Opiod Agonists And Antagonists Flashcards
3 classes of opioid drugs
Full agonists
Partial agonists
Antagonists
Opioid analgesics
Control moderate to severe pain -can produce dependence
Full agonists
Codeine, hydrocodone, fentanyl, Lopermide, Methadone, Morphine, Oxycodone
Partial agonists
Buprenorphine, Pentazocine, Tramadol
Agonists when given alone
Antagonists when on board with full agonists
Most are kappa receptor agonists and Mu receptor antagonists
Antagonist
Naloxone
Antitussive agent
Dextromethorphan
Types of opiate receptors
Mu- morphine-like actions,Euphoria,Respiratory depression,Physical dependence,GI Actions
All full agonists act here
Kappa- Pentazocine like actions, miosis, sedation, dysphoria, hallucinations
Delta - Enkephalins like receptors, dependence, euphoria,analgesia
Endogenous opioid peptide families
Enkephalins
Short, opiate receptor agonists, short lived
Dynorophins
Longer, opiate receptor agonists, longer lived
Endorphins
Opiate receptor agonists, longest acting endogenous peptide
Prototype and standard for opioid drugs
Morphine
Metabolism of morphine
Conjugation w/glucaronic acid in the liver
Most metabolizes are inactive
Tolerance develops
Actions of morphine
Analgesia
Block pain transmission
Most effective against continuous dull pain
Raises the pain threshold
Anti-anxiety effect
Respiratory depression (primary cause of overdose death)
Nausea and vomiting
GI effects -constipation
Little to no tolerance develops
Drowsiness and sedation
Miosis
Euphoria and tranquility
Pruritis
Orthostatic HTNMorphine analgesia
Symptomatic relief of pain Moderate to severe Used primarily against acute pain Sickle cell crisis pain Dyspnea in end stage lung cancer
Morphine side effects
Dependence Increased pressure in biliary and urinary tracts Allergic rxns Neonates and elderly much more sensitive Dysphoria and excitement
Morphine contraindications
Those with decreased respiratory reserve
Head injuries- May obscure important signs
Pregnancy
Don’t combine with any CNS depressant
Codeine
More reliable when given orally than morphine
Metabolized by CYP2D6 into morphine
Used to treat mild to moderate pain
Cough suppressant
More constipation
Less potential for abuse and addiction than morphine
Methadone
Same effects as morphine
Pharmacokinetics different
Metabolized by CYP3A4 and excreted slowly
Longer lasting than morphine if used chronically
Can have serious cardiovascular effects (prolonged QT interval)
Used for tx of drug dependence
Fentanyl
Extremely potent opioid agonists
Primarily used as anesthetic medsd
Treating chronic and breakthrough pain
Analgesia - short onset time, shorter duration of action
Less effect on cardiovascular system
More likely to produce muscle rigidity of chest and ab muscles
Hydrocodone (Vicodin)
Most commonly prescribed drug 2002-2012
Metabolized by conjugation
Oxycodone
More potent than codeine
Effective orally
Abuse of timed release formulations is major problem
Loperamide (Imodium)
Potent anti-diarrheal drug
Action limited to GI tract bc it crosses mucosal membranes poorly
Dextromethorphan
Cough suppressant
No analgesia
Pentazocine
Synthetic opioid generally similar to morphine
Kappa agonist, Mu antagonist
Analgesia
Dysphoria ( in high doses, why it’s not generally used for severe pain)
Increase BP and HR
Will precipitate withdrawal in opioid defendant ppl due to antagonist action ( not morphine withdrawal)
Buprenorphine
Agonist at Mu, kappa antagonist (opposite)
Analgesia in moderate to severe pain
Tx for opioid dependence
Tramadol
Very weak partial agonist opioid
Weak Mu partial agonist
Also inhibits NE and 5HT transport
Can produce dependence
Seizures and serotonin syndrome seen
Naloxone
Opioid antagonist
Used to counteract the effects of opioids
Must be given continuously, not effective orally
Diagnosis of opioid overdose
Respiratory depression
Miosis
Coma
