Table 1. Synergy volume of double and triple combinations of antivirals against 2009 H1N1 viruses A/California/04/09 (CA04), A/California/05/09 (CA05), and A/California/10/09 (CA10) as determined by Neutral Red assay.

Regimen	CA04	CA05	CA10
Double combinations (µg/mL2%)
Zanamivir/Oseltamivir carboxylate	−24±116	−155±89	−197±98
Zanamivir/Peramivir	−35±112	−197±108	−239±93
Amantadine/Oseltamivir carboxylate	112±154	133±80	135±67
Amantadine/Ribavirin	12±82	22±36	69±59
Ribavirin/Oseltamivir carboxylate	178±188	222±143	166±73
TCAD at fixed concentrations of amantadine (µg/mL3%)
0.1 µg/mL amantadine	106±208	312±195	226±84
0.32 µg/mL amantadine	292±212	293±154	296±82
1.0 µg/mL amantadine	346±212	337±196	311±139
3.2 µg/mL amantadine	475±221	485±97	413±163
TCAD at fixed concentrations of ribavirin (µg/mL3%)
0.1 µg/mL ribavirin	92±119	146±82	171±137
0.32 µg/mL ribavirin	114±250	135±95	271±105
1.0 µg/mL ribavirin	179±292	478±138	353±108
3.2 µg/mL ribavirin	691±144	763±256	632±216
TCAD at fixed concentrations of oseltamivir carboxylate (µg/mL3%)
0.001 µg/mL oseltamivir carboxylate	66±92	104±53	153±84
0.0032 µg/mL oseltamivir carboxylate	69±285	248±93	193±101
0.01 µg/mL oseltamivir carboxylate	359±256	583±122	442±153
0.032 µg/mL oseltamivir carboxylate	465±291	437±355	317±164

Synergy volumes represent the sum of the synergy or antagonism across all concentrations of two drugs for a double combination, or all concentrations of two drugs at a fixed concentration of the third drug for the TCAD regimen. The concentrations of each drug used are provided in Table S1. Combinations with synergy volumes >100 µg/mL²% for double combinations or >100 µg/mL³% for triple combinations are considered to be strongly synergistic (using the lower 95% confidence interval). Conversely, combinations with synergy volumes <−100 µg/mL²% or µg/mL³% are considered to be strongly antagonistic. Bold numbers denote volumes that are defined as strongly synergistic or antagonistic. Synergy volumes are presented as the mean between replicates with 95% confidence intervals. Typically, between 3 and 6 experiments were run for each combination, with each experiment having 3 replicate wells for each condition.