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Opium

Nicknames: ‘Big O’, ‘Chinese molasses’
Last reviewed: October 2026

Pharmacology

Opium exerts its effects through a synergy of natural alkaloids. The principal active component is morphine (typically 10–16% of raw opium weight), alongside codeine (0.5–2.5%), which act as agonists at µ-opioid receptors (MOR) throughout the brain and spinal cord.

Opium also contains non-analgesic alkaloids such as papaverine (a smooth muscle relaxant) and noscapine (a non-sedating cough suppressant), which modify the overall physiological response.

Upon entering the bloodstream, the active alkaloids cross into the central nervous system, binding to opioid receptors to inhibit pain signal transmission and elicit feelings of tranquility. Chronic use downregulates opioid receptors, creating dependence and withdrawal symptoms upon cessation. In excessive quantities, opioid-induced respiratory depression presents fatal risks, particularly if combined with other sedating substances.

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