This is a PK study of a multi-dose oral cefixime regimen (three 800 mg doses given on a q 8-hour schedule) alone and also co administered with a single 1000 mg oral dose of azithromycin, both within a 24-hour period, in order to achieve total serum cefixime levels of mcg/mL for at least 20 hours. This will determine the tolerability of the regimen and whether there are significant changes in cefixime PK after co-administration. The primary pharmacokinetic objectives are: to determine if a cefixime dosing regimen of three 800 mg doses given alone, on a q 8-hour schedule achieves a total serum cefixime level that exceeds 2.0 mcg/mL for at least 20 hours; to determine if a cefixime dosing regimen of three 800 mg doses given on a q 8 hour schedule co-administered with a single 1000 mg of azithromycin, achieves a total serum cefixime level that exceeds 2.0 mcg/mL for at least 20 hours; and to evaluate whether a single 1000 mg dose of azithromycin alters the PK of a three dose regimen of 800 mg cefixime given on a q 8-hour schedule. The primary safety objectives are to assess the safety and tolerability of a treatment regimen that includes three doses of 800 mg cefixime; to assess the safety and tolerability of a treatment regimen that includes three doses of 800 mg cefixime co-administered with a single 1000 mg dose of azithromycin. The study will take place for 10 weeks.