Prazosin is used for many conditions including:
- Cardiovascular conditions such as high blood pressure and Reynaud’s phenomenon;
- Sleep problems such as nightmares, especially if due to an overactive “fight/flight” system from stress, anxiety or trauma (such as post-traumatic stress disorder).
Prazosin is in a class of medications called alpha-blockers (specifically, an alpha-1 adrenoceptor antagonist).
In conditions such as anxiety and PTSD, the body’s alarm becomes turned on, leading to a state of “sympathetic” activation -- like a fire alarm that turns on, but fails to turn off.
Prazosin blocks some of this excessive activation in order to help with nightmares and sleep, and may also help with other symptoms such as flashbacks, being startled easily, and irritability or anger.
How is it taken?
- It is usually taken by mouth, with or without food.
- You usually start at a low dose, and increase to a higher dose that works for you.
When to take it?
- When taken for sleep and insomnia, it is usually taken one hour before bedtime.
- Note that the first dose might make you feel a bit dizzy or faint; if so, then just get into bed earlier that day.
- It is always best to try to take it the same time each day, which helps you remember and helps your body adjust to it.
When used for blood pressure, prazosin works within hours. When used for sleep or nightmares, improvements are usually noticed by five days or so (Consumer Reports, 2011).
When taken for sleep and nightmares, usually at least several weeks to months.
Prazosin is not addictive. People do not get “cravings” for this medication like they might with nicotine or street drugs. If you and your doctor decide it is best for you to stop taking this medication, your doctor will explain how to safely come off this medication so you don’t feel negative effects as your body adjusts to being without it.
Side effects are more likely during the first week of treatment or after an increase in dose.
Common side effects are
- Daytime sedation,
- Fatigue or
Prazosin can cause low blood pressure -- in fact, the original use for prazosin was to treat high blood pressure.
What can I do If I feel light headed or dizzy?
- Take caution when you are getting out of bed in the morning and when you are going up and downstairs. Changing your position more slowly from sitting to standing will help to prevent lightheadedness, dizziness and feeling like you might faint or pass out.
- Drink plenty of fluids and avoid dehydration. Try to drink at least 2 L of water per day especially during periods of hot weather and when you exercise.
- Avoid drinking excessive caffeine. Avoid more than the equivalent of 2 cups of coffee, tea or cola per day as this may you urinate more, leading to dehydration; too much caffeine can also worsen sleep, anxiety and irritability. Avoid energy drinks as only one energy drink may contain the equivalent of 2-4 cups of coffee.
Side effects are generally mild and go away with time as you get used to the medication.
Are side effects severe or persistent, such as the following:
- Feeling faint or lightheaded, feel a rapid heartbeat, feel like your heart is pounding, racing, has skipped a beat or if you feel short of breath.
- If so, then let your prescriber know. They can monitor your blood pressure, or recommend increasing at a slower rate, decreasing or stopping the medication.
Tell your doctor or pharmacist if you:
- Have any allergies, or have experienced a reaction to a medication
- Are taking, or plan to start taking any other prescription or non-prescription medications (including herbal products), as there may be medication interactions.
- Have any other medical conditions, especially high or low blood pressure, heart disease, and diabetes.
- Miss a period, are pregnant (or are planning to become pregnant) or are breast-feeding. Tell your doctor if you become pregnant while taking this medication.
- Are currently using alcohol or street drugs. These substances may interfere with how well this medication works for you and/or make you feel drowsy.
Has the dose been adjusted to the effective dose that is best tolerated?
- Do not stop taking prazosin suddenly, as this can cause symptoms to “rebound”.
- When it is time to stop the treatment, your doctor will decrease the dose gradually and monitor your systems.
Notice any allergy symptoms such as skin rash or hives, shortness of breath, itching, swelling, and cough?
- If so, then stop taking this medication and let your prescriber know.
Did you miss a dose? If so, then just go back to your usual dose and usual time the next time you are scheduled to have a dose.
Keep this medication in the original container, stored at room temperature away from
moisture and heat (e.g. not in the bathroom or kitchen) and protected from light.
Keep this medication out of reach and sight of children.
Raskind M et al.: A Trial of Prazosin for Combat Trauma PTSD With Nightmares in Active-Duty Soldiers Returned From Iraq and Afghanistan, Am. J. Psychiatry, 2013 Sep, 170(9): 1003-1010.
Raskin M et al.: Higher Pretreatment Blood Pressure Is Associated With Greater Posttraumatic Stress Disorder Symptom Reduction in Soldiers Treated With Prazosin, Biological Psychiatry, 2016 Nov 15, 80(10): 736-742.
Prazosin for post-traumatic stress disorder, Consumer Reports, Updated Aug 2011. Retrieved Dec 31, 2020 from https://www.consumerreports.org/cro/2012/04/prazosin-for-post-traumatic-stress-disorder/index.htm
Healthwise Handout on Prazosin via Healthlink BC
Looking for more information about sleep?
- Link to eMH handouts on sleep
- Link to eMH handout on nightmares
Looking for more information about PTSD?
- Link to eMH handout on PTSD in Children/Youth
- Link to eMH handout on PTSD in adults
Written by the health professionals at CHEO, including Marla Sullivan, Pharmacist and Helen Spenser, Psychiatrist.
You are free to copy and distribute this material unchanged and in its entirety as long as 1) this material is not used in any way that suggests we endorse you or your use of the material, 2) this material is not used for commercial purposes (non-commercial), 3) this material is not altered in any way (no derivative works). View full license at http://creativecommons.org/licenses/by-nc-nd/2.5/ca/. For any other uses, please contact the original rights holder, the Kelty Mental Health Centre.
Information in this pamphlet is offered ‘as is' and is meant only to provide general information that supplements, but does not replace the information from your health provider. Always contact a qualified health professional for further information in your specific situation or circumstance.
Date of Last Revision: Jan 1, 2021