Disorders Due to Use of Other Specified Psychoactive Substances, Including Medications (ICD-11: 6C4E)

1. Introduction

Disorders due to use of other specified psychoactive substances, including medications, represent a growing diagnostic and therapeutic challenge in contemporary clinical practice. This category encompasses problems related to substance use that do not fit into classes traditionally recognized as alcohol, cannabis, opioids, or classic stimulants. It is a heterogeneous group that includes everything from plants with psychoactive properties such as khat, to prescribed medications that may be used inappropriately, such as antidepressants, anticholinergics, and antihistamines.

The clinical importance of this category has increased significantly in recent decades. Inappropriate use of prescribed medications has become a global public health concern, especially considering that many of these drugs are legally available and often not perceived as potential substances of abuse. Patients and healthcare professionals may underestimate the risks associated with prolonged use or excessive doses of apparently "safe" medications.

The prevalence of these disorders varies considerably among different regions and populations, reflecting cultural factors, substance availability, and medical prescribing practices. The impact on public health manifests through hospitalizations for intoxication, development of dependence, functional impairment, and costs associated with treatment.

Correct coding of these disorders is critical for health service planning, epidemiological monitoring, clinical research, and ensuring that patients receive appropriate treatment. The ICD-11 classification offers greater specificity and diagnostic clarity compared to previous versions, allowing better tracking and understanding of these emerging problems.

2. Correct ICD-11 Code

Code: 6C4E

Description: Disorders due to use of other specified psychoactive substances, including medications

Parent category: Disorders due to substance use

Official definition: Disorders due to use of other specified psychoactive substances, including medications characterized by the pattern and consequences of psychoactive substance use that are not included in the main classes of specifically identified substances. Examples include khat, antidepressants, medications with anticholinergic properties (e.g., benztropine) and some antihistamines.

This code was developed to fill an important gap in the classification of substance use disorders. Previously, many psychoactive substances did not have specific categorization, leading to underreporting or inadequate classification. ICD-11 recognizes that substances beyond those traditionally associated with abuse can cause clinically significant disorders.

Category 6C4E has eight subcategories that allow greater diagnostic specificity, reflecting different patterns of use, severity, and clinical manifestations. This hierarchical structure facilitates accurate documentation and allows health systems to identify specific trends related to different substances or patterns of use.

The explicit inclusion of medications in this category represents an important advance, recognizing that legitimately prescribed drugs can be subject to problematic use, whether through prolonged self-medication, use in doses higher than prescribed, or use for reasons different from the original therapeutic indications.

3. When to Use This Code

Code 6C4E should be used in specific clinical situations where the patient presents a problematic pattern of substance use not covered by other main categories. Below are detailed practical scenarios:

Scenario 1: Problematic use of sedative antihistamines Patient using diphenhydramine or hydroxyzine in increasing doses to induce sedation and sleep, developing tolerance and requiring progressively higher doses. The patient reports inability to stop use despite adverse effects such as daytime drowsiness, cognitive impairment, and falls. There is evidence of withdrawal syndrome with rebound insomnia and anxiety when attempting to stop.

Scenario 2: Anticholinergic dependence Individual with prolonged use of benztropine or biperiden beyond the original therapeutic indication, seeking euphoric or hallucinogenic effects. The patient presents substance-seeking behavior, neglect of responsibilities, and symptoms such as dry mouth, blurred vision, urinary retention, and mental confusion. There are failed attempts to reduce or discontinue use.

Scenario 3: Recreational use of khat Patient with an established pattern of chewing khat leaves, developing psychological dependence and functional impairment. Presents irritability, anxiety, and depressive symptoms when without access to the substance. There is negative impact on social relationships, work, and physical health (dental problems, gastrointestinal issues).

Scenario 4: Antidepressant abuse Inappropriate use of tricyclic antidepressants or selective serotonin reuptake inhibitors in doses higher than therapeutic, seeking sedative or other psychoactive effects. The patient obtains medications through multiple prescriptions or non-medical sources, presenting toxicity symptoms such as tremors, sweating, cardiac changes.

