MINIPRESS TABLET 2mg

Prazosin

Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.

Active Ingredient / Synonyms

1-(4-Amino-6,7-dimethoxy-2-quinazolinyl)-4-(2-furanylcarbonyl)piperazine | 2-(4-(2-Furoyl)piperazin-1-yl)-4-amino-6,7-dimethoxyquinazoline | Prazosina | Prazosine | Prazosinum | Prazosin |

Description

Prazosin is a selective α-1-adrenergic receptor antagonist used to treat hypertension. It has also been used to decrease urinary obstruction and relieve symptoms associated with symptomatic benign prostatic hyperplasia. α1-Receptors mediate contraction and hypertrophic growth of smooth muscle cells. Antagonism of these receptors leads to smooth muscle relaxation in the peripheral vasculature and prostate gland. Prazosin has also been used in conjunction with cardiac glycosides and diuretics in the management of severe congestive heart failure. It has also been used alone or in combination with β-blockers in the preoperative management of signs and symptoms of pheochromocytoma.

Indication

For treatment of hypertension, symptomatic benign prostatic hyperplasia, and severe congestive heart failure. May also be used alone or in combination with β-blockers in the preoperative management of signs and symptoms of pheochromocytoma.

Mechanism of Action

Prazosin 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.

Pharmacodynamics

Prazosin is an alpha-adrenergic blocking agent used to treat hypertension and benign prostatic hyperplasia. Accordingly, Prazosin is a selective inhibitor of the alpha1 subtype of alpha adrenergic receptors. In the human prostate, Prazosin 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 Prazosin competitively antagonized the pressor effects of phenylephrine (an alpha1 agonist) and the systolic pressor effect of norepinephrine. The antihypertensive effect of Prazosin results from a decrease in systemic vascular resistance and the parent compound Prazosin is primarily responsible for the antihypertensive activity.

Pharmacokinetics

Absorption:

Well-absorbed from gastrointestinal tract; bioavailability is variable (50 to 85%).

Distribution:

Not Available

Metabolism:

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).

Elimination:

Animal studies indicate that prazosin hydrochloride is extensively metabolized, primarily by demethylation and conjugation, and excreted mainly via bile and feces. Less extensive human studies suggest similar metabolism and excretion in man.

Half-life

2-3 hours

Clearance

Not Available

Toxicity

Not Available

References

  1. Health Science Authority of Singapore - Reclassified POM
  2. Drugbank

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Approval Information

MINIPRESS TABLET 2mg was registered with Health Science Authority of Singapore by PFIZER PTE LTD. It is marketed with the registration number of SIN00974P with effective from 1988-10-05.

This product contains 2mg of Prazosin in the form of TABLET.

The medicine was manufactured by PFIZER AUSTRALIA PTY LTD in AUSTRALIA

It is a Presciption Only Medicine which can only be obtained from a doctor or a dentist, or from a pharmacist with a prescription from a Singapore-registered doctor or dentist.

Anatomical Therapeutic Chemical (ATC) Classification

ATC Code: C02CA01

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