Thin-layer densitometric determination of muzolimine (BAY g 2821), a structurally new diuretic drug, at the nanogram level in biological fluids.

A sensitive and specific thin-layer densitometric method was developed for the determination of muzolimine (BAY g 2821), a structurally new diuretic drug of the pyrazolinone type. For detection of the drug on thin-layer chromatographic plates, a colour reaction with 4-dimethylaminocinnamaldehyde is carried out. The detection limit was 50 pg per spot on commercially available silica gel 60 plates. A nearly linear relationship between integrated peak area and amount per spot was obtained in the range from 100 pg to 1 mug per spot. For quantitative determination in biological fluids, a recovery of about 100% is achieved by a single extraction with dichloromethane, and the extract is spotted directly on to the plate. The detection limit of muzolimine in plasma and urine was 1 ng/ml, and inaccuracy in the nanogram range was found to be 5-8%. The assay was applied to pharmacokinetic studies and can be recommended for monitoring plasma levels of muzolimine in patients.