What is the recommended starting dose of mirtazapine (an antidepressant medication) for an elderly patient with panic disorder?

Mirtazapine Starting Dose for Elderly Patients with Panic Disorder

Start mirtazapine at 7.5 mg at bedtime in elderly patients with panic disorder, which is half the standard starting dose of 15 mg recommended for younger adults. 1, 2

Rationale for Dose Reduction in Elderly Patients

The standard FDA-approved starting dose of mirtazapine is 15 mg once daily, preferably in the evening prior to sleep 2. However, elderly patients require dose modification for several critical reasons:

• Elderly patients are more susceptible to adverse effects including sedation, dizziness, and falls, necessitating lower initial dosing 1
• The American Family Physician guidelines specifically recommend starting mirtazapine at 7.5 mg at bedtime in elderly patients, with a maximum dose of 30 mg per day 1
• This represents a 50% dose reduction from the standard adult starting dose, reflecting the increased sensitivity of older adults to psychotropic medications 1

Dosing Strategy and Titration

After initiating treatment at 7.5 mg:

• Assess response for at least 1-2 weeks before making any dose adjustments, as this allows sufficient time to evaluate therapeutic response and tolerability 2
• If inadequate response occurs, gradually increase the dose up to a maximum of 30 mg per day in elderly patients (compared to 45 mg maximum in younger adults) 1, 2
• Mirtazapine's sedating effects are paradoxically more prominent at lower doses, so some patients may actually tolerate higher doses better once titrated appropriately 3

Special Considerations for Panic Disorder in the Elderly

While mirtazapine is not FDA-approved specifically for panic disorder, the evidence supports its use:

• Panic disorder in elderly patients is often comorbid with depression, making mirtazapine a reasonable choice given its dual benefits for both conditions 4, 5
• SSRIs are generally considered first-line for panic disorder in the elderly, but mirtazapine represents a viable alternative, particularly when anxiety and sleep disturbance are prominent features 4, 5
• Starting antidepressants at low doses in anxious elderly patients is crucial to avoid initial exacerbation of anxiety symptoms and enhance adherence 4

Monitoring and Safety

Key safety considerations in elderly patients:

• Monitor closely for sedation, dizziness, and orthostatic hypotension, which can increase fall risk 1
• Weight gain and increased appetite are common and may be beneficial in elderly patients with poor appetite, but problematic in those with diabetes or obesity 3, 6
• Provide frequent follow-up during the first few weeks to address concerns about adverse effects and improve medication adherence 4

Drug Interactions Requiring Dose Adjustment

Be aware of interactions that may necessitate further dose modifications:

• Strong CYP3A4 inhibitors (ketoconazole, clarithromycin) may require dose reduction of mirtazapine 2
• Cimetidine increases mirtazapine levels and may require dose reduction 2
• Strong CYP3A4 inducers (carbamazepine, phenytoin, rifampin) may require dose increases 2

Duration of Treatment

• For panic disorder, continue treatment for at least 6-12 months after symptom resolution before considering tapering, as panic disorder is typically chronic or recurrent 4
• Always taper gradually rather than stopping abruptly to minimize discontinuation symptoms 2