Oxcarbazepine
Oxcarbazepine is an anticonvulsant used primarily to treat epilepsy, particularly focal (partial) seizures. It is a derivative of carbamazepine and is considered to have a similar therapeutic effect with a different side-effect profile. Oxcarbazepine is often used as a monotherapy or adjunctive therapy for seizures.
Trade Name
Oxcarbazepine is marketed under several brand names, including Trileptal and Oxtellar XR.
Chemical Properties
Chemical structure: Oxcarbazepine is a keto-derivative of carbamazepine.
Molecular formula: C₁₇H₁₆N₂O₃
Molecular weight: 312.33 g/mol
Solubility: Oxcarbazepine is moderately soluble in water, and it is available in oral tablet and liquid formulations.
Biochemical Properties
Mechanism of action: Oxcarbazepine works by stabilizing neuronal membranes and inhibiting the repetitive firing of neurons. It is thought to primarily exert its anticonvulsant effects by blocking voltage-gated sodium channels, similar to carbamazepine. Additionally, oxcarbazepine’s active metabolite, 10-hydroxy-oxcarbazepine (MHD), contributes to its therapeutic effects.
Pharmacology
Administration: Oxcarbazepine is administered orally in the form of tablets, oral suspension, or extended-release tablets (Oxtellar XR).
Bioavailability: Oxcarbazepine has excellent bioavailability (approximately 93%) and is rapidly absorbed after oral administration.
Metabolism: Oxcarbazepine is primarily metabolized in the liver by CYP3A4 into its active metabolite, MHD. Unlike carbamazepine, oxcarbazepine does not induce its own metabolism, which results in fewer drug interactions.
Half-life: The half-life of oxcarbazepine is approximately 9 hours for the parent drug and 9–10 hours for the active metabolite (MHD). This allows for twice-daily dosing in most patients.
Clinical Indications
Epilepsy: It is effective for focal (partial) seizures, including those that are partial with secondary generalization. It can be used as monotherapy or as adjunctive therapy in combination with other antiepileptic drugs.
Other indications: Oxcarbazepine may also be used off-label for the treatment of bipolar disorder, neuropathic pain, and certain anxiety disorders, though these indications are less common.
Side Effects
Dizziness and drowsiness: These effects are particularly noticeable during the early stages of treatment or dose escalation.
Headache: Some patients report headaches while taking oxcarbazepine.
Gastrointestinal issues: Nausea, vomiting, and abdominal pain may occur, especially during the initiation of therapy.
Hyponatremia: Low sodium levels (hyponatremia) are a known side effect and can lead to symptoms like confusion, dizziness, and weakness.
Skin rash: Oxcarbazepine can cause skin rashes, and in rare cases, it may lead to more serious conditions such as Stevens-Johnson syndrome or toxic epidermal necrolysis, although these are very uncommon.
Ataxia and coordination issues: Some patients experience problems with coordination or balance.
Behavioral changes: Rarely, some individuals may experience mood changes, irritability, or aggression, particularly in children or adolescents.
Cognitive effects: Similar to other anticonvulsants, oxcarbazepine can cause issues with concentration, memory, or mental fog.
Monitoring and Considerations
Therapeutic drug monitoring: Routine monitoring of drug levels is generally not required for oxcarbazepine, although sodium levels should be regularly checked, as hyponatremia can occur.
Dose adjustments: Oxcarbazepine is usually started at a low dose with gradual titration to minimize side effects. It is important to monitor for any adverse effects and adjust the dose as necessary.
Pregnancy: Oxcarbazepine is classified as a Category C drug during pregnancy, which means it should only be used if the potential benefits outweigh the risks to the fetus. Like other anticonvulsants, oxcarbazepine is associated with a higher risk of birth defects, particularly in the first trimester.
Drug interactions: Oxcarbazepine has a lower potential for drug interactions compared to carbamazepine because it does not induce liver enzymes. However, it can still interact with other medications, particularly those that affect sodium levels or are metabolized by the CYP3A4 enzyme.
Oxcarbazepine is a widely used anticonvulsant with a generally favorable side effect profile compared to carbamazepine. It is effective for managing focal seizures and is well tolerated by most patients. However, it requires monitoring for hyponatremia, especially in older adults and individuals on high doses. Although oxcarbazepine has fewer drug interactions than carbamazepine, careful monitoring for side effects and dose adjustments is still important.
