lamotrigine vs phenytoin
Side-by-side comparison of lamotrigine and phenytoin. Data from FDA drug databases (Orange Book, NDC Directory, recalls, shortages) covering 20,000+ approved drugs, plus CMS pricing; see our methodology.
minor Known Drug Interaction
Phenytoin ↓ lamotrigine Decreased lamotrigine concentration approximately 40%. ( 7 , 12.3 ) Carbamazepine, phenytoin, phenobarbital, primidone, and rifampin decrease lamotrigine concentrations by approximately 40%.
Recommendation: Your doctor may need to adjust your dose of lamotrigine to make sure it is still helping you.
Lamictal
Dilantin
Lamotrigine is a medicine that can treat seizures and bipolar disorder. It works by reducing irregular electrical activity in the brain.
Phenytoin injection is used to treat certain types of seizures. It can also prevent seizures during or after neurosurgery.
Lamotrigine can treat epilepsy in adults and children 2 years and older. It can help with partial-onset seizures, primary generalized tonic-clonic seizures, and generalized seizures of Lennox-Gastaut syndrome. It can also be used to delay mood episodes in adults with bipolar I disorder.
This medicine treats generalized tonic-clonic status epilepticus, a type of prolonged seizure. It also helps prevent and treat seizures that may happen during or after brain surgery. Sometimes, it can be used for a short time instead of the oral form of phenytoin when you cannot take the medicine by mouth.
Lamotrigine affects how nerves in the brain send signals to each other. It is thought to work by decreasing the release of certain chemicals. This helps to stabilize electrical activity and prevent seizures or mood swings.
Phenytoin works by slowing down the signals in the brain that cause seizures. It stabilizes nerve cell membranes, reducing excessive electrical activity. This helps to prevent seizures from starting or spreading.
- • Dizziness
- • Headache
- • Double vision
- • Uncoordinated movements
- • Nausea
No common side effects listed.
- Skin rash 8,408
- Seizure 6,527
- Feeling sick to your stomach 6,151
- Tiredness 5,914
- Feeling lightheaded 5,771
- The medicine is reacting with another medicine 1,547
- Seizure 1,382
- Poisoning from different substances 1,353
- Convulsion 1,260
- Prolonged seizure 790
Lamotrigine can cause a serious skin rash that may require you to go to the hospital. This rash can be life-threatening. The risk is higher in children. Stop taking lamotrigine and see a doctor right away if you get a rash, fever, or swollen lymph nodes.
This medicine can cause serious heart problems if given too quickly. The injection rate should not be faster than 50 mg per minute for adults, and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) for children. Your heart will be monitored closely during and after the injection.
Tell your doctor if you are pregnant or plan to become pregnant. Lamotrigine may cause harm to an unborn baby. There is a pregnancy registry for women who take lamotrigine during pregnancy. You can enroll by calling 1-888-233-2334.
Taking phenytoin during pregnancy may increase the risk of birth defects. If you are pregnant or plan to become pregnant, talk to your doctor about the risks and benefits of this medicine.
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How to Read This lamotrigine vs phenytoin Comparison
lamotrigine is classified in the Anticonvulsant drug class, while phenytoin sits within the Anticonvulsant (Hydantoin) class. Drugs from different classes work through distinct mechanisms, so a head-to-head comparison illustrates trade-offs rather than equivalence. Both drugs are prescription-only, so a licensed provider must authorize use.
Adverse event totals above are pulled from the FDA's Adverse Event Reporting System (FAERS). For these top-ranked reactions alone, lamotrigine has 32,771 submissions while phenytoin has 6,332. Those figures reflect cumulative reporting volume, not per-patient risk, so older, widely dispensed drugs typically look worse on count alone. These two drugs have a known minor interaction flagged in FDA labeling, attributed to phenytoin speeds up the way your body processes lamotrigine, which reduces the amount of medicine in your blood by about 40%.. Serious warnings, pregnancy guidance, and contraindications can differ even when indications overlap.
A table cannot substitute for clinical judgment. Effectiveness, tolerability, drug-drug interactions with your other medications, kidney and liver function, pregnancy status, insurance formulary, and price all feed into a decision that only a licensed prescriber can make responsibly. Data here is sourced from FDA Structured Product Labels (SPL) and FAERS, both of which update as manufacturers and clinicians submit new information. This page is for educational purposes only, is not medical advice, and should not be used to self-switch between lamotrigine and phenytoin - always consult your physician or pharmacist first.
Important: This comparison is for informational purposes only. Drug effects vary between individuals. Always consult your doctor or pharmacist for personalized medical advice.