1. Determination of furosemide in urine samples by direct injection in a micellar liquid chromatographic system
S. Carda-Broch, J. Esteve-Romero, M. J. Ruiz-Angela and M. C. García-Alvarez-Coque*. Analyst, 2002, 127, 29–34
Photochemical degradation of aqueous and methanolic solutions of furosemide under the influence of UV radiation has been reported by several workers. In acidic solution, rapid degradation takes place. Furosemide seems to undergo photooxidation, photohydrolysis and photodechlorination. At high temperature, furosemide is hydrolysed to 4-chloro-5-sulfamoylanthranilic acid (CSA) and furfuryl alcohol, which is quickly converted into levulinic acid (Fig. 1). The degradation may be even faster if sulfate ion is present, as in normal urine. Urine is usually weakly acidic and may be made more acidic by the action of furosemide.16 In contrast, in alkaline solution, furosemide has been reported to show high stability. However, in humans, furosemide is metabolized to its acylglucuronide,18 which is unstable in alkaline media; therefore, urine has been recommended to be kept acidic at pH 5 for analysis in order to prevent the hydrolysis and isomerisation of this metabolite. Beermann et al. found no evidence of furosemide degradation in the upper digestive tract after analysing gastrointestinal aspirates and that furosemide was stable when incubated in gastric or duodenal juice, bile or urine for up to 2 h.
2. Carbonic anhydrase inhibitors. Sulfonamide diuretics revisited—old leads for new applications
Claudia Temperini, Alessandro Cecchi, Andrea Scozzafava and Claudiu T. Supuran*. Org. Biomol. Chem., 2008, 6, 2499–2506
But what is the relevance of this study for the drug design of CAIs with diverse pharmacological applications? We think that there are at least several aspects that need to be considered here for answering this question. First, these widely used drugs were considered to be inactive as CAIs, due to the fact that they were launched in a period when only CA II was well known (and considered to be responsible for all physiological effects of CAIs). It may indeed be observed that in contrast to the classical CAIs of type 1–5 (generally low nanomolar CA II), all compounds 6–12 (except furosemide 11)aremuch weaker inhibitors of this isozyme, usually in themicromolar range. Indeed, only furosemide 11 is a good CA II inhibitor among these diuretics, with a Ki of 65 nM, whereas all others show Ki sinthe range of 138–6980 nM (Table 1). Again with the exception of furosemide 11, the diuretics 6–12 have low affinity for CA I, the other isoform known when these drugs were discovered.
3. Mono- and dinuclear Ru(II) complexes of 1,4-bis(3-(2-pyridyl)pyrazol-1-ylmethyl)benzene): Synthesis, structure, photophysical properties and electrochemiluminescent determination of diuretic furosemide
Qiao-Hua Wei,* Yan-Fang Lei, Ya-Nan Duan, Fan-Nan Xiao, Mei-Jin Li and Guo-Nan Chen*. Dalton Trans., 2011, 40, 11636–11642
Furosemide, 5-(aminosulfonyl)-4-chloro-2-[(2-furanylmethyl)-amino]benzoic acid, has been used to treat excessive ﬂuid accumulation and swelling of the body caused by heart failure, cirrhosis, chronic kidney failure, and nephrotic syndrome. Furosemide has long attracted the attention of many analysts because of its extensive use as a powerful diuretic. A variety of analytical methods have been proposed for the determination of furosemide, such as coulometric titration, electrochemical detection, spectrophotometry, ﬂuorescent detection, liquidmchromatography, and chemiluminescent detection. To our best knowledge, no ECL method has been reported for the determination of furosemide.
4. A new mechanistic approach to elucidate furosemide electrooxidation on magnetic nanoparticles loaded on graphene oxide modified glassy carbon electrode
Mohammad Hasanzadeh, Mohammad Hossein Pournaghi-Azar, Nasrin Shadjouc and Abolghasem Jouyban*. RSC Adv.,2014, 4,6580–6590
Monitoring of furosemide was requested in drug quality control and therapeutically drug monitoring investigations. Several methods have been used for the determination of furosemide in pharmaceutical formulations and biological fluids. Chromatography (especially LC/MS/MS) is now widely and routinely used for the analysis of furosemide. Chromatographic analyses are generally performed using expensive instruments. It requires extensive labor and analytical resources, and often results in a lengthy turn-around time. Given the low cost, ease of use, and sensitivity, electrochemical techniques are alternative methods for determining furosemide. But, surveying the literature revealed that electrochemical methods have been rarely applied to determination of pharmaceutical furosemide in serum and urine samples. Therefore, development of simple, sensitive, rapid and reliable electrochemical methods/sensors for the determination of furosemide is of great importance.