Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.
Before taking this medicine
You should not use prazosin if you are allergic to it.
Tell your doctor if you have ever had:
low blood pressure, especially if caused by taking medications.
Prazosin can affect your pupils. If you have cataract surgery, tell your surgeon ahead of time that you use  prazosin.
Tell your doctor if you are pregnant or plan to become pregnant. It is not known whether prazosin will harm an unborn baby. However, having high blood pressure during pregnancy may cause complications such as diabetes or eclampsia (dangerously high blood pressure that can lead to medical problems in both mother and baby). The benefit of treating hypertension may outweigh any risks to the baby.
It may not be safe to breastfeed while using this medicine. Ask your doctor about any risk.
Prazosin is not approved for use by anyone younger than 18 years old.
How should I take prazosin?
Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.
Prazosin lowers blood pressure and may cause dizziness or fainting, especially when you first start taking it, or whenever your dose is changed. You may feel very dizzy when you first wake up.
Your blood pressure will need to be checked often.
Swallow the capsule whole and do not crush, chew, break, or open it.
Keep using this medicine as directed, even if you feel well. High blood pressure often has no symptoms. You may need to use blood pressure medication for the rest of your life.
Prazosin is only part of a complete treatment program that may also include diet, exercise, weight control, and special medical care. Follow your doctor's instructions very closely.
Some things can cause your blood pressure to get too low. This includes vomiting, diarrhea, or heavy sweating. Call your doctor if you are sick with vomiting or diarrhea.
Store at room temperature away from moisture and heat.
What happens if I miss a dose?
Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include extreme drowsiness or underactive reflexes.
