Timox (Oxcarbazepine)

Uses

Timox (Oxcarbazepine) is used for:

Adults: Monotherapy or adjunctive therapy in the treatment of partial seizures

Pediatrics:

• Monotherapy in the treatment of partial seizures in children 4-16 years
• Adjunctive therapy in the treatment of partial seizures in children 2–16 years

Timox (Oxcarbazepine) is also used to associated treatment for these conditions: Partial-Onset Seizures

How Timox (Oxcarbazepine) works

The exact mechanism through which oxcarbazepine and its active metaoblite, MHD, exert their anti-epileptic effects is unclear, but is thought to primarily involve the blockade of voltage-gated sodium channels. The opening and closing of sodium channels allows for the propagation of action potentials along neurons - in epilepsy, these action potentials can occur in excess of that required for normal function, and the repetitive and pathological firing of these action potentials leads to seizure activity. Both oxcarbazepine and MHD are thought to inhibit seizure activity by binding to the inactive state of voltage-gated sodium channels, thus prolonging the period in which the receptor is unavailable for action potential propagation. This helps to stabilize hyperexcited neuronal membranes, inhibit repetitive neuron firing, and prevent the spread of seizure activity within the CNS without affecting normal neuronal transmission.

Increased potassium conductance and modulation of voltage-activated calcium channels is also thought to play a role in the anti-seizure activity of oxcarbazepine. Inhibition of glutamatergic activity was thought to contribute to oxcarbazepine's activity, but this effect could not be replicated in vivo.

Dosage

Timox (Oxcarbazepine) dosage

Adults: initiate with a dose of 600 mg/day, given twice-a-day

• Adjunctive Therapy: Maximum increment of 600 mg/day at approximately weekly intervals. The recommended daily dose is 1200 mg/day
• Conversion to Monotherapy: withdrawal concomitant over 3 to 6 weeks;reach maximum dose of Timox (Oxcarbazepine) in 2 to 4 weeks with increments of 600 mg/day at weekly intervals to a recommended daily dose of 2400 mg/day
• Initiation of Monotherapy: Increments of 300 mg/day every third day to a dose of 1200 mg/day.
• Creatinine Clearance <30 mL/min: Initiate at one half the usual starting dose and increase slowly

Pediatrics: initiation with 8 to 10 mg/kg/day, given twice-a-day. For patients aged 2 to <4 years and under 20 kg, a starting dose of 16 to 20 mg/kg/day may be considered. Recommended daily dose is dependent upon patient weight.

• Adjunctive Patients (Aged 2–16 Years): For patients aged 4 to 16 years, target maintenance dose should be achieved over 2 weeks. For patients aged 2 to <4 years, maximum maintenance dose should be achieved over 2 to 4 weeks and should not to exceed 60 mg/kg/day
• Conversion to Monotherapy for Patients (Aged 4-16 Years): Maximum increment of 10 mg/kg/day at weekly intervals, concomitant antiepileptic drugs can be completely withdrawn over 3 to 6 weeks
• Initiation of Monotherapy for Patients (Aged 4–16 Years): Increments of 5 mg/kg/day every third day

Side Effects

The most commonly reported adverse reactions are somnolence, headache, dizziness, diplopia, nausea; vomiting and fatigue. Very rarely clinically significant hyponatraemia can develop during Oxazep use. Class I (immediate) hypersensitivity reactions including rash, pruritus, urticaria, angioedema and reports of anaphylaxis have been received.

Toxicity

The oral LD₅₀ of oxcarbazepine in mammals is 1240 mg/kg and the oral TDLo in children has been reported to be 73 mg/kg. Isolated cases of oxcarbazepine overdose have been reported - patients who ingested up to 24,000mg recovered with symptomatic treatment. Symptoms may include respiratory and CNS depression, movement-related disorders (e.g. dyskinesia, ataxia), nausea/vomiting, hyponatremia, or QTc prolongation. There is no antidote for oxcarbazepine overdose - management should consist of supportive and symptomatic treatment, and consideration should be given to the use of gastric lavage or activated charcoal.

