Lacosamide is a prescription antiseizure medicine used for certain focal (partial-onset) seizures and, in some people, primary generalized tonic-clonic seizures. It can be effective, but it also has important safety considerations involving dizziness, coordination, mood changes, allergic reactions, and heart conduction.
Do not stop lacosamide suddenly or change the dose on your own. Antiseizure medicines are generally withdrawn gradually because abrupt changes can increase seizure risk. If side effects are bothering you, contact the prescriber so the treatment plan can be reviewed safely.
Common Lacosamide Side Effects
Common effects reported with lacosamide include dizziness, sleepiness, headache, nausea, blurred or double vision, and problems with balance or coordination. These effects can increase the risk of falls, driving problems, or accidents.
- Dizziness or lightheadedness
- Sleepiness or fatigue
- Headache
- Nausea
- Blurred or double vision
- Unsteadiness or poor coordination
Until you know how lacosamide affects you, use caution with driving, machinery, heights, or other activities where dizziness or slowed reactions could be dangerous.
Heart Rhythm and Conduction Risks
Lacosamide can affect electrical conduction in the heart. FDA labeling advises extra caution in people with underlying heart-conduction problems, significant structural heart disease, heart failure, a history of heart attack, certain rhythm disorders, or medicines that also affect cardiac conduction.
For people with these risk factors, clinicians may consider an ECG before treatment and again after the medicine has been titrated to a steady maintenance dose. This is a clinician-directed decision; it is not a reason to change treatment on your own.
Symptoms that need prompt medical attention
- Fainting or near-fainting
- Chest pain
- Shortness of breath
- A very slow heartbeat
- A fast, pounding, or irregular heartbeat
Mood and Behavior Changes
Antiseizure medicines, including lacosamide, carry a warning about possible suicidal thoughts or unusual mood or behavior changes in a small number of people. Contact a healthcare professional promptly for new or worsening depression, severe agitation, unusual behavior, or thoughts of self-harm. If there is immediate danger, seek emergency help.
Serious Allergy or Multi-Organ Reaction
Rarely, lacosamide can be associated with serious hypersensitivity reactions such as DRESS (drug reaction with eosinophilia and systemic symptoms). Seek urgent medical care for a widespread rash with fever, facial swelling, swollen glands, trouble breathing, marked tiredness, yellowing of the skin or eyes, or dark urine.
Kidney, Liver, Pregnancy, and Breastfeeding
Tell the prescriber if you have kidney or liver disease, are pregnant or planning pregnancy, or are breastfeeding. Treatment decisions should be individualized. Do not stop seizure medicine during pregnancy without medical guidance because uncontrolled seizures can also be dangerous.
Alcohol and Other Medicines
Alcohol and other medicines that cause dizziness or drowsiness may worsen lacosamide’s effects. Give your doctor or pharmacist a complete list of prescription medicines, over-the-counter medicines, supplements, and herbal products. Medicines that affect cardiac conduction may also require extra caution.
For more medication-focused safety information, visit our Medication Safety section.
When Should You Contact a Doctor?
Contact the prescriber if dizziness, vision changes, sleepiness, or coordination problems are persistent, worsening, or interfering with daily activities. Prompt medical assessment is especially important for fainting, palpitations, chest symptoms, serious rash, facial swelling, breathing difficulty, or major mood changes.
Frequently Asked Questions
Can lacosamide be stopped suddenly?
No. Do not stop or reduce lacosamide on your own. Antiseizure medicines are usually withdrawn gradually under medical supervision to reduce the risk of increased seizure frequency.
Does everyone taking lacosamide need an ECG?
No. ECG monitoring is particularly relevant for people with underlying proarrhythmic conditions or those taking medicines that affect cardiac conduction. The prescriber decides whether monitoring is appropriate.
Can alcohol make lacosamide side effects worse?
It can. Alcohol may add to dizziness, drowsiness, or impaired coordination, so discuss alcohol use with your prescriber or pharmacist.
What should I do if I miss a dose?
Follow the instructions provided with your prescription or contact your pharmacist. Do not double up unless a healthcare professional specifically tells you to do so.
Bottom Line
Lacosamide can help control seizures, but dizziness, vision changes, coordination problems, mood changes, serious hypersensitivity reactions, and heart-conduction effects deserve attention. Take it exactly as prescribed and contact the prescriber before making dose or timing changes.
Reliable Sources
- MedlinePlus: Lacosamide
- FDA Prescribing Information: Lacosamide Extended-Release
- FDA: Sodium-Channel Antiseizure Medicines and Cardiac Safety Review
Last reviewed for medical accuracy: September 2026.