OverviewDosageSide EffectsInteractionsHalf-Life

Lamotrigine (Lamictal) was the 68 most commonly used drug in the United States in 2018. In that year alone, there were over 11,582,775 estimated prescriptions. Considering the number of prescriptions for this drug, it is ideal to know a bit more about taking this medication, how long lamotrigine stays in the system, and other details.

Basic Information

Mean effective half-life: 24 hours (when taken alone), 70 hours (taken with valproate), 14 hours (taken with AED)

Time to steady-state: 3-15 days depending on whether it is taken alone or with valproate or AED

Mean accumulation ratio: X

Terminal phase half-life: 32 hours for single dose when taken no other medication, 48.3 to 58.8 hours when taken with valproate, 14.4 hours when taken with AEDs other than valproate, 27.2 hours when taken with valproate and other AEDs

Lamotrigine has an oral bioavailability of 98% according to the FDA. This medication is completely absorbed by the body at a rapid rate. The absorption of lamotrigine is not impacted when taken with food. It will reach a peak concentration within a person’s blood (plasma) within 1.4 hours to 4.8 hours. It is eliminated from the body mainly in urine (94%) and very little in feces (2%)


What is the half-life of lamotrigine?

The half-life of lamotrigine, meaning the amount of time it will take for your body to absorb and eliminate the drug by half of its concentration, will vary depending on whether the medication is taken alone, if it is taken with valproate, or if it is taken with valproate and other AED medications. When taken alone, lamotrigine has a half-life of 24 hours. It will take 70 hours to reach half-life for people who are taking lamotrigine with valproate and 14 hours to reach half-life if taken with other AED medication without valproate.

How long does lamotrigine stay in your system?

Lamotrigine is detectable in your system for the following time frames:

  • Your blood for 14 days
  • Your saliva for 24 hours
  • Your urine for 14 days
  • Your hair for: N/A

The drug lamotrigine will be detectable in drug tests when taking urine, blood/plasma/serum, and saliva samples. The detection window for blood is 14 days as it becomes absorbed or eliminated from the body. Lamotrigine is detectable in urine for up to 14 days as this is the main method of elimination for the medication.

If a person is being tested for phencyclidine (PCP), lamotrigine may give a false positive result in these drug tests. You should inform the drug tester if you are taking lamotrigine before the test is given.

What happens if you suddenly stop taking lamotrigine?

If you stop taking lamotrigine without telling your doctor, which you should never do, you may experience seizures, according to MedlinePlus. Even if you are experiencing side effects caused by the lamotrigine, you should talk with your doctor before ending use. Your doctor may adjust the dosage or decrease it in a safe manner.

Does Lamictal wear off?

The side effects of Lamictal will typically wear off within several weeks to several months. Lamictal is a long-term prescription medication that is taken once to twice a day for tablets and once a day for extended release. It will slowly be eliminated from the body within 14 days after the last dosage.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

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