Theophylline radioimmunoassay: synthesis of antigen and characterization of antiserum.

Antisera to theophylline (T) have been obtained by immunizing rabbits with a conjugate of 8-(3-carboxypropyl)-1,3-dimethylxanthine and bovine serum albumin. Comparison of 50% displacement values indicated good selectivity for T vs. a number of other xanthine derivatives. An analytical procedure using this antiserum can measure 200 pg of T and direct analysis of 0.1 mug/ml in plasma or 0.02 mug/ml in saliva is feasible.