Drug interaction between carbapenems and extended-release divalproex sodium in a patient with schizoaffective disorder.
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
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.


CONCLUSIONS
Our case report is the first to document this drug-drug interaction in a patient diagnosed with schizoaffective disorder, bipolar type.
Muzyk
Andrew J
AJ
Campbell University School of Pharmacy and Health Sciences, Duke University Hospital, Durham, NC 27710, USA. andrew.muzyk@duke.edu
Candeloro
Christina L
CL
Christopher
Eric J
EJ
D000927:Anticonvulsants / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology; D015780:Carbapenems / Q000009:adverse effects* / Q000627:therapeutic use; D002481:Cellulitis / Q000097:blood / Q000188:drug therapy*; D003692:Delayed-Action Preparations; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D006801:Humans; D008297:Male; D008875:Middle Aged; D011618:Psychotic Disorders / Q000097:blood / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology; D014635:Valproic Acid / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000627:therapeutic use
D000927:Anticonvulsants; D015780:Carbapenems; D003692:Delayed-Action Preparations; D014635:Valproic Acid