Does Lamictal Cause Weight Gain?
No, Lamictal (lamotrigine) does not cause weight gain and is considered weight-neutral among anti-epileptic medications. 1
Evidence-Based Classification
Lamotrigine is consistently classified as weight-neutral across multiple clinical guidelines and research studies. The American Gastroenterological Association's 2017 guidelines on pharmacotherapy for obesity explicitly categorize lamotrigine alongside levetiracetam and phenytoin as weight-neutral anti-epileptic agents. 1
Comparative Context Among Anti-Epileptic Drugs
Understanding lamotrigine's weight profile requires context within its medication class:
Anti-Epileptic Drugs That CAUSE Weight Gain:
- Gabapentin, pregabalin, and valproic acid are consistently associated with significant weight gain 1
- Carbamazepine is generally included in the weight-gain category 1
- Valproate causes particularly problematic weight gain, with studies showing mean weight gain of 12.8 ± 9.3 lbs after 32 weeks of treatment 2
Anti-Epileptic Drugs That PROMOTE Weight Loss:
- Topiramate and zonisamide are consistently associated with weight loss and are even FDA-approved for weight management (topiramate as part of Qsymia) 1
Weight-Neutral Anti-Epileptic Drugs:
- Lamotrigine, levetiracetam, and phenytoin do not significantly affect weight 1
Clinical Research Supporting Weight Neutrality
Direct comparative studies confirm lamotrigine's weight-neutral profile. A randomized, double-blind study comparing lamotrigine versus valproate monotherapy over 32 weeks demonstrated that lamotrigine-treated patients had minimal weight change (mean gain of only 1.3 ± 11.9 lbs), while valproate-treated patients experienced significant weight gain (12.8 ± 9.3 lbs). 2
Long-term studies in bipolar disorder confirm no weight gain with lamotrigine. Research specifically notes that "lamotrigine did not appear to cause bodyweight gain" in maintenance studies, and this was identified as a distinct advantage over lithium and other mood stabilizers. 3
Clinical Implications for Practice
For patients with weight concerns requiring anti-epileptic therapy, lamotrigine represents an optimal choice when clinically appropriate for their seizure type or mood disorder. 1
If a patient reports weight gain while taking lamotrigine, investigate alternative causes rather than attributing it to the medication, including:
- Concurrent medications (antipsychotics, other antidepressants, antidiabetic agents) 1
- Changes in disease activity affecting physical activity levels 4
- Lifestyle factors or other medical conditions 4
Important Caveats
Individual responses may vary despite the general weight-neutral classification. While population-level data consistently shows weight neutrality, some patients may experience modest weight changes in either direction. 2
The weight-neutral profile of lamotrigine should not be the sole determinant of drug selection. Clinical efficacy for the specific indication (seizure type, bipolar disorder subtype) must guide treatment decisions, with weight effects as an important but secondary consideration. 1