Prospective Clinical Drug-Drug Interaction study between Rifampicin and Fusidic Acid

For many years, two oral antibiotics, rifampicin (RifadinTM) and fusidic acid (Fucidin TM), have been used effectively in combination in Australia for patients with serious staphylococcal infections. These antibiotics are important as they are one of the few antibiotic combinations available to treat staphylococcal infections resistant to other antibiotics. These antibiotics are known to affect the levels of other drugs that a person might be taking at the same time, however very little is known about how they affect the levels of each other. This study involves taking blood samples from people being treated with rifampicin and fusidic acid and measuring levels of these antibiotics in the blood at different times to see if they affect the levels of each other. Identifying how these antibiotics affect each other could help doctors use these antibiotics in a better way in the future to treat patients and reduce side-effects. Our hypothesis is that there is a drug-drug interaction between rifampicin and fusidic acid but with currently used dosing in Australia, drug levels are appropriate for most patients. We hypothesize that some patients may have elevated or decreased drug levels of one or both drugs and the knowledge of this may be able to help improve treatment for patients in the future.