Abuse Potential of Therapeutic Ketamine: Risk Stratification and Monitoring

Introduction: Navigating the Abuse Potential Paradox

The abuse potential of therapeutic ketamine presents a clinical paradox: a medication with established recreational misuse patterns and Schedule III controlled substance classification is being prescribed with increasing frequency for conditions -- depression, pain, and substance use disorders -- that themselves confer elevated vulnerability to substance misuse. Assessing the abuse potential of therapeutic ketamine requires distinguishing between the drug's inherent reinforcing properties, the clinical context in which it is administered, and the risk profiles of individual patients receiving treatment (Schak et al., 2016). Effective risk stratification and monitoring strategies are essential for maintaining the favorable benefit-risk profile observed in controlled clinical settings when extending ketamine therapy to broader clinical populations.

The regulatory framework surrounding ketamine reflects these concerns. Ketamine is classified as Schedule III under the Controlled Substances Act in the United States, indicating recognized medical use with moderate potential for physical and psychological dependence. The intranasal esketamine formulation (Spravato) received FDA approval with an accompanying Risk Evaluation and Mitigation Strategy (REMS) program mandating supervised administration and post-dose monitoring. Off-label racemic ketamine use, by contrast, operates without a standardized regulatory framework for abuse prevention, placing greater responsibility on prescribers to implement appropriate safeguards.

Pharmacological Basis of Abuse Potential

Reinforcing Properties

Ketamine's abuse potential derives from its capacity to produce reinforcing subjective effects -- including euphoria, dissociation, altered sensory perception, and feelings of detachment from distress -- mediated through NMDA receptor blockade and downstream modulation of dopaminergic, serotonergic, and opioidergic signaling (Morgan and Curran, 2012). In animal models, ketamine supports self-administration behavior, indicating positive reinforcement, though its reinforcing efficacy is lower than that of cocaine, amphetamine, or opioids (De Luca and Bhatt, 2017).

The subjective effects of ketamine that contribute to its abuse potential overlap with, but are not identical to, the effects hypothesized to mediate therapeutic benefit. The dissociative experience during infusion has been variably correlated with antidepressant response -- some studies find positive associations (Luckenbaugh et al., 2014), while others find no significant relationship (Ballard and Zarate, 2020). If dissociation is not required for antidepressant efficacy, strategies that minimize dissociative effects (lower doses, slower infusion rates, adjunctive medications) could reduce abuse potential without sacrificing therapeutic benefit.

Dopaminergic Mechanisms

Ketamine indirectly enhances dopaminergic neurotransmission in the mesolimbic reward pathway through NMDA receptor blockade-mediated disinhibition of VTA dopamine neurons and, at higher concentrations, through direct dopamine transporter inhibition (Nishimura et al., 1998). This dopaminergic enhancement contributes to the acute hedonic experience and the drug's positive reinforcement potential. The magnitude of dopaminergic stimulation is dose-dependent, with sub-anesthetic doses producing modest effects relative to the substantial dopaminergic stimulation produced by abused doses.

Tolerance and Dependence

Chronic ketamine exposure produces tolerance to both its subjective and analgesic effects, necessitating dose escalation to achieve equivalent experiences in recreational users. Tolerance development in therapeutic settings has been less consistently documented, with some long-term clinical studies reporting maintained efficacy without dose escalation (Cusin et al., 2017). Physical dependence -- characterized by a withdrawal syndrome upon cessation -- has been described in heavy recreational users, with withdrawal symptoms including anxiety, tremor, palpitations, and diaphoresis. The incidence of physical dependence following therapeutic sub-anesthetic exposure has not been systematically assessed but is expected to be substantially lower than in recreational populations (Morgan et al., 2012).

