How to Treat Life-Threatening Lamotrigine Ingestion in Pets
Lamotrigine is a phenyltriazine anticonvulsant that is used in human medicine, but it can cause severe cardiovascular and CNS signs in companion animals.
In an animal exposed to Lamotrigine you may see lethargy, ataxia, tremors, seiures, agitation, bradycardia, VPCs, AV block, ventricular tachycardia, cardiac arrest, opitsotnus, aspiration pneumonia and death.
Life-threatening cardiovascular signs, such as arrhythmias and seizures, are generally seen over 40 mg/kg. Clinical signs typically occur within four hours post-exposure, but can be delayed up to 12 hours, especially with the extended release products. Signs usually last 24-48 hours.
If the pet is asymptomatic, decontamination can be performed. Emesis with recent ingestions is helpful, as well as activated charcoal with a cathartic such as sorbitol.
Vomiting should be controlled with antiemetics.
Methocarbamol can be used with tremoring pets.
Diazepam may be given to control seizures, but refractory seizures may require the administration of phenobarbital or gas anesthesia.
Pets with potassium levels of less than 2.5 mEq/L should be supplemented with potassium chloride.
Intravenous fluid therapy is required for symptomatic pets.
What About Arrhythmias?
Lidocaine or amiodarone can be administered for VPCs or Vtach.
Treatment for bradyarrhythmias, such as AV block, includes either atropine or isoproterenol.
If these don’t work, see Intralipids.
What About Intralipids?
Intralipids have been used in some cases with severe CNS signs and in some cases have improved mentation. They have also been used in cases where arrhythmias are refractory to antiarrhythmic therapy.
In some cases, intralipids have converted severe dysrhythmias to a normal rhythm, often during or very shortly after the infusion. In some of these cases that are refractory to the standard treatments, the use of intralipids is thought to have been lifesaving.
Many of the antiarrhythmic medications (especially lidocaine and amiodarone) will be ineffective until the dose of intralipids has cleared from the pet’s system (often 4+ hours).
Because of this, it is typically recommended to attempt to treat the arrhythmia first before resorting to intralipids.