Medicines & Supplements A to Z > Prazosin  


Last updated on 18/03/2021.

Overview   |   Dosage   |    Side Effects   |   Precautions  |   Tips  |   Where To Buy  



BRAND NAME(S) IN HONG KONG: Apo-Prazo, CP-Prazo, Mizosin

DRUG CLASS: Alpha-1 blocker; Antihypertensive

USED FOR: Hypertension, benign prostatic hyperplasia

OTHER DRUGS IN THE SAME CLASS: Alfuzosin, Tamsulosin, Terazosin

AVAILABLE DOSAGE FORMS: 1mg, 2mg, 5mg (tablets)

What is Prazosin for?

Prazosin belongs to a class of medications called alpha blockers (like Tamsulosin) that causes vasodilation and therefore it is mainly indicated for hypertension, benign prostatic hyperplasia (BPH), and Raynaud phenomenon. It can also be used for treating post-traumatic stress disorder, nightmares and sleep disorders.

How to use it?

Prazosin is taken by mouth as conventional tablets. For patients who are taking this drug for the first time, it is advised to take it before bedtime to reduce the chance of symptomatic hypotension. 

When used for high blood pressure (hypertension), the usual adult starting dose of Prazosin is 1 mg 2-3 times daily. Your doctor will then gradually increase the dose as needed. The maximum daily dose is 20 mg. 

For other uses of Prazosin, adult dosing can begin at 0.5-1 mg daily at bedtime.

What are the side effects of Prazosin?

Common side effects of Prazosin are low blood pressure, dizziness, headache, swelling of limbs, and nasal congestion.

Who should not take Prazosin?

People who are allergic to quinazolines, Prazosin, or any formulation ingredient.

Pharmacist Tips:

– Patients, particularly the elderly, should get up slowly from sitting or lying positions as dizziness may occur.
– Avoid alcohol while you are taking Prazosin. 

Common dosing schedule:
You can take Prazosin with or without food. 

Take at bedtime if Prazosin is used for benign prostatic hyperplasia to reduce nighttime symptoms. 

This schedule is for reference only, adjustments may be made according to individual needs.

Some common medications Prazosin may interact with:
– Certain erectile dysfunction drugs, e.g. Sildenafil (Viagra), Tadalafil, Vardenafil
– Other antihypertensive drugs, such as beta blockers (e.g. Propranolol), calcium channel blockers (e.g. Amlodipine)

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Prazosin in Hong Kong?

In Hong Kong, Prazosin is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.

For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at

Need more information?

For detailed information about the use of Prazosin in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.