Risk Stratification

Patient Risk Factors

Identifying patients at elevated risk for ketamine misuse is essential for appropriate prescribing. Risk factors include:

High risk:

• Active substance use disorder (any substance other than nicotine)
• History of ketamine or dissociative drug misuse
• Active diversion behavior with other controlled substances
• Antisocial personality features or conduct disorder

Moderate risk:

• Substance use disorder in sustained remission (less than 2 years)
• Family history of substance use disorders
• History of alcohol use disorder
• Current use of benzodiazepines or opioids with evidence of dose escalation
• Borderline personality disorder (impulsivity features)

Lower risk:

• No personal or family history of substance use disorders
• Stable psychotropic regimen without controlled substance use
• Substance use disorder in sustained remission (greater than 5 years)
• Strong social support and treatment engagement

Assessment Tools

Structured instruments for substance abuse risk assessment include:

• Screener and Opioid Assessment for Patients with Pain-Revised (SOAPP-R): Validated for predicting aberrant medication-related behavior; applicable to ketamine risk assessment by analogy
• Drug Abuse Screening Test (DAST-10): Brief screening for current drug-related problems
• Alcohol Use Disorders Identification Test (AUDIT): Screening for alcohol misuse, a common comorbidity
• Prescription Drug Use Questionnaire (PDUQ): Assessment of behaviors suggestive of prescription drug misuse
• Structured Clinical Interview for DSM-5 (SCID-5): Comprehensive assessment of substance use disorder diagnoses

Monitoring Strategies

Structural Safeguards

Clinical program design can incorporate structural safeguards that reduce abuse potential:

• Supervised administration only: All ketamine doses administered in the clinical setting under direct medical observation. No take-home supplies for intravenous or intramuscular formulations.
• Inventory and documentation: Strict drug inventory management, documentation of each dose administered, and reconciliation protocols to prevent diversion.
• Urine drug screening: Baseline and periodic urine drug testing to detect undisclosed substance use. Ketamine-specific metabolite testing can identify patients who may be supplementing prescribed doses with recreational sources.
• Prescription monitoring programs: Checking state prescription drug monitoring programs (PDMPs) to identify concurrent controlled substance prescriptions and patterns suggestive of doctor-shopping.
• Treatment agreements: Written agreements outlining the terms of ketamine therapy, including expectations for compliance, monitoring requirements, and conditions for treatment discontinuation.

Take-Home Ketamine: Special Considerations

The prescribing of oral or sublingual ketamine for at-home use -- an increasingly common practice for depression -- introduces unique abuse potential concerns that are not present with clinic-based infusion models. Take-home formulations create opportunities for dose escalation, stockpiling, diversion to others, and concurrent use with other substances. Safeguards for take-home prescribing include:

• Prescribing limited quantities per dispensation (typically one to two weeks supply)
• Requiring regular in-person follow-up visits for refill authorization
• Random urine drug screening including quantitative ketamine/norketamine levels
• Pill/lozenge counts at follow-up visits
• Involving family members or support persons in monitoring when appropriate
• Establishing clear criteria for transitioning from take-home to supervised-only administration if concerns emerge

Behavioral Monitoring

Clinicians should monitor for behavioral indicators of problematic ketamine use:

• Requests for early refills or dose escalation beyond clinical indication
• Reports of "lost" or "stolen" medication
• Escalating frequency of treatment requests not explained by clinical deterioration
• Subjective emphasis on the acute experiential effects rather than sustained mood improvement
• Use of multiple prescribers or pharmacies
• Reluctance to engage in non-ketamine treatment modalities
• Positive urine drug screens for non-prescribed substances

Managing Patients with Comorbid Substance Use Disorders

The Clinical Tension

A significant clinical tension exists in managing patients with comorbid substance use disorders who might benefit from ketamine therapy. On one hand, the comorbid SUD population carries the highest risk for ketamine misuse. On the other hand, this population may derive particular benefit from ketamine's rapid-acting antidepressant and anti-craving effects, and categorical exclusion denies a potentially valuable treatment to a vulnerable group (Jones et al., 2018).

