A Wayne State University School of Medicine researcher has secured a substantial grant from the National Institute on Drug Abuse to fund a study that focuses on behavioral modification for cocaine abusers.
Mark Greenwald, Ph.D., director of the Substance Abuse Research Division and chief of the Human Pharmacology Laboratory in the Department of Psychiatry and Behavioral Neurosciences, will use the $890,000 over two years to investigate a non-drug reward system to combat cocaine addiction.
"As we develop cocaine treatment medications, it is critical to recognize that no medication will be universally effective. No 'magic bullet' is likely to be found or adhered to by patients," Dr. Greenwald said. "Non-medication factors such as environmental conditions and individual differences will constrain the efficacy of any medication. Thus, tests of cocaine medications need to be conducted in synchrony with behavior therapies also taking into account individual differences in order to understand the mechanisms of interaction and potential boundary conditions of a medication's efficacy."
The study, Dr. Greenwald said, will develop a human laboratory model of behavioral "contingency management" treatment with cocaine abusers who are not seeking treatment and are thus more resistant to changing their drug abuse behavior. Contingency management is based on the idea that non-drug rewards such as financial incentives or vouchers are earned when the patient provides evidence of drug abstinence, like a cocaine-free urine sample. The process, he said, is generally more effective when rewards are delivered immediately, are larger and increase in value with repeated evidence of drug abstinence.
A newer form of contingency management arranges for drug-abstinent patients to draw in a lottery style for chances to earn prizes. The magnitude and probability of rewards may encourage continued abstinence, Dr. Greenwald said.
"In this laboratory model, we will investigate the relative importance of magnitude and probability of non-drug rewards in reducing actual cocaine-seeking behavior," he said. "Subjects will be given opportunities to make choices between various cocaine and money options under medically safe and scientifically controlled experimental conditions. The results will enable us to determine the scientific basis for the efficacy of this behavioral treatment approach. It will also enable us to make preliminary recommendations on how to combine this behavioral approach with medications to optimize treatment outcomes.
"We expect to find that higher- versus lower-magnitude, and higher- versus lower-probability monetary rewards will significantly reduce cocaine-seeking," Dr. Greenwald added. "We also experimentally vary the 'price' of cocaine (i.e. the response requirement the subject has to complete to earn a unit dose) when subjects choose between cocaine and money options. We expect increasing price to reduce demand for (choice of) cocaine. We will also evaluate whether drug price interacts with non-drug (money) reward magnitude and probability to influence cocaine seeking."
The study also will evaluate the effects of selected individual factors (severity of cocaine dependence and level of pre-experimental cocaine use) on the data. "It's important to study multiple influences on the data because cocaine abuse is a complex problem that is often resistant to change," said Dr. Greenwald, who noted that this information could ultimately be used to tailor treatments according to the individual.
The reward system for cocaine abusers will mirror an earlier study in at least one aspect. In that experiment, Dr. Greenwald identified about a dozen "hardcore" heroin addicts who spent at least $40 per day on the drug. The addicts were placed on the heroin substitute buprenorphine, and had to report for urinalysis three times a week. Their levels of buprenorphine were decreased over the course of several weeks. If they tested negative for heroin use for consecutive days, they received a check for $30. The majority of those who received the reward for remaining "clean" stayed off of heroin longer, even though their physical environment and acquaintances did not change. Dr. Greenwald believes that the $30 "reward" somehow became more valuable in the minds of the addicts than the need for heroin or a substitute.
Those initial findings, he said, may lead to tailored treatment for addicts. Some may need a shorter course of rehabilitation and contact with those providing treatment to successfully abandon drug habits. Others may be identified in the opening rounds of rehabilitation as needing more intensive treatment or longer contact with healthcare providers for successful rehabilitation.
Dr. Greenwald expects the research to involve up to 16 cocaine abusers, but will need to screen about 100 people to find subjects to complete the study. All the subjects screened, including those who are excluded from the laboratory study for medical or psychiatric reasons, will provide clinical information, and will be asked to provide blood for genotyping that will be used for additional scientific purposes.