@article {SPECTOR253, author = {SYDNEY SPECTOR}, title = {QUANTITATIVE DETERMINATION OF MORPHINE IN SERUM BY RADIOIMMUNOASSAY}, volume = {178}, number = {2}, pages = {253--258}, year = {1971}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {The haptenic group morphine was coupled to a protein and the conjugate possessed immunogenic properties. The method for preparing the carboxymethylmorphine protein conjugate is described. Evidence is presented for the formation of antibodies with specificity for the alkaloid as demonstrated by precipitin reaction and by binding of dihydromorphine-8H by the antisera. The details of a simple and convenient procedure for the immunoassay of morphine in plasma are described in this report. The absolute sensitivity of the radioimmunoassay in serum was 50 to 100 pg of morphine in a final assay mixture of 0.5 ml. Levels of morphine in serum from four rats given morphine sulfate (5 mg/ kg i.v.) showed a biphasic decay curve. The first phase had a T1/2 of approximately 50 minutes, whereas the second phase had a T1/2 of 6.8 hours. {\textcopyright} 1971 by The Williams \& Wilkins Co.}, issn = {0022-3565}, URL = {https://jpet.aspetjournals.org/content/178/2/253}, eprint = {https://jpet.aspetjournals.org/content/178/2/253.full.pdf}, journal = {Journal of Pharmacology and Experimental Therapeutics} }