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PRECAUTIONS: Before taking prazosin, tell your doctor or pharmacist if you are allergic to it; or to other alpha blockers (such as doxazosin, terazosin); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: heart problems (such as low blood pressure), kidney disease, uncontrolled attacks of deep sleep (narcolepsy), prostate cancer.This drug may make you dizzy or drowsy or cause blurred vision. Do not drive, use machinery, or do any activity that requires alertness or clear vision until you are sure you can perform such activities safely. Do not drive or participate in hazardous activities for 24 hours after your first dose, any increase in your dosage, or restarting treatment. If your doctor prescribes any additional blood pressure drugs, avoid driving and hazardous activities for 24 hours after your first dose of the new medication. Limit alcoholic beverages.To reduce the risk of dizziness and fainting, be careful when standing for long periods. Avoid getting overheated during exercise and hot weather. When first starting this drug, avoid situations where you may be injured if you faint.Before having surgery (including cataract eye surgery), tell your doctor or dentist that you are taking this medication and about all the products you use (including other prescription drugs, nonprescription drugs, and herbal products).Older adults may be more sensitive to the side effects of this drug, especially dizziness and fainting.During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.Prazosin passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: The effects of some drugs can change if you take other drugs or herbal products at the same time. This can increase your risk for serious side effects or may cause your medications not to work correctly. These drug interactions are possible, but do not always occur. Your doctor or pharmacist can often prevent or manage interactions by changing how you use your medications or by close monitoring.To help your doctor or pharmacist give you the best care, be sure to tell your doctor or pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products) before starting treatment with this product. While using this product, do not start, stop, or change the dosage of any other medicines you are using without your doctor's approval.Some of the products that may interact with this drug include: beta blockers (such as atenolol, metoprolol, propranolol), verapamil, drugs for sexual function problems (such as sildenafil, tadalafil, vardenafil).Tell your doctor or pharmacist if you also take drugs that cause drowsiness, lower blood pressure, or make it difficult for you to urinate, such as: certain antihistamines (such as diphenhydramine), anti-seizure drugs (such as carbamazepine), medicine for sleep or anxiety (such as alprazolam, diazepam, zolpidem), muscle relaxants, narcotic pain relievers (such as codeine), psychiatric medicines (such as chlorpromazine, risperidone, amitriptyline, trazodone).Check the labels on all your medicines (such as cough-and-cold products, diet aids, nonsteroidal anti-inflammatory drugs-NSAIDs for pain/fever reduction) because they may contain ingredients (such as pseudoephedrine, phenylephrine, chlorpheniramine, diphenhydramine, clemastine, ibuprofen, naproxen) that could increase your blood pressure or cause a fast heartbeat. Ask your pharmacist about the safe use of those products.This medication may interfere with certain laboratory tests (including pheochromocytoma screening test), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.This document does not contain all possible interactions. Keep a list of all the products you use. Share this list with your doctor and pharmacist to lessen your risk for serious medication problems.

Report Problems to the Food and Drug Administration   You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088. Need help identifying pills and medications? Use the pill identifier tool on RxList.