Evaluation of the stability of frusemide in intravenous infusions by reversed-phase high-performance liquid chromatography

Abstract A rapid, flexible method based on ion-pair reversed-phase high-performance liquid chromatography is described for the separation and quantitation of frusemide and its principal hydrolysis product, saluamine, in the presence of potential contaminants, photolytic products and other degradants. The method is stability-indicating and has been shown to be applicable to the determination of frusemide and saluamine in injectable forms of frusemide. Response was linear both for frusemide (0−50 jug/ml; r = 0.9999) and saluamine (0−10 μ g/ml; r = 1.0000). The on-column sensitivity of the assay was 1.3 ng frusemide and 1.1 ng saluamine. The method was applied to intravenous admixtures of frusemide and in studies on the effect of heat and/or light stress on other intravenous dosage forms. The saluamine assay was found to be sufficiently sensitive to monitor low levels of degradation of frusemide in the absence of photolytic degradation. When frusemide injection was transferred to a polypropylene syringe for slow intravenous injection and stored at room temperature unprotected from light for 24 h, the level of frusemide degradation, as indicated by saluamine, remained at 0.2%, which was within the 1% compendial limit of saluamine in frusemide. When used as an additive in Compound Sodium Lactate Injection BP (Hartmann's Solution) or Sodium Chloride Injection BP 0.9% w/v, frusemide injection was stable for 24 h without protection from light. An autoclaved infusion of frusemide was stable for 10 weeks at room temperature when protected from light. A preliminary investigation of photolytic degradation of frusemide indicated a fall in pH of 3 units, precipitation and the presence of a number of uncharacterized photolytic degradation products. A number of impurities were detected in Saluamine BP Chemical Reference Substance.