Drug information of Terazosin

Terazosin

Drug group:

Terazosin is in a group of drugs called alpha-adrenergic blockers. Terazosin relaxes your veins and arteries so that blood can more easily pass through them. Terazosin also relaxes the muscles in the prostate and bladder neck, making it easier to urinate.

Terazosin is used to treat hypertension (high blood pressure), or to improve urination in men with benign prostatic hyperplasia (enlarged prostate).

Mechanism of effect

Terozosin produces its pharmacological effects by inhibiting α1A-receptor activation. Inhibition of these receptors in the vasculature and prostate results in muscle relaxation, decreased blood pressure and improved urinary outflow in symptomatic benign prostatic hyperplasia.

Blocks postsynaptic alpha-1 receptor; alpha blockade causes arterial and venous dilation .

Selective agents cause less tachycardia than do nonselective agents

Pharmacodynamic

Terazosin, classified as a quinazoline, is similar to doxazosin and prazosin. As an α-adrenergic blocking agent, terazosin is used to treat hypertension and BPH.

Terazosin produces vasodilation and reduces peripheral resistance but in general has only a slight effect on cardiac output. The antihypertensive effect with chronic dosing is not usually accompanied by reflex tachycardia.

Pharmacokinetics

Absorbtion :

 Essentially completely absorbed in man

Bioavailability: 90%

Onset (hypertension): 3 hr

Onset (benign prostate hyperplasia): 2 weeks

Duration: 24 hr

Peak response (benign prostate hyperplasia): 4-6 weeks

Peak plasma time: 1 hr

Metabolism : Metabolized extensively via hydrolysis, O-demethylation, and N-dealkylation in liver

Eliminamtion :

Approximately 10% of an orally administered dose is excreted as parent drug in the urine and approximately 20% is excreted in the feces.

Half-life: 9-12 hr

Renal clearance: 9-12.5 mL/min

Excretion: Feces (55-60%); urine (40%)

Distribution : Protein binding ;90-94%

Drug indications

Benign Prostatic Hyperplasia

Dosage

 

Benign Prostate Hyperplas

Initial: 1 mg PO qHS

May gradually increase to 5 mg PO qHS; up to 20 mg/day beneficial for some 

Dosing considerations

- Give first dose and subsequent increases at bedtime to avoid syncope

 - May take with food 

Hypertension

Initial: 1 mg PO qHS

Maintenance: 1-5 mg/day or q12hr; may increase to ≤20 mg/day 

Dosing considerations

- Give first dose and subsequent increases at bedtime to avoid syncope

- May take with food 

Dosing Modifications

Hepatic impairment: Use with caution

Drug contraindications

hypersensitivity to this drug

Alerts

  1. Terazosin May cause first-dose syncope/sudden LOC and orthostatic hypotension; minimize effect by using small first dose at bedtime; increase dose slowly
  2. Concomitant use of other antihypertensives (additive hypotensive effects)
  3. May exacerbate heart failure
  4. Concomitant administration with PDE-5 inhibitor (eg, sildenafil) can result in additive blood pressure-lowering effects and symptomatic hypotension; initiate PDE-5 inhibitor therapy at lowest dose
  5. Risk of priapism (rare but needs medical attention)

Points of recommendation

  • Terazosin may cause dizziness or fainting, especially when you first start taking it or when you start taking it again. You may wish to take this medication only at bedtime if it causes you to feel light-headed. Be careful if you drive or do anything that requires you to be alert. Avoid standing for long periods of time or becoming overheated during exercise and in hot weather. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy.
  • You should not use this medication if you are allergic to terazosin.
  • If you stop taking terazosin for any reason, call your doctor before you start taking it again. You may need a dose adjustment.
  • Terazosin can affect your pupils during cataract surgery. Tell your eye surgeon ahead of time that you are using terazosin. Do not stop using terazosin before surgery unless your surgeon tells you to.

Pregnancy level

C

Related drugs

Prazosin , Tamsulosin , Doxazosin , Alfuzosin


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