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Drug interaction between carbapenems and extended-release divalproex sodium in a patient with schizoaffective
Andrew J Muzyk1, Christina L Candeloro, Eric J Christopher
1Campbell University School of Pharmacy and Health Sciences, Duke University Hospital, Durham, NC 27710, USA. andrew.muzyk@duke.edu
Background:
Clinicians prescribing divalproex sodium (DVX) are well aware of its potential to cause a drug-drug interaction. One specific interaction occurs between the carbapenem antibiotics and DVX resulting in decreased valproic acid (VPA) levels immediately following the initiation of this antibiotic class.
Objective/Method:
We describe a case of a 46 year-old Caucasian male who had an undetectable VPA level following treatment with carbapenems.
Results:
On admission the patient's VPA level was 115 μg/ml; however, a routine VPA level on day 19 of his hospitalization returned a value of 16 μg/ml. At this point, he had received a total of 15 days of carbapenem antibiotics for treatment of lower leg cellulitis. His DVX dose was increased to a maximum of 6g daily, twice his home dose, but it did not produce a therapeutic VPA concentration. The patient was lost to follow-up before an outpatient VPA level was drawn.
Conclusion:
Our case report is the first to document this drug-drug interaction in a patient diagnosed with schizoaffective disorder, bipolar type.
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