Cannabinoids

Tetrahydrocannabinol (THC) is the main psychoactive agent in the leaves of cannabis (marijuana) plants. Many synthetic cannabinoids have been recently developed. Cannabis is the most commonly used illicit drug in the United States; almost 20 million Americans currently consume cannabis. People who use cannabis may experience relaxation, euphoria, and mild hallucinogenic effects. Some may experience nausea and vomiting after use. Synthetic cannabinoids have been associated with more serious complications. Cessation after regular use may result in drug craving, insomnia, anorexia, and restlessness. Metabolites of THC can be detected in the urine up to 1 month after last use; some medications can cause false-positive tests. Serious medical complications of cannabis use are uncommon; the most concerning are neuropsychological problems among adolescent users and acute cognitive and motor impairment. Synthetic cannabinoid use is associated with significant neuropsychological effects. Psychosocial modalities appear to help those who wish to stop or reduce use. There are no medications that have been shown to be effective.

Nicotine and Tobacco

Nicotine is responsible for the psychoactive and habit-forming effects of tobacco. Approximately 30% of Americans use tobacco products; half of them are nicotine-dependent. Nicotine has mild stimulant effects. Overdose is rare in experienced users. Some may develop nausea, vomiting, weakness, and dizziness. Withdrawal symptoms include craving, irritability, anxiety, restlessness, and increased appetite. Smokers have elevated exhaled carbon monoxide and serum carboxyhemoglobin levels. Cotinine, a metabolite of nicotine, can be detected in blood and urine. Many medical conditions are associated with tobacco use (particularly smoking), including cardiovascular disease, chronic lung disease, and a variety of malignancies. A number of interventions can help increase smoking cessation rates, including physician advice, counseling, nicotine replacement, varenicline, and bupropion. Electronic cigarettes may help smokers quit or reduce their smoking.

Psychiatric Co-Occurring Disorders

Substance use disorders commonly co-occur with psychiatric disorders. Psychiatric illnesses are associated with substance use disorders. Recognition of psychiatric symptoms, especially suicidal ideation, is essential. Factors such as substance use or withdrawal, related psychosocial stressors, and co-occurring somatic health problems complicate the diagnostic process. Addressing psychiatric symptoms is essential to optimize treatment of substance use disorders. Medications can help but may be unnecessary once substance use is stabilized. Other approaches include counseling, psychotherapy, case coordination, and inpatient/residential care. The affective disorders, especially bipolar disorder, are associated with substance use disorders. Depression is common and often improves with addiction treatment. For those who do not improve, antidepressant medication or psychotherapy may help. Anxiety disorders and post-traumatic stress disorder are associated with substance use disorders. If left unaddressed, persistent worry and anxiety worsen treatment outcomes. Although there are effective pharmacotherapies, psychotherapeutic approaches are a mainstay of treatment. Schizophrenia is particularly disabling and associated with an increased risk for substance use disorders. Antipsychotic medications can be effective, but persistent “negative” symptoms warrant comprehensive, supportive approaches with sufficient ancillary services. Those with personality disorders have high rates of substance use disorders and can be a challenge to treat. A strong team-based approach, psychosocial treatments, and sometimes medications can improve outcomes. Those with attention-deficit/hyperactivity disorder are at increased risk for substance use disorders. Impairing symptoms of inattention and impulsivity may persist into adulthood, complicating substance use disorder treatment engagement and outcomes. Medications can be helpful, but care must be taken when considering prescribing stimulants.

Prescription Drugs

A variety of prescription and over-the-counter drugs are used for purposes other than intended. Approximately 2% of Americans report current nonmedical use of a prescription drug. Opioids are the class most commonly used for purposes other than intended. Other drugs include sedatives (primarily benzodiazepines); stimulants; and a variety of agents, including clonidine, muscle relaxants, tricyclic antidepressants, bupropion, antiemetics, gabapentinoids, and atypical antipsychotics. Over-the-counter drugs associated with nonmedical use include dextromethorphan, loperamide, and antihistamines. The most prominent risk factor for nonmedical use is a history of a substance use disorder. A number of aberrant behaviors are indicative of nonmedical use. Screening instruments may help gauge risk. The most serious complication is overdose, particularly opioid overdose. Strategies to address nonmedical prescription drug use include limiting the prescribing of controlled substances, monitoring patients who are prescribed these medications, and providing treatment for those who have a substance use disorder.

