ABSTRACT
Purpose: The aim of this study is to evaluate the in vitro interaction of some penicillins (amoxicillin; ampicillin and benzylpenicillin) and caffeine against Staphylococcus aureus. Method: The interaction between the penicillins and caffeine was studied using the Overlay Inoculum Susceptibility Disc (OLISD) method. Minimum inhibitory concentrations (MIC) of the drugs were determined separately and in combination with caffeine (5 and 10 mg/ml). Result: At 5 and 10 mg/ml; caffeine decreased the MIC of amoxicillin by 22 and 25 times respectively; while that of ampicillin was decreased by 6 and 8 times. The MIC of benzylpenicillin against Staphylococcus aureus was; however; increased by 59 and 40 times at caffeine concentrations of 5 and 10 mg/ml respectively. The inhibition zone diameter increment above 19(index of synergism in OLISD method) was recorded only for amoxicillin at amoxicillin concentrations of 7.81; 15.3; 31.25 and 62.5 mg/ml. Conclusion: The results of this study revealed that the concomitant use of caffeine and the studied antibiotics may potentiate the antibacterial effect of amoxicillin against Staphylococcus aureus; decrease that of benzylpenicillin and has virtually no effect on that of ampicillin. This implies that the intake of caffeine in form of analgesic combination or as tea; coffee; beverages or from other food sources may affect the effectiveness of a co-administered amoxicillin and bezylpenicillin