Article Highlights

  • Prazosin is a high blood pressure medication that comes in 1 mg, 2 mg and 5 mg capsules. Adults can take Prazosin by mouth, in 1 mg dosage, up to 3 times daily.
  • Prazosin is also used to treat benign prostatic hyperplasia, post-traumatic stress disorder, Raynaud’s syndrome and Alzheimer’s disease.
  • Prazosin has shown promise in helping with Alzheimer’s-related aggressive agitation.
  • Side effects of Prazosin include reactions of central nervous system, respiratory system, cardiovascular system, etc.
  • It is important that the patient’s healthcare provider is aware of all of the meds that are being taken as some medications can interact with Prazosin.
  • Older adults require a lower dose because Prazosin may cause significant hypotension.
  • A person taking Prazosin should change positions slowly if he or she experiences dizziness. If this does not work, the healthcare provider should be notified immediately.



Prazosin is a medication that is used to treat high blood pressure. Prazosin is classified as an antihypertensive, and it can be given alone or in combination with other medications. Prazosin lowers a person’s blood pressure and decreases the risk of cardiovascular events such as heart attack or stroke.

This article covers Prazosin, how it is used, the conditions it is used to treat, and the side effects a person taking this medication may experience. As this article is only meant to provide the reader with general knowledge about the medication and its most common uses, there may well be various other conditions for which Prazosin is prescribed that are not covered in this article.

Availability and Dosages of Prazosin

Prazosin is available as both a generic and a brand name medicine. Prazosin was approved by the Food and Drug Administration (FDA) in 1976, and there are a number of different brand names for this medication including:

  • Minipress
  • Prazin
  • Prazo

The medication comes in 1 mg, 2 mg and 5 mg capsules, and the capsules may be white, pink and white or blue and white, depending on the manufacturer. To ensure that you are using the right medication and dosage, it is always best to check with your pharmacy as they may have changed manufacturers.

Generic Versus Brand Names of Prazosin

If you are wondering if you should take the generic or brand name product, please continue reading. When a generic product is approved by the Food and Drug Administration (FDA), it means that the drug has met the standards of strength, quality, purity and potency, as set by the FDA.

Generic drugs are required to have the same active ingredient, strength, dosage form, and administration route as brand name medications. Generic drug manufacturers are required to pass the same quality standards as brand name drug manufacturers, and research has shown that generic drugs work just as well their brand name medications. The one big difference between brand name and generic drugs is price, with generic drugs on average costing 80 to 85 percent less than the brand name product.

Use, Route, and Dosage of Prazosin

Adults can take this medication by mouth, usually in 1 mg dosage, up to 3 times daily. It is recommended that the first dose of the medication be taken at bedtime. This medication may also be used in children for the treatment of hypertension, and the dose is individualized based on the weight of the child.

Wendy’s Story

Wendy: No medicine could lower my blood pressure from approximately 145/ 90, though Prazosin did it. Now my blood pressure is normal with a systolic pressure of 125 or less, and diastolic pressure of 65 or less. This is absolutely fantastic, and I still can’t believe it despite taking measurements regularly. I have side effects occasionally, like light headedness, and I may at times be a little weak or a little shaky. Note I only take a half tablet in the morning and a half tablet at night before I go to bed. Also, when the doctor prescribed Prazosin for me, I was taking two other blood pressure medications. After some adjustments made by my physician, I am now only taking Prazosin. My blood pressure is normal, and once I lost weight and stopped smoking, I started to feel fantastic. I continue to go to my scheduled appointments and get checked by my doctor, and I seem to be doing great. I would highly recommend Prazosin for blood pressure control, subject to your doctor agreeing and prescribing it for you. For me, it’s been an effective medication with very few side effects.

Benign Prostatic Hyperplasia

Men suffering with enlarged prostates are also prescribed Prazosin. However, it is recommended that a person be checked for cancer prior to being prescribed the medication. The medication is taken by mouth and the patient is given 1-5 mg up to twice daily.

