Drug Detail:Oxcarbazepine (Oxcarbazepine [ ox-kar-bay-zeh-peen ])
Drug Class: Dibenzazepine anticonvulsants
1. How it works
- Oxcarbazepine is an anticonvulsant that reduces the frequency of certain types of seizures.
- Once in the body, it is metabolized in the liver to another compound, called MHD, which also helps to reduce seizure frequency. The exact way oxcarbazepine and its active metabolite exert their antiseizure activity is not known; however, it is thought to be by stabilizing nerve membranes, which reduces repetitive firing.
- Oxcarbazepine belongs to the class of medicines known as dibenzazepine carboxamides.
2. Upsides
- May be used for the treatment and prevention of partial seizures in adults, either alone or in addition to other anti-seizure medicines.
- May be used as the sole therapy for the treatment and prevention of partial seizures in children over the age of four, or in addition to other medications for epilepsy in children over the age of two.
- It may be used off-label (not an FDA-approved use) to treat other conditions such as bipolar disorder or migraine.
- Oxcarbazepine does not appear to cause dependence or tolerance, although a slow withdrawal is recommended to avoid precipitating seizures. The abuse potential of oxcarbazepine is unknown.
- Oxcarbazepine is available in tablet form or as a suspension.
- Brand names of oxcarbazepine include Trileptal and Oxtellar.
- Cost-saving, generic oxcarbazepine is available.
3. Downsides
If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:
- Central nervous system (CNS) side effects, including a slowing in the speed of information processing, difficulty with concentration, dizziness, speech and language problems, sleepiness and fatigue, and coordination difficulties including muscle movement disorders and gait disturbances.
- Nausea, vomiting, double vision, headache, and nystagmus (rapid side-to-side eye movements) are also common. Anaphylaxis (serious allergic reactions) is rare.
- Oxcarbazepine can inhibit some liver enzymes (notably CYP2C19 and CYP3A4/5), which may affect plasma levels of some other medications, including oral contraceptives and felodipine.
- Although dosages greater than 1200 mg/day in adults have shown greater efficacy, most people cannot tolerate the CNS side effects that occur with these dosages.
- The dosage of oxcarbazepine needs reducing in people with kidney disease.
- Oxcarbazepine may cause low sodium levels (hyponatremia), usually during the first three months of therapy, although hyponatremia may occur at any time. May be life-threatening. Hyponatremia generally resolves once oxcarbazepine has been discontinued.
- The risk of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (both serious dermatological reactions) may be greater in people carrying the HLA-B 1502 allele (predominantly found in people from China, the Philippines, Malaysia, Thailand, India, and Korea).
- As with other drugs used to treat epilepsy or depression, oxcarbazepine has been associated with a higher risk of suicidal thoughts and behaviors. Monitor for the emergence of worsening mood or unusual behaviors.
- Oxcarbazepine is best withdrawn slowly on discontinuation unless it is an emergency. Sudden discontinuation has been associated with an increase in seizure frequency and status epilepticus.
- May not be suitable for everybody including those with liver or kidney disease, previous mental health issues, or planning to become pregnant.
- There are no controlled data in human pregnancy. Animal studies have reported higher rates of structural abnormalities, spontaneous abortions, growth retardation, fetal malformations, decreased fetal body weight, and maternal toxicity in fetuses of animals exposed to oxcarbazepine. Oxcarbazepine and its active metabolite, MHD, cross the human placenta and oxcarbazepine is structurally related to carbamazepine, which is a known human teratogen. Do not use during pregnancy unless the benefits outweigh the risks. If a woman inadvertently becomes pregnant while taking oxcarbazepine, encourage her to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry by calling the toll-free number 1-888-233-2334 or online at http://www.aedpregnancyregistry.org/. Oxcarbazepine and its active metabolite (MHD) are found in breastmilk, but the effects on a breastfed infant are unknown.
Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects
4. Tips
- May be taken with or without food.
- Oxcarbazepine suspension may be substituted for oxcarbazepine tablets in people or children who have difficulty swallowing (the dosages are equivalent).
- Oxcarbazepine may make you sleepy or impair your reaction times and affect your ability to drive or operate machinery. Do not drive or operate machinery if oxcarbazepine affects you in this way. Alcohol may make these effects worse.
- Talk to your doctor if you experience any signs of hyponatremia (low blood sodium levels) such as confusion, headache, nausea, tiredness, or an increase in seizure frequency.
- Seek urgent medical advice if you develop any allergic-type reactions including facial swelling or a rash. 25-30% of people who are allergic to carbamazepine will also be allergic to oxcarbazepine. Also seek urgent advice if you develop any unusual bruising or bleeding, swollen lymph nodes, abdominal pain, painful mouth sores, yellowing of the skin, frequent or persistent infections, or different or more frequent seizures.
- If you are taking hormonal contraceptives, talk with your doctor. Your dosage may need to be increased or an alternative method of contraception may be needed.
- Do not stop oxcarbazepine suddenly, unless your doctor has told you to do so. It is best to discontinue oxcarbazepine slowly.
- Tell your doctor if you are pregnant, intending to become pregnant, or breastfeeding because oxcarbazepine may not be suitable for you.
5. Response and effectiveness
- Oxcarbazepine is completely absorbed after oral administration with over 70% being converted to its active metabolite, MHD. MHD is responsible for more antiseizure effects than oxcarbazepine. Peak concentrations of MHD are reached within 3 to 13 hours (average time of 4.5 hours).
- Food does not affect the absorption of oxcarbazepine. Reductions in seizure frequency have been noted within ten days of regular administration of oxcarbazepine.
6. Interactions
Medicines that interact with oxcarbazepine may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with oxcarbazepine. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.
Common medications that may interact with oxcarbazepine include:
- antidepressants, such as citalopram, sertraline, St John’s Wort, and monoamine oxidase inhibitors
- cyclosporine
- HIV combination drugs such as elvitegravir/cobicistat
- other medications for seizure control such as phenytoin or phenobarbital
- other medications that cause drowsiness, such as anti-anxiety medications, muscle relaxants, narcotics, psychiatric medications, sedating antihistamines, or sleeping pills
- oral contraceptives (oxcarbazepine may make them less effective)
- proton pump inhibitors such as lansoprazole, omeprazole, or pantoprazole
- some heart medications, such as amiodarone, calcium channel blockers (eg, amlodipine, felodipine, nifedipine).
Alcohol may also increase drowsiness associated with oxcarbazepine, so is best avoided.
Note that this list is not all-inclusive and includes only common medications that may interact with oxcarbazepine. You should refer to the prescribing information for oxcarbazepine for a complete list of interactions.