Terazosin hydrochloride is a selective alpha-1 adrenoreceptor competitive blocking agent with a longer duration of action. Terazosin is a quinazoline derivative. It is very rapidly absorbed and performed activity within 15 minutes after oral ingestion.

Pharmacology

Terazosin is selective for alpha-1-adrenoceptors but not their individual subtypes. Inhibition of these alpha-1-adrenoceptors results in relaxation of smooth muscle in blood vessels and the prostate, lowering blood pressure and improving urinary flow. Smooth muscle cells accounts for roughly 40% of the volume of the prostate and so their relaxation reduces pressure on the urethra.

It has also been shown that catecholamines induce factors responsible for mitogenesis and alpha-1-adrenergic receptor blockers inhibit this effect. A final long term mechanism of terazosin and other alpha-1-adrenergic receptor blockers is the induction of apoptosis of prostate cells. Treatment with terazosin enhances the expression of transforming growth factor beta-1 (TGF-beta1), which upregulates p27kip1, and the caspase cascade

Terazosin Hydrochloride is indicated in-

• Single therapy is used to relieve from signs and symptoms of benign prostatic hyperplasia (BPH).
• For the treatment of hypertension.

Benign Prostatic Hyperplasia-

• Initial dose: 1 mg at bedtime is starting dose of all patients and this dose should not be exceeded.
• Subsequent dose: The dose slowly increases to achieve the desired response. The usual recommended dose range is 5-10 mg administered once a day.

Hypertension-

• Initial dose: 1 mg at bedtime is starting dose of all patients and this dose should not be exceeded.
• Subsequent dose: The dose slowly increases to achieve the desired response. The usual recommended dose range is 2-10 mg administered once a day.

Terazosin is contraindicated in patients known to be hypersensitive to Terazosin or its analogues.

Postural hypotension is more commonly reported side effect. Dizziness, lack of energy, peripheral oedema; urinary frequency and priapism reported.

Overdose Effects

Acute overdose may lead to acute hypotension, cardiovascular support is of first importance. Restoration of blood pressure and normalization of heart rate may be accomplished by keeping the patient in a supine position. At the same time expansion of plasma volume and noradrenergic vasopressor may also be needed.

• First dose may cause hypotension (within 30-90 minutes). Therefore should be taken on retiring to bed.
• Caution should be observed when Terazosin is administered with other antihypertensive agents, avoid the possibility of significant hypotension. When adding Terazosin to a diuretic or other antihypertensive agent, dosage reduction and retitration may be necessary.
• The patients should be cautioned to avoid situation such as driving and hazardous tasks where injury could result due to syncope after initiation of Terazosin therapy.

Pregnancy & Lactation

The safety of Terazosin during pregnancy has not been established. So Terazosin is not recommended during pregnancy unless the potential benefit justifies the potential risk to mother and fetus. It is not known whether Terazosin is excreted in breast milk. As many drugs are excreted in breast milk, caution should be exercised when Terazosin is administered to a nursing mother.