Lean is a recreational polysubstance drink made by mixing prescription-strength cough syrup with a soft drink and often hard candy. The prescription syrup typically contains two active pharmaceutical ingredients: codeine, an opioid, and promethazine, an antihistamine. Codeine acts as the primary psychoactive agent, while promethazine enhances the sedative effects. The soda and candy are added to mask the bitter taste of the concentrated medication.
The Immediate Psychoactive Effects
The immediate effects of Lean stem from the rapid influence of codeine and promethazine on the central nervous system (CNS). Codeine is metabolized in the liver into morphine, which binds to mu-opioid receptors in the brain. This action triggers the release of dopamine, leading to euphoria, pleasure, and detachment from the surrounding environment. Promethazine, a powerful antihistamine, acts as a CNS depressant and significantly amplifies the opioid’s sedation. This combination induces extreme drowsiness, lethargy, and motor-skill impairment, which is the source of the term “lean.”
Acute Physical Risks and Overdose Potential
The most serious danger of using Lean is the potential for a fatal overdose, primarily driven by respiratory depression. Both codeine and promethazine slow the central nervous system, and high doses can cause breathing to become dangerously shallow or stop entirely. Respiratory arrest is the leading cause of death in opioid overdoses.
Acute non-fatal physical consequences include severe dizziness, pronounced drowsiness, and significant impairment of motor coordination. Users often experience extreme nausea and vomiting, which, combined with heavy sedation, raises the risk of aspiration, where vomit is inhaled into the lungs. The danger of respiratory failure is dramatically amplified when Lean is consumed alongside other CNS depressants, such as alcohol or benzodiazepines.
Development of Tolerance and Physical Dependence
Repeated use of Lean leads to neurobiological adaptations in the brain, initiating the cycle of tolerance and physical dependence. Tolerance develops as the brain adjusts to the constant presence of codeine, requiring the user to consume increasingly higher doses to achieve the initial euphoric or sedative effects. This escalating dosage dramatically increases the risk of accidental overdose.
Physical dependence occurs when the body adapts to functioning with the drug present, and its absence results in severe withdrawal symptoms. When a person abruptly stops using Lean, they can experience distressing physical symptoms like muscle aches, restless legs, and profuse sweating. Psychological symptoms are also common, including intense anxiety, agitation, and powerful drug cravings. This cycle of dependence on the opioid component is the defining factor in the development of an opioid use disorder.
Chronic Health and Organ Damage
Prolonged use of Lean can result in significant long-term physical damage. A common complication is severe chronic constipation, which occurs because the opioid component of codeine slows the movement of the gastrointestinal tract. In extreme cases, this effect can lead to a potentially life-threatening bowel obstruction.
The mixture’s high sugar content, combined with opioid-induced suppression of saliva production, creates an ideal environment for rapid and severe dental decay. The constant processing of high drug concentrations puts a strain on the body’s detoxification organs. This sustained stress can contribute to long-term liver or kidney damage, especially if the syrup contains acetaminophen or if the mixture includes alcohol.