title: The extent of potential antihypertensive drug interactions in a Medicaid population.
abstract: BACKGROUND
  Drug interactions are a frequent cause of adverse drug events and these might be avoided by computer alerts to physicians or pharmacists. We evaluated the frequency of potential drug-drug interactions in patients receiving medications commonly used for hypertension.
  
  
  METHODS
  Patients more than 30 years of age with hypertension who were receiving Medicaid and who were enrolled in the Iowa Pharmaceutical Case Management (PCM) program were evaluated. All prescription claims for patients were obtained on their date of eligibility. A drug interaction database was developed to examine potential drug interactions in each patient's regimen.
  
  
  RESULTS
  There were 1574 patients who received a drug typically used for hypertension. Depending on age and sex, 23% to 48% of patients had a potential interaction of high significance and 55% to 84% had at least one potential interaction. Both increasing age (P =.0007, odds ratio [OR] 1.012 [1.005,1.019]) and number of drugs (P <.0001, OR 1.120 [1.092,1.150]) were significantly associated with the potential for a highly significant drug interaction in the univariable models. Female sex was not significant (P =.56, OR 1.074 [0.845,1.364]). The multivariable model found that there was a significant interaction between age and the number of drugs in the regimen (P <.0001).
  
  
  CONCLUSIONS
  This study found a very high frequency of potential drug interactions with agents typically used for hypertension. Because of the large volume of potential interactions, these data raise the concern that any attempt to provide physicians and pharmacists with computer alerts about these interactions will result in alerts for the vast majority of patients.
authors.affiliation: Division of Clinical and Administrative Pharmacy, College of Pharmacy, College of Medicine, University of Iowa, Iowa City, IA 52242, USA. barry-carter@uiowa.edu
authors.forename: Barry L
authors.initials: BL
authors.lastname: Carter
authors.forename: Brian C
authors.initials: BC
authors.lastname: Lund
authors.forename: Nobumasa
authors.initials: N
authors.lastname: Hayase
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Chrischilles
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000009:adverse effects / Q000627:therapeutic use*; D003157:Community Pharmacy Services / Q000191:economics / Q000458:organization & administration; D004347:Drug Interactions; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D007484:Iowa; D008297:Male; D008484:Medicaid; D008875:Middle Aged; D014481:United States
chemical_list: D000959:Antihypertensive Agents