Opioids - Functions and Classification MCQs

The opioids contract biliary smooth muscle, which can result in biliary colic. The sphincter of Oddi may constrict, resulting in reflux of biliary and pancreatic secretions and elevated plasma amylase and lipase levels. Reference : LANG’ Basic & clinical pharmacology by Bertram G. Katzung, Susen B. Masters and Anthony J. Trevor 12 th edition. Chapter 31- Opioid Analgesics & Antagonists by Dr. Mark A. Schumacher,PhD,MD, Dr. Alan I. Basbaum,PhD,& Dr. Walter L. Way,MD. Page no. 552

The opioid derivatives most commonly used as antitussives are dextromethorphan, codeine, levopropoxyphene, and noscapine (levopropoxyphene and noscapine are not available in the USA). They should be used with caution in patients taking monoamine oxidase inhibitors (see Table 31–5 ). Antitussive preparations usually also contain expectorants to thin and liquefy respiratory secretions. Reference: LANG’ Basic & clinical pharmacology by Bertram G. Katzung, Susen B. Masters and Anthony J. Trevor 12 th edition. Chapter 31- Opioid Analgesics & Antagonists by Dr. Mark A. Schumacher,PhD,MD, Dr. Alan I. Basbaum,PhD,& Dr. Walter L. Way,MD. Page no. 559

Importantly, due to increasing reports of death in young children taking dextromethorphan in formulations of over-the-counter “cold/cough” medications, its use in children less than 6 years of age has been banned by the FDA. Moreover, because of variations in the metabolism of codeine, its use for any purpose in young children is being reconsidered. Reference: LANG’ Basic & clinical pharmacology by Bertram G. Katzung, Susen B. Masters and Anthony J. Trevor 12 th edition. Chapter 31- Opioid Analgesics & Antagonists by Dr. Mark A. Schumacher,PhD,MD, Dr. Alan I. Basbaum,PhD, PhD,& Dr. Walter L. Way,MD. Page no. 559

Administration of mu opioid analgesics, such as morphine, can cause contraction of smooth muscle cells in the sphincter of Oddi, leading to spasm and an increase in common bile duct pressures. Although uncommon, pressures in the gallbladder can also increase, potentially leading to biliary colic. Patients who develop biliary colic will have severe pain and cramping in the right upper abdomen. Management involves discontinuation of mu opioid analgesics and pain control with alternative agents such as nonsteroidal anti-inflammatory drugs (eg, ketorolac, diclofenac). Reference: Basic & Clinical Pharmacology, Fourteenth Edition By Bertram G. Katzung Pg no. 1103

Opioids have effect on both sensory and emotional pain whereas NSAIDs have no significant effect on emotional pain. Reference: LANG’ Basic & clinical pharmacology by Bertram G. Katzung, Susen B. Masters and Anthony J. Trevor 12 th edition. Chapter 31- Opioid Analgesics & Antagonists by Dr. Mark A. Schumacher,PhD,MD, Dr. Alan I. Basbaum,PhD,& Dr. Walter L. Way,MD. Page no. 549

Fentanyl is more potent than Morphine. The doses of fentanyl are given in micrograms to produce the same effect produced by morphine in milligrams (0.1mg per kg) Reference: Morgan and Mikhail’s clinical anesthesiology, page no 1285

Opioids bind to specific receptors located throughout the central nervous system and other tissues Four major opioid receptor types have been identified: mu, kappa, delta, and sigma All opioid receptors couple to G proteins binding of an agonist to an opioid receptor causes membrane hyperpolarization Acute opioid effects are mediated by inhibition of adenylyl cyclase (reductions in intracellular cyclic adenosine monophosphate concentrations) and activation of phospholipase C Reference : Stoelting's pharmacology and physiology in anaesthetic practice 5th edition

Methyl naltrexone is a peripheral mu opioid receptor antagonist It is a quaternary ammonium compound and hence cannot cross the blood brain barrier Thus, it can reverse the effects of opioid mediated by peripheral opioid receptors , since it cannot cross the blood brain barrier, it does not affect the opioid effects mediated by opioid receptors in the CNS , such as analgesia It was introduced in the treatment of opioid induced constipation refractory to other measures Alvimopan is a similar acting peripheral mu opioid receptor antagonist Reference : Stoelting's pharmacology and physiology in anaesthetic practice 5th edition