Turbidimetric latex agglutination inhibition immunoassay for primidone

We have developed a quick, highly sensitive immunoassay method for drugs by latex agglutination inhibition. An antiserum against primidone (PRM) was obtained by immunizing rabbits with PRM-bovine serum albumin conjugate. PRM-rabbit serum albumin conjugate sensitized latex was agglutinated with diluted antiserum, and the agglutination was inhibited by free PRM quantitatively. Turbidity of the agglutination suspension was measured by spectrophotometry as absorbance. Larger latex gave higher sensitivity than the smaller, because its agglutination was inhibited more intensely by free PRM. The assay values of this method were correlated well with those obtained by an enzyme immunoassay method.