Morphine - IV Flashcards
What is the pharmacologic category/class of morphine?
- Opioid Analgesic — Naturally occuring
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 4. Classification, Relative Potency & Opioid Abuse
What is the mechanism of action of morphine?
Opioid rececptor agonism, especially mu and some delta, with resultant increase in pain threshold, altered pain perception, and inhibition ascending pain pathways
- Presynaptic: decreases cAMP-dependent influx of calcium ions → inhibition of neurotransmitter release
- Post synaptic: increased outward K+ conductance → hyperpolarization of nerve cell
Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lesson 2. Opioid Receptors
Nagelhout (7th ed.), pp. 141 - Fig. 11.2, 142, 1295-1296
Stoelting’s Pharmacology (5th ed.), pp. 218-219
What is the typical dose range of morphine for analgesia in adults?
Emphasis because ranges may vary depending on patient/procedure
- 1-4 mg IV q 1-2 hrs PRN
Ranges are as wide a 1-20 mg, but IV morphine is not very popular…
What is the onset of action for morphine?
- Rapid/immediate with maximal effects in ~20 minutes
Nagelhout (7th ed.), p. 1298
Stoelting’s Pharmacology (5th ed.), p. 231
What is the duration of action for morphine?
- 4-6 hrs
Duration related to hydrophilic properties, active metabolites
Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Nagelhout (7th ed.), p. 1298
What organ(s) are responsible for morphine’s clearance (metabolism/elimination)?
- Metabolism: Liver
- Elimination: Kidneys
Half-life: ~2-4 hours
Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Stoelting’s Pharmacology (5th ed.), p. 228
True or False:
Morphine-6-glucuronide, a metabolite of morphine, is more potent than the parent drug
- True — this is a major consideration for patients with renal failure
Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1
Nagelhout (7th ed.), p. 147
Cardiovascular effects of morphine include:
- Bradycardia
- Arterial/venous dilation → ↓ SVR/BP — likely minimal in healthy, supine, normovolemic patients
attributed to release of histamine
Note that these are similar to those of other opioids
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3
Nagelhout (7th ed.), pp. 143, 147
Stoelting’s Pharmacology (5th ed.), p. 221
What are the respiratory effects of morphine?
- Dose dependent depression of ventilation — RR affected before Vt
(shifting of the CO2 response curve) - Inhibits hypoxic ventilatory drive
- Apnea at large doses
Note that these are similar to those of other opioids
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3
Nagelhout (7th ed.), p. 142
Stoelting’s Pharmacology (5th ed.), p. 222
What are the effects of morphine on the CNS?
- Sedation
- Miosis/pinpoint pupils
- Mild hypothermia
resets hypothalamic temperature setpoint - N/V
Partial dopamine agonists at CTZ
Note that these are similar to those of other opioids
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3
Nagelhout (7th ed.), p. 142
Stoelting’s Pharmacology (5th ed.), p. 222
True or false:
Because of morphine’s pharmacokinetic profile, sedation serves as a reliable indicator of appropriate analges
- False
Sedation precedes analgesia following IV morphine administration
Nagelhout (7th ed.), p. 147
What are the GI/GU effects of morphine?
- Slowed peristalsis → CONSTIPATION
- N/V
- Contraction of sphincter of Oddi → biliary colic
evidence is kind meh on this - Delayed gastric emptying
- Urinary retention (IDGAF)
detrusor relaxation, urinary sphincter constriction
Note that these are similar to those of other opioids
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 2 & 3
Nagelhout (7th ed.), pp. 143-144
Stoelting’s Pharmacology (5th ed.), pp. 223-224
BONUS
Which of these opioids is more hydrophilic?
- Morphine
- Fentanyl
- Morphine
Nagelhout (7th ed.), p. 147
Stoelting’s Pharmacology (5th ed.), p. 231
The experience of pain can be divided into four steps: transduction, transmission, modulation, and perception. Which of these does morphine have an effect on?
Along with other opioids, fentanyl effects
- transduction
peripheral nerves - modulation
spinal cord - perception
brain/brainstem
Apex Unit 5: Pharmacology 2; Opioid & Non-Opioid Analgesics; Lessons 1 & 2