A report on Morphine

However, in other cases, such as codeine and morphine, the administered drug is enzymatically activated to form sugar derivatives (morphine-glucuronides) that are more active than the parent compound.

In combination with agonists of the MOR such as morphine however, naltrexone appears to become an inverse agonist of the MOR.

Full agonists bind to and activate a receptor with the maximum response that an agonist can elicit at the receptor. One example of a drug that can act as a full agonist is isoproterenol, which mimics the action of adrenaline at β adrenoreceptors. Another example is morphine, which mimics the actions of endorphins at μ-opioid receptors throughout the central nervous system. However, a drug can act as a full agonist in some tissues and as a partial agonist in other tissues, depending upon the relative numbers of receptors and differences in receptor coupling.

Notable drugs that experience a significant first-pass effect are imipramine, morphine, propranolol, buprenorphine, diazepam, midazolam, pethidine, tetrahydrocannabinol (THC), ethanol (drinking alcohol), cimetidine, lidocaine, and chlorpromazine.

Morphine-6-glucuronide (M6G) is a major active metabolite of morphine.

Alkaloids have a wide range of pharmacological activities including antimalarial (e.g. quinine), antiasthma (e.g. ephedrine), anticancer (e.g. homoharringtonine), cholinomimetic (e.g. galantamine), vasodilatory (e.g. vincamine), antiarrhythmic (e.g. quinidine), analgesic (e.g. morphine), antibacterial (e.g. chelerythrine), and antihyperglycemic activities (e.g. piperine).

Strong opiates (such as fentanyl, heroin, and morphine), barbiturates, and certain benzodiazepines (short acting ones and alprazolam) are known for depressing respiration.

Heroin, is the brand name for diacetylmorphine or morphine diacetate, which is an inactive prodrug that exerts its effects after being converted into the major active metabolite morphine, and the minor metabolite 6-MAM - which itself is also rapidly converted to morphine. Some European countries still use it as a potent pain reliever in terminal cancer patients, and as second option, after morphine sulfate; it is about twice as potent, by weight, as morphine and, indeed, becomes morphine upon injection into the bloodstream. The two acetyl groups attached to the morphine make a prodrug which delivers morphine to the opioid receptors twice as fast as morphine can.

Friedrich Sertürner derived the name of the opiate drug morphine from the name of Morpheus.

LSD, MDMA, morphine, alprazolam, clonazepam, diazepam, and many other substances including the psychedelic tryptamines and phenethylamines, and even recreational cannabis edibles, i.e. (THC) are all viable candidates for administration via this route.