A booster dose of MDMA prolongs the acute subjective drug effects compared with a single dose, without increasing peak effects. In a double-blind, randomized, placebo-controlled crossover study with 23 healthy volunteers, a 120 mg dose of MDMA followed by a 60 mg booster after 2 hours extended the duration of subjective effects to an average of 5.6 hours, versus 4.6 hours with a single dose. Adverse effects were more common after both MDMA conditions than placebo. Whether the prolonged effect translates into clinical benefit for MDMA-assisted psychotherapy remains unknown.
Bolus injections of DMT produce very strong subjective effects that peak within 2 minutes and subside completely within 12–30 minutes, consistent with a short elimination half-life of about 6–7 minutes. A ceiling effect for peak subjective effects occurred at the 15 mg dose, and no tolerance developed to the acute effects. Tolerability markedly improved when doses were escalated openly rather than given double-blind, and at equivalent doses the subjective effects were rated as less intense. These results indicate that blinding and expectancy influence the subjective experience and that individual dose-escalation may improve tolerability and guide dose selection in future DMT studies.