Table 4.

Plasma concentrations of benzodiazepines (μg/ml) with more than five users. Values are means (95% confidence intervals) unless stated otherwise

	Cases		Controls	P value*
Alprazolam	10.9 (0.3 to 423.0)		9.1 (1.2 to 71.3)	1.00
Bromazepam	137.0 (16.2 to 1159.9)		139.8 (24.9 to 785.0)	0.63
Clorazepate	295.9 (7.3 to 11939.7)		242.3 (25.9 to 2266.9)	0.08
Flunitrazepam	6.3 (2.0 to 19.4)		5.7 (0.9 to 34.4)	0.30
Lorazepam	17.3 (4.6 to 64.3)		16.0 (2.5 to 100.5)	0.58
Oxazepam	56.8 (0.3 to 12771.7)		144.0 (15.6 to 1330.1)	0.50
Zolpidem	75.2 (10.3 to 546.3)		60.3 (5.7 to 634.5)	0.24
Zopiclone	40.4 (7.6 to 215.5)		26.8 (4.4 to 163.3)	0.23
All	66.7 (2.4 to 1823.6)		78.3 (3.8 to 1625.7)	0.43

Mean values and upper and lower bounds of the 95% confidence intervals computed after logarithmic transformation. 

^*Probability according to Mann-Whitney U test.