API: Lamotrigine

What Is Lamotrigine and How Does It Work?

Lamotrigine is a synthetic phenyltriazine that works as an anticonvulsant and a mood stabilizer. Though not fully understood, its effects are believed to be mediated through multiple mechanisms. The drug inhibits voltage-gated sodium ion channels by selectively binding to the inactive form, which prevents the release of glutamate, an excitatory neurotransmitter.1 Lamotrigine also increases the activity of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that has relaxant and depressive effects because it blocks nerve transmission in the brain. In addition, lamotrigine may block calcium ion channels, which contributes to its antiepileptic effects. It may also prevent serotonin reuptake, increasing its efficacy as an antidepressant.2


  • Epilepsy: Lamotrigine is approved to treat partial seizures. On its own, lamotrigine can treat tonic-clonic seizures, including simple partial, complex partial, and secondarily generalized seizures. It is also used in combination with other drugs to treat refractory seizures, seizures associated with Lennox-Gastaut syndrome, temporal lobe epilepsy, and juvenile myoclonic epilepsy.3
  • Bipolar Disorder: Lamotrigine can delay the onset of extreme mood swings in patients with bipolar disorder, but it is less effective for treating patients during a depressive or manic episodes.4
  • Off-Label Uses: The drug is sometimes prescribed off-label for psychiatric disorders, such as post-traumatic stress disorder and major depressive disorder.5 It is also used off-label for the prevention of migraine headaches.6

Side Effects and Drug Interactions

Common side effects of lamotrigine include: 

  • Dizziness
  • Drowsiness
  • Headache
  • Blurred vision
  • Loss of coordination
  • Nausea, vomiting, upset stomach

Patients should contact a doctor immediately if they experience worsening depression, suicidal thoughts, or serious side effects, which may include fainting, unusual bruising, extreme fatigue, muscle pain or weakness, jaundice, abdominal pain, dark urine, persistent vomiting, or a change in the amount of urine. Patients should also seek medical attention in the event of a serious allergic reaction, which may be characterized by rash, extreme dizziness, difficulty breathing, or swelling of the face, tongue, or throat.7

Some drugs can change the rate at which lamotrigine is metabolized, so doctors may need to adjust the dosage for patients who take the following medications: estrogen replacement drugs, seizure medications (such as carbamazepine, phenobarbital, phenytoin, primidone, and valproic acid), HIV protease inhibitors, and rifampin. Lamotrigine can decrease the effectiveness of hormonal birth control products, including pills, patches, and rings. Patients are more likely to experience drowsiness as a side effect when lamotrigine is taken in conjunction with other drugs that cause drowsiness, such as alcohol, antihistamines, sleep aids, muscle relaxants, and narcotic pain relievers.8

Latest News and Research

Lamotrigine was developed in the early 1990’s after scientists observed the strong anticonvulsant effects of phenyltriazine compounds in animal models. The FDA approved lamotrigine for the treatment of partial seizures in December 1994.9 In 2003, lamotrigine became the first drug since lithium to be approved for the treatment of patients with Bipolar I Disorder.10 Originally marketed as Lamictal, the drug has since gone to generic. 

Recent research continues to probe the chemical interactions that mediate the drug’s clinical effects. Because lamotrigine affects so many different signaling pathways,these mechanisms remain unclear. There is also a longstanding debate within the research community about the efficacy of using lamotrigine to for the treatment of chronic and acute pain.11 Many studies have focused particularly on the drug’s ability to relieve neuropathic pain and pain from fibromyalgia, but evidence remains inconclusive.12

Many studies have also explored the safety of lamotrigine. In particular, scientists have asked whether the use of lamotrigine by pregnant women poses risks for the developing fetus13 and whether taking lamotrigine while breastfeeding can harm an infant, but findings are mixed. There are also studies on the safety and efficacy of using lamotrigine to treat children with epilepsy. The results suggest that taking the drug is relatively safe, but children are more likely to experience side effects.14

Buying Guide

Many compound pharmacists prefer Phenytoin Sodium or Gabapentin, which also treat epilepsy. Please find more information about our Bulk APIs here.


Show 14 footnotes

  1. “Lamotrigine (Code C38703),” May 31, 2016, https://ncit.nci.nih.gov/ncitbrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&ns=NCI_Thesaurus&code=C38703
  2. “Lamotrigine,” 2016, https://pubchem.ncbi.nlm.nih.gov/compound/lamotrigine#section=Top
  3. “Lamotrine,” 2016, http://www.epilepsy.com/medications/lamotrigine
  4. “Lamotrigine: a review of its use in bipolar disorder,” 2003, https://www.ncbi.nlm.nih.gov/pubmed/12962521
  5. “Use of Lamotrigine as a Mood Stabilizer,” 2016, http://www.psycom.net/depression.central.lamotrigine.html
  6. “Medication Profile – Lamictal Off-Label Use for Migraine,” November 9, 2012, http://www.healthcentral.com/migraine/c/202/157009/medication-profile/
  7. “Lamotrigine Uses,” 2016, http://www.webmd.com/drugs/2/drug-4582-7217/lamotrigine-oral/lamotrigine—oral/details#side-effects
  8. “Lamotrigine Interactions,” 2016, http://www.webmd.com/drugs/2/drug-4582-7217/lamotrigine-oral/lamotrigine—oral/details#interactions
  9. “Lamotrigine,” 2011, http://www.medmerits.com/index.php/article/lamotrigine
  10. “Maintenance Treatment for Bipolar Disorder,” 2016, http://www.webmd.com/bipolar-disorder/bipolar-disorder-maintenance-treatment
  11. “Lamotrigine for acute and chronic pain,” February 16, 2011, http://www.ncbi.nlm.nih.gov/pubmed/21328280
  12. “Lamotrigine for chronic neuropathic pain and fibromyalgia in adults,” December 3, 2013, http://www.ncbi.nlm.nih.gov/pubmed/24297457
  13. “Lamotrigine use in pregnancy and risk of orofacial cleft and other congenital anomalies,” May 3, 2016, http://www.ncbi.nlm.nih.gov/pubmed/27053714
  14. “Safety of lamotrigine in paediatrics: a systematic review,” June 12, 2015, http://www.ncbi.nlm.nih.gov/pubmed/26070796