After oral administration, lysergic acid diethylamide (LSD) reaches peak plasma concentrations of 1.3 ng/mL (100 µg dose) and 3.1 ng/mL (200 µg dose) within about 1.5 hours, with a plasma half-life of 2.6 hours. Subjective effects last 8 to 12 hours depending on dose, and peak effects occur around 2.5 to 2.8 hours after ingestion. A close relationship exists between LSD concentration and subjective response within individuals, but no correlation was found between plasma levels and effects across different people at peak concentration. The effects are related to changing plasma concentrations over time, without evidence of acute tolerance.
A 19-year-old male was admitted to the emergency department with severe hallucinations, dilated pupils, rapid heart rate, agitation, and confusion after using a substance sold as 2C-B. Laboratory analysis using liquid chromatography-mass spectrometry detected the more potent synthetic phenethylamine derivative 2C-P instead. Based on two blood samples, the estimated elimination half-life was 19 hours. The case illustrates how small structural variations in the 4 position of the phenyl ring, such as a propyl group in 2C-P versus bromine in 2C-B, can lead to significant differences in drug potency and duration of action, contributing to adverse effects.