Abuse liability testing plays an important role in informing drug development, regulatory processes, and clinical practice. This paper describes the current "gold standard" methodologies that are used for laboratory assessments of abuse liability in non-human and human subjects. Particular emphasis is given to procedures such as non-human drug discrimination, self-administration, and physical dependence testing, and human dose effect abuse liability studies that are commonly used in regulatory submissions to governmental agencies. The potential benefits and risks associated with the inclusion of measures of abuse liability in industry-sponsored clinical trials is discussed. Lastly, it is noted that many factors contribute to patterns of drug abuse and dependence outside of the laboratory setting and positive or negative signals in abuse liability studies do not always translate to high or low levels of actual abuse or dependence. Well-designed patient and physician education, pharmacovigilance, and postmarketing surveillance can reduce the diversion and misuse of drugs with abuse liability and can effectively foster the protection and promotion of public health.

Rationale: Primary treatment of obstructive sleep apnea can be accompanied by a persistence of excessive sleepiness despite adherence. Furthermore, effectiveness of sleep apnea treatment is limited by poor adherence. Currently available pharmacologic options for the treatment of sleepiness in this population are limited. Objectives: To evaluate the efficacy and safety of solriamfetol (JZP-110), a selective dopamine and norepinephrine reuptake inhibitor with robust wake-promoting effects, for the treatment of excessive sleepiness in participants with obstructive sleep apnea with current or prior sleep apnea treatment. Methods: This was a double-blind, randomized, placebo-controlled, parallel-group, 12-week trial comparing solriamfetol, 37.5, 75, 150, and 300 mg, with placebo. Measurements and Main Results: Of 476 randomized participants, 459 were included in the prespecified efficacy analyses. Coprimary endpoints (Maintenance of Wakefulness Test sleep latency and Epworth Sleepiness Scale score) were met at all solriamfetol doses (P , 0.05), with dose-dependent effects observed at Week 1 maintained over the study duration. All doses except 37.5 mg resulted in higher percentages of participants reporting improvement on Patient Global Impression of Change (key secondary endpoint; P , 0.05). Adverse events were reported in 47.9% of placebo-and 67.9% of solriamfetol-treated participants; five participants experienced serious adverse events (two [1.7%] placebo, three [0.8%] solriamfetol); none were deemed related to study drug. The most common adverse events with solriamfetol were headache (10.1%), nausea (7.9%), decreased appetite (7.6%), anxiety (7.0%), and nasopharyngitis (5.1%). Conclusions: Solriamfetol significantly increased wakefulness and reduced sleepiness in participants with obstructive sleep apnea and excessive sleepiness; most adverse events were mild or moderate in severity. Clinical trial registered with www.clinicaltrials.gov (NCT02348606) and www.eudract.ema.europa.eu (EudraCT 2014-005514-31).

Objective Solriamfetol (JZP‐110) is a selective dopamine and norepinephrine reuptake inhibitor with wake‐promoting effects. This phase 3 study (NCT02348593) evaluated the safety and efficacy of solriamfetol in narcolepsy. Methods Patients with narcolepsy with mean sleep latency <25 minutes on the Maintenance of Wakefulness Test (MWT), Epworth Sleepiness Scale (ESS) score ≥10, and usual nightly sleep ≥6 hours were randomized to solriamfetol 75, 150, or 300 mg, or placebo for 12 weeks. Coprimary endpoints were change from baseline to week 12 in MWT and ESS. Improvement on the Patient Global Impression of Change (PGI‐C) was the key secondary endpoint. Results Safety and modified intention‐to‐treat populations included 236 and 231 patients, respectively. Solriamfetol 300 and 150 mg were positive on both coprimary endpoints. Least squares mean (standard error [SE]) changes from baseline were 12.3 (SE = 1.4) and 9.8 (SE = 1.3) minutes for solriamfetol 300 and 150 mg on the MWT, respectively, versus 2.1 (SE = 1.3) minutes for placebo, and −6.4 (SE = 0.7) for 300 mg and −5.4 (SE = 0.7) for 150 mg on the ESS versus −1.6 (SE = 0.7) for placebo (all p < 0.0001). At week 12, higher percentages of patients treated with solriamfetol 150 mg (78.2%) and 300 mg (84.7%) reported PGI‐C improvement relative to placebo (39.7%; both p < 0.0001). Adverse events ≥5% across all solriamfetol doses included headache (21.5%), nausea (10.7%), decreased appetite (10.7%), nasopharyngitis (9.0%), dry mouth (7.3%), and anxiety (5.1%). Interpretation Solriamfetol has the potential to be an important therapeutic option for the treatment of impaired wakefulness and excessive sleepiness in patients with narcolepsy. ANN NEUROL 2019;85:359–370.

GHB is used therapeutically and recreationally, although the precise mechanism of action responsible for its different behavioral effects is not entirely clear. The purpose of this review is to summarize how behavioral procedures, especially drug discrimination procedures, have been used to study the mechanism of action of GHB. More specifically, we will review several different drug discrimination procedures and discuss how they have been used to qualitatively and quantitatively study different components of the complex mechanism of action of GHB. A growing number of studies have provided evidence that the behavioral effects of GHB are mediated predominantly by GABA B receptors. However, there is also evidence that the mechanisms mediating the effects of GHB and the prototypical GABA B receptor agonist baclofen are not identical, and that other mechanisms such as GHB receptors and subtypes of GABA A and GABA B receptors might contribute to the effects of GHB. These findings are consistent with the different behavioral profile, abuse liability, and therapeutic indications of GHB and baclofen. A better understanding of the similarities and differences between GHB and baclofen, as well as the pharmacological mechanisms of action underlying the recreational and therapeutic effects of GHB, could lead to more effective medications with fewer adverse effects.