Active ingredient: Terazosin - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

• Antineoplastic Agents
• Adrenergic alpha-Antagonists
• Platelet Aggregation Inhibitors

Dosage Forms

• Tablet

Brands / Synonyms

Abbott 45975; Blavin; Flumarc; Fosfomic; Heitrin; Hytracin; Hytrin; Hytrinex; Itrin; Terazosin HCl; Terazosin hydrochloride; Terazosina [Inn-Spanish]; Terazosine; Terazosine [Inn-French]; Terazosinum [Inn-Latin]; Trazosin HCl; Urodie; Vasocard; Vasomet; Vicard

Indications

For the treatment of symptomatic benign prostatic hyperplasia (BPH) and also for hypertension.

Pharmacology

Terazosin, classified as a quinazoline, is similar to doxazosin and prazosin. As an alpha-adrenergic blocking agent, terazosin is used to treat hypertension and benign prostatic hypertrophy (BPH). Terazosin produces vasodilation and reduces peripheral resistance but in general has slight effect on cardiac output. Antihypertensive effect with chronic dosing is usually not accompanied by reflex tachycardia.

Mechanism of Action

Terazosin selectively and competitively inhibits vascular postsynaptic alpha(1)-adrenergic receptors, resulting in peripheral vasodilation and a reduction of vascular resistance and blood pressure. Unlike the nonselective alph-adrenergic blockers phenoxybenzamine and phentolamine, terazosin does not block presynaptic alpha(2)-receptors and, hence, does not cause reflex activation of norepinephrine release to produce reflex tachycardia.

Absorption

Essentially completely absorbed in man (90% bioavailability).

Toxicity

LD₅₀=259.3mg/kg (i.v. in mice)

Biotrnasformation / Drug Metabolism

Hepatic. One of the four metabolites identified (piperazine derivative of terazosin) has antihypertensive activity.

Contraindications

HYTRIN capsules are contraindicated in patients known to be hypersensitive to terazosin hydrochloride.

Drug Interactions

In controlled trials, terazosin has been added to diuretics, and several beta-adrenergic blockers; no unexpected interactions were observed. Terazosin has also been used in patients on a variety of concomitant therapies; while these were not formal interaction studies, no interactions were observed. Terazosin has been used concomitantly in at least 50 patients on the following drugs or drug classes: 1) analgesic/anti-inflammatory (e.g., acetaminophen, aspirin, codeine, ibuprofen, indomethacin); 2) antibiotics (e.g., erythromycin, trimethoprim and sulfamethoxazole); 3) anticholinergic/sympathomimetics (e.g., phenylephrine hydrochloride, phenylpropanolamine hydrochloride, pseudoephedrine hydrochloride); 4) antigout (e.g., allopurinol); 5) antihistamines (e.g., chlorpheniramine); 6) cardiovascular agents (e.g., atenolol, hydrochlorothiazide, methyclothiazide, propranolol); 7) corti-costeroids; 8) gastrointestinal agents (e.g., antacids); 9) hypoglycemics; 10) sedatives and tranquilizers (e.g., diazepam).

Use with Other Drugs

In a study (n=24) where terazosin and verapamil were administered concomitantly, terazosin’s mean AUC_0-24 increased 11% after the first verapamil dose and after 3 weeks of verapamil treatment it increased by 24% with associated increases in C_max (25%) and C_min (32%) means. Terazosin mean T_max decreased from 1.3 hours to 0.8 hours after 3 weeks of verapamil treatment. Statistically significant differences were not found in the verapamil level with and without terazosin. In a study (n=6) where terazosin and captopril were administered concomitantly, plasma disposition of captopril was not influenced by concomitant administration of terazosin and terazosin maximum plasma concentrations increased linearly with dose at steady-state after administration of ter-azosin plus captopril.