Can Lamictal Cause Constipation?
Lamictal (lamotrigine) is not commonly associated with constipation as a significant adverse effect. The most common side effects of lamotrigine are primarily neurological, gastrointestinal (but not specifically constipation), and dermatological, with skin rash being the most frequent cause of treatment withdrawal 1.
Evidence on Lamotrigine's Gastrointestinal Effects
Lamotrigine's adverse event profile includes gastrointestinal symptoms, but these are generally non-specific and do not prominently feature constipation 1.
In a comprehensive review of lamotrigine's pharmacology and therapeutic use, constipation was not identified as a notable adverse effect, unlike other antiepileptic medications 1.
The drug's mechanism of action—blocking voltage-dependent sodium channels to prevent excitatory neurotransmitter release—does not directly affect gastrointestinal motility in the way that anticholinergic medications do 1.
Comparison with Other Antiepileptic Drugs
Other antiepileptic medications, such as pregabalin, have been documented to cause severe and disabling constipation in up to 7.5% of patients, with constipation being dose-dependent and requiring drug withdrawal in some cases 2.
Lamotrigine appears to be better tolerated than older antiepileptic agents like carbamazepine and phenytoin, producing less drowsiness, asthenia, and ataxia 1.
Clinical Considerations for Patients with GI History
If constipation develops in a patient taking lamotrigine who has a history of gastrointestinal issues, consider other contributing factors such as:
First-line management of constipation in these patients should include osmotic laxatives such as polyethylene glycol (PEG), lactulose, or magnesium hydroxide 3.
If constipation persists, add stimulant laxatives like bisacodyl (10-15 mg, 2-3 times daily) or senna 3.
Encourage adequate fluid intake and physical activity when appropriate 3.
Important Caveats
The absence of constipation as a prominent side effect in lamotrigine literature does not mean it cannot occur in individual patients, but it is not a characteristic adverse effect of this medication 1.
If constipation develops during lamotrigine therapy, conduct a thorough medication review to identify other potential causative agents, particularly anticholinergic medications, opioids, or antipsychotics 3, 5.
Rule out other treatable causes of constipation including hypercalcemia, hypokalemia, hypothyroidism, and diabetes mellitus 3.