Subjective, or self-reported, responses to cocaine peak and decline more rapidly than those of methamphetamine, the study shows. Cardiovascular responses to the two stimulants are similar at onset but responses to cocaine decline more rapidly.
In press with the peer-reviewed journal Pharmacology, Biochemistry and Behavior, the study is the first to use identical procedures in measuring and comparing subjective and cardiovascular responses to the two stimulants.
"These differences help explain patterns of use by addicts. Methamphetamine users, for instance, report using the drug daily throughout each day, while cocaine users typically engage in binges that occur most often in the evening," said Dr. Thomas F. Newton, the study's principal investigator and a research scientist at the Semel Institute.
"In addition, the study results may impact development of medication treatments for addiction to these two very different stimulants," said Newton, a professor of psychiatry and biobehavioral sciences at the David Geffen School of Medicine at UCLA.
The study examined the onset, pattern and duration of the response to cocaine in 14 cocaine dependent volunteers and the response to methamphetamine in 11 methamphetamine dependent volunteers. None of the volunteers were seeking treatment.
Study volunteers reported subjective effects using a sliding rating scale ranging from 0, or "no drug effect," to 100, "most drug effect ever." Ratings were obtained just prior to administration of the drug and at regular intervals for 30 minutes following administration.
Heart rate and blood pressures were assessed using an automated device just prior to administration of the drug and at regular intervals for 60 minutes following administration.
The study was funded by the National Institute on Drug Abuse. Other members of the research team included Richard De La Garza II, Ari D. Kalechstein and Liam Nestor, all of UCLA's Semel Institute and Geffen School of Medicine.