A new study, published March 14 in Antimicrobial Agents and Chemotherapy, suggests that oxacillin (brand name Bactocill) may be safer than nafcillin (Unipen, Nallpen). Both drugs are antibiotics commonly prescribed in hospitals to treat methicillin-susceptible Staphylococcus aureus (MSSA) infections.
Researchers at the University of Pittsburgh Medical Center analyzed clinical and laboratory records of 224 patients who had received either antibiotic for at least 24 hours.
Half of all patients taking nafcillin developed low potassium, which may lead to abnormal heart rhythms, as compared to 17 percent of those on oxacillin. Nearly 18 percent of patients receiving nafcillin showed altered kidney function, which may lead to kidney damage, compared to about 6 percent of patients on oxacillin.
Adverse events forced discontinuation of treatment in 18 percent of patients on nafcillin, as compared to only 2 percent of those on oxacillin.
Current guidelines, now called into question, recommend both antibiotics as first-line treatments for MSSA infections — without preference for either.
Grants from the National Institutes of Health funded this research. The authors disclosed no conflicts of interest.