Peter’s Story

Peter has benign prostatic hypertrophy (BPH). He describes how he had problems with urgency, urine dribbling, and frequent trips to the bathroom at night that prevented him from getting good sleep. He found it embarrassing when taking road trips with his family. He would have to plan his trips around the nearest bathroom. He now takes Prazosin 2 mg twice daily and is happy with the results. “It has worked wonders for me, and there have been no side effects.”

Post-Traumatic Stress Disorder (PTSD) and Related Sleep Disruptions

Post-traumatic Stress Disorder (PTSD) is a disabling anxiety that affects one in four Americans, as per 2011 Consumer Reports. Traumatic events such as military combat, abuse, violent physical or sexual assaults or accidents can trigger this disabling condition, and nearly 70 percent of people that have PTSD experience sleep difficulties. Prazosin is one of the treatment recommendations to alleviate this condition, for Prazosin blocks the body’s release of the hormone adrenaline. Current recommended dosage is 1 mg of Prazosin by mouth at bedtime.

Wilbur’s Story

Wilbur is a Gulf-War veteran. He has experienced PTSD for the last eighteen years. Wilbur describes experiencing nightmares related to his combat experience. The nightmares would be so bad that they would cause disabling anxiety the following day. He had been prescribed Restoril to help him sleep, and Valium and Xanax for anxiety, but these medications had no effect on the PTSD-related nightmares. Wilbur remembers discussing other possible options with his doctors, and he was skeptical when he heard about Prazosin. Now he has been using the medication for the past two years at bedtime. Wilbur is very pleased with the performance of the medication and finds it has a positive effect on the nightmares caused by PTSD.


Raynauds’ Phenomenon

Raynaud’s’ Phenomenon is a disorder that affects the blood vessels of fingers and toes. It causes the blood vessels to narrow when the person is cold or feeling stress, a known “fight or flight” response. People of all ages can have this disorder, and according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, it can run in families as well. This disorder is most common in women and people living in cold places. Prazosin may be prescribed for these individuals at 1-5 mg by mouth every 12 hours.

George’s Story

George’s story is interesting: prior to taking Prazosin for nightmares, he had a bad case of Raynaud’s syndrome. Once he started taking the medication for the nightmares, he also noticed an improvement in his fingers and toes with the Raynaud’s. He has been taking Prazosin for 5 years and has not had any issues with Raynaud’s. He did however build up a tolerance for the medication and had to be put on a different medication for the nightmares.

Prazosin’s Use
Prazosin’s Use

Prazosin and Alzheimer’s Disease

Alzheimer’s disease (AD), the most common form of dementia, is a progressive disease that takes away mental function, memory and the ability to perform daily tasks and care for oneself over time. Though there is no cure for AD, there are some medications that temporarily improve the symptoms that are associated with Alzheimer’s, helping a person with dementia maintain their independence for a longer period of time.

As Alzheimer’s disease progresses, individuals often experience agitation and aggression that can be difficult for individuals and their families to manage. This is also the reason why many people suffering with Alzheimer’s disease often end up in long term care facilities. In Alzheimer’s disease, the brain experiences serious shrinkage secondary to the buildup of plaques and tangles in the brain. Plaques are clumps of protein also known as beta-amyloids, and they destroy brain cells by blocking cell to cell communication. Tangles occur when tau proteins, normally in the brain, twist into abnormal shapes. Tau proteins are the brain’s transport system and require normal shape and structure in order to work properly.

Prazosin has shown promise in helping those experiencing Alzheimer’s-related aggressive agitation. Prazosin is a vasodilator and causes the smooth muscles to relax by blocking alpha one adrenergic receptors. This is important because in Alzheimer’s, the alpha one adrenergic receptors degenerate, which can lead to changes in arousal, mood and memory.

The use of Prazosin for agitation secondary to Alzheimer’s has shown promise and is still being tested by the Alzheimer’s Disease Cooperative Study, with funding from the National Institutes of Health. The University of Washington conducted a study of Prazosin in 22 people with Alzheimer’s-related aggressive agitation. The control group was given 6 mg per day of Prazosin over eight weeks. The control group and the placebo group were evaluated on global impression of change and the neuropsychiatric inventory (NPI), and Prazosin outperformed the placebo in the study.