Hallucinogens and Dissociatives

Hallucinogens, also referred to as psychedelics, are a broad range of agents that alter perception in different ways. An estimated 1.3 million Americans are current (past month) users of hallucinogens. Hallucinogen use is highest among young adults; 3,4-methylenedioxymethamphetamine (MDMA) is the most commonly used agent, followed by lysergic acid diethylamide (LSD) and phencyclidine (PCP). Hallucinogens alter sensory perception and change the qualities of thought or emotion. PCP, MDMA, and LSD can be detected in urine drug tests. There appear to be few serious lasting complications associated with hallucinogen use. There are few data on the treatment of individuals who use hallucinogens or dissociatives.

Stimulants

Stimulants are sympathomimetic substances that include cocaine, amphetamines, and cathinones. Approximately 1% of Americans have used illicit stimulants in the past month, and nearly 25,000 deaths were attributed to stimulant overdose in 2017. Acute effects include tachycardia, elevated blood pressure, and euphoria. High doses of stimulants may lead to cardiac arrhythmias, severe hypertension, agitation, myocardial infarction, aortic dissection, stroke, hyperthermia, or rhabdomyolysis. Abstinence after regular use of stimulants may lead to dysphoria, fatigue, insomnia, and agitation. People who use stimulants may present with acute effects or medical complications. Cocaine metabolites and amphetamines can be detected in urine for a few days after use. The most serious complications of acute use are cardiovascular (especially myocardial infarction and stroke) and psychiatric (agitation and delirium); the risk of hyperthermia is also increased. A number of psychosocial modalities appear to reduce stimulant use among selected individuals, including individual and group counseling, cognitive–behavioral therapy, contingency management, and community reinforcement. No medication has been consistently shown to reduce complications and use of stimulants, although prescription stimulants and topiramate show some promise for treating cocaine use disorder. Syringe exchange programs and safe consumption sites are associated with decreased stimulant use-related complications. Caffeine has mild stimulant effects and may lead to a mild dependence syndrome.

Introduction

The use of a variety of psychoactive substances is common, and substance use disorders are responsible for a tremendous amount of preventable morbidity and mortality. Addiction is increasingly understood as a chronic disorder that involves a complex interplay of genetics, physiology, environment, and behavior. A range of terms and definitions are used when describing these disorders. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders provides criteria for “substance use disorders.” The other major source of terminology and diagnostic criteria is the World Health Organization’s International Classification of Diseases, 10th revision, which divides this into “harmful use” and “dependence syndrome.”

Medical Care for Patients with Substance Use Disorders

Primary care clinicians commonly encounter patients with substance use disorders and can provide effective treatment for their problems. Many of the medical complications associated with drug use are due to the use of needles; these include transmission of HIV and hepatitis C, soft tissue infections, and endocarditis. Harm reduction strategies reduce the harms associated with drug use without targeting use itself; these include syringe distribution, safe consumption facilities, naloxone distribution, and pre-exposure HIV prophylaxis. Patients on opioid agonist treatment may develop a number of problems, including hypogonadism, constipation, and psychomotor impairment; those on methadone may develop prolonged QT syndrome. Other issues include drug interactions, treatment of acute pain, and perioperative care. Treating pain in patients with substance use disorder can be complicated; for many, especially those with opioid use disorder, treatment with buprenorphine or enrollment in methadone maintenance is the best option.

Opioids

Opioids are a class of drugs that include heroin and prescription pain relievers that produce analgesia and euphoria. More than 2 million Americans have an opioid use disorder. Acute effects include analgesia, respiratory depression, miosis, and euphoria. Overdose is a serious complication of opioid use, characterized by depressed level of consciousness and respiratory depression. It can be treated with naloxone. Withdrawal symptoms include dysphoria, yawning, tearing, diarrhea, cramps, nausea, and piloerection. Buprenorphine, methadone, clonidine, and lofexidine can be used to ameliorate the symptoms of withdrawal. However, supervised withdrawal alone rarely leads to long-term abstinence. There are a number of psychosocial treatments, including self-help groups, outpatient therapy, and residential treatment; the data on their effectiveness are limited. Pharmacotherapy with an opioid agonist (methadone or buprenorphine) is the most effective treatment. Long-acting injectable naltrexone, an opioid antagonist, is also effective, but it is more difficult to initiate.

Ethical and Legal Considerations

Providing care to individuals with substance use disorders raises legal and ethical issues. The two major legal issues are regulation of scheduled drugs and patient confidentiality. Many patients make poor choices; nevertheless, all deserve medical care incorporating the principles of ethical care. General ethical principles apply to the treatment of substance use disorders. These include autonomy, beneficence, nonmaleficence, justice, fidelity, and futility. Treatment of individuals with substance use disorders may create situations in which there is conflict or disagreement with clinicians. Effective strategies can help avoid or mitigate dilemmas. Drug testing, employment, and pregnancy raise specific legal and ethical issues.