Eighteen volunteers participated in a crossover , double-blind study in which they received placebo ; 5 mg hydrocodone/1 .5 mg homatropine , 10 mg hydrocodone/3 mg homatropine , 20 mg hydrocodone/6 mg homatropine ( all PO ) ; 40 mg morphine ( PO ) ; and 2 mg lorazepam ( PO ) .
