TABLE 2.

Dose-effect relationships of the combination of AmB and allicin on Leishmania infantum promastigotes^a

D1-D2 combination ratio	% growth inhibition (EDn)	CI	DRI		Dose required (μM)
			AmB	Allicin	AmB	Allicin
0.01:5	50	0.79 (moderate synergism)	3.89	1.89	0.023	11.69
	75	0.65 (synergism)	5.48	2.13	0.035	17.69
	90	0.54 (synergism)	7.73	2.39	0.053	26.75
	95	0.49 (synergism)	11.52	2.74	0.071	35.45
0.01:10	50	1.23 (moderate antagonism)	4.14	1.01	0.022	21.94
	75	1.16 (slight antagonism)	5.31	1.03	0.037	36.49
	90	1.09 (nearly additive)	6.81	1.05	0.061	60.71
	95	1.05 (nearly additive)	8.06	1.07	0.085	85.82
0.01:20	50	1.33 (moderate antagonism)	6.92	0.84	0.015	31.22
	75	1.19 (slight antagonism)	9.47	0.91	0.023	47.48
	90	1.07 (nearly additive)	12.96	1.01	0.036	72.23
	95	0.99 (nearly additive)	16.05	1.06	0.048	96.07

^aDrugs were combined at constant ratios (0.01:5, 0.01:10, and 0.01:20), and their dose-effect relationships were assessed by the Chou-Talalay method (17) using CalcuSyn software. CI was calculated by the combination index equation. CI of <1, 1, and >1 indicate synergism, additive effect, and antagonism, respectively, at different effective doses (ED₅₀, ED₇₅, ED₉₀, and ED₉₅). Synergistic effects (CI < 1) are in bold. DRI indicates the fold dose reduction allowed in a drug combination to reach a given degree of inhibition compared to the drug as a single agent. Computer-simulated dose-required values of each drug in combination to reach a given effect level are included.