Prazosin is used for treatment of intrusive nightmares and flashbacks symptoms of PTSD.
Prazosin has limitation in some patients due to:
- Need for multiple dosings in 24 hour period: due to short half life of 2-3 hours with duration of action of 6-10 hours.
- Effect wearing off during later part of night due to short duration of action.
- Increased risk of hypotension.
If patient is not tolerating prazosin, you can consider doxazosin as an alternative medication to target intrusive nightmares symptoms of PTSD.
- Prazosin and doxazosin are both α1-adrenergic antagonists.
- FDA approved for hypertension and benign prostatic hyperplasia.
- ==> Not approved for PTSD (off label use).
- In contrast to Prazosin, Doxazosin have half life of 16-30 hr and hence can be taken as once daily dosing.
- The risk of hypotension is low due to better absorption profile of doxazosin.
- The slower onset of action also reduces the risk of first-dose postural hypotension as compared to prazosin.
- The controlled-release gastrointestinal therapeutic system (GITS) is also available as XL formulation and this can controls fluctuations in plasma drug levels.
- Initiate at 1 mg daily and titrate to 4-8 mg/day (based on toleration and response).
- Can be given at any time of the day as AM or HS dosing, with or without food.
- Doxazosin extended release [XL] GITS formulation: initiating dose is 4 mg daily and titrate to 16 mg daily over 2 weeks (based on toleration and response).
This dose recommendation is based on following studies:
- 4 mg/day for 8 weeks resulted in improved sleep quality, decreased frequency and intensity of trauma-related nightmares, and improved ability to function during the daytime. (2)
- 4-8 mg/day was effective in 12 week open label study with 12 participants. (4)
- Doxazosin extended release [XL] GITS titrated from 4 mg daily to 16 mg daily over the course of 12 days resulted in significant improvement in a double-blind, placebo-controlled study in 8 participants. (5)
Case reports showing efficacy of Doxazosin for PTSD nightmares:
- Patient #1: Doxazosin 1 mg dosing improved nightmares in 1 week but no improvement in sleep.
- Patient #2: Doxazosin 2 mg dosing improved nightmares and sleep.
- Patient #3: Doxazosin 1 mg dosing improved nightmares in 2 weeks.
Read reference 6 (pdf)
Important clinical fact:
Doxazosin is used for erectile dysfunctions due to it’s effect on vasodilation and enhancing blood flow to the area. This makes Doxazosin a good option for PTSD patient with underlying sexual dysfunction.
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- Prim Care Companion CNS Disord. 2012; 14(5): PCC.12l01356.
- BJU Int. 2006 Mar; 97(3):559-66.
- J Clin Psychopharmacol. 2010 Feb; 30(1):84-5.
- J Clin Psychiatry. 2016 May; 77(5):e561-5.
- Braz J Psychiatry. 2019 Mar-Apr;41(2):189-190.
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