conducted a study in which six volunteers were administered 30 mg d-methamphetamine from a pipe that was heated to approximately 300°C. Blood samples and physiological and subjective measures were collected after drug administration. Plasma methamphetamine concentrations rose rapidly after the start of smoking. However, concentrations plateaued (40 to 44 ng/mL) after 1 h with a slight increase in concentration over the next 1h. Thereafter, concentrations in plasma declined slowly, reaching the same concentration at 8 h on the downward side of the curve as reached at 30 min on the upward side. The authors used a noncompartmental model to determine an average elimination half-life of 11.7 h with a range of 8 to 17 h. These authors also administered methamphetamine (0.250 mg/kg) orally and the resulting plasma data were fit to a one compartment model with first order elimination and a lag time. A maximum plasma concentration of 35 to 38 ng/mL was achieved at 3.1 h with a terminal elimination half-life of 10 h. Although the plasma concentration time curves for smoked and oral methamphet-amine appeared similar, the subjective effects were markedly different, with a greater "high" being reported after smoked methamphetamine. This indicates that it may be the rate of change of plasma drug concentrations that is a significant factor in determining subjective effects.
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