Highly Specific Radioimmunoassay for the Measurement of Caffeine in Saliva

摘要

Using a tritiated (3H) caffeine tracer and a murine monoclonal anti-caffeineantibody, we developed a radioimmunoassay (RIA) for the detection of caffeine (1,3,7 trimethylxanthine) in saliva. The assay shows <2% cross reactivity with theophylline and avoids interference from anti-mouse immunoglobulin (IgG) constituents found in serum but not in saliva. Saliva caffeine represents the unbound (biologically active) fraction of the drug. Assay values correlate well (r=.44, p<.05) with oral caffeine doses between 150 and 400 mg. The half-life of salivary caffeine of about six hours, based on the elimination curve for the subjects who received 400 mg, agrees with previous measurements of its half-life in serum. Caffeine, Saliva, Radioimmunoassay, Half-life.