Indications

Alphapress XR is indicated for several conditions:

• Hypertension: Used to treat all grades of essential and secondary hypertension. It can be used alone or in combination with other antihypertensive drugs.
• Left Ventricular Failure: Used to treat left ventricular failure, especially in patients who have not responded to or have become resistant to conventional therapies (diuretics, cardiac glycosides).
• Raynaud's Phenomenon and Raynaud's Disease: Used in the treatment of these conditions.
• Benign Prostatic Hyperplasia (BPH): Indicated as an adjunct for the symptomatic treatment of urinary obstruction caused by BPH. It is also useful for patients awaiting prostatic surgery.

Pharmacology

Prazosin, the active ingredient in Alphapress XR, works by selectively blocking alpha-1-adrenoceptors on vascular smooth muscle. This action decreases total peripheral vascular resistance, which lowers blood pressure in both supine and standing positions. The effect is particularly pronounced on diastolic blood pressure.

In patients with congestive heart failure, Prazosin reduces left ventricular filling pressure and cardiac impedance, which improves cardiac output without causing a reflex increase in heart rate. For Raynaud's disease, it reduces the severity, frequency, and duration of attacks. In BPH, it antagonizes alpha-1 receptors on prostatic and urethral smooth muscle, which helps improve urinary flow.

Dosage & Administration

• Prazosin Tablet: The starting dose should be low and gradually increased.
  • Hypertension:
    • No prior therapy: Start with 0.5 mg in the evening, then increase to 0.5 mg two or three times a day. The dosage can be gradually increased up to a maximum daily dose of 20 mg.
    • With diuretics or other antihypertensives: The dose of the other agent should be reduced, and Prazosin should be started at 0.5 mg in the evening, then adjusted carefully.
  • Left Ventricular Failure: Start with 0.5 mg two, three, or four times a day. The dose is adjusted based on the patient's response, with typical daily doses ranging from 4 mg to 20 mg.
  • Raynaud's Phenomenon/Disease: Start with 0.5 mg twice a day. The usual maintenance dose is 1 mg or 2 mg twice a day.
  • Benign Prostatic Hyperplasia: Start with 0.5 mg twice daily. The usual maintenance dose is 2 mg twice daily.
• Prazosin XR Extended-Release Tablet: Tablets must be swallowed whole. The initial dose for hypertension is 2.5 mg once daily. The dose can be increased slowly over 7 to 14 days, up to a maximum of 20 mg once daily.

Interaction

Alphapress XR has been administered without adverse interactions with a variety of medications, including:

• Cardiac glycosides (digitalis, digoxin)
• Hypoglycemic agents (insulin, chlorpropamide)
• Tranquilizers and sedatives (diazepam, phenobarbital)
• Antiarrhythmics (propranolol, quinidine)
• Analgesics and anti-inflammatories (aspirin, indomethacin)

Contraindications

Prazosin is contraindicated in patients with a known sensitivity to quinazolines.

Side Effects

The most common side effects are dizziness, headache, drowsiness, lack of energy, weakness, palpitations, and nausea. These often resolve with continued therapy. Other side effects may include vomiting, diarrhea, constipation, abdominal pain, liver function abnormalities, edema, fainting, and various neurological, respiratory, and skin reactions.

Pregnancy & Lactation

Alphapress XR is not recommended during pregnancy unless the potential benefit justifies the potential risk to the mother and fetus. Prazosin has been shown to be excreted in small amounts in human milk, so caution should be used when administering it to nursing mothers.

Precautions & Warnings

• Initial Dose: A low initial dose is crucial to avoid a sharp, exaggerated drop in blood pressure and postural hypotension, which can cause dizziness, weakness, or fainting.
• Left Ventricular Failure: In patients who have been treated with diuretics, the initial dose may cause a significant drop in blood pressure. The dose must be carefully titrated.
• Special Conditions: For patients with Raynaud's Phenomenon/Disease or BPH, blood pressure should be carefully monitored during the initial administration and dose adjustments.

Use in Special Populations

• Children: Not recommended for children under 12, as safety has not been established.
• Left Ventricular Failure: Not recommended for failure caused by mechanical obstructions (e.g., aortic or mitral valve stenosis) or recent myocardial infarction due to a lack of data.

Overdose Effects

An overdose may cause profound drowsiness and low blood pressure. Treatment should involve supportive care for the cardiovascular system, including keeping the patient supine and, if necessary, using volume expanders or vasopressors. Prazosin is highly protein-bound and not dialyzable.

Therapeutic Class

Alphapress XR is classified as an alpha adrenoceptor blocking drug.

Storage Conditions

Store below 30°C, away from light and moisture. Keep out of the reach of children.