Can I add mirtazapine (Remeron) 7.5mg to a regimen of propranolol (propranolol) 10mg orally (po) twice a day (bid) for an older female patient with severe post-traumatic stress disorder (PTSD) and sleep disturbances?

Adding Mirtazapine to Propranolol for PTSD-Related Sleep Disturbances

Yes, you can safely add mirtazapine 7.5mg at bedtime to her current propranolol regimen for sleep improvement in this older female patient with severe PTSD. Mirtazapine is well-tolerated, promotes sleep, and has no significant drug interactions with propranolol, making it a reasonable choice for this clinical scenario 1.

Rationale for Mirtazapine in This Case

• Mirtazapine at 7.5mg at bedtime is specifically recommended as a starting dose for sleep promotion, with the option to titrate up to 30mg at bedtime based on response 1.
• The medication is described as "potent and well tolerated" and specifically "promotes sleep, appetite, and weight gain" 1.
• For older patients, the 7.5mg starting dose you've selected is appropriate and conservative 1.

Important Clinical Considerations

The Nightmare Problem

• Your patient's lack of dream recall may actually indicate REM sleep suppression or fragmented sleep architecture, which mirtazapine can help normalize 1.
• However, mirtazapine is NOT a first-line treatment specifically for PTSD-related nightmares 2, 3.
• If nightmares emerge or worsen as her sleep improves and dream recall returns, you should consider adding prazosin (starting at 1mg at bedtime, titrating to 3-4mg for civilians) as the most evidence-based treatment for PTSD nightmares 2, 3, 4.

Drug Interaction Monitoring

• Monitor blood pressure when combining these medications, as both propranolol and mirtazapine can cause orthostatic hypotension, particularly in older patients 2, 3.
• The propranolol dose of 10mg BID is quite low, which reduces interaction risk 1.
• No significant cytochrome P450 interactions exist between these two medications 1.

Alternative Considerations if Mirtazapine Fails

If mirtazapine proves ineffective or poorly tolerated, consider these evidence-based alternatives for PTSD-related sleep disturbances:

• Prazosin remains the gold standard for PTSD nightmares specifically, with medium-to-large effect sizes (starting 1mg at bedtime, titrating to 3-4mg for civilians) 2, 4, 5.
• Trazodone 25-200mg decreased nightmares in 72% of veterans, though 60% experienced side effects including orthostatic hypotension 2, 3.
• Clonidine 0.1mg twice daily (titrating to 0.2mg/day average) is an alternative alpha-2 agonist with Level C evidence for PTSD nightmares 2, 3.

Common Pitfalls to Avoid

• Do not use benzodiazepines or non-benzodiazepine hypnotics (zolpidem) as they are ineffective for PTSD-related sleep disturbances and carry addiction risk 5, 6.
• Avoid clonazepam and venlafaxine as they are specifically not recommended for nightmare disorder 2.
• If nightmares become prominent as sleep improves, do not delay adding prazosin as untreated nightmares predict worse PTSD outcomes and increased relapse risk 7, 8.
• Monitor for weight gain with mirtazapine, which may be beneficial or problematic depending on her baseline nutritional status 1.

Monitoring Plan

• Reassess sleep quality and nightmare frequency at 4 weeks, as full therapeutic response to antidepressants requires 4-8 weeks 1.
• Check orthostatic blood pressures at follow-up visits given the combination therapy 2, 3.
• If she begins recalling dreams or nightmares emerge, this may indicate improved sleep architecture and should prompt consideration of prazosin addition 2, 4.