TABLE 3.
Observed and predicted discriminative stimulus effects of binary mixtures of cocaine and caffeine, MDPV and caffeine, and cocaine and MDPV
| Mixture | ED50 (mg/kg; Cocaine Equivalents) | Potency Ratio | Potency Ratio | Potency Ratio | |
|---|---|---|---|---|---|
| Predicted | Observed | ED20OBS / ED20PRED | ED50OBS / ED50PRED | ED80OBS / ED80PRED | |
| Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | |
| Cocaine:Caffeine | |||||
| 3:1 | 5.4 (4.0–7.4) | 4.7 (3.4–6.7) | 1.31 (0.77–1.85) | 0.92 (0.67–1.14) | 0.67 (0.52–0.82)+ |
| 1:1 | 5.1 (3.7–7.0) | 3.8 (2.7–5.5) | 1.23 (0.82–1.64) | 0.78 (0.59–0.97)+ | 0.52 (0.36–0.68)+ |
| 1:3 | 4.9 (3.7–6.5) | 4.3 (3.3–5.7) | 1.60 (0.42–2.79) | 0.95 (0.61–1.28) | 0.67 (0.34–0.99)+ |
| MDPV:Caffeine | |||||
| 3:1 | 4.3 (3.2–5.9) | 4.9 (3.7–6.5) | 1.69 (1.00–2.38) | 1.20 (0.76–1.64) | 0.87 (0.60–1.15) |
| 1:1 | 4.4 (3.2–5.9) | 4.4 (3.3–5.8) | 1.52 (0.86–2.17) | 1.07 (0.69–1.44) | 0.76 (0.51–1.02) |
| 1:3 | 4.3 (3.1–5.8) | 4.4 (3.5–5.6) | 1.62 (1.03–2.21)+ | 1.10 (0.73–1.46) | 0.76 (0.50–1.02) |
| Cocaine:MDPV | |||||
| 3:1 | 4.3 (3.2–5.8) | 3.3 (2.3–4.9) | 1.12 (0.48–1.76) | 0.84 (0.46–1.23) | 0.67 (0.37–0.97)+ |
| 1:1 | 4.3 (3.2–5.8) | 4.3 (3.1–5.9) | 1.37 (0.87–1.87) | 1.06 (0.63–1.49) | 0.82 (0.47–1.17) |
| 1:3 | 4.4 (3.3–5.9) | 3.5 (2.4– 4.9) | 1.25 (0.70–1.80) | 0.84 (0.54–1.13) | 0.60 (0.44–0.77)+ |
+
Significant difference between observed and predicted ED20, ED50, or ED80 values for an additive interaction as defined by 95% confidence interval (CI) that does not include 1.