Proper use of Prazosin
Proper use of Prazosin

Instructions for Taking Prazosin

Any person taking Prazosin should be instructed on the proper use of the medication. The following constitute some recommendations about taking the drug:

  • Take the medication at the same time everyday.
  • It is recommended that the initial dose of Prazosin be taken at bedtime.
  • Take any missed dose as soon as remembered. Never double up on doses.
  • Record the patient’s weight twice weekly and note any signs of fluid retention (swelling in the feet, legs, or hands).
  • Keep scheduled appointments, and blood pressure should be checked regularly to determine the patient’s response to the medication.
  • If the patient is having laboratory tests, inform the personnel because this medication may affect drug-related results.
  • The medication may cause dizziness -avoid activities that require alertness (driving, operating heavy machinery, etc.).
  • Avoid sudden changes in position, for it may cause dizziness due a drop in blood pressure.
  • Avoid hot showers and standing for long periods of time, for this may cause dizziness.
  • Avoid exercising in hot weather and avoid central nervous system depressants like alcohol, for these may cause the blood pressure to drop and could lead to dizziness or drowsiness.
  • Inform your healthcare provider if you are taking any over the counter or herbal medications, for these may interact with Prazosin (it is a good idea to take the bottles to your appointments).
  • Consult with your healthcare provider before taking any over the counter cold or allergy remedies.
  • Keep Prazosin in a container that it came in tightly closed, at room temperature, and away from excess moisture and heat.
  • Keep this and all medications out of the reach of children.
  • Continue taking this medication even if you start feeling better.
  • Please comply with any extra interventions suggested by your healthcare provider, such as weight reduction, low-sodium diet, regular exercise, stress management, smoking cessation, etc.
  • Inform all of the patient’s physicians of all of the medications that the patient is taking; take all of the patient’s med bottles to the doctors’ appointments so that they know the names and strengths of the patient’s medications, and so that they will also know which pharmacy the patient goes to; this helps to prevent over-medicating and mixing medications that are contraindicated
  • Fill all prescriptions at the same pharmacy; this helps with convenience and will also keep the pharmacist aware of any new medications that may interact with current medications
  • Do not stop taking Prazosin abruptly, without consulting your healthcare provider. Some conditions could get worse, and the medication may need to be gradually reduced.
Role of norepinephrine

Desired Effect of Prazosin

Prazosin acts by increasing the inner diameter of the arteries and veins, a process that is referred to as dilation. It has a direct effect on the smooth muscles of the vasculature. Prazosin blocks the alpha-adrenergic receptors, a process that leads to a decrease in contractions in the smooth muscles of the prostate, which in turn leads to lowering blood pressure, decreasing the cardiac work load, and decreasing symptoms of enlarged prostates (urinary urgency, urinary hesitancy and nocturia)

Side effects of Prazosin
Side effects of Prazosin

Adverse Reactions and Side Effects of Prazosin

Adverse reactions and side effects are possible responses to medication outside of the desired effect. Not every person will experience the following reactions; it is important, however, to be aware of what to expect in case reactions occur:

Central Nervous System Reactions

  • Dizziness
  • Fatigue
  • Headache
  • Vertigo
  • Depression
  • Nervousness

Respiratory System Reactions

  • Cough
  • Shortness of breath
  • Angioedema (an allergic reaction where the tongue swells)
  • Nasal congestion

Cardiovascular System Reactions

  • Atrial fibrillation
  • Bradycardia
  • Hypertension
  • Orthostatic Hypotension
  • Peripheral edema (swelling in the feet, legs, arms and hands)
  • Syncope (fainting)

Skin Reactions

  • Allergic reaction
  • Rash
  • Thrombocytopenic purpura (excessive bruising and/or bleeding)
  • Itching
  • Alopecia (loss of hair)

Musculoskeletal System Reactions

  • Back pain
  • Extremity pain
  • Non-cardiac chest pain

Gastrointestinal System Reactions

  • Nausea
  • Vomiting
  • Diarrhea
  • Constipation

Genitourinary Reactions

  • Incontinence
  • Impotence
  • Priapism (painful erection)
  • Urinary frequency

