In vitro and in vivo synergism between tetracycline and the cardiovascular agent oxyfedrine HCl against common bacterial strains.

The cardiovascular drug oxyfedrine HCl revealed noteworthy in vitro antibacterial action against 501 strains of Gram positive and Gram negative bacteria. It also offered significant protection to mice challenged with a mouse-virulent bacterial strain. Prompted by such results, the present study was carried out to ascertain whether this drug could augment the efficiency of an antibiotic when used in combination with it. For this purpose, ten bacterial strains were selected, which were sensitive to oxyfedrine as well as to six antibiotics, like benzyl penicillin, chloramphenicol, ciprofloxacin, erythromycin, streptomycin and tetracycline. Distinct and statistically significant (p<0.01) synergism was observed between oxyfedrine and tetracycline by disc diffusion tests, compared with their individual effects. The fractional inhibitory concentration (FIC) index of this combination, evaluated by checkerboard analysis, was 0.37, which confirmed synergism between the pair. This synergistic drug duo was further dispensed to infected mice. The results of the mouse-protection tests advocated that the combination was significantly synergistic (p<0.0001), according to Student's 't' test. Hence, the capacity of extended antibiotic therapy in several microbial diseases may be improved with the help of this synergistic drug pair, and the study might throw light on newer directions to contest drug-resistant bacterial infections.

Experimental analysis of antimicrobial action of dicyclomine hydrochloride.

Dicyclomine hydrochloride is an antispasmodic agent. The MIC of dicyclomine against standard strains of Gram positive and Gram negative bacteria were performed by NCCLS broth dilution technique. These drugs showed a rapid killing action on Gram positive bacteria, Staphylococcus aureus NCTC 6571, 8530 and several other reference strains. The killing effect against Gram negative bacteria, Shigella boydii 8 NCTC 254/66 and Salmonella typhimurium NCTC 74 showed that the drug was bacteriostatic with respect to these strains. High rate of killing was achieved for most strains of Gram positive bacteria within 2 h. When administered to Swiss strain of white mice at doses of 30 and 60 microg/g of mouse, the drug could significantly protect the animals challenged with 50 MLD of Salmonella typhimurium NCTC 74. According to chi2 test, the in vivo data were highly significant (p<0.001). Since dicyclomine showed a remarkable inhibitory action against several pathogenic bacteria, in the course of time, it may be developed as a potent antimicrobial agent for many bacterial infections.