Purpose <p>Lamotrigine is a common anticonvulsant drug used to treat bipolar disorder and epilepsy. It primarily works by stabilizing neuronal membranes and altering the release of neurotransmitters at the presynaptic level through the inhibition of voltage-gated sodium channels. Oral suspensions, chewable dispersible tablets, and tablets are among the dosing forms of lamotrigine. For quality assurance, stability research, and regulatory compliance, a trustworthy HPLC method for the quantitative measurement of lamotrigine in oral suspension must be developed.</p> Methods <p>An RP-HPLC method was optimized using a mobile phase of buffer, acetonitrile, and Milli-Q water, with detection at 270&#xa0;nm and a 30-minute runtime. Linearity, accuracy, precision, and stability-indicating capability were evaluated across relevant concentration ranges. Forced degradation studies under acidic and alkaline conditions were performed.</p> Results <p>The method showed excellent linearity (R² = 0.999, accuracy and precision within the concentration range of 0.2–1.2 ppm and 200–600 ppm. Forced degradation revealed 46.3% degradation in acidic and 67.7% in alkaline conditions, confirming sensitivity to degradation pathways and minimal excipient interference.</p> Conclusion <p>Lamotrigine in oral suspension was effectively analyzed using the High-Performance Liquid Chromatography (HPLC) method, which was successfully optimized and validated. The technique proved to be reliable, accurate, and precise in identifying lamotrigine concentrations that fell within the specified range. To provide sufficient resolution and little interference from excipients, some parameters were modified, including flow rate, composition of the mobile phase, and detecting wavelength. With a correlation coefficient (R²) showing a strong linear relationship between concentration and response, the method demonstrated good linearity.</p> Graphical Abstract <p></p>