Refilling and switching of antiepileptic drugs and seizure-related events.
We sought to estimate the risk of seizure-related events associated with refilling prescriptions for antiepileptic drugs (AEDs) and to estimate the effect of switching between brand-name and generic drugs or between two generic versions of the same drug. We conducted a case-crossover study using health-care databases from British Columbia, Canada, among AED users who had an emergency room visit or hospitalization for seizure (index seizure-related event), defined using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9) codes 345.xx (epilepsy and recurrent seizures) and 780.3x (convulsions), between 1997 and 2005. AED prescription refilling itself was associated with 2.3-fold elevated odds of seizure-related events when the refill occurred within 21 days before the index event (odds ratio (OR) 2.31; 95% confidence interval (CI) 1.56-3.44). The OR was 2.75 (95% CI 0.88-8.64) for refills that involved switching, yielding a refill-adjusted OR for switching of 1.19 (95% CI 0.35-3.99). Refilling the same AED prescription was associated with an elevated risk of seizure-related events whether or not the refill involved switching from a brand-name to a generic product.
Gagne
J J
JJ
Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA. jgagne1@partners.org
Avorn
J
J
Shrank
W H
WH
Schneeweiss
S
S
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001955:British Columbia; D016022:Case-Control Studies; D002648:Child; D018592:Cross-Over Studies; D016208:Databases, Factual; D016568:Drugs, Generic / Q000009:adverse effects / Q000493:pharmacokinetics / Q000627:therapeutic use*; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012306:Risk; D055502:Secondary Prevention; D012640:Seizures / Q000517:prevention & control*; D013810:Therapeutic Equivalency; D016896:Treatment Outcome; D055815:Young Adult
D000927:Anticonvulsants; D016568:Drugs, Generic