title: Extended-release nifedipine and the risk of intestinal obstruction: a population-based study.
abstract: OBJECTIVE
  To examine the risk of bowel obstruction in older adults during treatment with extended-release nifedipine compared with patients treated with amlodipine.
  
  
  METHODS
  Retrospective cohort study using multiple linked healthcare databases.
  
  
  METHODS
  Ontario, Canada from 1 April 1997 to 31 December 2010.
  
  
  METHODS
  We identified patients aged 66 years and older who started treatment with Adalat XL, an extended-release nifedipine product employing a tablet delivery system associated with mechanical bowel obstruction. For comparison, we studied patients receiving amlodipine, a long-acting calcium channel blocker that does not utilise the same delivery system and has not been implicated as a cause of bowel obstruction. Propensity score matching was used to ensure similarity of patients receiving the two drugs.
  
  
  METHODS
  HR for the association between extended-release nifedipine relative to amlodipine and hospitalisation for bowel obstruction during therapy.
  
  
  RESULTS
  Over the 13-year study period, we identified 103 657 patients treated with extended-release nifedipine and 204 733 patients treated with amlodipine. In these two groups, 591 (0.6%) and 1185 (0.6%) of patients were hospitalised for bowel obstruction, respectively. We found no difference in the risk of bowel obstruction among patients treated with extended-release nifedipine compared with amlodipine (HR 1.09, 95% CI 0.96 to 1.24).
  
  
  CONCLUSIONS
  Bowel obstruction during treatment with extended-release nidefipine is rare, and the risk is not appreciably greater than that during treatment with amlodipine.
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Sunnybrook Research Institute, Toronto, Ontario, Canada Department of Medicine, University of Toronto, Toronto, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada.
authors: David N
authors: DN
authors: Juurlink
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors: Chelsea
authors: C
authors: Hellings
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada Applied Health Research Center, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada.
authors: Tara
authors: T
authors: Gomes
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors: Anjie
authors: A
authors: Huang
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada.
authors: J Michael
authors: JM
authors: Paterson
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
authors: David R
authors: DR
authors: Urbach
authors: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada Department of Medicine, University of Toronto, Toronto, Ontario, Canada Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada Applied Health Research Center, Li Ka Shing Knowledge Institute of St. Michael's Hospital, Toronto, Ontario, Canada Department of Medicine, St. Michael's Hospital, Toronto, Ontario, Canada.
authors: Muhammad M
authors: MM
authors: Mamdani
mesh_terms: D000368:Aged; D017311:Amlodipine / Q000009:adverse effects*; D002121:Calcium Channel Blockers / Q000009:adverse effects*; D015331:Cohort Studies; D003692:Delayed-Action Preparations; D005260:Female; D006801:Humans; D007415:Intestinal Obstruction / Q000139:chemically induced*; D008297:Male; D009543:Nifedipine / Q000009:adverse effects*; D012189:Retrospective Studies; D018570:Risk Assessment
chemical_list: D002121:Calcium Channel Blockers; D003692:Delayed-Action Preparations; D017311:Amlodipine; D009543:Nifedipine
keywords: GASTROENTEROLOGY