabolites have been identified in humans and animals (6- O -demethyl, 7- O -demethyl, 2-[1-piperazinyl]-4-amino-6, 7-dimethoxyquinazoline, 2,4-diamino-6,7-dimethoxyquinazoline).
Half Life: 2-3 hours
Dosage Forms of Furazosin: Tablet Oral
Chemical IUPAC Name: [4-(4-amino-6,7-dimethoxyquinazolin-2-yl)piperazin-1-yl]-furan-2-ylmethanone
Chemical Formula: C19H21N5O4
Prazosin on Wikipedia: https://en.wikipedia.org/wiki/Prazosin
Organisms Affected: Humans and other mammals