Opioids Agonists (Exam II) Flashcards
What are opioids effects on the CO₂ medullary center?
- Opioids inhibit the CO₂ medullary center.
Differentiate opioids from narcotics.
- Opioids = all exogenous substances that bind to endogenous opioid receptors.
- Narcotic = any substance that can produce dependence (stupor)
What two types of opioid chemical structures are there?
- Phenanthrenes
- Benzylisoquinolines
What types of drugs are Phenanthrenes?
What types of drugs are benzylisoquinolines?
- Phenanthrenes: Morphine & codeine
- Benzylisoquinoline: Papaverine
What is papaverine mostly used for?
Treating intra-arterial barbiturate administration (dilates the highly constricted artery).
What portions of the brain are the source of descending inhibitory signals?
- Thalamus
- PAG
- Locus Coeruleus
What endogenous substances have the same effect as opioids?
Endorphins, Enkephalins, and Dynorphines.
Presynaptic inhibition of what neurotransmitters occurs with opioid administration?
- ACh
- Dopamine
- NE
- Substance P
How do opioids modulate pain at the cellular level?
- ↑ pK⁺ (hyperpolarization)
- Ca⁺⁺ channel inactivation
Where are opioid receptors located in the brain?
- PAG
- Locus Ceruleus
- RVM (rostral ventral medulla)
- Hypothalamus
Where is the primary site of opioid receptors in the spinal cord?
Substantia gelatinosa (aka Laminae 2)
Where is/are opioid receptors found outside the CNS?
- Sensory neurons & immune cells
What are the four (most important) types of opioid receptors?
- Μu1 (μ₁)
- Μu2 (μ₂)
- Κappa (κ)
- Delta (δ)
Which opioid receptor(s) is/are responsible for respiratory depression & physical dependence?
- Μu2 and δ
Which receptors are responsible for constipation?
- Μu2 primarily
- δ (less)
Which receptors can cause urinary retention?
Are there any receptors that cause diuresis when bound?
- Retention: Μu1 and δ
- Diuresis: κ
All opioid receptors induce analgesia at both the brain the spinal cord. T/F?
- False. Μu2 receptors only cause at analgesia at the spinal cord level.
What opioid receptors have low abuse potential when bound?
Μu1 and κ
Which opioid receptor is responsible for euphoria, bradycardia, hypothermia, and miosis when bound?
Mu1
What agonists bind to the four opioid receptors?
- Mu1 & Mu2 = endorphins, morphine, synthetics.
- κ = dynorphins.
- δ = enkephalins.
Describe the adverse side effects of opioids on the cardiovascular system.
- ↓BP from ↓SNS tone
- ↓HR + histamine release = ↓BP
What possible cardiovascular benefits do opioids provide?
- Myocardial ischemia protection (won’t cause myocardial depression)
What are the respiratory effects of opioids?
What would symptoms of overdose be?
- Depressed CNS response to CO₂ causing a right shift of PaCO₂ (↑)
- Overdose = apnea, miosis, ↓RR, coma.
What drug would treat opioid ventilatory depression but not reverse analgesia?
How?
- Physostigmine would by increasing CNS ACh levels.
What is normal PaO₂?
What shift in PaO₂ would be seen with metabolic acidosis?
What shift in PaO₂ would be seen with general anesthesia?
- Normal PaO₂ is 80 mmHg
- Left shift
- Right shift
What would cause a leftward shift in PaO₂?
What would cause a rightward shift?
- Leftward: Metabolic acidosis (to breathe off all that CO₂)
- Rightward: sleep → opiates → anesthesia
Why should caution be used when administering opioids to head trauma patients?
- Opioids ↓CBF and possibly ICP
What musculoskeletal abnormality occurs with opioid administration?
What makes this condition worse?
How is it treated?
- Skeletal chest wall and abdominal muscle rigidity.
- Mechanical ventilation
- Muscle relaxants and/or naloxone
What are sphincter of Oddi spasms?
Which drugs can cause this?
- Biliary smooth muscle spasm
- Fentanyl (99%), Morphine (53%), and Meperidine (61%).
I think maybe all opioids can cause this but these are the primary culprits
What drugs should be used for ERCP cases?
- Non-opioids (multimodal approach w/ NSAIDs, gabapentin, etc.)
How are opioid-induced sphincter of Oddi spasm’s treated?
- Naloxone
- Glucagon (2mg IV given incrementally) and causes no opioid antagonism.
How long does it take (generally) to develop tolerance to opioids?
What causes tolerance?
- 2-3 weeks
- Downregulation
What is the dosage of morphine?
When does it peak?
How long does it last?
- 1 - 10 mg IV
- Peak: 15 - 30 minutes
- Duration: 4 hours
How is morphine metabolized?
What is the active metabolite and its significance?
