Exploring differential prescribing between anti-epileptic drugs in epilepsy patients with a history of mood disorders.
OBJECTIVE
To explore differential prescribing of anti-epileptic drugs (AEDs) to patients with epilepsy by history of mood disorder.


METHODS
Epilepsy was defined as at least one diagnosis code and one AED prescription, and all patients must have been on the database 182 days before and after their first AED prescription. The Integrated HealthCare Information Services (IHCIS) insurance claims database included 44 557 patients with epilepsy between January 1997 and March 2007. The General Practice Research Database (GPRD) included 16 904 patients with epilepsy up to March 2007. Patients were categorized by their first use of specified AEDs. Mood disorders were defined as diagnosis codes for depression and bipolar disorder, or anti-depressant use. The unadjusted odds ratios and 95% confidence intervals for a history of mood disorder diagnosis ever or within the three months prior to AED use were calculated with carbamazepine and oxcarbazepine (CBZ) as the referent.


RESULTS
In the US IHCIS, a history of mood disorders was significantly more common in new users of most AEDs compared to CBZ new users, indicating differential prescribing. Clonazepam and gabapentin were the most commonly prescribed AEDs in patients with epilepsy and a history of mood disorders.In the UK GPRD, there was less evidence of differential prescribing of AEDs, although gabapentin was prescribed most often to epilepsy patients with a history of mood disorders.


CONCLUSIONS
Any observational studies of AEDs and suicidality would have to consider potential channeling bias by history of mood disorders, which is a major risk factor for suicide.
Ishihara
Lianna
L
Department of Epidemiology, GlaxoSmithKline, Harlow, Essex CM19 5AW, United Kingdom. lianna.2.ishihara@gsk.com
Webb
David J
DJ
Irizarry
Michael
M
Weil
John
J
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000627:therapeutic use*; D001714:Bipolar Disorder / Q000150:complications; D016208:Databases, Factual / Q000706:statistics & numerical data; D003863:Depression / Q000150:complications; D004827:Epilepsy / Q000150:complications / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019964:Mood Disorders / Q000150:complications*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012307:Risk Factors; D006113:United Kingdom; D014481:United States; D055815:Young Adult
D000927:Anticonvulsants