While effective, codeine commonly causes several adverse reactions: Codeine - StatPearls - NCBI Bookshelf - NIH
: Effectiveness varies significantly between individuals. Some are "ultra-rapid metabolizers" who convert codeine too quickly, leading to potentially toxic morphine levels, while others may feel no effect at all because their bodies cannot process the drug. codeine
: It is often paired with non-opioids like acetaminophen or ibuprofen to enhance pain relief through synergistic effects. Common Side Effects leading to potentially toxic morphine levels
Codeine is a "prodrug," meaning it is relatively inactive until it is metabolized in the liver. An enzyme called converts codeine into morphine, which then acts on the brain's opioid receptors to block pain signals and produce feelings of relaxation or pleasure. codeine