Fluorimetric determination and pharmacokinetic studies of fazadinium bromide in dogs.

A rapid fluorimetric method for the estimation in biological fluids of the neuromuscular-relaxant drug 1,1'-azobis-3-methyl-2-phenyl-1H-imidazo-[1,2-a]-pyridinium dibromide (fazadinium bromide, AH 8165) is described. The drug is hydrolized by alkali to give 3-methyl-2-phenyl-1H-(1,2-a)-imidazo-pyridinium bromide, which is extracted by cyclohexane and measured for fluorescence. Intravenous administration (1 mg/kg) in dogs gives initial blood levels of unchanged drug of 4.34 +/- 0.25 microgram/ml. The decay of serum concentrations is rapid. The extent of urinary excretion of unchanged drug is 15% within 6 h.