Table 4.
Factors that Influence Whether Patients Switch to Generic Medications
| Patient characteristics | Relative risk | 95% C.I. lower limit | 95% C.I. upper limit | p-value |
|---|---|---|---|---|
| Males age* | ||||
| 25–39 | 5.92 | 0.87 | 40.01 | 0.07 |
| 40–55 | 4.96 | 0.74 | 33.16 | 0.10 |
| >55 | 7.56 | 1.13 | 50.54 | 0.04 |
| Females age† | ||||
| 25–39 | 1.97 | 1.39 | 2.80 | 0.002 |
| 40–55 | 2.72 | 1.86 | 3.97 | 0.001 |
| >55 | 2.88 | 1.84 | 4.50 | 0.001 |
| Median household income in zip code‡ | ||||
| $30–60,000 | 0.99 | 0.77 | 1.27 | 0.93 |
| > $60,000 | 1.08 | 0.81 | 1.43 | 0.61 |
| Avg. number of prescriptions per month§ | ||||
| 1–3 | 0.79 | 0.53 | 1.17 | 0.23 |
| >3 | 0.90 | 0.61 | 1.35 | 0.62 |
| Pharmacy characteristics// | ||||
| Chain pharmacy | 1.17 | 0.93 | 1.48 | 0.19 |
| Mail-order pharmacy | 1.65 | 1.18 | 2.30 | 0.003 |
| Pharmacy benefit design characteristics¶ | ||||
| No copayments | 1.47 | 0.49 | 4.43 | 0.50 |
| 3 or 4 tiers with lower copayments | 2.61 | 1.12 | 6.09 | 0.03 |
| 3 or 4 tiers with higher copayments | 3.95 | 1.72 | 9.11 | 0.001 |
| Physician characteristics | ||||
| Age# | ||||
| 46–55 | 0.85 | 0.72 | 1.00 | 0.06 |
| >55 | 1.00 | 0.84 | 1.19 | 0.96 |
| Male | 1.17 | 0.999 | 1.39 | 0.051 |
| Specialty** | ||||
| Medical subspecialist | 1.06 | 0.84 | 1.34 | 0.33 |
| Cardiologist | 1.09 | 0.75 | 1.59 | 0.63 |
| Obstetrics–Gynecology | 0.73 | 0.56 | 0.94 | 0.01 |
| Other | 1.04 | 0.72 | 1.52 | 0.80 |
Results of generalized estimating equations; n = 4,062; controlling for drug class
*Males age 25
†Females age 25
‡Income $30,000
§1 or less avg. prescription filled per month
//Independent or “other” pharmacy
¶1- or 2-tier of copayment benefit design
# Physician age 45 or less
**Generalist physician