What is the ICD-10 (International Classification of Diseases, 10th Revision) code for nightmares and what is the typical starting dose of prazosin for treating nightmares?

ICD-10 Code and Prazosin Dosing for Nightmares

The ICD-10 code for nightmare disorder is G47.52, and prazosin should be started at 1 mg at bedtime, titrating by 1-2 mg every few days until an effective dose is reached (typically around 3 mg for nightmares). 1, 2

ICD-10 Coding

• G47.52 is the specific ICD-10 code for "REM sleep behavior disorder" which encompasses nightmare disorder as classified under parasomnias 3
• If nightmares are associated with PTSD, you may also need to code F43.10 (Post-traumatic stress disorder, unspecified) as a secondary diagnosis 3

Prazosin Dosing Protocol for Nightmares

Initial Dosing

• Start with 1 mg at bedtime as the initial dose 1, 4, 2
• This low starting dose minimizes the risk of orthostatic hypotension, which is the primary safety concern 4, 2

Titration Schedule

• Increase by 1-2 mg every few days based on patient response and tolerability 1, 4, 2
• The average effective dose is approximately 3 mg for nightmare suppression 2
• Some patients may require higher doses: studies with military veterans used 9.5-13.3 mg/day 2
• Therapeutic benefit can occur within one week of initiation 5

Maximum Dosing

• While the FDA label for hypertension indicates doses up to 40 mg daily in divided doses 6, nightmare treatment typically requires much lower doses (1-16 mg/day) 7
• The dose range across clinical studies was 2-4 mg for older adults and up to 16 mg for combat veterans 8, 7

Critical Monitoring Requirements

Blood Pressure Monitoring

• Monitor blood pressure after the initial dose and with each significant dose increase to assess for orthostatic hypotension 1, 4, 2
• Specifically assess for orthostatic changes, especially after the first dose, as hypotension symptoms can mimic drowsiness 4

Expected Clinical Response

• Patients should experience reduced nightmare frequency and intensity rather than sedation 4, 2
• Successfully treated patients report feeling more rested on awakening and less daytime fatigue, which is paradoxical but expected 4
• Prazosin reduces CNS adrenergic activity rather than acting as a traditional sedative 4, 2

Evidence Base and Clinical Context

Strength of Evidence

• Prazosin has Level A evidence from the American Academy of Sleep Medicine for PTSD-associated nightmares 1, 2
• Three Level 1 placebo-controlled studies demonstrated statistically significant reduction in trauma-related nightmares 2
• A meta-analysis of 8 trials (575 patients) showed significant improvement in nightmares (SMD = -1.13) 9

Important Clinical Considerations

• Prazosin is generally well-tolerated across studies, with orthostatic hypotension being the main adverse effect 2, 5
• The medication works by blocking alpha-1 adrenergic receptors, reducing the elevated CNS noradrenergic activity that disrupts REM sleep and causes nightmares 2
• Patients should maintain concurrent psychotherapy and other psychotropic medications during prazosin treatment 2
• Prazosin has been used successfully for both PTSD-associated and non-PTSD nightmares, including healthcare-associated nightmares in palliative care settings 10

Common Pitfall to Avoid

• Do not use clonazepam or venlafaxine for nightmare disorder, as studies show no benefit over placebo 1, 2
• Do not discontinue prazosin abruptly if the patient is on higher doses, as rebound hypertension can occur (though this is more relevant for hypertension treatment) 6