Influence of refill adherence method when comparing level of adherence for different dosing regimens

Area of Science:

• Pharmacoeconomics and Pharmacoepidemiology
• Drug Utilization Research
• Medication Adherence Studies

Background:

• Bisphosphonates are crucial for osteoporosis management, requiring long-term adherence for efficacy.
• Accurate assessment of refill adherence is vital for understanding treatment persistence and outcomes.
• Different dosing regimens (daily, weekly) may influence patient adherence patterns.

Purpose of the Study:

• To compare the impact of two distinct methods for estimating refill adherence in bisphosphonate users.
• To evaluate how different bisphosphonate dosing frequencies affect adherence estimates.

Main Methods:

• Utilized the Swedish Prescribed Drug Register to identify 18,203 new bisphosphonate users (aged 18-85).
• Followed patients for up to 2 years, categorizing them by dosing regimen (daily, weekly, switching, other).
• Estimated refill adherence using Continuous measure of Medication Acquisition (CMA ≥ 80%) and the maximum gap method (<45 days), analyzing differences with logistic regression.

Main Results:

• The Continuous measure of Medication Acquisition (CMA) classified a higher proportion of patients as adherent compared to the maximum gap method.
• Patients on weekly bisphosphonate dosing exhibited significantly lower adherence than those on daily dosing, irrespective of the method used (CMA: 84% vs. 88%; maximum gap: 73% vs. 80%).
• Other dosing regimens also demonstrated significantly lower adherence compared to the daily regimen.

Conclusions:

• The choice of adherence estimation method significantly influences the observed refill adherence rates for bisphosphonates.
• Weekly bisphosphonate dosing is associated with lower patient adherence compared to daily dosing, a finding consistent across both estimation methods.