TABLE 1.

Effect of combinations of amantadine, oseltamivir carboxylate, and ribavirin on an influenza A/Duck/MN/1525/81 (H5N1) amantadine-sensitive virus infection in MDCK cells

Drug	Concn (μM)	Virus titers with:b
		Amantadine (μM)a						Ribavirin (μM)c
		10	3.2	1.0	0.32	0.1	0	100	32	10	3.2	1.0	0
Oseltamivir carboxylate	1.0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0
	0.32	0 ± 0	0 ± 0	0.4 ± 0.8	0.3 ± 0.6	1.9 ± 2.3	3.5 ± 2.5	0 ± 0	0.3 ± 0.6	2.5 ± 2.3	2.7 ± 3.4	2.3 ± 2.8	2.7 ± 3.4
	0.1	0 ± 0	0 ± 0	2.9 ± 2.7	3.2 ± 3.2	3.7 ± 3.3	5.1 ± 0.7	0 ± 0	1.1 ± 1.9	3.1 ± 2.9	3.2 ± 3.3	2.7 ± 3.1	3.0 ± 3.0
	0.032	0 ± 0	0 ± 0	3.6 ± 2.6	3.5 ± 2.2	4.0 ± 2.7	5.2 ± 0.6	0 ± 0	0.9 ± 1.0	4.9 ± 0.8	5.0 ± 0.7	5.3 ± 0.9	5.3 ± 0.9
	0.01	0 ± 0	0 ± 0	4.1 ± 2.1	4.5 ± 1.1	4.7 ± 2.0	5.7 ± 0.7	0 ± 0	1.7 ± 1.9	5.0 ± 1.2	5.2 ± 1.3	5.4 ± 1.0	5.5 ± 0.7
	0	0 ± 0	0 ± 0	5.3 ± 0.9	5.9 ± 0.4	5.9 ± 0.5	5.6 ± 0.6	0 ± 0	1.5 ± 1.4	5.0 ± 0.6	5.7 ± 0.9	5.5 ± 0.2	5.5 ± 0.2
Amantadine	10							0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0	0 ± 0
	3.2							0 ± 0	0 ± 0	0.4 ± 0.8	0.5 ± 0.9	0.5 ± 0.9	4.3 ± 2.1
	1.0							0 ± 0	0.3 ± 0.6	1.0 ± 1.7	3.5 ± 1.3	2.6 ± 2.7	5.8 ± 0.7
	0.32							0 ± 0	0 ± 0	5.2 ± 0.6	4.9 ± 1.0	5.4 ± 0.2	5.9 ± 0.5
	0.1							0 ± 0	1.5 ± 2.6	5.8 ± 0.8	5.7 ± 0.4	5.7 ± 0.9	5.6 ± 0.7
	0							0 ± 0	2.4 ± 0.3	5.6 ± 0.3	5.4 ± 0.6	6.1 ± 0.5	5.7 ± 0.4

^aThe volume of synergy, as calculated by the method of Prichard and Shipman (23), for oseltamivir carboxylate and amantadine was 22.11.

^bValues are means ± standard deviations (n = 3 independent assays) of virus titers (log₁₀ CCID₅₀/0.1 ml). Boldface values indicate regions of synergy.

^cThe volume of synergy was 1.21 for oseltamivir carboxylate and ribavirin and 22.74 for amantadine and ribavirin.