Synergistic risks: Lamotrigine induced rash potentiating lithium toxicity

Lithium and lamotrigine are mood stabilizers approved for the treatment of bipolar disorder. Lithium's narrow therapeutic index and comparatively minor alterations in plasma concentrations can have significant clinical sequelae (McKnight et al., 2012). Several classes of drugs have been implicated in developing lithium toxicity, including diuretics and nonsteroidal anti-inflammatory compounds (Finley, 2016). Lithium is not metabolized and is eliminated almost entirely via the renal route (Rust et al., 2018). Consequently, plasma concentrations are exquisitely sensitive to physiological factors affecting renal function, such as age, dehydration, and sodium imbalance. Sodium depletion can cause increased lithium reabsorption in the kidneys, potentially leading to toxicity (Joshi et al., 2019). Lamotrigine is known to carry the risk of causing rash, which in severe cases can be fatal. The rash leads to cutaneous and extracutaneous involvement, with impaired alimentation leading to fluid and electrolyte imbalance. In this case report, we present a patient prescribed a combination of lamotrigine and lithium. The patient developed rash due to lamotrigine, leading to lithium toxicity and acute kidney injury, emphasising the importance of monitoring patients closely when using these medications in combination.