[Radioimmunoassay of n-butylbiguanide in human serum].

A radioimmuno assay for butylbiguanide in human serum is described. The detection limit is 1.5 ng per assay tube, the intra assay variance 3 percent, and the inter assay variability 12 percent. Antibodies to the biguanide group were obtained by immunizing rabbits with p-carboxy-phenethyl-biguanide coupled to bovine serum albumin. The affinity of the antibodies for tyrosine, urea, guanidine, butylbiguanide, phenethyl-biguanide, and p-hydroxy-phenethyl-biguanide is shown by competitive binding studies. The recovery rate is 100 percent.