Bannon: Opiod Drugs Flashcards
Hydromorphone (Dilaudid)
Older semi-synthetic morphine derivative used as painkiller
More potent than morphine; equivalent efficacy
Oft-requested in ER
Was used primarily as immediate release, but now other formulations (extended-release in ‘11)
Opiate Receptors:
Mu
Kappa
Delta
Mu:
Encoded by:
Mu: for morphine (endogenous ligands are beta-endorphin and more recently recognized endomorphins)
- Encoded by MOP gene
- Many opioid agonists and antagonists show preference here
Kappa:
Encoded by:
What is relatively strong here?
In some cases, have actions opposite to:
Kappa: for ketoclazocine (endogenous ligand is dynorphin)
- Encoded by KOP gene
- Partial agonists relatively strong here
- May have more importance in spinal anesthesia
- In some cases, have actions opposite to mu receptors
Delta:
Encoded by:
Morphine and other opioid drugs:
Delta: for vas deferens (endogenous ligand is enkephalin)
- Encoded by DOP gene
- Morphine and other opioid drugs weaker here
Opioid-Like Receptor NOP:
Insensitive to:
Elicits : (2)
Opioid-Like Receptor NOP: nociceptin/orphanin FQ peptide receptor
o Insensitive to classical opioid antagonists
o Elicits hyperalgesia (increased sensitivity to pain) and anti-opiod effects suprasinally
o Elicits antinociceptive spinal effects
Single Gene Results in Several Receptor Subtypes Seen Pharmacologically
Example:
Single Gene Results in Several Receptor Subtypes Seen Pharmacologically:
Example: MOP gene elicits μ1, μ2, and μ3
Single Gene Results in Several Receptor Subtypes Seen Pharmacologically
Possible Explanations: (3)
Alternative splicing of common gene products (really not important)
Receptor dimerization to give different subtypes (may be important)*
Interaction of common gene product with signaling proteins (may be important)*
- For example, drug dependent activation of signaling pathways (which pathway gets activated depends on which drug bind)
Morphine (Gold Standard)
Absorption:
Metabolism:
Absorption: well absorbed by multiple routes of administration (oral, IM, IV, subQ, rectal, epidural or intrathecal)
Metabolism: extensive first-pass metabolism limits oral use (~35% bioavailability)
Morphine (Gold Standard)
Excretion:
Polar metabolites excreted in the urine
- After chronic use, polar metabolite morphine-6-glucuronide is responsible for analgesic effects
- Therefore, toxicity may result in renal insufficiency due to decreased clearance of this active metabolite (confusion, agitation)
- Morphine-3-glucuronide is another minor metabolite that may be proconvulsant (CNS excitatory properties; again, take care with renal insufficiency)
Glucoronide conjugates also secreted in bile
Morphine (Gold Standard)
Formulations: (4)
Long-Acting SR Beads
Morphine SR + Naltrexone (Embeda)
Post-Surgical Formulations (DepoDur)
Infumorph/Astromorph/Duramorph
Morphine
Long-Acting SR Beads:
Long-Acting SR Beads: to be swallowed; if chewed or combined with alcohol, can cause release of too much morphine
Morphine
Morphine SR + Naltrexone (Embeda):
Morphine SR + Naltrexone (Embeda): for continual use with decreased risk of abuse (if crushed, opioid antagonist naltrexone will be freed)
Morphine
Post-Surgical Formulations (DepoDur):
Post-Surgical Formulations (DepoDur): single liposomal injection (last 48 hours)
Morphine
Infumorph/Astromorph/Duramorph:
Infumorph/Astromorph/Duramorph: continual epidural or intrathecal infusion formulations
Uses/Effects of Morphine:
Analgesia
Basics:
Basics:
- Pain relief without general sensory loss or loss of consciousness
- Pain reported as present but no longer bothers the patient
- Better against continuous dull pain than sharp, intermittent pain
- Multiple supraspinal (ie. brain) and spinal sites of action
Uses/Effects of Morphine:
Analgesia
Issues: (2)
SIGNIFICANT tolerance to this effect (as well as most others)
Paradoxical hyperalgesia may occur (MOA unclear- possibly increased glutamate transmission in the dorsal horn)
Uses/Effects of Morphine:
Analgesia
Use:
Use: surgical anesthesia (in combination with other drugs- multimodal anesthesia)
Uses/Effects of Morphine
Mood and Cognitive Effects
Basics:
In normal (Pain-Free) Individuals:
Basics: cause euphoria and tranquility
Normal (Pain-Free) Individuals: often unpleasant
o Dysphoria (intense feelings of depression or discontent)
o Difficulty thinking
o Drowsiness
o Nausea
Uses/Effects of Morphine
Mood and Cognitive Effects
Site of Action:
Side Effects:
Use in Combat Injured Subjects:
Site of Action: unclear (locus ceruleus, mesolimbic DA, nucleus accumbens all possible)
Side Effects: confusion and sedation (especially in the elderly)
Use in Combat Injured Subjects: prompt administration of morphine reduced risk for PTSD
Uses/Effects of Morphine
Miosis
Cause:
Sign of Toxicity/Abuse:
Cause: excitation of the PS innervation to the pupil
Sign of Toxicity/Abuse: little/no tolerance to this effect with chronic use
Uses/Effects of Morphine
Cough Inhibition
Mechanism:
Mechanism: depression of cough reflex mediated by medullary cough center (can administer a dose that easily provides cough suppression without respiratory depression)
Uses/Effects of Morphine
Respiratory Depression
Mechanism:
Importance:
Mechanism: dose-related depression mediated via brainstem centers
- Decreased response to CO2
- Synergistic depression seen with many other CNS drugs
Importance: especially of concern in patients with COPD and pain
Uses/Effects of Morphine
Increased Intracranial Pressure
Mechanism:
Importance:
Mechanism: due to increased pCO2 (causes cerebrovascular dilation)
Importance: needs to be taken into consideration with head trauma
Uses/Effects of Morphine
Nausea/Emesis
Mechanism:
Mechanism: mediated by area postrema chemoreceptor trigger zone
- Relatively uncommon in supine patients but common in ambulatory patients (hints at possible vestibular component to mechanism)
- Tolerance to this effect develops rapidly
Uses/Effects of Morphine
Cardiovascular
Effects:
Mechanism:
Effects: peripheral vasodilation (reduced peripheral resistance) and inhibition of baroreceptor reflex
- Not evident in supine patient, however, orthostatic hypotension and fainting can be seen upon standing
Mechanism: may be due in part to histamine release
Uses/Effects of Morphine
Cardiovascular
Use:
Use: IV morphine used for immediate relief of dyspnea from acute pulmonary edema associated with left ventricular failure
- Decreases anxiety, venous tone and peripheral resistance