Brands, Medical Use, Clinical Data
- Antineoplastic Agents
- Adrenergic alpha-Antagonists
- Platelet Aggregation Inhibitors
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
For the treatment of symptomatic benign prostatic hyperplasia (BPH) and also for hypertension.
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.
Essentially completely absorbed in man (90% bioavailability).
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.
HYTRIN capsules are contraindicated in patients known to be hypersensitive to terazosin
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
Use with Other Drugs
In a study (n=24) where terazosin and verapamil were administered concomitantly, terazosin’s
mean AUC0-24 increased 11% after the first verapamil dose and after 3 weeks of verapamil treatment it
increased by 24% with associated increases in Cmax (25%) and Cmin (32%) means. Terazosin mean
Tmax 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.