Examination of antimicrobial activity of selected non-antibiotic products

A variety of pharmaceutical preparations, which are applied in the management of non-infectious diseases, have shown in vitro some antimicrobial activity. These drugs are called “non-antibiotics”. So far, a lot of attention has been focused on phenothiazines, thioxanthenes and other agents with affinities to cellular transport systems or agents showing other inhibition mechanism. Several authors confirmed that some non-antibiotics are “helper compounds”, which enhance the in vitro activity of certain antibiotics against specific bacteria (ex. omeprazole and nizatidine enhance the effect of metronidazole on Helicobacter pylori). The aim of this study was to detect and characterise the antimicrobial activity of non-antibiotic drugs, selected from the pharmaceutical products analysed during the state control performed in National Medicines Institute in Warsaw. Over 100 pharmaceutical preparations were randomly chosen from different groups of drugs. The surveillance study was performed on standard ATCC microbial strains used for drug control: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus brasiliensis. It was shown that the drugs listed below inhibited growth of at least one of the examined strains: Cyclaid 100 mg cap. (ciclosporine), Heminevrin 300 mg cap. (clomethiazole edisylate), Hydroxycarbamid Teva 500 mg caps. (hydroxycarbamide), Ibandronat Apotex 150 mg tab., Ossica 150 mg tab. (ibandronic acid), Lazivir 150 mg + 300 mg tab. (lamivudyne, zydovudine), No-Spa Max 80 mg tab. (drotaverine HCl) and Rupafin 10 mg tab. (rupatadine). The MIC values of active substances of above drugs were evaluated. The broad spectrum of activity was found in case of clomethiazole which inhibited growth of all tested strains ( MIC: 1.6 – 3.2 mg/ml ). All tested bacterial strains were inhibited by hydroxycarbamide (MIC: 0.8 - 1.6 mg/ml). The high activity against Gram-positive strains was found for drotaverine and rupatadine (MIC: 0.4 mg/ml). Mould strain A. brasiliensis was inhibited by ibandronic acid (MIC 3.2 mg/ml), clomethiazole (MIC 1.6 mg/ml) and cyclosporine (MIC 0.8 mg/ml). Moreover ibandronic acid was active against P. aeruginosa in relatively low concentration (MIC: 0.2 mg/ml). In case of antiviral tablets Lazivir (two active substance: lamivudine and zidovudine) only zidovudine inhibited growth of E. coli in very low concentration 0.00125 mg/ml whereas lamivudine to concentration 1.6 mg/ml did not show any inhibition towards tested strains. The antimicrobial activity of the drugs emphasize a necessity of neutralization of their activity during microbial purity assays of pharmaceutical products.