Role of intravenous cloxacillin for inpatient infections

One of the issues of antibiotic treatment is to warrant its optimal effectiveness while minimizing the risk for emergence of resistance. The time above minimal inhibiting concentration (MIC) (T>MIC) is the best predictive pharmacological parameter of effectiveness for antibiotics with time-dependent activity, such as cloxacillin. Cloxacillin is the first line antibiotic in a great number of clinical situations generated by methicillin sensitive staphylococci, because of its intrinsic properties: bactericidal effect, tissue distribution and safety. The most recent anti-staphylococcal agents do not improve treatment of MSSA infections compared to penicillin M and especially cloxacillin. Cloxacillin has a narrow microbiological spectrum. This ecological feature is in line with the recommendation to use antibiotics with the narrowest spectrum to reduce the pressure of selection. The consensus is to have T>MIC for at least 40% of the dosing interval and is achieved by infusing 2g of cloxacillin per day (T>MIC=50%) or four infusions of 3g per day (T>MIC=42%) in adults.