Stability of cefatrizine in aqueous solution and in sera

Cefatrizine (SK & F 60771; BL--S640), like most other phenylglycine-type cephalosporins, has a tendency to lose potency in aqueous solutions and in normal sera even at low temperatures. Cefatrizine can be stabilized during storage by sodium metabisulphite (Na2S2O5), a reducing agent partially in tap water, better in deionized water, and to a lesser degree in citric acid-phosphate buffer (pH 6). Although this partial stabilizing effect of sodium metabisulphite is temperature-dependent, storage at 4 degrees C gives better results than storage in the frozen state (-20 degrees C). In these aqueous solutions and in sera, the potency of cefatrizine can be preserved even at room temperature for up to four weeks by the addition of 0.1 ml of 2 N hydrochloric acid to each 2 ml of aqueous solutions or sera.