In Vitro Susceptibility of Canine Influenza A (H3N8) Virus to Nitazoxanide and Tizoxanide

Table 1

In vitro activity of nitazoxanide (NTZ) and its active metabolite tizoxanide (TIZ) on clinical isolates of canine influenza virus (CIV).

Virus	Drug	EC50	EC90	SI
Ca/CO-1	NTZ	$0.20\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.70\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	331
	TIZ	$0.20\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.72\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	644
Ca/CO-3	NTZ	$0.17\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.60\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	391
	TIZ	$0.17\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.62\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	751
Ca/Co-4	NTZ	$0.20\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.71\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	329
	TIZ	$0.19\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.01$	$0.70\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	374
CIV	NTZ	$0.21\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.02$	$0.76\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	309
	TIZ	$0.21\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.02$	$0.75\mathrm{\hspace{0.17em}\hspace{0.17em}}\pm \mathrm{\hspace{0.17em}\hspace{0.17em}}0.03$	619

EC_{50  or   90}: Concentration ($\mu$M) of NTZ or TIZ at which a 2-fold (50%) or 10-fold (90%) reduction of viral titer is relative to untreated controls. EC₅₀ and EC₉₀ are expressed as means $\pm$ standard deviation.
SI: Selectivity Index (CC₅₀/EC₅₀).
Viral titers of three CIV isolates were analyzed using polynomial regression analysis. 95% confidence intervals for each value are displayed in parenthesis.