Oxcarbazepine 300 mg is a prescription medication used to treat partial-onset seizures, a type of epilepsy where abnormal electrical activity starts in one area of the brain. It’s approved as both a first-line treatment on its own and as an add-on to other seizure medications in adults. For children, it can be used alone starting at age 4 or added to other medications starting at age 2.
How Oxcarbazepine Controls Seizures
Seizures happen when nerve cells in the brain fire too rapidly and in unison. Oxcarbazepine works by blocking sodium channels on the surface of nerve cells, which stabilizes their electrical activity and prevents the kind of repetitive, runaway firing that triggers a seizure. It may also affect calcium and potassium channels, adding another layer of control over nerve signaling.
Your body converts oxcarbazepine almost immediately into an active form that does most of the therapeutic work. The original drug clears your system within about 2 hours, but this active form sticks around for 7 to 11 hours, which is why the medication is typically taken twice a day to maintain steady levels.
Why the 300 mg Tablet Specifically
The 300 mg tablet is the building block of oxcarbazepine dosing. Adults typically start at 600 mg per day, split into two 300 mg doses taken morning and evening. From there, the dose is gradually increased every few days, often in 300 mg steps, until seizures are controlled. Most adults end up on 1,200 mg per day, though some need more.
This gradual approach matters because side effects are dose-dependent. Starting low and increasing slowly gives your body time to adjust and helps your doctor find the lowest effective dose.
How It Compares to Other Seizure Medications
Oxcarbazepine is considered a first-line treatment for focal (partial-onset) epilepsy, meaning it’s one of the medications doctors reach for first when someone is newly diagnosed. Clinical trials have shown it works as well as older medications like phenytoin and carbamazepine for controlling focal seizures, with potentially fewer side effects. A 2025 review from the American Academy of Neurology lists it alongside lamotrigine and levetiracetam as a standard first-choice option, supported by the highest level of clinical evidence.
It’s closely related to carbamazepine, an older seizure drug, but was designed to cause fewer drug interactions and be easier for the liver to process.
Off-Label Uses
Doctors sometimes prescribe oxcarbazepine for conditions beyond epilepsy, though these uses aren’t FDA-approved. The most common off-label application is trigeminal neuralgia, a condition that causes intense, shock-like facial pain, particularly in people with multiple sclerosis. It’s also sometimes tried for bipolar disorder as a mood stabilizer.
Evidence for neuropathic pain conditions like diabetic nerve pain is weaker. Clinical reviews have found little support for using oxcarbazepine to treat these types of pain, so it’s generally not a go-to option for that purpose.
Common Side Effects
The most frequent side effect is dizziness, which affects roughly 20% of people at a standard dose of 1,200 mg per day. At higher doses (2,400 mg per day), that number jumps to about 41%. Other common effects include drowsiness (about 12% at standard doses) and double vision (about 10%). These tend to be worst in the first few weeks and often improve as your body adjusts.
Side effects increase noticeably with higher doses. This is one reason doctors titrate up gradually rather than starting at the target dose.
Low Sodium Levels: A Risk to Know About
Oxcarbazepine can lower sodium levels in the blood, a condition called hyponatremia. In large studies, severe drops in sodium occurred in roughly 5% to 12% of patients. Symptoms of low sodium include nausea, headache, confusion, and in serious cases, seizures, which is particularly problematic for someone already managing epilepsy.
The risk is higher if you take diuretics (water pills), are on higher doses of oxcarbazepine, or take certain other medications like valproate. Your doctor will likely check your sodium levels with blood tests, especially during the first few months of treatment. Drinking excessive amounts of water can worsen the problem, so maintaining normal fluid intake is important.
Effect on Birth Control
Oxcarbazepine speeds up how your liver processes hormonal contraceptives, including birth control pills, patches, and rings. This can make them significantly less effective, leading to breakthrough bleeding or unintended pregnancy. If you rely on hormonal birth control, you’ll need to discuss alternative or additional contraceptive methods with your doctor while taking this medication. Non-hormonal options like copper IUDs are unaffected.