Evidence from Addiction Treatment Studies

Paradoxically, the ketamine-for-addiction literature provides some reassurance about the feasibility of administering ketamine to patients with active or remitted substance use disorders. Across published clinical trials of ketamine for alcohol, cocaine, and opioid use disorders -- populations with inherently elevated substance abuse risk -- no cases of emergent ketamine use disorder or problematic ketamine-seeking behavior have been reported (Dakwar et al., 2020). This suggests that the supervised, therapeutic context and the structured psychotherapeutic framework may mitigate abuse risk even in high-risk populations.

Risk Mitigation Strategies for SUD Patients

When ketamine therapy is considered for patients with comorbid SUDs:

• Require active engagement in SUD-specific treatment (counseling, mutual support groups, medication-assisted treatment)
• Administer ketamine exclusively in supervised clinical settings (no take-home formulations)
• Intensify monitoring with weekly substance use assessment and regular urine drug screening
• Involve addiction medicine specialists in treatment planning and monitoring
• Establish a priori discontinuation criteria (positive drug screens, missed appointments, behavioral concerns)

Comparison with Other Controlled Substance Prescribing

The risk management approach for therapeutic ketamine can be informed by established frameworks for other controlled substances with abuse potential prescribed in clinical settings -- including stimulants for ADHD, benzodiazepines for anxiety, and opioids for chronic pain. Each of these contexts involves prescribing an inherently reinforcing substance to populations that may include individuals at elevated misuse risk, and each has developed risk mitigation strategies (screening, monitoring, treatment agreements, supervised prescribing) that can be adapted for ketamine.

The abuse potential of sub-anesthetic ketamine, when administered in therapeutic contexts with appropriate safeguards, appears to be lower than that of prescribed opioids and comparable to or less than that of prescribed benzodiazepines (Schak et al., 2016). This comparison, while imperfect, provides clinical context for the level of monitoring and safeguarding that is proportionate to the risk.

Regulatory Framework Considerations

REMS Program for Esketamine

The esketamine REMS program provides a regulatory template for managed risk, requiring administration in certified healthcare settings, supervised by healthcare providers, with observation for a minimum of two hours post-administration. The program restricts dispensing to certified pharmacies and requires patient enrollment in a registry. These safeguards have been effective in preventing widespread diversion or misuse within the approved esketamine treatment population (FDA, 2019).

Generic Ketamine: Regulatory Gap

Off-label racemic ketamine lacks a comparable regulatory framework, creating a gap in standardized abuse prevention. The absence of REMS, the availability of compounded oral formulations for home use, and the lack of mandatory prescriber certification create conditions that may be more permissive of misuse than the esketamine model. Professional society guidelines (Sanacora et al., 2017) provide voluntary best-practice recommendations, but adherence is variable across clinical settings.

Conclusion

The abuse potential of therapeutic ketamine is a manageable but non-negligible safety concern that requires systematic risk stratification, structural safeguards, and ongoing behavioral monitoring. The inherent reinforcing properties of ketamine, combined with the vulnerability of many patients receiving treatment, necessitate a clinical approach that balances therapeutic access against abuse prevention. Evidence from clinical trials -- including studies in substance use disorder populations -- suggests that the supervised therapeutic context substantially mitigates abuse risk. Implementation of risk stratification tools, supervised administration protocols, take-home prescribing safeguards, and behavioral monitoring frameworks provides a comprehensive approach to maintaining the favorable safety profile of therapeutic ketamine while preserving access for patients who stand to benefit most.

References

• NIDA: National Institute on Drug Abuse — Federal research institute providing information on ketamine abuse potential and substance use disorder pharmacology
• DEA: Drug Scheduling — DEA resource on controlled substance classification including ketamine's Schedule III status
• PubMed: Ketamine Abuse Potential and Use Disorder — Review of ketamine's abuse liability profile and use disorder characteristics
• SAMHSA: Substance Abuse and Mental Health Services Administration — Federal agency providing substance abuse screening tools and treatment resources