Increase Mirtazapine to 3mg First—Do Not Add Gabapentin
You should increase mirtazapine to 3mg before considering gabapentin, as your current 2mg dose is far below the therapeutic range for insomnia, and gabapentin lacks evidence-based support for primary insomnia treatment. 1, 2, 3
Why Your Current Regimen Is Subtherapeutic
Mirtazapine 2mg is pharmacologically insufficient. The FDA-approved starting dose is 15mg, with the recommended dosing for insomnia typically 7.5-15mg at bedtime 3, 4. Your 2mg dose is approximately 1/7th of the minimum therapeutic dose and unlikely to provide meaningful sedative effects 5.
Melatonin 300mcg has weak evidence for chronic insomnia. The American Academy of Sleep Medicine explicitly recommends against melatonin for sleep onset or maintenance insomnia in adults, showing only a 9-minute reduction in sleep latency compared to placebo 1, 2, 6. While you're taking it, it's contributing minimally to your sleep improvement.
The Mirtazapine Dosing Strategy
Increase mirtazapine incrementally to reach therapeutic levels:
Move to 7.5mg immediately. This represents the lower end of the therapeutic range for insomnia and is supported by recent high-quality evidence showing clinically relevant improvement at this dose 7.
If insufficient after 1-2 weeks, increase to 15mg. The FDA label specifies dose changes should not occur in intervals less than 1-2 weeks to allow evaluation of response 3. A 2025 randomized controlled trial demonstrated that mirtazapine 7.5-15mg produced statistically significant and clinically relevant reduction in insomnia severity at 6 weeks, with 52% achieving improvement (>7-point reduction in Insomnia Severity Index) 7.
Consider 30mg if sleep maintenance remains problematic. While lower doses (7.5-15mg) are typically used for insomnia, the FDA-approved therapeutic range extends to 45mg daily, and contrary to older beliefs, higher doses do not necessarily cause more activation 3, 8. A 2019 study found no significant increase in noradrenergic side effects (anxiety, agitation, insomnia) at higher mirtazapine doses 8.
Why NOT Gabapentin
Gabapentin has no evidence-based role in primary insomnia treatment:
The American Academy of Sleep Medicine explicitly recommends against anticonvulsants for insomnia. Tiagabine (another anticonvulsant) is specifically not recommended for sleep onset or maintenance insomnia 1, 2.
Gabapentin is FDA-approved only for postherpetic neuralgia and partial seizures—not insomnia 9. Its use for sleep would be entirely off-label without supporting guideline recommendations.
Adding gabapentin creates unnecessary polypharmacy risks. Combining multiple CNS depressants (mirtazapine + melatonin + gabapentin) significantly increases risks of cognitive impairment, falls, daytime sedation, and complex sleep behaviors 2, 10.
Gabapentin's primary side effects include drowsiness and dizziness 9, which would compound mirtazapine's sedative effects without addressing the root issue: your mirtazapine dose is too low to be effective.
The Correct Treatment Algorithm
Follow this stepwise approach:
Discontinue or continue melatonin 300mcg (it's providing minimal benefit but is generally safe) 1, 6.
Reassess after 1-2 weeks. Evaluate sleep onset latency, wake after sleep onset, total sleep time, and daytime functioning 2, 3.
If insufficient improvement, increase to 15mg and reassess again in 1-2 weeks 3, 7.
If sleep maintenance problems persist at 15mg, consider increasing to 30mg rather than adding another agent 1, 3.
Only if mirtazapine fails at therapeutic doses (15-30mg) should you consider alternative agents—and gabapentin would not be the next choice. The American Academy of Sleep Medicine recommends first-line agents like zolpidem, eszopiclone, or ramelteon, or second-line agents like low-dose doxepin 3-6mg for sleep maintenance 1, 2, 10.
Critical Safety Considerations
Mirtazapine must be taken nightly on a scheduled basis, not PRN. It has a 20-40 hour half-life and requires consistent dosing to maintain therapeutic blood levels 2. You cannot use it "as needed."
Monitor for excessive sedation, weight gain, and increased appetite as you increase the dose—these are the most common side effects 5, 7.
Gradually taper if discontinuing. The FDA warns that adverse reactions may occur upon abrupt discontinuation 3.
What You Should NOT Do
Do not add gabapentin at this time. It lacks evidence for insomnia, creates polypharmacy risks, and doesn't address the fundamental problem: subtherapeutic mirtazapine dosing 1, 2, 9.
Do not continue at 2mg mirtazapine expecting improvement. This dose is pharmacologically insufficient and well below any studied therapeutic range 3, 5, 7.
Do not rely on melatonin as your primary sleep intervention. While generally safe, it has weak evidence for chronic insomnia and should not be considered effective monotherapy 1, 2, 6.