Drug-drug interaction may explain failed antibiotic effectiveness - an <i>in vivo</i> study

Abstract

Non-steroidal anti-inflammatory drugs (NSAIDs) are often co-administered with antibiotics such as Ciprofloxacin, a second generation fluoroquinolone, in situations in which Staphylococcus aureus infections are accompanied with pain and inflammation. The contra- indications have not been found to attract deliberate study. This study was therefore to investigate possible interactions in co -administration of ciprofloxacin and some NSAIDs. The in vivo effect of co-administration of the NSAIDs (acetyl salicylic acid (ASA), piroxicam, indomethacin and paracetamol) with ciprofloxacin against Staphylococcus aureus in Swiss mice, rendered neutropenic by pre-treatment with cyclophosphamide, was evaluated using animal model. Using the murine thigh model, aliquots of the infected,
homogenised thigh muscle were plated out in duplicate plates and incubated at 37°C. Growth of Staphylococcus aureus was observed and number of colony, forming units noted. All information obtained were recorded and analysed by standard statistical methods. Values of p< 0.05 were taken as significant. Co-administration of the NSAIDs with ciprofloxacin significantly reduced the number of CFU of Staphylococcus aureus in the order ASA > Indomethacin > Piroxicam > Paracetamol (52 cfu; 47 cfu; 8 cfu; and 5 cfu) respectively. The four NSAIDs significantly exhibited varying degrees of inhibitory effect on Staphylococcus aureus, when compared with organism alone in broth, yielding 33 cfu; 25 cfu; 11 cfu; and 3 cfu, for ASA, Indomethacin, Piroxicam and Paracetamol, respectively when introduced without ciprofloxacin (p<0.001). These results demonstrate that these NSAIDs when co-administered with ciprofloxacin produce significant reduction in its antibacterial effect.

Keywords: In vivo; Ciprofloxacin; NSAIDs