- Glucuronidation in the kidneys.
- Morphine-6-glucuronide = comprises only 5-25% of morphine metabolites but is an active anaglesic causing late resp depression.
What would occur with morphine overdose in a renal failure patient?
- Prolonged ventilatory depression.
What receptors does meperidine agonize?
- μ and κ receptors
- α2 receptors as well
What are the analogues of meperidine?
What other drugs does meperidine have a similar organic structure to?
- Fentanyl & it’s derivatives
- Lidocaine & Atropine
How potent is Meperidine?
How long does it last?
- 10% as potent as morphine
- Duration: 2-4 hours
What is the primary indication for meperidine?
What dose is used?
- Post-operative shivering
- 12.5mg IV
When should meperidine not be used?
- Bronchoscopies (promotes coughing)
How potent is fentanyl?
- 75 - 125 x morphine.
What is the blood-brain equilibration of fentanyl?
What does this mean?
- 6.4 minutes
- Potent with rapid onset and ↑ lipid solubility.
What percent of fentanyl is subject to lung first-pass effect?
What does this mean?
- 75%
- Drug is taken up into lung tissue and possibly subjected to breakdown via pulmonary esterases.
Where is fentanyl metabolized?
What is its principal metabolite?
- Liver via CYP3A
- Norfentanil
How does fentanyl dosing change for the elderly or liver patients?
No change in elderly or cirrhotic patients.
Describe what the graph below is showing.
Fentanyl has the greatest context-sensitive half-time of any of the fentanyl derivatives.
What is the analgesia dosage of fentanyl?
Induction dose?
- Analgesia: 1 - 2 μg/kg IV
- Induction: 1.5 - 3 μg/kg IV
1mg of PO fentanyl = ____ mg of IV morphine
5
What is the intrathecal dosage of fentanyl?
25 mcg
What is the adult oral dose of fentanyl?
Pediatric?
- Adult: 5 - 20 mcg/kg
- Peds: 15 - 20 mcg/kg
What is the transdermal dose of fentanyl?
- 75 - 100 μg (18 hours steady state)
What cardiovascular side effects should be known about fentanyl?
What CNS side effects should be known?
- ↓BP & ↓CO
- Can cause seizures & modestly increase ICP.
How much more potent is sufentanil than fentanyl?
- 5-12 times more potent.
How much of sufentanil is subject to first pass effects?
- 60% lung first-pass
How much of sufentanil is protein bound? What protein is it bound to?
92.5% α-1 acid glycoprotein bound.
What is the analgesia dose of sufentanil?
- Analgesia: 0.1 - 0.4 μg/kg IV
What is the induction dose of sufentanil?
18.9 mcg/kg IV
What an odd number
I don’t think that this is right, a quick google search shows completely different numbers.
What is the potency of alfentanil?
What is its onset?
- 20% as potent as fentanyl
- Onset: 1.4 min (faster than all derivatives except remifentanil)
What is the alfentanil induction dose?
What about laryngoscopy dose?
What about maintenance?
- Induction: 150 - 300 mcg /kg IV
- Laryngoscopy: 15 - 30 mcg/kg IV
- Maintenance: 25 - 150 mcg/kg/hr with inhaled anesthetics
What drug can cause acute dystonia when given to a Parkinson’s patient?
Alfentanil
What receptor affinity does remifentanil have?
How potent is it?
μ opioid agonist that is equipotent to fentanyl
What is remifentanil’s structure and why is it important?
Ester Structure = hydrolyzed by plasma & tissue esterases.
- Rapid onset & recovery
- Very titratable
- No accumulation
What drug was said to be a great choice for carotid procedures in lecture?
Remifentanil
Answer the following characteristics of remifentanil below:
Clearance:
Peak effect:
- Clearance: 3-L/min (8x faster than alfentanil)
- Peak: 1.1 min (fastest fentanyl derivative)
What is the induction dose of remifentanil?
- 1 mcg/kg IV over 1 min
What is the maintenance dosing of remifentanil?
- 0.005 - 2 μg/kg/min IV
How potent is hydromorphone?
What dose should be given?
What benefits does hydromorphone have over morphine?
- 5x more potent than morphine
- 0.5mg → 1-4 mg total
- No histamine release & no active metabolites.
Why is codeine not given IV?
- Induced hypotension via histamine release.
What is the dose of codeine for cough suppression?
Analgesia?
- Cough: 15mg
- Analgesia: 60mg (= about 5mg morphine)
Which opioid is most cleared?
- Remifentanil (3-4L/min)
Which opioid(s) is/are the most protein bound?
Which is the least?
- Sufentanil, alfentanil, & remifentanil
- Least = morphine
Which opioid is the highest percent non-ionized?
- Alfentanil
Morphine tends to relieve _____ type pain more than _____ type pain.
Dull: sharp