Declassified: National Institutes of Mental Health "Addiction Research"

Dated 14 July 1954, this document outlines CIA experiments in tolerance to LSD at the Addiction Research Center in Lexington, Kentucky

"Our experiments on tolerance to LSD-25 have been proceeding well, although I continue to be somewhat surprised by the results, which to me are the most amazing demonstration of drug tolerance I have ever seen. I have seven patients who have now been taking the drug for more than forty two days. One of these patients receives 1 mcgm./kg. daily, four receive 1.5 mcgm/kg. daily, and two receive 2 mcgm/kg. daily. All seven are quite tolerant to both the physiological and mental effects of the drug. We have attempted to break through this tolerance by administering double, triple and quadruple doses..."

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