ATC Group: N02AA Natural opium alkaloids

Dihydrocodeine is a semisynthetic narcotic analgesic with a potency between morphine and codeine. It is also a centrally-acting anti-tussive. Dihydrocodeine works on the cough centre to lessen the incidence and intensity of coughing fits.

Hydromorphone is an agonist of mu receptors. The pharmacological actions of hydromorphone and morphine do not differ significantly. Hydromorphone and related opioids produce their major effects on the central nervous system and bowel. Hydromorphone is indicated for the relief of severe pain in cancer.

Morphine is a narcotic analgesic obtained from opium. Morphine acts as an agonist at opiate receptors in the CNS particularly Mu and to a lesser extent Kappa receptors. Mu receptors are thought to mediate supraspinal analgesia, respiratory depression and euphoria, and Kappa receptors, spinal analgesia, miosis and sedation.

Nicomorphine is the 3,6-dinicotinate ester of morphine. Nicomorphine is a strong opioid agonist analgesic two to three times as potent as morphine with a side effect profile similar to that of dihydromorphine, morphine, and diamorphine. The 3,6-diesters of morphine are drugs with more rapid and complete central nervous system penetration due to increased lipid solubility and other structural considerations.

Opium alkaloids (opioids and isoquinoline derivatives) induce constipation, euphoria, analgesia and sedation dependent on the dose and derivative. The constipating effect is caused by inhibition of the intestines' peristalsis.

Oxycodone is a full opioid agonist with no antagonist properties. It has an affinity for kappa, mu and delta opioid receptors in the brain and spinal cord. Oxycodone is similar to morphine in its action. The therapeutic effect is mainly analgesic, anxiolytic, antitussive and sedative.

Oxycodone and naloxone have an affinity for kappa, mu and delta opiate receptors in the brain, spinal cord and peripheral organs (e.g. intestine). Oxycodone acts as opioid-receptor agonist at these receptors and binds to the endogenous opioid receptors in the CNS. By contrast, naloxone is a pure antagonist acting on all types of opioid receptors. Naloxone counteracts opioid-induced constipation by blocking the action of oxycodone at opioid receptors locally in the gut.

Oxymorphone is a full opioid agonist and is relatively selective for the mu-opioid receptor, although it can bind to other opioid receptors at higher doses. The principal therapeutic action of oxymorphone is analgesia. The precise mechanism of the analgesic action is unknown. However, specific CNS opioid receptors for endogenous compounds with opioid-like activity have been identified throughout the brain and spinal cord and are thought to play a role in the analgesic effects of this drug.