title: Incidence of and factors associated with manipulation of nimodipine dosage in patients with aneurysmal subarachnoid hemorrhage.
abstract: BACKGROUND
  Aneurysmal subarachnoid hemorrhage is a significant cause of death and disability. Nimodipine 60 mg administered enterally every 4 h improves neurologic outcomes in these patients. However, hypotension is an adverse effect of nimodipine and is believed to prompt clinicians to prescribe an unproven, nonstandard nimodipine dosing regimen.
  
  
  OBJECTIVE
  The primary objective was to determine the prescribing incidence of a nonstandard nimodipine dosing regimen (30 mg every 2 h) after initial prescription of the standard dose (60 mg every 4 h). The secondary objective was to determine factors associated with this dosage change.
  
  
  METHODS
  This retrospective cohort study evaluated participants receiving nimodipine for aneurysmal subarachnoid hemorrhage at a tertiary care teaching hospital between October 2005 and December 2011. Univariate and multivariate regression analyses were performed to identify factors associated with dosage manipulation.
  
  
  RESULTS
  A total of 166 eligible patients were identified. For all of these patients, nimodipine 60 mg every 4 h was prescribed initially. Subsequently, 81 (49%) of the patients were switched to nimodipine 30 mg every 2 h, whereas 85 (51%) continued on the original dosage (nimodipine 60 mg every 4 h) for the duration of their treatment. Multivariate analysis revealed that occurrence of vasospasm (odds ratio [OR] 5.30, 95% confidence interval [CI] 2.08-13.47; p < 0.001) and exposure to vasopressor therapy (OR 3.29, 95% CI 1.27-8.50; p = 0.014) were associated with increased odds of receiving the nonstandard nimodipine regimen.
  
  
  CONCLUSIONS
  Half of patients for whom nimodipine was prescribed for aneurysmal subarachnoid hemorrhage were exposed to an unproven regimen. Vasospasm and exposure to vasopressor therapy were associated with higher odds of receiving the nonstandard regimen. Further research is needed to evaluate whether nimodipine 30 mg every 2 h is efficacious and safe for patients in this population.
authors.affiliation: BSc(Pharm), ACPR, PharmD, is Clinical Coordinator-Critical Care and Emergency Medicine, Pharmacy Department, Capital District Health Authority, and Assistant Professor, College of Pharmacy, Dalhousie University, Halifax, Nova Scotia. This study was undertaken while she was completing her Pharmacy Residency at Capital Health/Dalhousie.
authors.forename: Meghan
authors.initials: M
authors.lastname: MacKenzie
authors.affiliation: BSc(Pharm), ACPR, PharmD, is Regional Coordinator - Clinical Quality and Research and Pharmacotherapeutic Specialist - Critical Care with Pharmacy Services, Interior Health Authority, Kelowna, British Columbia. He is also a Clinical Associate Professor in the Faculty of Pharmaceutical Sciences, The University of British Columbia, Vancouver, British Columbia.
authors.forename: Sean K
authors.initials: SK
authors.lastname: Gorman
authors.affiliation: MSc, is Senior Biostatistician in the Research Methods Unit, Capital District Health Authority, Halifax, Nova Scotia.
authors.forename: Steve
authors.initials: S
authors.lastname: Doucette
authors.affiliation: BSc, MD, FRCPC, DABEM, is a Professor in the Department of Anesthesia, Division of Critical Care Medicine, and the Department of Emergency Medicine, Dalhousie University, and is also Medical Director of the Nova Scotia Trauma Program, Halifax, Nova Scotia.
authors.forename: Robert
authors.initials: R
authors.lastname: Green
keywords: dosage regimen; nimodipine; subarachnoid hemorrhage