Miscellaneous Reactions

  • Bleeding
  • Leukopenia (increased white blood cell count)
  • Hyperlipidemia (high cholesterol
  • Fever
  • Blurred vision
  • Nose bleeds
  • Reddened sclera

Drug Interactions with Prazosin

It is important to inform your healthcare provider of any medications that you are taking. Some medications that can interact with Prazosin include:

  • Beta blockers (atenolol, metoprolol, and propranolol)
  • Verapamil
  • Erectile dysfunction medications
  • Pulmonary hypertension medications
  • Nitrates (nitroglycerine)
  • Antihistamines
  • Anti-seizure medications (Tegretol)
  • Medications for sleep or anxiety (alprazolam, valium, or ambien)
  • Muscle relaxants (cyclobenzaprine)
  • Narcotic pain relievers (codeine)
  • Psychiatric medications (chlorpromazine, amitriptyline, trazodone)
  • Alcohol
  • Nonsteroidal Anti-inflammatory Drugs (NSAIDs)
Precautions for Prazosin
Precautions for Prazosin

These medications can have an increased hypotensive effect and cause the person’s blood pressure to drop dangerously low, or they can cause the medication to be ineffective. It is important that the patient’s healthcare provider is aware of all of the meds that are being taken.


The following people should avoid taking Prazosin or take with caution under the care of their physician:

  • Patients with kidney disease (May have increased sensitivity to the medication and require a lower dose)
  • Women who are pregnant or breastfeeding (Safety has not been established for use)
  • Patients with Angina Pectoris
  • Patients using diuretics (Decrease dose of prazosin, due to additive effects)
  • Patients that are having cataract surgery (Increased risk of intraoperative floppy iris syndrome, which can lead to trauma and tears in the iris)
  • Older patients (May cause significant hypotension and or syncope – will require a lower dose if indicated, and can increase the likelihood of a fall).
Prazosin overdose
Prazosin overdose

What to Do in Case of a Prazosin Overdose

If too much Prazosin is taken, seek emergency medical attention right away. Symptoms of overdose include feeling drowsy or faint. If you are unsure, contact Poison Control at 1-800-222-1222. Take the bottle to the hospital so that healthcare personnel will know when the medication was last filled, how many pills are in the bottle and where the medication was filled. This is important information for healthcare personnel when trying to determine if an overdose has occurred accidentally or on purpose.

When to Call the Doctor

With all of the possible side effects of this medication, it is important to know when to call the physician. One of the most common side effects of Prazosin is dizziness. A person taking Prazosin should change positions slowly, as this usually helps to alleviate the symptoms. If this does not work and dizziness is unrelieved or gets worse, the healthcare provider should be notified. Other symptoms include:

  • Fast or pounding heartbeat
  • Fluttering in your chest
  • Trouble breathing
  • Swelling in the hands, legs, feet, or ankles
  • An erection that is painful or lasts more than four hours (if not treated immediately could lead to permanent tissue damage and loss of potency)
  • Angioedema (this is swelling that could involve the lips, eyes, face, tongue or laryngeal mucosa and can be life threatening due to airway blockage; this is a medical emergency)

Final Thoughts

Prazosin is a medication that has many uses. It was originally used to treat hypertension, but over the years, it was found to be useful in treating several other conditions. Prazosin has improved the lives of people suffering from hypertension, nightmares and daytime mental disturbances that may relate to post-traumatic stress disorder, Raynaud’s phenomenon, and benign prostatic hypertrophy (BPH).

Prazosin has also shown promise in the treatment of aggression and agitation in individuals with Alzheimer’s disease. There are certain people that should avoid using the medication; these include those with kidney disease, the elderly, and people having surgery (particularly eye surgery). It is best to work closely with a healthcare provider to determine if the benefits of using the medication outweigh the costs. Even though not every person experiences side effects, it is best to be familiar with potential side effects and know when to contact your health provider.

June 14, 2017
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