A New FDA Pharmacogenetic Entry for Lamotrigine
On September 10, 2026, the U.S. Food and Drug Administration (FDA) updated its Table of Pharmacogenetic Associations to add lamotrigine and the HLA-B*15:02 genetic variant to Section 1, the category for associations that support therapeutic management recommendations. The FDA states that people known to carry this allele may face a higher risk of severe skin reactions when taking lamotrigine, a medication sold under the brand name Lamictal and widely dispensed in generic form. Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are among the most serious reactions relevant to this warning.
This is a meaningful regulatory recognition of a genetic risk association, not a newly discovered SJS/TEN adverse effect. Lamotrigine has carried serious-rash warnings for years. The distinction matters when patients, families, clinicians, and attorneys examine what was known at the time of a particular prescription.
What the FDA Actually Said
The FDA’s September 2026 table entry states that the HLA-B*15:02 allele is associated with increased risk of severe skin reactions and advises weighing risks and benefits when considering lamotrigine for patients already known to carry the allele. It also cautions that carriers may be at greater risk from other SJS/TEN-associated drugs and that genotyping does not replace clinical vigilance.
Crucially, placement in the FDA table does not mean the agency requires genetic testing for every patient before lamotrigine treatment. The FDA explains that a pharmacogenetic association’s inclusion does not, by itself, establish a universal pre-prescription testing requirement. A positive test is not proof that a patient will develop SJS/TEN; a negative test does not rule out the reaction. Individual clinical decisions remain dependent on the patient, indication, alternatives, concomitant medications, and prescribing information.
How the 2026 Entry Fits the Earlier Lamictal Warning Chronology
The September 2026 table update should be read alongside—not confused with—the October 2025 revision of U.S. Lamictal prescribing information. That 2025 revision identified HLA-B*15:02 as an additional risk factor in the boxed warning and serious-rash precautions. The boxed warning also identifies potentially life-threatening SJS/TEN, pediatric risk, valproate coadministration, and excessive initial dosing or dose escalation.
Accordingly, the September 2026 event is a new FDA pharmacogenetic-table listing, not the first U.S. labeling disclosure of lamotrigine-associated SJS/TEN or of the HLA-B*15:02 concern. In a case involving earlier exposure, attorneys must obtain the precise label in effect on the prescription date rather than apply the 2026 table retroactively as if it created a new legal duty.
Why This Can Matter in an Individual SJS/TEN Case
A lamotrigine case requires more than identifying a genetic association. Medical experts must determine whether the reaction was true SJS/TEN, whether lamotrigine was a plausible culprit given the start date and latency, and whether competing drugs or infections better explain the presentation. Records of the initial dose, titration schedule, valproate use, early symptoms, instructions given, and medication discontinuation may be especially important.
When HLA-B*15:02 status was known before treatment, documentation of the prescriber’s risk-benefit discussion and consideration of alternatives may become relevant. When status was unknown, the legal question is not automatically “Why was no test ordered?” The applicable clinical standard, prevailing guidance at that time, patient-specific risk factors, available evidence, and whether testing would have changed the treatment decision require separate expert analysis. A genetic association does not establish that a manufacturer, prescriber, or pharmacist was negligent.
Brand Versus Generic Lamotrigine and Potential Defendants
Patients often say they took “Lamictal” when the pharmacy actually supplied generic lamotrigine. For any potential pharmaceutical claim, the dispensing record, National Drug Code (NDC), manufacturer, formulation, pharmacy labels, and fill dates should be obtained immediately. Brand-versus-generic identity can affect which entities can be sued and what federal preemption defenses may apply to a labeling theory.
For branded exposure, a lawyer may examine the manufacturer’s historical labeling, evidence available before the reaction, warning adequacy, and whether an alternative warning could have altered the prescriber’s decision. For generic exposure, federal sameness requirements and Supreme Court preemption precedent can materially restrict certain failure-to-warn and design-defect theories. Medical-negligence and dispensing-related theories require their own factual and state-law analysis. A strong drug-causation assessment does not guarantee a collectible defendant or a viable claim.
California Implications and Time Limits
California deserves particular attention because it has a large and diverse patient population, but ancestry alone cannot determine an individual’s genotype or whether genetic screening was indicated. The FDA entry does not create a California-specific screening mandate. For a California referral, counsel should document the treatment location, prescriber, pharmacy, medication manufacturer, any prior genetic results, warning chronology, and medical decision-making.
Limitations analysis must begin promptly. California product-liability and medical-negligence claims can involve different deadlines and discovery rules, with additional procedural requirements in some settings. A new FDA table entry does not automatically revive a claim arising from an older injury or restart the limitations period. Any potential tolling or delayed-discovery issue needs individualized review.
What Patients and Families Should Preserve
For an SJS/TEN event following lamotrigine, preserve the complete pharmacy dispensing history, bottles or packaging, prescribing and dose-escalation instructions, all medications taken in the preceding weeks, photographs, emergency and hospital records, dermatology and pathology evaluations, and long-term ophthalmology and mucosal-injury records. If genetic testing was performed, retain the original report and the date it was available to the treating clinician. Do not stop antiseizure medication abruptly without medical direction; suspected SJS/TEN symptoms require urgent medical evaluation.
The September 2026 FDA entry strengthens the documentary record for evaluating genetic susceptibility, but it does not establish that any particular patient’s SJS/TEN was caused by lamotrigine or that a legal claim exists. Careful reconstruction of exposure, causation, warnings, and injuries remains essential.
Sources
FDA, Table of Pharmacogenetic Associations, update history dated September 10, 2026.
FDA-approved Lamictal prescribing information, October 2025 boxed-warning revision.
FDA, Drug Safety-related Labeling Changes (SrLC) Database Overview.