Can a Patient Take 7.5mg Mirtazapine for 2 Weeks Then Increase to 15mg?
Yes, a patient can start with 7.5mg mirtazapine for 2 weeks before increasing to 15mg, though this approach uses a lower-than-standard starting dose and may delay therapeutic benefit.
Standard FDA-Approved Dosing
The FDA-approved starting dose is 15mg once daily, preferably in the evening prior to sleep, with dose changes not recommended in intervals less than 1-2 weeks 1. This represents the evidence-based standard approach that balances efficacy with tolerability.
Rationale for Lower Starting Dose (7.5mg)
Starting at 7.5mg can be justified as a "test dose" strategy in specific clinical situations:
- Patients particularly sensitive to medication side effects may benefit from subtherapeutic initial dosing 2
- The 1-2 week interval before increasing to 15mg aligns with FDA guidance on minimum time between dose changes 1
- Mirtazapine reaches steady state in 4-6 days, so 2 weeks provides adequate time to assess tolerability at the lower dose 3
Important Caveats About the 7.5mg Dose
Increased sedation is paradoxically more common at subtherapeutic doses like 7.5mg 4. This occurs because:
- Lower doses preferentially block histamine H1 receptors without fully engaging the noradrenergic mechanisms that provide antidepressant effects 5
- Sedation is reported in substantially fewer patients when appropriate therapeutic doses (≥15mg) are used from treatment initiation 4
Timeline to Therapeutic Effect
Starting at 7.5mg will delay the onset of antidepressant action:
- Assessment of therapeutic response should begin within 1-2 weeks of treatment initiation 6
- Adequate response evaluation requires 6-8 weeks at therapeutic doses 6
- Mirtazapine shows early onset effects on sleep and anxiety within the first week, but full antidepressant effects take 2-4 weeks at therapeutic doses 7, 8
- By starting at 7.5mg for 2 weeks, you're essentially adding 2 weeks to the expected time to therapeutic benefit
Recommended Approach
For most patients, start directly at 15mg once daily at bedtime 1. This provides:
- Faster onset of therapeutic benefit 6
- Less paradoxical sedation compared to subtherapeutic dosing 4
- Alignment with FDA-approved dosing that has been studied in clinical trials 1
Reserve the 7.5mg starting approach for:
- Elderly patients who may have higher plasma concentrations 3
- Patients with hepatic or renal impairment (30-50% decreased clearance) 3
- Patients with documented extreme sensitivity to psychotropic medications 2
Monitoring During Titration
After 2 weeks at 15mg, if inadequate response occurs, increase to 30mg, then potentially to the maximum of 45mg 1. The effective therapeutic range is 15-45mg daily, with plasma concentrations averaging 5-100 microg/L 3.