No, a 3.75 mg dose of mirtazapine is not commercially available as a standard formulation.
The FDA-approved mirtazapine tablets are manufactured only in 15 mg and 30 mg strengths 1. These are the sole commercially available dosage forms for oral administration in the United States.
Available Dosage Forms
According to the FDA drug label, mirtazapine tablets contain 1:
- 15 mg tablets (scored, film-coated)
- 30 mg tablets (scored, film-coated)
Both formulations are scored tablets, which theoretically allows for splitting, but this would only yield 7.5 mg or 15 mg doses—not 3.75 mg.
Clinical Context for Low-Dose Use
While 3.75 mg is not commercially available, clinical guidelines do reference low-dose mirtazapine use:
For insomnia: Guidelines mention mirtazapine as a sedating low-dose antidepressant option, though they do not specify 3.75 mg dosing 2. One guideline notes a starting dose of 7.5 mg at bedtime for certain indications 3.
Emerging evidence: Recent research has explored ultra-low-dose mirtazapine (3.75 mg) for chronic insomnia, showing potential efficacy 4. However, this remains investigational and would require compounding or tablet manipulation to achieve.
Veterinary use: Interestingly, 3.75 mg dosing has been studied in cats for appetite stimulation 5, but this has no bearing on human pharmaceutical availability.
Practical Implications
To obtain a 3.75 mg dose, you would need to:
- Split a 7.5 mg tablet (which itself requires splitting a 15 mg scored tablet) in half, or
- Use a compounding pharmacy to prepare a custom 3.75 mg formulation
Important caveats:
- Tablet splitting introduces dosing variability and is not FDA-approved for achieving 3.75 mg
- The scored tablets are designed for splitting into 7.5 mg or 15 mg doses only
- Compounded formulations lack the quality control and stability data of commercial products
- Insurance typically does not cover compounded medications when commercial alternatives exist
For clinical practice: If considering sub-therapeutic dosing for off-label indications like insomnia, the lowest practical commercially available dose is 7.5 mg (half of a 15 mg tablet), which aligns with guideline recommendations 3.