title: Adherence to osteoporosis medications amongst Singaporean patients.
abstract: Compliance and persistence to bisphosphonates amongst Singaporean patients with osteoporosis were estimated. Mean medication possession ratio (MPR) ± standard deviation (SD) was 78.9 ± 27.5%, and 69.0% was persistent at 1 year. In contrast to US and Europe where poor adherence is noted, our study suggests higher adherence rates to bisphosphonate therapy amongst patients.
  
  
  BACKGROUND
  Adherence to bisphosphonate therapy during treatment of osteoporosis has been reported to be poor. We aimed to estimate the compliance and persistence to prescribed bisphosphonate therapy amongst patients at the largest public restructured hospital in Singapore.
  
  
  METHODS
  This is a retrospective analysis of records of patients who were prescribed the two most commonly used oral bisphosphonates-alendronate and risedronate. The study was conducted between January 2007 and December 2008. Prescription and pharmacy refill records of all patients were extracted and matched. Compliance was calculated using the MPR, while persistence, a dichotomous variable, was defined as continuous refill of bisphosphonates for at least 12 months with a permissible gap of 30 days.
  
  
  RESULTS
  Seven hundred ninety-eight patients were included in the study. Mean MPR ± SD was 78.9 ± 27.5%, and 69.0% of the patients were persistent with bisphosphonate therapy at 1 year. The proportion of patients with MPR ≥ 80% at 6, 12 and 18 months was 90%, 72% and 62%, respectively. Age <69 years was associated with better compliance (OR, 1.34; 95% CI, 0.99-1.82; P = 0.043), and history of fractures was associated with better compliance (OR, 1.38; 95% CI, 1.02-1.87; P = 0.038) and persistence (OR, 1.33; 95% CI, 0.97-1.82; P = 0.046).
  
  
  CONCLUSIONS
  In contrast to studies conducted in the US and Europe that show poor adherence, our study suggests higher adherence rates to bisphosphonate therapy amongst Singaporean patients.
authors.affiliation: Department of Pharmacy, Singapore General Hospital, Singapore, Singapore.
authors.forename: M H H
authors.initials: MH
authors.lastname: Cheen
authors.forename: M C
authors.initials: MC
authors.lastname: Kong
authors.forename: R F
authors.initials: RF
authors.lastname: Zhang
authors.forename: F M H
authors.initials: FM
authors.lastname: Tee
authors.forename: M
authors.initials: M
authors.lastname: Chandran
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019386:Alendronate / Q000008:administration & dosage / Q000627:therapeutic use; D050071:Bone Density Conservation Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D004164:Diphosphonates / Q000008:administration & dosage / Q000627:therapeutic use; D004334:Drug Administration Schedule; D012968:Etidronic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000627:therapeutic use; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy* / Q000208:ethnology; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy; D058866:Osteoporotic Fractures / Q000453:epidemiology / Q000517:prevention & control; D012189:Retrospective Studies; D000068296:Risedronic Acid; D012846:Singapore / Q000453:epidemiology; D016903:Drug Monitoring
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D000068296:Risedronic Acid; D012968:Etidronic Acid; D019386:Alendronate