Figure 1. Ascorbic acid and pyruvate stabilize tigecycline in saline solution.

Tigecyline (1 mg/mL) was dissolved in saline solution with or without supplementation with various excipients and incubated in the light. Tigecycline concentrations were detected over time by HPLC and expressed as a relative percentage of that detected immediately following fresh dilution in saline ( = 100%). Tigecycline was dissolved in (A) saline with or without 0.6 mg/mL ascorbic acid, 6 mg/mL pyruvate, 50 mg/mL 2-hydroxypropyl-β-cyclodextrin (HPCD), 0.3 U/mL Oxyrase with 20 mM sodium lactate, 6 mg/mL EDTA sodium, 5% (w/v) glucose, 5% (w/v) mannitol, 10% (v/v) ethanol, 10 mM sodium phosphate (Na-PO₄) buffer pH 6.9, or 10 mM sodium bicarbonate (Na-HCO₃) buffer pH 6.8; (B) saline containing 0–30 mg/mL ascorbic acid; or (C) saline containing 0–300 mg/mL pyruvate; (D) Iscove's modified Dulbecco's medium (IMDM). In all panels, data indicate the mean ± standard deviation of 3 independent experiments.