Scenario 5: Problematic use of nasal decongestants Patient developed dependence on topical nasal decongestants, using them continuously for months or years beyond the recommended period. Presents medication-induced rhinitis with rebound congestion, requiring use of the medication with increasing frequency. There is significant anxiety when without access to the medication and multiple failed attempts at discontinuation.

Scenario 6: Abuse of cough medications Recreational use of medications containing dextromethorphan in doses much higher than therapeutic, seeking dissociative or hallucinogenic effects. The patient presents a compulsive pattern of use, increasing tolerance, impairment of daily activities, and neuropsychiatric symptoms.

Essential criteria that must be present include: pattern of use that causes clinically significant impairment or distress, difficulty controlling use, persistence of use despite negative consequences, and the substance in question not being covered by other specific ICD-11 categories.

4. When NOT to Use This Code

The code 6C4E should not be used in several important situations that require different coding:

Substance use with specific codes: Do not use 6C4E for disorders related to alcohol (6C40), cannabis (6C41), synthetic cannabinoids (6C42), opioids (6C43), sedative-hypnotics (6C44), cocaine (6C45), stimulants including amphetamines (6C46), or hallucinogens (6C48). These substances have their own categories and should be coded specifically.

Appropriate therapeutic use of medications: When a patient uses medications as prescribed, even if experiencing side effects or expected physiological dependence (such as with corticosteroids), substance use disorder is not configured. Predicted physical dependence that is medically managed does not equate to substance use disorder.

Isolated acute intoxication: A single episode of intoxication without an established pattern of problematic use does not justify this diagnosis. Intoxication should be coded separately if clinically relevant.

Adverse drug reactions: Unwanted side effects from appropriately used medications should be coded as adverse drug reactions, not as substance use disorder.

Primary mental disorders: When psychiatric symptoms are not caused by substance use but represent independent mental disorders, use the appropriate codes for those disorders. The distinction can be challenging and requires careful evaluation of the temporal and causal relationship.

Experimental or occasional use: Sporadic use without development of a problematic pattern, dependence, or significant consequences does not constitute a disorder and should not be coded as such.

5. Step-by-Step Coding Process

Step 1: Assess diagnostic criteria

The first essential step is to confirm that the patient meets the diagnostic criteria for substance use disorder. Conduct a detailed clinical interview investigating:

Pattern of use: Frequency, quantity, duration of use, routes of administration, contexts of use
Impaired control: Failed attempts to reduce or stop, use in larger amounts or for longer periods than intended
Functional impairment: Impact on work, studies, family relationships, social activities
Risky use: Use in physically dangerous situations or despite physical or psychological problems caused or exacerbated by the substance
Dependence phenomena: Tolerance (need for increasing doses), withdrawal syndrome, craving (intense desire to use)

Utilize standardized assessment instruments when available, such as structured interviews or validated questionnaires for substance use disorders. Obtain collateral history from family members or other informants when possible, as patients frequently minimize problematic use.

Complementary tests may be useful: urine or blood toxicology to confirm recent use, laboratory tests to assess medical consequences (liver function, renal function, complete blood count), electrocardiogram if there is suspicion of cardiac effects.

Step 2: Verify specifiers

After confirming the diagnosis, determine relevant specifiers that characterize the disorder:

Severity: Mild, moderate, or severe, based on the number of criteria met and degree of functional impairment
Temporal pattern: Continuous versus episodic use, total duration of the disorder
Current status: Active use, early remission (1-12 months without problematic use), sustained remission (more than 12 months)
Specific characteristics: Presence of intoxication, withdrawal, substance-induced mental disorders

Identify the specific substance involved with maximum possible detail, as this guides treatment and prognosis. Document whether there is simultaneous use of multiple substances.

Step 3: Differentiate from other codes

6C40 - Disorders due to use of alcohol: Use when the problematic substance is specifically ethyl alcohol. The key difference is the substance itself. Alcohol has a distinct pattern of use, medical consequences, and therapeutic approach, justifying a separate category.

