Effect of Clonidine on Responses to Imagery Scripts

Background. Stress and exposure to drug-related cues (environmental stimuli previously associated with drug availability) are considered factors that increase the risk of relapse to heroin and/or cocaine use. The two factors may act through different neural mechanisms. Alpha-2 adrenergic agonists, such as clonidine, have been shown to block stress-induced relapse, but not cue-induced relapse, to heroin and cocaine self-administration in rodents. The ability of clonidine to attenuate stress- or cue-induced heroin and cocaine craving in drug abusers has not been tested. It is important to determine, in humans, whether clonidine blocks the acute effects of only one putative class of relapse precipitants, or whether its effects are more general.

Scientific goal. To compare the ability of clonidine to reduce stress-induced and cue-induced cocaine and heroin craving in drug abusers.

Participant population. A total of up to 160 drug abusers using cocaine, heroin, or both will be enrolled. Target enrollment will include 40% women and 60% minorities (mostly African-American).

Experimental design and methods. Participants will be randomized to one of three groups receiving clonidine 0.1 mg, clonidine 0.2 mg, or placebo orally under double-blind conditions. The study will consist of a single 5-6 hr experimental session in which there will be baseline measures, drug administration, and four script-guided imagery sets, each followed by a period of data collection. Three hours after dosing (when peak plasma clonidine concentrations are reached), participants will be exposed to four scripts: one stress-inducing, one describing drug cues, and two with neutral content. The standardized script-guided imagery procedure has previously been shown to reliably induce negative affective states (stress scripts) and/or craving (stress and drug-cue scripts) compared to the neutral scripts and to have internal and external validity (Tiffany and Drobes, 1990; Maude-Griffin and Tiffany, 1996; Taylor et al., 2000; Sinha et al., 1999, 2000, 2003; Singleton et al., 2003; Tiffany and Haekeneworth, 1991; Elash et al., 1995; Drobes and Tiffany, 1997; Taylor et al., 2000; Singleton et al., 2003). Outcome measures will include subjective ratings of drug craving and mood, autonomic response (galvanic skin response [GSR]), and endocrine responses (salivary cortisol and salivary ?-amylase, a measure of endogenous adrenergic activity during stress (Chatterton et al., 1996; Nater et al., 2005; van Stegeren et al., 2005)).

Benefits to participants and/or society. There are no direct benefits to participants. However, if clonidine is effective in blocking stress-induced and/or cue-induced craving, then the results will be used as a basis for designing a treatment trial, and drug abusers and society may benefit from the eventual use of clonidine or other alpha agonists for prevention of relapse in cocaine and heroin users. In addition, this research will provide information on the clinical relevance of a preclinical model of relapse, possibly strengthening arguments for its use in medication development.

Risks to participants. Participants may experience side effects from clonidine such as sedation and are expected to experience brief, mild psychological stress and drug craving from the laboratory script procedures. Prior to leaving the session, participants will be assessed for the presence of continued drug effects. If participants are experiencing any stress or craving at the end of the session, they will undergo a 10-minute guided relaxation session, which will be repeated until feelings of stress or craving dissipate, before being released from the laboratory. Participants may be kept longer than the planned session length, up to and including staying overnight on the inpatient ward, because of continued side effects or elevated stress or craving. If the MRP deems it medically necessary, participants will be sent to JHBMC emergency department for further evaluation and treatment.