An aqueous or powder composition includes anti-gram-negative antibiotic orsalt thereof being present at an amount ranging from about 100 mg/ml to about 200mg/ml. Another aqueous or powder composition includes anti-gram-positiveantibiotic or salt thereof being present at a concentration ranging from about0.6 to about 0.9 of the water solubility limit, at 25°C and 1.0 atmosphere,of the anti-gram-positive antibiotic or salt thereof. Other embodiments includeunit doses, kits, and methods.