6C41 - Disorders due to use of cannabis: Reserve for problematic use of marijuana or products derived from the Cannabis sativa plant. It differs by being specifically natural cannabis, not synthetic, with a characteristic profile of effects and risks.

6C42 - Disorders due to use of synthetic cannabinoids: Apply when the problem involves synthetic cannabinoids (K2, Spice, etc.), not natural cannabis. The key difference is that synthetic cannabinoids frequently cause more intense and unpredictable effects than natural cannabis.

If the substance does not fit into any existing specific category and meets the criteria for substance use disorder, then 6C4E is appropriate. Always prioritize the most specific code available.

Step 4: Required documentation

Document adequately in the medical record:

Checklist of mandatory information:

Specific identification of the substance (generic and trade name if applicable)
Dose, frequency, and route of administration
Total duration of use and problematic use
Circumstances of initiation of use (medical prescription, self-medication, recreational use)
Specific diagnostic criteria met
Severity and specifiers
Documented medical, psychological, and social consequences
Previous attempts at cessation or treatment
Medical and psychiatric comorbidities
Risk assessment (suicide, violence, dangerous situations)
Proposed therapeutic plan

Record the clinical reasoning that led to the choice of code 6C4E, especially if there is diagnostic ambiguity. This facilitates continuity of care and case review.

6. Complete Practical Example

Clinical Case

A 42-year-old patient seeks medical care reporting severe insomnia and anxiety. During detailed evaluation, he reveals that approximately three years ago he started using diphenhydramine (first-generation antihistamine) to help with sleep, following a family member's recommendation. Initially he used 25-50mg occasionally with good effect.

He progressively increased the frequency and dose, currently using 200-300mg daily. He reports that without the medication he cannot sleep and experiences intense anxiety, mild tremors, and restlessness. He has attempted to stop three times in the last six months, but always resumes use after 2-3 days due to rebound insomnia and unbearable anxiety.

The patient obtains diphenhydramine through over-the-counter pharmacy purchases without prescription, spending significant amounts monthly. He reports that family members express concern about the use. At work, he presents with daytime somnolence, difficulty concentrating, and has made recent errors that he attributes to "mental confusion." He denies problematic alcohol use or other substances.

On physical examination: dry mucous membranes, mild tremor of extremities, slightly dilated pupils. Cognitively he presents with discrete slowing and subjective memory complaints. He denies hallucinations or delusions. Anxious mood, without suicidal ideation.

Basic laboratory tests without significant abnormalities. Electrocardiogram shows mild QT prolongation, possibly related to chronic antihistamine use.

Step-by-Step Coding

Criteria analysis:

The patient presents multiple criteria for substance use disorder:

Use in greater quantities and for a longer period than initially intended
Persistent and unsuccessful attempts to control use
Considerable time spent obtaining and using the substance
Evident tolerance (need for increasing doses)
Clear withdrawal syndrome (rebound insomnia, anxiety, tremors)
Continued use despite negative consequences (work problems, family concern)
Functional impairment in multiple areas

The substance involved is diphenhydramine, an antihistamine not included in the specific substance categories of ICD-11.

Code chosen: 6C4E - Disorders due to use of other specified psychoactive substances, including medications

Complete justification:

This code is appropriate because:

There is clinically significant substance use disorder with multiple criteria met
The substance (diphenhydramine) is an antihistamine medication that does not have a specific category in ICD-11
It does not fit 6C44 (sedative-hypnotics) since antihistamines are not classified in this category
It presents moderate to severe severity based on the number of criteria and degree of impairment
Current state of active use

Applicable complementary codes:

Code for insomnia, if it persists independently of diphenhydramine use
Code for anxiety disorder, if subsequent evaluation identifies primary anxiety disorder
Code for adverse effects of antihistamines (QT prolongation) if clinically significant

Therapeutic plan: Supervised gradual reduction of diphenhydramine, treatment of underlying insomnia with sleep hygiene and possibly other non-pharmacological interventions, anxiety management, cardiac monitoring, supportive psychotherapy, and regular follow-up.

