title: Choice of initial antiepileptic drug for older veterans: possible pharmacokinetic drug interactions with existing medications.
abstract: OBJECTIVE
  To identify clinically meaningful potential drug-drug interactions (PDIs) with antiepileptic drugs (AEDs), the AEDs and co-administered drugs commonly associated with AED-PDIs, and characteristics of patients with high likelihood of AED-PDI exposure.
  
  
  METHODS
  Five-year retrospective cohort study of veterans with new-onset epilepsy.
  
  
  METHODS
  National Veterans Affairs and Medicare databases.
  
  
  METHODS
  Veterans aged 66 and older with a new diagnosis of epilepsy between October 1, 1999, and September 30, 2004 (N=9,682).
  
  
  METHODS
  AED-PDI was restricted to clinically meaningful PDIs identified using prior literature review. AED-PDIs were identified using participants' date of initial AED prescription and overlapping concomitant medications. Logistic regression analysis identified factors associated with AED-PDI, including demographic characteristics, chronic disease states, and diagnostic setting.
  
  
  RESULTS
  AED-PDI exposure was found in 45.5% (4,406/9,682); phenytoin, a drug with many PDIs, was the most commonly prescribed AED. Cardiovascular drugs, lipid-lowering medications, and psychotropic agents were the most commonly co-administered AED-PDI medications. Individuals with AED-PDI exposure were more likely to have hypertension (odds ratio (OR)=1.46, 99% confidence interval (CI)=1.24-1.82) and hypercholesterolemia (OR=1.40, 99% CI=1.24-1.57) than those without and to be diagnosed in an emergency or primary care setting than a neurology setting (emergency: OR=1.30, 99% CI=1.08-1.58; primary care: OR=1.29 99% CI=1.12-1.49).
  
  
  CONCLUSIONS
  Exposure to AED-PDI was substantial but less common in patients with epilepsy diagnosed in a neurology setting. Because potential outcomes associated with AED-PDI include stroke and myocardial infarction in a population already at high risk, clinicians should closely monitor blood pressure, coagulation, and lipid measures to minimize adverse effects of AED-PDIs. Interventions to reduce AED-PDIs may improve patient outcomes.
authors.affiliation: South Texas Veterans Health Care System, VERDICT REAP, San Antonio, Texas 78229, USA. pughm@uthscsa.edu
authors.forename: Mary Jo V
authors.initials: MJ
authors.lastname: Pugh
authors.forename: Anne C
authors.initials: AC
authors.lastname: Vancott
authors.forename: Michael A
authors.initials: MA
authors.lastname: Steinman
authors.forename: Eric M
authors.initials: EM
authors.lastname: Mortensen
authors.forename: Megan E
authors.initials: ME
authors.lastname: Amuan
authors.forename: Chen-Pin
authors.initials: CP
authors.lastname: Wang
authors.forename: Janice E
authors.initials: JE
authors.lastname: Knoefel
authors.forename: Dan R
authors.initials: DR
authors.lastname: Berlowitz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects* / Q000493:pharmacokinetics; D015897:Comorbidity; D004347:Drug Interactions; D016903:Drug Monitoring; D004827:Epilepsy / Q000188:drug therapy* / Q000453:epidemiology; D005260:Female; D015577:Geriatric Assessment; D006801:Humans; D008297:Male; D019338:Polypharmacy; D014481:United States / Q000453:epidemiology; D014728:Veterans
chemical_list: D000927:Anticonvulsants
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