First Glance-Oxtellar XR (oxcarbazepine
extended-release tablets)
Approved Indication
Adjunctive treatment of partial seizures in adults and children 6-17 years of age.
Dosing Availability
150 mg, 300 mg, and 600 mg extended-release tablets
Mechanism of Action
The exact mechanism of action is unknown, but the antiseizure effect is thought to be due to blockade
of voltage-sensitive sodium channels which results in stabilization of hyperexcited neural membranes.
Activity is largely due to the 10-monohydroxy metabolite (MHD)
Dosing
Adults:
o
Initiate dose of 600 mg once daily and increase at 600mg per day at weekly intervals until
target dose is achieved.
Maintenance dose: 1,200 mg to 2,400 mg once daily.
For geriatric patients it is suggested to start at 300 mg to 450 mg/day and increase slowly.
o
o
Children:
o Initiate with 8 to 10 mg/kg once daily and increase in weekly intervals of 8 to 10 mg/kg
once daily
o Do not exceed 600mg
o Maintenance dose is based on weight and titrated over 2 to 3 weeks
Weight
Target Daily Dose
20 kg to 29 kg
900 mg/day
29.1 kg to 39 kg
1200 mg/day
Greater than 39 kg
1800 mg/day
Conversion from immediate release tablets have a higher bioavailability and conversion to
extended-release Oxtellar XR tablets may require a higher dose.
o At steady state active metabolite levels (Cmax and Cmin) were approximately 16% lower
Pharmacokinetics
Peak plasma concentration 7 hours (after steady state was achieved) compared to 4-6 for immediate
release tablets
1—Footer text as needed
Steady state reached in 5 days compared to 2-3 days with immediate release BID or TID dosing
Top Drug Interactions (for all inclusive list refer to the package insert)
Oxcarbazepine can inhibit CYP2C19 and induce CYP3A4/5
o CYP2C19 inhibition (dose related):
 May increase phenytoin or fosphenytoin levels
o CYP3A4/% induction:
 Hormonal contraceptives may be less effective
 Calcium Channel Blockers (CCBs) may be less effective
Precautions and Adverse Drug Events
Hyponatremia
Patients who are hypersensitive to carbmazepine may also be sensitive to oxcarbazepine
Clinical worsening and suicide risk
The most common ADEs that result in adult discontinuation include:
o Dizziness
o Nausea/Vomiting
o Diplopia
o Somnolence (dose relegated)
Clinical Considerations
No head to head trials conducted to show efficacy better than IR formulation
Average cost per tablet is $5.88
o Generic immediate release oxcarbazepine is approximately $0.25 to $0.75 per tablet.
In 2009, CANMAT removed oxcarbazepine from second line recommended therapy to third line for
the treatment of manic episodes associated with bipolar disorder due to more recent negative trials
and clinical experience.
Full prescribing information can be found at: http://www.oxtellarxr.com/pdf/PI.pdf
References:
1. Oxtellar XR™ (oxcarbazepine extended release tablets) Package Insert. Revised: October 2012. Patheon Inc. Available
at: http://www.oxtellarxr.com Accessed 1/23/2013.
2. Clinical Pharmacology. Available at: http://www.clinicalpharmacology-ip.com/default.aspx Accessed: 1/23/2013.