This document discusses opioids, including their definition, classification, pharmacokinetics, pharmacodynamics, pharmacotherapeutics, adverse effects, and drug interactions. Opioids are natural or synthetic compounds that bind to opioid receptors in the central nervous system and gastrointestinal tract, mediating both beneficial and undesirable effects. They are classified as natural opiates from the opium poppy, semi-synthetic opiates created from natural opioids, fully synthetic opioids, and endogenous opioid peptides produced in the body. Opioids are prescribed to relieve severe pain but can cause adverse effects like respiratory depression, nausea, constipation, and dependence with chronic use.