7. Related Codes and Differentiation

Within the Same Category

6C40: Disorders due to use of alcohol

Use 6C40 when the problematic substance is specifically ethyl alcohol, regardless of the form of consumption (distilled beverages, fermented, etc.).

Main difference: The substance involved. Use 6C4E only when the substance is not alcohol. If there is concomitant problematic use of alcohol and another substance covered by 6C4E, code both separately.

6C41: Disorders due to use of cannabis

Apply 6C41 for problematic use of marijuana, hashish, or other products derived from the natural Cannabis sativa plant.

Main difference: 6C41 is specific to natural cannabis. Use 6C4E for other psychoactive substances. Some medicinal cannabis preparations may create ambiguity; in these cases, consider the source (natural cannabis plant = 6C41; other substances = 6C4E).

6C42: Disorders due to use of synthetic cannabinoids

Reserve 6C42 for synthetic cannabinoids such as K2, Spice, and similar chemical compounds that mimic cannabis effects but are artificially synthesized.

Main difference: 6C42 is exclusive to synthetic cannabinoids. Use 6C4E for other synthetic substances or medications that are not cannabinoids. The distinction is chemical and pharmacological, not merely legal.

Differential Diagnoses

Primary anxiety disorders: Patients with anxiety disorders may use medications inappropriately for symptomatic relief. Differentiate through history: did the anxiety disorder precede and exist independently of substance use? Are there complete criteria for substance use disorder? There is often comorbidity; code both when applicable.

Primary sleep disorders: Chronic insomnia may lead to self-medication with antihistamines or other sedatives. Assess whether there is an independent sleep disorder that requires specific treatment beyond substance use management.

Adverse drug reactions: Side effects of medications used as prescribed do not constitute substance use disorder. The key difference is the pattern of use: appropriate versus problematic, controlled versus compulsive.

Substance-induced psychotic disorders: Some substances covered by 6C4E (such as anticholinergics) may cause psychotic symptoms. If these are prominent, consider additional coding for substance-induced psychotic disorder.

8. Differences with ICD-10

In ICD-10, the closest category would be F19 - Mental and behavioral disorders due to multiple drug use and use of other psychoactive substances. This was a broad and less specific category.

Main changes in ICD-11:

ICD-11 offers greater specificity by clearly separating different substances into distinct categories. Code 6C4E is more focused on "other specified substances" rather than indiscriminately grouping multiple substances as frequently occurred in ICD-10.

The ICD-11 structure allows better documentation of specific substances through subcategories and code extensions, facilitating epidemiological tracking of emerging substances or specific medications.

ICD-11 also incorporates diagnostic criteria more aligned with contemporary scientific evidence, including recognition that physiological dependence does not necessarily equate to substance use disorder when it occurs in appropriate therapeutic context.

Practical impact: Professionals accustomed to ICD-10 need to adapt to the greater granularity of ICD-11, investing time to identify the most specific code. Health systems can track trends with greater precision, identifying emerging problems with specific substances. Researchers have more internationally comparable data.

The transition requires adequate training of coders and clinicians to fully leverage the specificity offered by ICD-11.

9. Frequently Asked Questions

How is the diagnosis of disorders due to specified psychoactive substance use made?

The diagnosis is essentially clinical, based on detailed interview that investigates pattern of use, consequences, and dependence symptoms. The professional evaluates criteria such as impaired control over use, functional impairment, risky use, tolerance, and withdrawal. Complementary tests such as toxicology can confirm recent use, but the diagnosis fundamentally depends on clinical history. Collateral information from family members is valuable, as patients frequently minimize problems. Standardized instruments such as structured questionnaires can assist, but do not replace comprehensive clinical evaluation.

Is treatment available in public health systems?

The availability of treatment varies considerably among different regions and health systems. Many public systems offer services for substance use disorders, including assessment, detoxification when necessary, psychotherapy, and follow-up. However, resources may be limited and waiting lists are common. Specific treatments depend on the substance involved; for medications such as antihistamines or anticholinergics, the focus is generally supervised gradual reduction, treatment of underlying conditions, and psychotherapy. Mutual support groups are also important resources and often free.

