450 mg PO once daily Oxtellar XR (OXCBZ) is an appropriate starting geriatric antiepileptic dose (Lexi-Comp). Seizures secondary to arachnoid cysts are not necessarily indicative of their foci, so I don't see why that would complicate things. Of course, it also depends on what kind of seizure a given patient is experiencing. OXCBZ is indicated for partial (and secondarily generalized) seizures. Keep in mind the side effect profile of OXCBZ (fairly similar to carbamazepine), as well as any comorbidities a given patient may possess that would complicate treatment (e.g. concomitant use of diuretics for hypertension).

Note that the above information is not intended for use as medical advice, nor is it intended to substitute for professional advice, and is provided for purely informational purposes only.

Article What is the Relationship Between Arachnoid Cysts and Seizure Foci?

Oxcarbazepine extended-release tablets are used for:

Treating certain types of seizures. It is used in combination with other medicines. It may also be used for other conditions as determined by your doctor.

Oxcarbazepine extended-release tablets are an anticonvulsant. It works by slowing abnormal nerve impulses in the brain.

Do NOT use oxcarbazepine extended-release tablets if:

you are allergic to any ingredient in oxcarbazepine extended-release tablets

you have severe liver problems

you are taking bortezomib, bosutinib, cabazitaxel, etravirine, nilotinib, pazopanib, or rilpivirine

Contact your doctor or health care provider right away if any of these apply to you.

http://www.drugs.com/cdi/oxcarbazepine-extended-release-tablets.html

Oxcarbazepine is indicated for the treatment of focal seizures with or without secondary generalized tonic-clonic seizures (https://www.medicines.org.uk/emc/medicine/2673), whatever the cause of the seizures, and it could be used if the patient has such seizures. However, the answers above seem to miss what I think is the main thrust of the question, which is not why you might use oxcarbazepine as an antiepileptic drug, as opposed to any other antiepileptic drug, but why you would use an extended-release as opposed to an immediate-release formulation. I see no major grounds for doing so. The former can be given once a day, the latter twice a day, but there is no good evidence that adherence to therapy is improved by once-daily versus twice-daily administration. During the early phases of therapy, when the most effective and least harmful dose is being sought, it is easier to find the appropriate dose for an individual by using an immmediate-release formulation, since changes in effect occur more quickly. Some of the early adverse reactions, such as dizziness, tend to wear off with time, and a gradual increase in dosage may mitigate them; this can be more easily achieved with an immediate-release formulation. Presumably the extended-release formulations are also more expensive.

Dr. Aronson is correct in his assumption on cost (100 tablets of 150mg IR go for about $140, while the same quantity and strength of ER go for $525). The IR formulation can also be taken without regard to meals, while the ER must be taken on an empty stomach. If adherence is an issue, it may be more cost-effective to counsel the patient on medication adherence techniques (e.g. using a pill box, adding an alarm to a cell phone, using pictographs for the dosing schedule). Save for (obstinate) patient preference ("I just want ONE pill!"), I don't really see any significant indication for the ER. It's doable, but, as Dr. Aronson pointed out, you may want to consider titrating with the IR first, then switching to ER (because the ER extends the elimination half life of the parent drug and its active metabolite, increasing the time it takes for your drug to reach steady state plasma concentrations and stabilize).