Table 1.

Quantities of doxycycline under various conditions

	Day	Concentration (mg/mL; mean ± 1 SD)	% Recovered
Untinted bottle, acidified water
	0	1.5 ± 0.1	100
	7	1.5 ± 0.1	100
	14	1.4 ± 0.2	93.8b
Untinted bottle, nonacidified water
	0	1.5 ± 0.0	100
	7	1.5 ± 0.0	100
	14	1.3 ± 0.2	88
Tinted bottle, acidified water
	0	1.6 ± 0.1	100
	7	1.6 ± 0.1	98
	14	1.4 ± 0. 2	85
Tinted bottle, nonacidified water
	0	1.7 ± 0.2	100
	7	1.6 ± 0.1	95
	12a	1.4 ± 0.1	84

^aThis sample was collected on day 12 due to the appearance of fungal growth.

^bThis group is the only one that demonstrated no significant decrease in doxycycline concentration over 14 d.