Precaution

Alcohol: Caution should be exercised if alcohol is taken in combination with Oxazep therapy, due to a possible additive sedative effect.

Withdrawal: As with all antiepileptic medicinal products, Oxazep should be withdrawn gradually to minimise the potential of increased seizure frequency.

Interaction

Timox (Oxcarbazepine) and its metabolite inhibit the enzyme CYP2C19 and therefore, interactions could arise when co-administering high doses of Oxazep with medicinal products that are metabolised by CYP2C19 (e.g. phenobarbital, phenytoin). Concurrent use of Oxazep with hormonal contraceptives may render few contraceptives ineffective (e.g. Ethinylestradiol and Levonorgestrel preparations). Co-administration of Oxazep lowers AUC of felodipine and Verapamil decreases bioavailability of MHD.

Food Interaction

• Avoid alcohol. Timox (Oxcarbazepine) has CNS depressant properties that may be potentiated by co-administration with alcohol.
• Take with or without food. Co-administration with food does not significantly affect absorption.

[Moderate] GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents.

Use in combination may result in additive central nervous system depression and
MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol.

Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

Timox (Oxcarbazepine) Drug Interaction

Moderate: aripiprazole, diphenhydramine, duloxetine, clonazepam, lamotrigine, lurasidone, escitalopram, pregabalin, quetiapine, topiramate, cholecalciferol, alprazolam, sertraline, cetirizineUnknown: amphetamine / dextroamphetamine, omega-3 polyunsaturated fatty acids, levothyroxine, cyanocobalamin, ascorbic acid, lisdexamfetamine

Timox (Oxcarbazepine) Disease Interaction

Major: depression, liver disease, renal dysfunctionModerate: hyponatremia, suicidal tendency, arrhythmias, blood dyscrasias, thyroid dysfunction

Volume of Distribution

The apparent volume of distribution of oxcarbazepine is 49 L. The apparent volumes of distribution of (S)- and (R)-MHD were found to be 23.6 L and 31.7 L, respectively.

Elimination Route

Timox (Oxcarbazepine) is completely absorbed following oral administration. A single 600mg dose of oxcarbazepine resulted in an MHD C_max of 34 μmol/L and a median T_max of 4.5 hours. When administered twice daily, steady-state levels of MHD are attained within 2-3 days. The rate and extent of absorption of oxcarbazepine is not affected by food intake.

Half Life

The plasma half-life of oxcarbazepine is approximately 2 hours and the plasma half-life of MHD is approximately 9 hours.

Clearance

Plasma clearance of oxcarbazepine has been estimated to be approximately 84.9 L/h, whereas plasma clearance of its active metabolite, MHD, was estimated to be 2.0 L/h. Rapid metabolic clearance appears to be the main pathway for oxcarbazepine, while clearance of its metabolites occurs mainly via renal excretion.

Elimination Route

Following oral administration, more than 95% of the administered dose of oxcarbazepine is found in the urine. Of this, approximately 49% is MHD glucuronide metabolites, 27% is unchanged MHD, 3% is inactive DHD metabolites, 13% is conjugated oxcarbazepine, and less than 1% is unchanged parent drug. Fecal elimination accounts for only 4% of the administered dose.

Pregnancy & Breastfeeding use

Pregnancy: Data on a limited number of pregnancies indicate that Timox (Oxcarbazepine) may cause serious birth defects (e.g. cleft palate) when administered during pregnancy. In the newborn child. Bleeding disorders in the newborn caused by antiepileptic agents have been reported. As a precaution, vitamin K1 should be administered as a preventive measure in the last few weeks of pregnancy and to the newborn. Timox (Oxcarbazepine) and its active metabolite (MHD) cross the placenta. Neonatal and maternal plasma MHD concentrations were similar in one case.

Lactation: Timox (Oxcarbazepine) and its active metabolite (MHD) are excreted in human breast milk. Therefore, Oxazep should not be used during breast-feeding.

Contraindication

It is contraindicated to patients with hypersensitivity to the active substance or to any of the excipients.

Innovators Monograph

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