A slow-release silicone pellet for chronic amphetamine administration.

A slow release amphetamine pellet consisting of a silicone capsule containing d-amphetamine base in polyethylene glycol is described. When implanted s.c. in rats this pellet produces brain levels initially comparable to an i.p. dose of 2 mg/kg of d-amphetamine sulfate; these levels gradually fall but appreciable amphetamine remains present in the brain for over 10 days. Rats implanted with these pellets exhibit sustained motor stereotypies and constant hyperactivity in stabilimeters for 2-3 days. Four days after implantation activity declines to near control levels even though amphetamine is still present in the brain. During this later stage rats show exaggerated startle responses and resist handling. This pellet is a unique tool for the study of the behavioral and physiological effects of prolonged amphetamine intoxication.