Table 2.

The experimental ED₅₀ of naproxen and polyalthic acid, along with the theoretical and experimental ED₅₀ of the combination treatment.

Drug	ED50 (mg/kg)
Naproxen	20.1 ± 4.8
Polyalthic acid	101.6 ± 30.9
Theoretical ED50 of the polyalthic acid–naproxen combination	60.9 ± 15.7 CI (32.4–114.3)
Experimental ED50 of the polyalthic acid-–naproxen combination	2.4 ± 0.02 * CI (0.9–6.6)
Interaction index (γ)	0.04 ± 0.02 CI (0.02–0.10)

ED₅₀ = effective dose resulting in a 50% reduction in the hyperalgesic response found with the vehicle-treated control; CI = confidence interval. Data are expressed as the mean ± SEM (n = 8). * p < 0.05 vs. the theoretical ED₅₀ of the combination treatment, as determined by the Student’s t-test.