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Lamotrigine (Lamictal)

Anticonvulsantprescriptionoral · inferred

Phenyltriazine anticonvulsant and mood stabilizer that blocks voltage-gated sodium channels and inhibits glutamate release. First-line maintenance therapy for bipolar disorder, particularly effective for preventing depressive episodes. Requires very slow dose titration (over 6-8 weeks) to minimize risk of Stevens-Johnson syndrome. Half-life doubles when co-administered with valproate and halves with carbamazepine due to UGT enzyme interactions.

Projected serum levels — 100 mg, once daily

Lamotrigine (Lamictal)
Lamotrigine (Lamictal) modeled serum levels, 100 mg once daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 3 days. 0 62.5 125 188 250 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 3
Lamotrigine (Lamictal) modeled serum levels with a loading dose of 224 mg, then 100 mg once daily The first dose is larger so levels approach steady state faster. 0 62.5 125 188 250 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 100 mg once daily (oral).

Loading schedule: 224 mg on day 1, then 100 mg once daily — reaching therapeutic levels sooner.

Modeled steady state after ~3 days: peak ≈ 212 mg, trough ≈ 124 mg body load. Population-based estimate over 15 days for a 100 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Anticonvulsant
Route modeled
Oral
Model confidence
inferred
Half-life
29 h
Common dose
100 mg
Suggested maximum
400 mg/day
Reference dose range
25–400 mg (single dose)
Suggested cadence
once daily
Validated against
100 mg oral — Cmax 1.6 mg/L at 1.5 h

Documented interactions

  • caution
    Phenytoin (Dilantin) + Lamotrigine (Lamictal) Depletion

    Phenytoin induces glucuronidation of lamotrigine; reduces lamotrigine levels and anticonvulsant efficacy.

  • watch
    Carbamazepine (Tegretol) + Lamotrigine (Lamictal) Stacked effects

    Carbamazepine (Tegretol) and Lamotrigine (Lamictal) both push the voltage gated sodium channel in the same direction.

  • watch
    Cocaine + Lamotrigine (Lamictal) Stacked effects

    Cocaine and Lamotrigine (Lamictal) both push the voltage gated sodium channel in the same direction.

  • watch
    Diphenhydramine (Benadryl) + Lamotrigine (Lamictal) Stacked effects

    Diphenhydramine (Benadryl) and Lamotrigine (Lamictal) both push the voltage gated sodium channel in the same direction.

  • watch
    Gabapentin (Neurontin) + Lamotrigine (Lamictal) Stacked effects

    Gabapentin (Neurontin) and Lamotrigine (Lamictal) both push the cacna2d in the same direction.

  • watch
    Kava (Kavalactones) + Lamotrigine (Lamictal) Stacked effects

    Kava (Kavalactones) and Lamotrigine (Lamictal) both push the voltage gated sodium channel in the same direction.

Serum checks 14 modeled interaction pairings for lamotrigine (lamictal) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Efficacy of lamotrigine in bipolar disorder: a systematic review and meta-analysis Geddes JR et al. · American Journal of Psychiatry, 2009 DOI

    Meta-analysis of 5 RCTs confirming lamotrigine is effective for preventing relapse in bipolar disorder, with stronger evidence for preventing depressive episodes (HR 0.64) than manic episodes.

  2. Lamotrigine compared with lithium in mania: a double-blind randomized controlled trial Bowden CL et al. · Journal of Clinical Psychiatry, 2003 DOI

    18-month RCT (638 patients) demonstrating lamotrigine 200-400 mg/day was superior to placebo for preventing bipolar depression relapse and comparable to lithium for overall mood stabilization.

  3. Clinical pharmacokinetics of lamotrigine Rambeck B, Wolf P · Clinical Pharmacokinetics, 1993 DOI

    PK review establishing lamotrigine half-life of 24-35 hours in monotherapy, 60-90 hours with valproate co-administration, and 12-15 hours with carbamazepine, highlighting critical drug interaction effects.

3 published studies referenced in the app, each with a plain-language summary.