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Evaluation of clonidine and doxazosin for treating nightmares in adults with Post-traumatic Stress Disorder

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on treating nightmares in patients with Posttraumatic Stress Disorder (PTSD). PTSD is a mental health condition that can develop after experiencing or witnessing a traumatic event, often causing disturbing nightmares and sleep problems. The study aims to determine if two medications - clonidine and doxazosin - are more effective than placebo in reducing nightmares in PTSD patients.

The medications being tested belong to a group of drugs called alpha-adrenergic agents, which can affect how the body responds to stress. During the study, participants will receive either clonidine (0.075-0.375 mg), doxazosin (1-10 mg), or placebo in the form of capsules. The treatment period lasts for several weeks, during which the medication dose may be adjusted.

Throughout the study, participants will have their nightmare frequency and intensity monitored, along with their overall PTSD symptoms and sleep quality. The study will also track changes in depression symptoms, daily sleep patterns, and quality of life. Regular check-ups will be conducted to monitor the participants' progress and any potential effects of the medications.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial phase - Week 1

    You will receive placebo tablets (inactive medication) in swedish-orange colored capsules

    This initial phase helps establish baseline measurements

  2. Step 2

    Treatment phase - Weeks 2-11

    You will be randomly assigned to receive one of three treatments:

    Option 1: Clonidine tablets (75 micrograms), taken orally

    Option 2: Doxazosin tablets (starting at 1 mg, may increase up to 10 mg), taken orally

    Option 3: Placebo (inactive medication) in swedish-orange colored capsules

  3. Step 3

    Assessment visits

    You will attend regular assessment visits during weeks 2-9

    Medical staff will evaluate your symptoms using standardized questionnaires

    The final assessment will occur at week 10 (visit 9)

  4. Step 4

    Daily monitoring

    You will maintain a sleep diary throughout the study recording:

    Total sleep time in minutes

    Time taken to fall asleep

    Time spent awake during the night

    Number of nightmares (0, 1, 3, 4 or more)

    Nightmare intensity on a scale from 0 (not at all) to 5 (extreme)

    Sleep quality rating

  5. Step 5

    Final evaluation

    The study concludes after 10 weeks of treatment

    Final assessments will measure changes in:

    Frequency and intensity of nightmares

    Overall PTSD (post-traumatic stress disorder) symptoms

    Sleep quality

    Depression levels

    Quality of life indicators

Who can join the trial?

9 criteria

  • You must be diagnosed with posttraumatic stress disorder (PTSD) and score at least 26 points on a special assessment scale called CAPS-5
  • You must experience at least two nightmares per week that are moderately distressing or worse
  • You must be between 18 and 65 years old
  • You must be able to provide written consent and understand the nature and possible effects of the treatment
  • If you are a woman who can become pregnant, you must:
    • Have a negative pregnancy test (urine or blood)
    • Not be breastfeeding
    • Use reliable birth control methods during the study
    • Your current medications must be stable, meaning:
      • You have been taking the same dose for at least 4 weeks
      • You have not had any recent changes in how much or how often you take your medications

Who cannot join the trial?

14 criteria

  • Current diagnosis of severe depression or active thoughts of self-harm
  • History of allergic reactions to clonidine or doxazosin
  • Current pregnancy or breastfeeding
  • Severe heart conditions or uncontrolled blood pressure
  • Liver or kidney disease that could affect medication processing
  • Current use of medications that could interact with study drugs (such as other blood pressure medications)
  • Substance abuse or dependence within the past 3 months
  • Sleep apnea (a condition where breathing repeatedly stops during sleep) or other severe sleep disorders
  • Participation in other clinical trials within the past 30 days
  • Inability to provide informed consent (understanding and agreeing to study participation)
  • History of fainting or severe drops in blood pressure when standing up
  • Serious medical conditions that are not well-controlled
  • Regular use of medications that affect blood pressure or heart rate
  • History of not following prescribed medication schedules
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Investigated drugs

  • Clonidine

    is a medication that affects certain receptors in the brain and nervous system. It belongs to a group of drugs called alpha-agonists. In this trial, it is being studied for its potential to reduce nightmares in people with post-traumatic stress disorder (PTSD). This medication is already known to help with high blood pressure and certain attention disorders.

  • Doxazosin

    is a medication that works by relaxing blood vessels and affecting certain brain receptors. It belongs to a group of medications called alpha-blockers. While it is commonly used to treat high blood pressure and prostate problems in men, in this trial it is being tested for its ability to help reduce nightmares in people with PTSD.

What is already known about the treatment

  • Clonidine

    A centrally-acting alpha-2 adrenergic agonist medication that is typically taken orally in tablet form to treat various conditions, including posttraumatic stress disorder (PTSD) related nightmares. This medication works by reducing the release of norepinephrine in the brain, which helps decrease anxiety, blood pressure, and sympathetic nervous system activity. Clonidine belongs to the class of antihypertensive medications but has found additional therapeutic use in psychiatric conditions, particularly for managing nighttime symptoms of PTSD.

  • Doxazosin

    An alpha-1 adrenergic blocker medication administered orally in tablet form, originally developed for treating high blood pressure but now being studied for its effects on PTSD-related nightmares. This medication works by blocking alpha-1 receptors in both blood vessels and the central nervous system, leading to reduced sympathetic nervous system activity and potentially helping to manage trauma-related sleep disturbances. Doxazosin belongs to the class of alpha blockers and is being investigated for its potential therapeutic benefits in psychiatric conditions, particularly nighttime symptoms of PTSD.

Investigated diseases

Posttraumatic Stress Disorder - A mental health condition that develops after exposure to a traumatic event. The condition causes persistent distressing memories, nightmares, and flashbacks of the traumatic experience. People with PTSD often experience heightened anxiety, emotional numbness, and strong reactions to reminders of the trauma. Sleep problems, including recurring nightmares, are common symptoms that can significantly impact daily life. The disorder can affect both the emotional and physical responses to everyday situations, causing people to feel constantly alert and on guard.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2024-517537-40-00Protocol codeClonDOEstimated enrolment189 patientsSponsorCharite Universitaetsmedizin Berlin KöR

sourced from the EU Clinical Trials Register and site verification

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