Narcotic analgesics Flashcards
Endogenous ligands of opioid receptors
B-endorphin
Enkephalins
Dynorphins
(all called opioid peptides)
How do opioid analgesics work?
Uses endogenous mechanisms to inhibit the propagation of pain signals, alter the emotional perception of pain, elevate the pain threshold
What are the types of opioid receptors and where can they be found?
Mu, delta, kappa
Peripheral nociceptive terminals
Spine
Brain
What kind of receptor is opioid receptor
GPCR
which receptor is responsible for analgesia?
mu receptors
Dosing features of opioid analgesics?
Elderly patients require lower dose than younger patients for pain relief
Neuropathic pain requires higher opioid doses than nociceptive pain
Lower doses required for continuous maintenance of pain relief than in recurrence to pain
Clinical uses of opioid agonists
Analgesia (codeine, morphine, pethidine)
Anesthetic adjuvant (fentanyl)
Cough suppressant (codeine)
Antidiarrheal (diphenoxylate)
Strong opioid agonists
Morphine, methadone, fentanyl, pethidine
Side effects of pethidine
Hallucination and potential epilepsy
Restlessness
Antimuscarinic (dry mouth, constipation, blurring vision)
Which opioid agonist is used in labour?
Pethidine, as duration of action is especially short in neonates
Moderate opioid agonists
Codeine, tramadol
Why might some people show reduced analgesic effect to codeine?
Due to lack of demethylating enzymes, less codeine is converted to morphine
What is the most dangerous side effect of opioid medications?
Respiratory depression
Actions in the nucleus tractus solitarius and nucleus ambiguus reduces responses to CO2 and suppresses voluntary breathing
Which group of patients is respiratory depression a concern for?
Overdose Respiratory disease Hepatic dysfunction Combination with other CNS depressants Young children
Common side effects of opioids
N/V Drowsiness Constipation Miosis Urinary retention Postural hypotension and bradycardia Immunosuppressant effect with long term use
