Studies have previously shown that a broad drug interaction screening can be performed using enzyme specific probes such as oral caffeine for CYP1A2, N-acetyltrasferase-2 (NAT-2), and xanthine oxidase (XO), warfarin plus vitamin K for CYP2C9, omeprazole for CYP 2C19, dextromethorphan for CYP2D6, and midazolam for CYP3A4/5. This combination of probes has been validated in the Cooperstown 5+1 Cocktail (5+1).1 The use of the 5+1 cocktail provides information on the drug metabolizing enzymes that metabolize 90% of hepatically eliminated drugs for a fraction of the costs of the individual studies. Using a cocktail of biomarkers reduces the overall cost of drug interaction screening. The purpose of this study is to evaluate the effects of three Food and Drug Administration (FDA) approved oral antibiotics (azithromycin, telithromycin, and levofloxacin) on metabolism of other medications when taken together. This will be determined by the measuring the activity of drug metabolizing enzymes following administration of certain drug probes (caffeine, dextromethorphan, omeprazole, midazolam, and warfarin with vitamin K). A total of 16 subjects will complete four phases of the study: 1) Cooperstown 5+1 alone, 2) Azithromycin plus Cooperstown 5+1, 3) Telithromycin plus Cooperstown 5+1, and 4) Levofloxacin plus Cooperstown 5+1.