The antidepressant drug amitriptyline hydrochloride was obtained in a dry powder form and was screened
against 253 strains of bacteria which included 72 Gram positive and 181 Gram negative bacteria and
against 5 fungal strains. The minimum inhibitory concentration (MIC) was determined by inoculating a
loopful of an overnight peptone water culture of the organism on nutrient agar plates containing increasing
concentrations of amitriptyline hydrochloride (0, 10 μg/mL, 25 μg/mL, 50 μg/mL, 100 μg/mL, 200
μg/mL). Amitriptyline hydrochloride exhibited significant action against both Gram positive and Gram
negative bacteria at 25-200 μg/mL. In the in vivo studies it was seen that amitriptyline hydrochloride at a
concentration of 25 μg/g and 30 μg/g body weight of mouse offered significant protection to Swiss strain
of white mice when challenged with 50 median lethal dose (MLD) of a virulent strain of Salmonella
typhimurium NCTC 74. The in vivo data were highly significant (p<0.001) according to the chi-square test.
