Emergent Care / Stabilization:
Acute toxicity with methamphetamine presents with a sympathomimetic toxidrome. Due to its ability to release biogenic amines and produce psychomotor agitation, patients can manifest with hyperthermia, tachycardia, and hypertension. Central nervous system (CNS) effects include agitation, hallucinations, and seizures. Psychosis occurs more often with intoxication with methamphetamines than with other stimulants such as cocaine. Cardiopulmonary toxicity can manifest with dysrhythmias, acute myocardial infarction, aortic dissection, and acute respiratory distress syndrome (ARDS). Rhabdomyolysis and acute kidney failure are also potential complications of toxicity.

Patients with acute toxicity from methamphetamine should be treated with active cooling if hyperthermic and with benzodiazepines. Antipsychotics, including haloperidol, have been used as adjuvant therapy, but their risk of lowering the seizure threshold should be considered. Benzodiazepines remain the first-line agent in the treatment of methamphetamine toxicity. Intravenous (IV) hydration and cardiovascular monitoring should be instituted, with a goal urine output of 1-2 mL/kg/h for those with rhabdomyolysis, which occurs more often in a hyperthermic patient.

Diagnosis Overview:
Amphetamine was first marketed in 1932 as the nasal decongestant Benzedrine, and both amphetamine and methamphetamine were provided to soldiers during World War II as a stimulant. Abuse of this stimulant is reported as early as 1940, with the US Controlled Substance Act of 1970 naming amphetamine as a Schedule II substance.

Methamphetamine, or meth, is an illicit stimulant and sympathomimetic drug. It has the addition of an extra methyl group to amphetamine, which makes it more lipid soluble and allows faster penetration across the blood-brain barrier. It is available in a crystal, powder, and pill form, but its most common route of administration is intranasal (ie, snorted), which has a longer duration of action. Peak serum concentrations occur within 15 minutes when used via IV or intranasally. It is known by multiple street aliases, namely speed, ice, chalk, crystal, and crank.

Methamphetamine hydrochloride (Desoxyn) is a pharmaceutically available product for the treatment of attention deficit hyperactivity disorder (ADHD). It has some utility as a short-term anti-obesity medication.

Methamphetamine use disorder refers to the illicit use of methamphetamines as a drug of abuse. Methamphetamine use leads to a release of dopamine, norepinephrine, and serotonin and, to a lesser extent, the inhibitor of their reuptake. Intoxication results in a hyperalert, energetic state characterized by feelings of euphoria and increased libido. In overdose and toxicity, the leading causes of death are cardiovascular and cerebrovascular in origin. Insomnia, agitation with paranoia, psychosis, dry mouth with tooth decay, cognitive / memory impairment, and cardiomyopathy are also associated with chronic methamphetamine use.

The use of methamphetamines as an illicit drug of abuse is increasing in prevalence both in the United States and worldwide. An estimated 2% of the US population has used methamphetamines. Between 2015 and 2019, one study found a 300% increase in methamphetamine use in people aged 18-23 years. The Midwestern and Western regions have particularly high rates of abuse. Individuals with underlying psychiatric disorders, mood disorders, and ADHD are at increased risk for developing methamphetamine use disorder. Use disorder is associated with little education, early age of drug use, and underlying disability. Recent studies also report riskier use patterns with the coadministration of heroin and fentanyl. The addition of opioids has increased morbidity and mortality in this patient population.

The development of methamphetamine use disorder with compulsive use from first use is rapid. It is estimated that it can take less than 2 months to develop cravings and develop regular use patterns.

Methamphetamine use disorder, or amphetamine-type substance use disorder, falls under the category of stimulant use disorder in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and combines the former concepts of methamphetamine abuse and methamphetamine dependence into a single diagnostic concept ranging from mild to severe.

Methamphetamine use often results in high-risk sexual practices, increasing risk of pregnancy and sexually transmitted diseases. Studies have found a higher use pattern in men who have sex with men, with the potential for increased HIV transmission. Chronic use can predispose individuals to infections secondary to dental decay or IV drug use and subsequent septic shock with multiorgan failure. Users are also at risk for cardiovascular disease often driven by hypertension, tachyarrhythmia, or vasospasm, including myocardial ischemia, arterial dissection, cardiomyopathy, rhabdomyolysis, and cerebrovascular injury either due to hemorrhage or ischemia. Methamphetamines can function as a direct neurotoxin causing irreversible neuronal injury that may contribute to cognitive impairment associated with long-term use.

Methamphetamine is highly addictive with rapid-onset abstinence symptoms that contribute to the high rate of illicit abuse. Overdose can be fatal. With the increasingly common use of the combination with opioids, overdose fatalities are increasing.

Patients with this disorder may have an increased risk of various general medical conditions.

Methamphetamine use is associated with increased early mortality, with cardiac complications being the leading cause of death (eg, acute myocardial ischemia, aortic dissection, malignant hypertension).