Table 6.

Change in particle size (D₅₀) of spray dried formulations at 20% and 55% RH measured during storage using 4.0 bar dispersion pressure. Data is presented as mean ± standard deviation (n=3 or 4)

Formulation	D50 measured at 4.0 bar dispersion pressure (μm)
	20% RH			55% RH
	0 wk	2 wk	4 wk	0 wk	2 wk	4 wk
Colistin alone	2.21 ± 0.02	2.14 ± 0.07	2.14 ± 0.01	2.21 ± 0.02	2.16 ± 0.01	2.14 ± 0.01 *
1:1 Col-Tob	2.08 ± 0.03	2.02 ± 0.01 *	2.00 ± 0.02 *	2.08 ± 0.03	2.09 ± 0.00	2.06 ± 0.01 *
1:5 Col-Tob	1.95 ± 0.01	1.94 ± 0.01	1.94 ± 0.01	1.95 ± 0.01	1.96 ± 0.02	1.94 ± 0.03 *
Tobramycin alone	1.79 ± 0.03	1.87 ± 0.01 *	1.89 ± 0.00 *	1.79 ± 0.03	2.63 ± 0.02	57.4 ± 7.02 *

^*indicates significant difference with corresponding wk 0 value, p < 0.05

^aCol – colistin

^bTob – tobramycin