Oxcarbazepine 150mg, 300mg, 600mg; extended-release tablets.
Adjunctive therapy in the treatment of partial seizures in adults and in children 6–17 years of age.
The precise mechanism by which oxcarbazepine and 10-monohydroxy metabolite (MHD) exert their antiseizure effect is unknown; however, in vitro studies indicate that they produce blockade of voltage-sensitive sodium channels, resulting in stabilization of hyperexcited neural membranes, inhibition of repetitive neuronal firing, and diminution of propagation of synaptic impulses. In addition, increased potassium conductance and modulation of high-voltage activated calcium channels may contribute to the anticonvulsant effects of oxcarbazepine.
The safety and efficacy of Oxtellar XR was evaluated in a multicenter, randomized, double-blind, placebo-controlled, three-arm parallel-group study (Study 1) in adult patients with refractory partial epilepsy aged 18–65 years (n=366). The study included an 8-week baseline period, followed by a treatment period (4-week titration phase followed by a 12-week maintenance phase). The primary endpoint was median percentage change from baseline in seizure frequency per 28 days during treatment period relative to the baseline period. The criterion for statistical significance was p<0.05. Patients were randomized to one of three treatment groups and were given Oxtellar XR 1.2g/day (n=122), Oxtellar XR 2.4g/day (n=123), or placebo (n=121). The primary efficacy results demonstrated a median percent change in seizure frequency of -38.2% (p<0.078) and -42.9% (p<0.003) in the Oxtellar XR 1.2g/day and 2.4g/day treatment groups, respectively vs. -28.7% in the placebo group. Although the 1.2g/day vs. placebo contrast did not reach statistical significance, concentration-response analyses reveal that the 1.2g/day dose is an effective dose.
Take on empty stomach. Swallow whole. >17yrs: Initially 600mg once daily for 1 week, then may increase by 600mg/day increments at weekly intervals; usual range 1.2g–2.4g/day. Concomitant antiepileptics: consider initiating at 900mg once daily. Severe renal impairment (CrCl <30mL/min): initially 300mg/day; may increase by 300–450mg/day increments at weekly intervals. ESRD on dialysis: use oxcarbazepine immediate-release. Elderly: initially 300mg or 450mg once daily; may increase by 300–450mg/day increments at weekly intervals. Conversion from oxcarbazepine immediate-release: may need higher doses.
<6yrs: not recommended. 6–17yrs: initially 8–10mg/kg once daily; max 600mg/day in the 1st week, then may increase by 8–10mg/kg/day increments at weekly intervals; usual max 600mg/day. Target maintenance doses (attain over 2–3 weeks): 20–29kg: 900mg/day; 29.1–39kg: 1.2g/day; >39kg: 1.8g/day.
Risk of hyponatremia; monitor if signs/symptoms occur. Severe hepatic impairment: not recommended. Carbamazepine hypersensitivity. Suicidal behavior and ideation; monitor. Discontinue if multi-organ hypersensitivity occurs; use alternative treatment. Avoid abrupt withdrawal. Elderly. Pregnancy (Cat.C): risk of seizures; monitor during and postpartum. Nursing mothers: not recommended.
Antagonized by phenytoin, carbamazepine, phenobarbital, valproic acid; monitor and adjust dose. May decrease effectiveness of hormonal contraceptives (ethinyl estradiol, levonorgestrel), other oral or implant contraceptives; use additional non-hormonal forms. Caution with other drugs known to decrease serum sodium. May affect thyroid (T4) tests.
Dizziness, somnolence, headache, balance disorder, tremor, vomiting, diplopia, asthenia, fatigue; hyponatremia, serious skin reactions (eg, Stevens-Johnson syndrome and toxic epidermal necrolysis); rare: anaphylactic reactions, angioedema, hematological reactions; discontinue if occurs.