The present disclosure encompasses pharmaceutically acceptable antimicrobial compositions of an amount of levulinic acid and sodium dodecyl sulfate effective in reducing the microbial population of an internal cranial cavity of a recipient human or animal subject. The disclosure also provides methods for reducing a microbial population of an internal cranial cavity of a recipient human or animal comprising contacting the oral cavity or sinuses of the subject with a composition comprising between about 0.5% to about 5% by weight per volume of levulinic acid and between about 0.05% to about 2% by weight per volume of sodium dodecyl sulfate (SDS) and for a period effective in reducing a microbial population of the oral cavity.