How long does treatment last?

Duration varies widely depending on the substance, severity of the disorder, comorbidities, and individual response. Supervised detoxification may take days to weeks. Structured psychological treatment often lasts 3-6 months, but can be more prolonged. Maintenance follow-up to prevent relapse may continue for years. Severe disorders with multiple relapses may require intermittent or continuous long-term support. There is no "standard" duration; treatment should be individualized and adjusted according to clinical evolution. Sustained remission is possible, but requires commitment and frequently multiple interventions.

Can this code be used in medical certificates?

Yes, ICD-11 codes can be used in medical documentation including certificates, when clinically appropriate and necessary. However, consider confidentiality and stigma issues. In many jurisdictions, information about substance use disorders has special privacy protections. For work absence certificates, it may be sufficient to use more general categories without specifying substance use disorder, unless essential. Discuss with the patient what will be documented and to whom. Always balance the need for accurate documentation with protection of privacy and minimization of stigma.

Can prescribed medications really cause dependence?

Yes, various prescribed medications have the potential to cause dependence when used inappropriately or, in some cases, even when used as prescribed for prolonged periods. Sedative antihistamines, anticholinergics, some antidepressants, and many others can lead to psychological or physical dependence. It is important to distinguish expected physiological dependence (as with corticosteroids or some antidepressants) from substance use disorder, which involves a problematic pattern with functional impairment. Responsible prescribing, regular monitoring, and patient education are essential to minimize risks.

What is the difference between problematic use and physiological dependence?

Physiological dependence refers to bodily adaptations to the chronic presence of a substance, manifesting as tolerance and withdrawal symptoms when the substance is discontinued. This can occur with appropriate therapeutic use of various medications. Substance use disorder (problematic use) is a more comprehensive diagnosis that includes a compulsive pattern of use, loss of control, use despite negative consequences, and functional impairment. One can have physiological dependence without substance use disorder (example: patient using corticosteroid as prescribed) or substance use disorder without significant physiological dependence.

How to differentiate therapeutic use from medication abuse?

Therapeutic use is characterized by: medication prescribed by a qualified professional, use according to medical guidance (dose, frequency, duration), objective of treating a legitimate medical condition, regular medical monitoring, absence of compulsive drug-seeking behavior. Abuse involves: use without prescription or beyond prescription, excessive doses, use for reasons other than therapeutic indication (seeking euphoria, recreational sedation), obtaining through multiple prescribers or illicit sources, continuation despite negative consequences, loss of control over use. The distinction is not always clear; some cases begin as therapeutic use and evolve to problematic.

Is there risk of relapse after successful treatment?

Yes, relapse is common in substance use disorders, occurring in a significant proportion of patients even after successful treatment. This does not represent failure of treatment or the patient, but reflects the chronic and recurrent nature of these disorders. Risk factors include stress, exposure to environmental triggers, untreated psychiatric comorbidities, lack of social support, and premature discontinuation of follow-up. Preventive strategies include development of coping skills, identification and management of triggers, treatment of comorbidities, maintenance of therapeutic and social support, and action plan for high-risk situations. Relapse should be viewed as an opportunity for learning and adjustment of the therapeutic plan, not as definitive failure.

Conclusion

The ICD-11 code 6C4E represents an important advance in the classification of substance use disorders, offering a specific category for psychoactive substances and medications not covered by other classifications. Accurate coding requires clear understanding of diagnostic criteria, knowledge of the substances involved, and ability to differentiate from other related categories. Health professionals should be alert to the potential for problematic use of apparently safe medications, recognizing that legitimate prescription does not eliminate the risk of disorder development. Adequate documentation, individualized treatment, and compassionate approach are essential for effective management of these complex and often underdiagnosed disorders.

External References

This article was developed based on reliable scientific sources:

References verified on 2026-02-03

Disorders due to use of other specified psychoactive substances, including medications

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