A 46-year-old man was started on carbamazepine for his recently diagnosed Complex
Partial seizures. After 2 months of therapy, his seizures had not abated, and so valproic
acid was added to his regimen. This combination worked well and he remained seizure
free for 9 months. Although his serum level for the drug was within therapeutic limits,
the patient showed signs of hyponatremia, a side effect more commonly seen in
patients with higher serum concentrations of the agent. Why is this patient
experiencing hyponatremia while maintaining therapeutic levels of carbamazepine? A 46-year-old man was started on carbamazepine for his recently diagnosed Complex
Partial seizures. After 2 months of therapy, his seizures had not abated, and so valproic
acid was added to his regimen. This combination worked well and he remained seizure
free for 9 months. Although his serum level for the drug was within therapeutic limits,
the patient showed signs of hyponatremia, a side effect more commonly seen in
patients with higher serum concentrations of the agent. Why is this patient
experiencing hyponatremia while maintaining therapeutic levels of carbamazepine?
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