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30 Cards in this Set
- Front
- Back
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Definition:
Narcotic Analgesic |
Narcotic - sleep-inducing
Analgesic - pain-relieving |
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Endogenous opioids - three classes, how action of opioid drugs relates
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1)POMC/beta-endorphin
2)Enkephalins 3)Dynorphins Endogenous opioids contribute to endogenous anti-nociceptive response - bind opioid receptors Opioid drugs mimick |
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Opioid receptors - three classes, analgesic/antitussive?, which is major receptor for most drugs
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1)Mu - major receptor
-analgesia 2)Kappa - analgesia 3)Delta - analgesia 4)DM - antitussive effects (non-opioid receptor) |
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Opioid effect at cellular level
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INHIBITORY
Activation of receptor - inhibit cAMP/Ca2+ channels, activate K+ channels Neurons decrease spontaneous/evoked firing |
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Opioid therapeutic effects
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Analgeisa (not neuropathic pain)
Antitussive Antidiarrheal (can get constipation) Relief of acute pulmonary edema Mood enhancement |
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Opioid analgesia - sites of action, general effects
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Sites of action
-peripheral (afferent pain fibers) -spinal (dorsal horn) -supra-spinal (gray, thalamus, limbic, sensory cortex) Inhibit ascending pain pathways, activate descending inhibitory pathways Increased pain threshold, tolerance; other senses unaffected Good for slow, dull, burning, aching, constant pain |
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Antitussive effects - receptor, stereoselectivity
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DM receptor (non-opioid)
Not stereoselective - bind d/l l (endogenous/natural) causes opioid effects - can make d drugs that are antitussive w/o opioid effects |
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Antidiarrheal effects
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Mu receptor on enteric nerves --> decrease peristalsis/secretions --> delayed gastric emptying, increase transit time, increase water absorption
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Common adverse opioid side effects
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Constipation (most common), nausea, vomiting, sedation, miosis, tolerance, itch
Overdose - death via respiratory depression No direct cardiac effects - histamine causes vasodilation |
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Opioid drug interactions, ADME
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Meperidine and propoxyphene interact w/ MAOI - death
Many routes; 1st pass elimination (increase oral dose); liver metabolism/renal excretion Duration increased w/ slow-release oral preps (morphine, oxycodone) |
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High efficacy analgesics (strong agonists)
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Morphine, meperidine, heroin, fentanyl
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Morphine
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parenteral widley used; cheap
Slow-release oral forms |
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Fentanyl
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Short-acting (anesthesia), potent in micrograms
Novel forms (transdermal patch, oral lozenge, buccal tablet) |
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Heroin
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pro-drug (converted to morphine)
main difference between heroin/morphine - heroin rapidly penetrates BBB/CNS to give rush (high abuse potential) |
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Meperidine
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Toxic metabolite - normepereidine --> causes CNS stimulation/convulsions
Use only short-term Can have fatal interaction w/ MAOI |
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Medium/low efficacy analgesics
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Codeine, oxycodone, propoxyphene
Only oral admin Risk liver toxicity w/ acetaminophen |
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Codeine
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Less potent - only some of drug is converted to morphine
Good antitussive Significant histamine release, pruritis |
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Oxycodone
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Highest efficacy in this category
slow release prep (oxycontin) can crush up oxycontin - disables slow release mechanism |
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Propoxyphene
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very low efficacy
Toxicity due to norpropoxyphene metabolite Cardiotoxicity, CNS toxicity |
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Pentazocine
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Mixed agonist/antagonist opioid receptor effects
Agonist at kappa (analgesia, DYSPHORIA) Antagonist at mu (antagonizes opioid analgesia - can get withdrawl sx if tolerant) Ceiling of maximal effect |
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Dextromethorphan
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Non-angalgesic opioid
antitussive - active at DM, inactive at opioid |
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Loperamide
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Non-analgesic opioid
antidiarrheal - little BBB penetration, in Immodium AD |
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Naloxone
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Competetive antagonist at all opioid receptors (not DM)
parenteral only; rapid-acting, short duration Use for opioid overdose |
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Principles of Pain TX
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Assess pain type, intensity
Pain is subjective |
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Three step approach
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Mild pain - aspirin, acetaminophen, NSAIDS
Moderate pain - opioid (low/medium efficacy); aspirin, acetaminophen, NSAIDS Severe pain - high-efficacy opioids (parenteral/oral); anti-inflammatory adjunct |
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PRN (as-needed) admin
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Not good. give a schedule
Get cycle of pain due to lapse in time between when patient thinks they are in pain and when they benefit from drug |
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Fear of opioid addiction
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Iatrogenic addiction very rare
Addiction irrelevant w/ terminal patients |
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Tolerance, cross-tolerance
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w/ continuous use
doesn't affect safety (TI doesn't change) get cross-tolerance to other opioids |
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Physical and psychological dependence
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Physical - w/ chronic use; can get cross-dependence; intensity/time course depend on dose/kinetics
Withdrawl when drug is removed or antagonist given Psychological (addiction) - altered behavior, uncommon |
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Equi-analgesia
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All full (high-efficacy) agonists can achieve same maximal effects depending on dose/route of admin
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