Table 3.
Change in Generic Utilization by Drug Class for Subjects Aged 67–79 from 2005 to 2006
| Drug class | Medicare Part D enrollees | Non-enrollees | Part D*Time |
|---|---|---|---|
| Odds ratio (95% CI) | Odds ratio (95% CI) | Odds ratio (95% CI) | |
| Antihyperlipidemics | 1.41*** (1.37, 1.45) | 1.97*** (1.93, 2.01) | 0.95*** (0.92, 0.98) |
| Antidepresssants | 1.10*** (1.07, 1.13) | 1.21*** (1.19, 1.25) | 1.00 (0.96, 1.03) |
| Antiulcerants | 1.04** (1.01, 1.07) | 0.95*** (0.93, 0.98) | 1.02 (0.98, 1.06) |
| NSAIDs | 1.21*** (1.16, 1.25) | 1.27*** (1.23, 1.32) | 0.92*** (0.87, 0.97) |
| Antihistamines | 1.57*** (1.48, 1.67) | 2.78*** (2.66, 2.91) | 0.75*** (0.70, 0.82) |
| Antidiabetic drugs (excludes insulin) | 1.02* (1.00, 1.05) | 1.13*** (1.11, 1.16) | 1.00 (0.97, 1.03) |
| Calcium channel blockers | 1.18*** (1.15, 1.21) | 1.06*** (1.04, 1.09) | 0.98 (0.94, 1.01) |
| ACE inhibitors | 1.31*** (1.27, 1.34) | 1.09*** (1.07, 1.12) | 1.10*** (1.05, 1.14) |
| Beta-blockers | 1.13*** (1.11, 1.16) | 1.04*** (1.02, 1.06) | 0.97* (0.94, 0.99) |
| Special interest drugs | |||
| Barbiturates | – | – | – |
| Benzodiazepines | 1.96*** (1.80, 2.14) | 1.27*** (1.19, 1.36) | 1.19** (1.04,1.35) |
| Antipsychotics | 0.93 (0.85, 1.02) | 1.21*** (1.11, 1.32) | 0.91 (0.80, 1.02) |
| Anticonvulsants | 1.18*** (1.12, 1.24) | 0.70*** (0.67, 0.73) | 1.07* (1.00, 1.14) |
| Antivirals | 1.32*** (1.15, 1.50) | 1.32*** (1.15, 1.50) | 0.99 (0.83, 1.19) |
| Antineoplastics | 0.95 (0.87, 1.04) | 1.53*** (1.42, 1.65) | 0.90 (0.80, 1.01) |
| All drugs | 1.08*** (1.08, 1.09) | 1.12*** (1.12, 1.13) | 0.95*** (0.94, 0.95) |
=Part D*Time represents the net effect of Part D on enrollees compared with non-enrollees after adjusting for the time trend and other potential confounders. Estimates derived from a differences-in-differences regression, adjusting for beneficiaries’ age, gender, English language preference, socio-demographic characteristics measured through Census zip code, 29 comorbid conditions, out-of-pocket payout ratio, the number of pharmacy claims, and Medicaid eligibility in the base year; changes in barbiturate use could not be estimated due to the small number of observations; ACE inhibitor = angiotensin-converting enzyme inhibitor; NSAID = non-steroidal anti-inflammatory drug; * P < 0.05, **P< = 0.01, ***P< = 0.001