When it comes to clinical studies, particularly those examining human abuse potential (HAP), the way participants are selected and recruited is crucial. These studies are designed to evaluate whether a substance, such as a new medication or drug, has the potential to be abused for its psychoactive effects. To conduct these studies ethically and effectively, researchers must carefully select and recruit participants in a way that ensures valid results, while still protecting their safety and well-being.

The Importance of Participant Selection

HAP studies are typically required for any new centrally-acting drug, commonly conducted as single-dose, double-blind, placebo and active-controlled, randomized crossover studies, in individuals who “recreationally” use drugs.  Because researchers want to understand how different populations might respond to a substance in terms of its psychoactive or “subjective” effects and potential for abuse, participant selection becomes critically important.

Researchers focus on recruiting people who have a history of substance use but who are not dependent or “addicted” to drugs of abuse in HAP studies. Potential participants must have non-therapeutic experience with the drug class that is associated with the positive control drug; these drugs are typically opioids, stimulants, sedatives, or hallucinogens. Subject experience increases the face validity of the study, as participants represent those who might be expected to abuse the test drug once available in the community. In addition, inclusion of these participants increases the sensitivity of the studies and decreases the risk of study failure, namely, the failure of the positive control drug to separate from placebo.

Not everyone with a history of substance use is appropriate for every study. Researchers must balance the need for participants with relevant experience against ensuring that the study remains ethical and safe. For example, someone with a moderate-to-severe substance use disorder would not be selected for most studies, as participation could pose a risk to the subject’s recovery. While physically dependent subjects might be appropriate for some specialty studies, such as “opioid challenge studies,” these individuals may have different physiological responses than others, often requiring more intensive inpatient care and maintenance treatment.

The Recruitment Process

Recruitment needs to be transparent, respectful, and free from coercion. Recruitment in HAP studies at DVCR involves reaching out to participants in our active database who have previously been involved in similar studies. Our database contains thousands of volunteers with recreational experience in different drug classes associated with abuse, such as opioids, stimulants, sedatives, and hallucinogens. Recruitment may be supplemented by advertising through various channels, such as social media, radio, or television.

Study Enrichment

To make sure that HAP studies are well powered and produce reliable data, participants are tested in a pre-study “qualification” phase, to make sure that they can report appropriate responses to the study drugs. Because the key outcomes in HAP studies assess how much participants like the study drug, those who don’t use drugs recreationally are not preferable, as they may not report positive responses to drugs of abuse. In this early enrichment of the drug testing process, potential participants receive a test dose of the positive control and placebo in a randomized, double-blinded, crossover manner; their responses are then reviewed to confirm that they have shown appropriate responses. It is critical that experienced reviewers select participants who will provide robust data, as those later found to be unreliable will have to be dropped from the study analysis, decreasing the power of the study, wasting resources, and placing participants at unnecessary risk.

Ethical Considerations

Ethics are at the heart of participant selection and recruitment. Ensuring participants are treated with respect, dignity, and care is non-negotiable. Studies must minimize all potential harms and protect participants’ privacy. In HAP studies specifically, it is essential that researchers carefully consider the psychological impact that participating in the study might have due to histories of substance use.

Participants are housed in DVCR’s state-of-the-art clinical pharmacology unit to enhance retention and to mitigate other recreational drug use. As participants may be in the clinic for up to eight, or even ten weeks at a time, it is essential that the unit provides a safe, comfortable, and engaging environment.  DVCR’s high level of customer service and the clinical pharmacology unit’s extensive amenities lead to unparalleled participant retention in these operationally complex studies.

Conclusion

DVCR’s selection and recruitment processes in HAP studies are designed to provide valuable data while safeguarding participants’ health and well-being. By selecting the right participants and ensuring an ethical and transparent recruitment process, sponsors can assess the safety and abuse potential of their products effectively.