Morphine opioid analgesics

Most of the time, the powerful analgesia suppHed by morphine and the other opioid analgesics is not needed. Rather, a mild analgesic, such as aspirin, the most commonly employed analgesic agent, can be used for the treatment of simple pain associated with headaches, minor muscle pain, mild trauma, arthritis, cold and flu symptoms, and fever. 

Hypoventilation is defined as a reduction in the rate and depth of breathing. Inadequate ventilation results in hypoxemia, or a decrease in the concentration of oxygen in the arterial blood. Hypoventilation may be induced inadvertently by various pharmacological agents, including opioid analgesics such as morphine. These medications cause hypoventilation by way of their effects on the respiratory centers in the brainstem. Doses of... 

Hanks GW, O Neill WM, Simpson P, Wesnes K. (1995). The cognitive and psychomotor effects of opioid analgesics II. A randomized controlled trial of single doses of morphine, lorazepam, and placebo in healthy subjects. EurJ Clin Pharmacol. 48(6) 455-60. 

The chemical structures and biological activities of hundreds of opioid analgesics derived from the prototype opioid drug morphine are most comprehensively described in two books published in 1986, one entitled Opioid Analgesics, Chemistry and Receptors by Casy and Parfitt [1] and the other entitled Opiates by Lenz et al. [2]. Follow-up articles include those by Casy in 1989, entitled Opioid Receptors and their Ligands Recent Developments [3] which also includes sections on opioid peptides, affinity labelling and opioid receptor subtypes Rees and Hunter in 1990 [4] covering the... 

Pethidine is a less potent opioid analgesic than morphine. Pethidine is not suitable for continuous pain because of its short-lasting analgesia. 

Pethidine and morphine, used as opioid analgesics, may cause dependence following repeated administration. Zolmitriptan, a 5HT, agonist used in the treatment of acute migraine attacks, is not associated with dependence. 

Methadone is an opioid analgesic that is available for oral and parenteral administration. It is used in severe pain, in palliative care and as an adjunct in the management of opioid dependence. Compared with morphine, it is less sedating and has a longer duration of action. It may lead to addiction and can still cause toxicity when used in adults with non-opioid dependency. Because of the long duration of action, in overdosage, patients need to be monitored for long periods. 

Morphine is an opioid analgesic that may be used for pain relief in myocardial infarction. However, diamorphine is usually preferred because it causes a lower risk of nausea and hypotension than morphine. 

Fig. 7.26 Structure of morphine, which is metabolized to a more active opioid analgesic by glucuronidation at the 6 position.

As already mentioned, opioid analgesics, in particular morphine, fentanyl, alfentanil, and sufentanyl are widely used in the practice of anesthesiology as adjuncts. 

Initial therapy- There has been no evaluation of CR/ER/SR morphine as an initial opioid analgesic in the management of pain. Because it may be more difficult to titrate a patient to adequate analgesia using a CR/ER/SR morphine, it is ordinarily advisable to begin treatment using an immediate-release morphine formulation. 

Pharmacology Buprenorphine is a semisynthetic centrally acting opioid analgesic derived from thebaine a 0.3 mg dose is approximately equivalent to 10 mg morphine in analgesic effects. Buprenorphine exerts its analgesic effect via high affinity binding of CNS opiate receptors. 

The opium alkaloid morphine is representative for this group of opiates and also for other opioid analgesics. Morphine is a full agonist for both the jx and the k receptors. It is used to relieve severe acute pain, or chronic pain in terminally ill patients. Its oral bioavailability varies from 15% to 35% and its... 

The most important other opium alkaloid is codeine. In contrast to morphine, codeine has a high oral-parenteral potency ratio due to less first-pass metabolism. Codeine is considered a prodrug, since it is metabolised in vivo to the primary active compounds morphine and codeine-6-glucuronide. Approximately 10% is demethylated to morphine. The analgesic effect of codeine is due to the formation of these metabolites as codeine itself has a very low affinity for opioid receptors. The half-life of codeine in plasma is 2 hours. 

Levorphanol (Levo-Dromoran) is an L-isomer morphi-nan derivative of morphine that is five to seven times more potent than morphine. It produces all of the side effects associated with morphine but less nausea. It is indicated for moderate to severe pain as a preoperative anxiolytic. It is often used in combination with thiopental to reduce the latter drug s anesthetic dose and to decrease postoperative recovery time. The o-isomer of levorphanol, dextrorphan, does not possess opioid analgesic activity but is a useful antitussive. 

Endocrine system Morphine and other opioid analgesics stimulate the release of vasopressin and prolactin and inhibit the release of luteinizing hormone, ACTH and follicle stimulating hormone. 

It is a potent opioid analgesic. Chemically it is N-phenyl-N-propanamide. It interacts predominantly with opioid p-recep-tor in human brain, spinal cord and other tissues. It exerts its principle pharmacologic effects on the CNS. It is 80-100 times more potent than morphine, both in analgesia and respiratory depression. 

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