The Importance of Clinical Abuse Potential (CAP) Studies

Perspectives from Michael Brennan, MD

As a practicing pain clinician, I am committed to supporting my patients and working to create treatment plans that meet their unique clinical needs. For some patients living with chronic pain, prescription opioid medications are an important component of a multidisciplinary pain management plan. However, in all interactions with patients where opioids are being considered, one must always be aware of the possibility of prescription drug misuse, abuse, addiction, and diversion.

As such, it’s important for physicians to implement comprehensive strategies to help reduce the risk of abuse and misuse. Moreover, each stakeholder such as patients, pharmaceutical companies, insurers and the patient’s family plays an important role in this aspect of pain management.

The Food and Drug Administration (FDA) recognizes this and is encouraging the development of opioid medications with technologies intended to make prescription drug abuse more difficult. These formulations are referred to as abuse deterrent technologies. The goal of these formulations is to help mitigate the risk of abuse by one of several strategies. Evaluation of the effectiveness of any abuse deterrent opioid formulation, will in part be through a new type of testing many are not familiar with: clinical abuse potential studies, or CAP studies.

What is a Clinical Abuse Potential (CAP) Study?

First, it is important to recognize that many classes of pain medications have the potential to be abused. For example, opiates-mainstays of pain management-have a long history of abuse, and in fact are a major concern now in the United States as a cause of serious health consequences. Clinical Abuse Potential studies, also known as human abuse potential studies, human abuse liability (HAL) studies, or “drug-liking” studies, attempt to evaluate and quantify the abuse liability or abuse potential for certain prescription drugs.5

Why are CAP studies conducted?

These studies provide information on the relative abuse potential of medications in classes considered abuseable.5 Companies developing new opioid-based pain medications with abuse-deterrent formulations may conduct these studies as part of product development. For abuse deterrent formulations, these studies are conducted to obtain an understanding of the impact of the specific abuse deterrent technology on the product’s abuse potential.5

How are CAP studies conducted?

These studies are usually conducted among experienced, recreational drug users who have a recent or current history of using a drug in the pharmaceutical class of the test drug. These studies are typically double-blind, double-dummy, placebo-controlled, and positive-comparator controlled, utilizing a crossover design.5

How are study participants chosen?

For the study to be interpretable, the subjects should be able to reliably report “drug­-liking” of the test drug and rate the effects of the test drug compared with placebo and with the positive control, such as an immediate-release formulation.5

How is “drug-liking” measured?

Several instruments have been used to measure the potential for abuse including overall drug-liking, abuse, and likelihood of using the drug again.5 Key instruments include5:

  • Visual Analogue Scales (VAS) – a 100-point bipolar scale that measures drug liking, good effects or euphoria, bad effects or adverse events, and likelihood of repeated use


  • Profile of Mood States

How do CAP studies impact product labeling?

When abuse deterrence is proven or expected to lead to a substantial reduction in abuse potential, the data are included in the product labeling. The FDA has designated categories of labeling that correspond to premarket studies, including CAP studies, required to assess abuse potential, and postmarket studies that assess clinical outcomes.5

Not all abuse deterrence technologies are created equal, and no one technology can eliminate the risk of abuse and misuse.5 However, these evolving technologies are a step in the right direction as part of a larger effort to address the prescription drug abuse epidemic and its impact on our society. Whether one is a physician, a person affected by chronic pain, an advocate for pain care, or a supply chain partner, all stakeholders have a role to play in mitigating the risk of abuse and misuse and promoting responsible pain management.

Watch a short video to learn more about abuse deterrence technologies or read more about advancements in abuse deterrence.

About the Author: Michael Brennan, MD

Michael J. Brennan, MD, is Senior Attending Physician at Bridgeport Hospital and Assistant Clinical Attending Physician at St. Vincent’s Hospital in Bridgeport, CT. In addition, he has a private practice in physical medicine and rehabilitation that specializes in the diagnosis and management of acute and chronic pain syndromes, electrodiagnosis, and cancer-related disabilities.

Michael J. Brennan, MD, serves as a paid consultant for Teva Pharmaceuticals.

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