The biofilms produced and maintained by Pseudomonas aeruginosa in the lungs of cystic fibrosis patients are difficult to treat and can have fatal effects. Antibiotics are necessary to control and eliminate these bacterial biofilms, but in vivo administration may not be the most effective means. Tobramycin, a commonly used antibiotic for treating cystic fibrosis patients, has been commercially developed into a solution that is inhalable via nebulizer. Inhaling this mist form of the antibiotic will allow administration of higher concentrations at the site of infection. The goal of this study was to develop a model using COMSOL Multiphysics to better understand the distribution of tobramycin to bacterial biofilms in the lungs. Like nearly all medications, tobramycin can become toxic at high concentrations. Since filtration from the blood stream is the only significant mechanism of tobramycin elimination, the kidneys are at the greatest risk for toxicity. Therefore the study focused on the possibility of maintaining safe blood serum concentrations while providing sufficient doses to inhibit the bacteria occupying the lungs. The model showed that the bacteria’s minimum inhibitory concentration was easily achievable throughout the biofilm while keeping the blood serum concentrations at a safe level.