Lamotrigine (Lamictal) has been used to treat epilepsy and bipolar disorder since its approval in 1994.The Food and Drug Administration (FDA) has been evaluating in vitro studies of lamotrigine's effect on the heart after receiving reports of abnormal electrocardiograms and other serious problems such as chest pain, loss of consciousness, and cardiac arrest believed to be associated with the drug's use. The FDA has now issued a Drug Safety Communication to warn that lamotrigine has the potential to increase the risk of arrythmias in patients with heart disease. Previous FDA safety warnings for lamotrigine include the risk of serious immune system reactions (April 2018), aseptic meningitis (August 2010), and possible association with oral clefts in newborns if used during pregnancy (September 2006). Lamotrigine was also included in a class alert concerning an increased risk of suicidal thoughts and actions in those taking antiseizure drugs (May 2009).

Lamotrigine works to control seizures by inhibiting voltage-sensitive sodium channels, thereby stabilizing neuronal membranes and regulating the presynaptic release of excitatory amino acids (especially glutamate and aspartate). In this respect, it acts similarly to class IB antiarrhythmics. Like all antiarrhythmic drugs, which can create, worsen, or correct arrythmias, lamotrigine can lead to an irregular or slow ventricular conduction (widen QRS), and induce proarrhythmia, resulting in sudden death. The risk appears greatest for those with underlying cardiac disease or heart conduction problems (for example, patients with heart failure, valvular heart disease, congenital heart disease, conduction system disease, ventricular arrhythmias, cardiac channelopathies [such as Brugada syndrome], clinically important ischemic heart disease, or multiple risk factors for coronary artery disease) or who are taking other medications that affect heart conduction.

Nurses should teach patients prescribed lamotrigine about the potential risk of cardiac arrythmias and to report any signs or symptoms (abnormal heart rate or irregular rhythm, racing heartbeat, skipped or slow heartbeat, shortness of breath, dizziness, or fainting) to their health care provider right away or to go to an ED. NPs should carefully weigh the benefits of therapy against the risk of arrythmias for patients with clinically important structural or functional heart disease. The risk to patients may increase further if lamotrigine is used in combination with other sodium channel blockers. At this time, other sodium channel blockers should not be considered safer than lamotrigine. The FDA is requiring in vitro tests of these agents and will report more when findings are available. Postmarketing studies are required for carbamazepine (Carbatrol, Equetro, Tegretol, Tegretol XR), cenobamate (Xcopri), eslicarbazepine (Aptiom), fosphenytoin (Cerebyx, Sesquient), lacosamide (Vimpat), oxcarbazepine (Oxtellar XR, Trileptal), phenytoin (Dilantin-125), rufinamide (Banzel), topiramate (Qsymia [topiramate plus phentermine], Qudexy XR, Topamax, Trokendi XR), and zonisamide (Zonegran). It is important for patients to understand that they should not suddenly stop taking lamotrigine, as this can lead to uncontrolled seizures or new or worsening mental health problems.

To read the FDA Drug Safety Communication about lamotrigine, go to http://www.fda.gov/drugs/drug-safety-and-availability/studies-show-increased-ris.