Adherence to osteoporosis medications amongst Singaporean patients

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.

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.

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.

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).

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.