The potential for commonly infused drug solutions to support or inhibit microbial growth was explored in this study. Drugs examined were midazolam HCl, morphine sulphate, fentanyl citrate, pethidine HCl, bupivacaine HCl, atracurium besylate, vecuronium bromide, adrenaline, dopamine, dobutamine, noradrenaline, isoprenaline, glyceryl trinitrate, sodium nitroprusside and propofol. All drugs were studied in both diluted and undiluted forms. Of the 15 medications investigated, all except propofol were found to be bactericidal and to reduce fungal growth.