Drug persistency patterns for patients treated with rivastigmine or donepezil in usual care settings
OBJECTIVE: To compare levels of persistency with 2 cholinesterase (ChE) inhibitors-rivastigmine and donepezil for the treatment of Alzheimer's disease (AD) through the use of administrative claims data. METHODS: This retrospective cohort study identified treatment - naive, community- based AD patients having an initial prescription (index event) for rivastigmine or donepezil between June and December 2000, in the United States, from pharmacy claims in a proprietary administrative claims database. Patients were excluded if they received either drug during the 180 days prior to their index prescription or if they did not have continuous plan enrollment during this period and for at least 90 days following the index date. The probability of treatment discontinuation within the first 60 days of treatment was estimated. Time to treatment discontinua tion was analyzed for the cohort of patients that remained on therapy e60 days as well as for subgroups of the cohort reaching either approved or maximum recommended doses of donepezil or rivastigmine. Treatment discontinuation was defined as either a stop of therapy (no prescription refill within 60 days of estimated completion of prior prescription) or a switch to an alternative AD drug. Kaplan-Meier survival and proportional hazard model analyses were performed. Proportion of days covered (PDC) by an AD therapy was also evaluated in each quarter during the first year of follow-up. RESULTS: Of the newly treated AD study population, 30.4% (171/563) of rivastigmine patients and 31.2% (583/1,871) of donepezil patients discontinued treatment within 60 days of starting therapy (P=0.72). For the cohort of patients that remained on therapy 60 days, the mean time to treatment discontinuation was 331 days (95% confidence interval [CI], 307-355) for rivastigmine patients (n=392) versus 337 days (95% CI, 322-352) for donepezil patients (n=1288). The proportion of patients with a PDC e80% after 12 months of follow-up was 23% for the donepezil group and 19% for the rivastigmine group (P=0.34). For the cohort subgroup that reached an approved dose, the mean time to treatment discontinuation was 346 days (95% CI, 318-374) for rivastigmine patients (n=282) versus 338 days (95% CI, 323-353) for donepezil patients (n=1,283). For the cohort subgroup that reached the maximum recommended dose, the mean time to treatment discontinuation was 396 days (95% CI, 343-449) for rivastigmine patients (n=61) versus 364 days (95% CI, 344-384) for donepezil patients (n=712). CONCLUSION: Newly treated AD patients in a usual care setting who initiate therapy with either rivastigmine or donepezil have similar levels of persistency with treatment.