Table 5.

Change in particle size (D₅₀) of spray dried formulations at 20% and 55% RH measured during storage using 0.5 bar dispersion pressure. Data is presented as mean ± standard deviation (n=3 or 4)

Formulation	D50 measured at 0.5 bar dispersion pressure (μm)
	20% RH			55% RH
	0 wk	2 wk	4 wk	0 wk	2 wk	4 wk
Colistin alone	2.50 ± 0.07	2.52 ± 0.02	2.59 ± 0.02	2.50 ± 0.07	2.93 ± 0.22	2.92 ± 0.02 *
1:1 Col a -Tob b	2.59 ± 0.06	2.46 ± 0.03	2.55 ± 0.04	2.59 ± 0.06	2.84 ± 0.04	2.99 ± 0.01 *
1:5 Col-Tob	2.47 ± 0.02	2.34 ± 0.04 *	2.36 ± 0.03 *	2.47 ± 0.02	3.20 ± 0.09	3.76 ± 0.13 *
Tobramycin alone	30.2 ± 2.88	38.7 ± 0.85	78.7 ± 5.98 *	30.2 ± 2.88	51.3 ± 1.58 *	110 ± 11.0 *

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

^aCol – colistin

^bTob – tobramycin