Radioimmunoassay of cannabinoids in blood and urine.

A radioimmunoassay (R.I.A.), using a sheep antiserum and 3-H-T.H.C., has been developed for the measurement of tetrahydrocannabinol (T.H.C.) in plasma and urine. The antiserum cross-reacts with T.H.C. metabolites, but nevertheless possesses sufficient group specificity and sensitivity to permit measurement of cannabinoids in plasma and urine of animals and volunteers following the administration of pure T.H.C. Subjective effects experienced by the volunteers seemed to correlate with plasma-T.H.C. levels. The examination of random plasma urine samples collected from patients attending a drug-addiction clinic revealed the presence of measurable amounts of cannabinoids in several of them.