Influence of drug vehicle on ocular contact time of sulfacetamide sodium.

Sulfacetamide sodium drops and ointments were applied to the conjunctiva of patients and volunteers. Tear samples were taken and analyzed for sulfacetamide sodium content. The minimal inhibitory concentrations of the drug in para-aminobenzoic acid-free media were determined to be between 20 and 50 micrograms/mL against Escherichia coli and Staphylococcus aureus, and the effective concentrations of the sulfa were taken as 50 micrograms/mL. The concentration of sulfacetamide sodium in tears fell to the 50 micrograms/mL level in 30 minutes, two hours, and five and a half hours after the single application of 10 microL of 15% and 30% drops and 25 microL of all three ointments, respectively. The ocular contact time of the sulfa was increased by increasing the concentration of drug. The makeup of the three ointments differed greatly, yet the ocular contact time was similar.