Chemical Properties: Natural opioid, least lipophilic of opioids. Mechanism of Action: Mu-opioid receptor agonist, inhibits nociceptive transmission at the spinal cord and activates descending pain control pathways. Metabolism: Liver via glucuronidation to M3G (inactive) and M6G (active, potent). Prolonged effect in renal failure due to M6G accumulation. Uses: Moderate to severe pain, more effective for dull pain than sharp intermittent pain. Dosage: IV (0.03 - 0.15 mg/kg), IM (0.05 - 0.2 mg/kg). Onset: 20 min IV. Peak: 30-60 min. Duration: 4-5 hrs. CNS Effect: Sedation occurs before analgesia. Miosis due to inhibition of GABA and stimulation of Edinger-Westphal nucleus. Cardiovascular Effect: Bradycardia via medullary vagal stimulation. Minimal effect on BP in healthy patients, but peripheral vasodilation can occur. Respiratory Effect: Dose-dependent respiratory depression (mu/delta receptor action in brainstem). Reduces CO₂ responsiveness. Other Notes: Causes constipation, urinary retention, muscle rigidity with rapid administration. Pruritus common with neuraxial use.

Chemical Properties: Synthetic opioid, highly lipid-soluble, rapid onset. Mechanism of Action: Mu-opioid receptor agonist, inhibits ascending nociception. Most widely used opioid analgesic in anesthesia. Metabolism: Significant first-pass uptake in the lungs with temp accumulation before release. Liver via N-dealkylation and hydroxylation to inactive metabolites, excreted in urine and bile. Elimination prolonged in elderly and neonates. Uses: Profound dose-dependent analgesia, sedation, intra-op and post-op pain management. Dosage: Intra-op 2 - 50 mcg/kg, Post-op 0.5 – 1.5 mcg/kg. Transdermal: 25-100 mcg/hr for 24-72 hrs. Onset: Immediate IV. Duration: Short (20-40 min). CNS Effect: Minimal effect on EEG, used in neurophysiologic monitoring. Cardiovascular Effect: Minimal effects, can cause bradycardia. Respiratory Effect: Ventilatory depression, dose-dependent. Other Notes: Rapid redistribution terminates action for single doses; prolonged infusion shifts elimination to metabolism.

Chemical Properties: Less lipid-soluble but highly nonionized (90%) at physiological pH, small volume of distribution, rapid onset, short duration. Mechanism of Action: Mu-opioid receptor agonist. Metabolism: Liver via CYP450 (N-dealkylation, O-demethylation), inactive metabolites excreted renally. Uses: Intra-op anesthesia, effective epidural opioid but short duration limits popularity. Dosage: 8 - 100 mcg/kg, Maintenance: 0.5 – 3 mcg/kg/min. Onset: Immediate IV. Duration: Short. CNS Effect: Dose-dependent sedation, analgesia. Cardiovascular Effect: Minimal, but caution in hypovolemic patients. Respiratory Effect: Profound respiratory depression and sedation prolonged if combined with erythromycin (inhibits metabolism).

Opioids Flashcards by Jade Tra

Morphine

Chemical Properties: Natural opioid, least lipophilic of opioids.
Mechanism of Action: Mu-opioid receptor agonist, inhibits nociceptive transmission at the spinal cord and activates descending pain control pathways.
Metabolism: Liver via glucuronidation to M3G (inactive) and M6G (active, potent). Prolonged effect in renal failure due to M6G accumulation.
Uses: Moderate to severe pain, more effective for dull pain than sharp intermittent pain.
Dosage: IV (0.03 - 0.15 mg/kg), IM (0.05 - 0.2 mg/kg).
Onset: 20 min IV.
Peak: 30-60 min.
Duration: 4-5 hrs.
CNS Effect: Sedation occurs before analgesia. Miosis due to inhibition of GABA and stimulation of Edinger-Westphal nucleus.
Cardiovascular Effect: Bradycardia via medullary vagal stimulation. Minimal effect on BP in healthy patients, but peripheral vasodilation can occur.
Respiratory Effect: Dose-dependent respiratory depression (mu/delta receptor action in brainstem). Reduces CO₂ responsiveness.
Other Notes: Causes constipation, urinary retention, muscle rigidity with rapid administration. Pruritus common with neuraxial use.

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Fentanyl

Chemical Properties: Synthetic opioid, highly lipid-soluble, rapid onset.
Mechanism of Action: Mu-opioid receptor agonist, inhibits ascending nociception. Most widely used opioid analgesic in anesthesia.
Metabolism: Significant first-pass uptake in the lungs with temp accumulation before release. Liver via N-dealkylation and hydroxylation to inactive metabolites, excreted in urine and bile. Elimination prolonged in elderly and neonates.
Uses: Profound dose-dependent analgesia, sedation, intra-op and post-op pain management.
Dosage: Intra-op 2 - 50 mcg/kg, Post-op 0.5 – 1.5 mcg/kg. Transdermal: 25-100 mcg/hr for 24-72 hrs.
Onset: Immediate IV.
Duration: Short (20-40 min).
CNS Effect: Minimal effect on EEG, used in neurophysiologic monitoring.
Cardiovascular Effect: Minimal effects, can cause bradycardia.
Respiratory Effect: Ventilatory depression, dose-dependent.
Other Notes: Rapid redistribution terminates action for single doses; prolonged infusion shifts elimination to metabolism.

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Alfentanil

Chemical Properties: Less lipid-soluble but highly nonionized (90%) at physiological pH, small volume of distribution, rapid onset, short duration.
Mechanism of Action: Mu-opioid receptor agonist.
Metabolism: Liver via CYP450 (N-dealkylation, O-demethylation), inactive metabolites excreted renally.
Uses: Intra-op anesthesia, effective epidural opioid but short duration limits popularity.
Dosage: 8 - 100 mcg/kg, Maintenance: 0.5 – 3 mcg/kg/min.
Onset: Immediate IV.
Duration: Short.
CNS Effect: Dose-dependent sedation, analgesia.
Cardiovascular Effect: Minimal, but caution in hypovolemic patients.
Respiratory Effect: Profound respiratory depression and sedation prolonged if combined with erythromycin (inhibits metabolism).

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Hydromorphone

Chemical Properties: Semisynthetic opioid, more potent than morphine, highly lipid-soluble.
Mechanism of Action: Mu-opioid receptor agonist.
Metabolism: Liver, no active metabolites (safer in renal failure).
Uses: Moderate to severe pain.
Dosage: IV (0.01 – 0.02 mg/kg), IM (0.02 – 0.04 mg/kg).
Onset: IV: 15-30 min.
Peak: 30-90 min.
Duration: 4-5 hrs.
CNS Effect: Similar to morphine, sedation before analgesia.
Cardiovascular Effect: Minimal effect.
Respiratory Effect: Dose-dependent depression.
Other Notes: Recommended in renal failure due to lack of active metabolites.

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Meperidine

Chemical Properties: Synthetic mu receptor agonist, structurally similar to atropine.
Mechanism of Action: Mu-opioid receptor agonist, kappa receptor activity.
Metabolism: Liver via demethylation to normeperidine (active, neurotoxic, long half-life).
Uses: Analgesia, antispasmodic (atropine-like), shivering reduction (kappa receptor effect).
Dosage: Variable, IV preferred.
Onset: IV rapid.
Duration: Moderate.
CNS Effect: Accumulation of normeperidine leads to CNS excitation, tremors, seizures.
Cardiovascular Effect: Mild vasodilation.
Respiratory Effect: Mild depression.
Other Notes: Avoid in renal failure, elderly, and chronic use due to neurotoxicity. Interacts dangerously with MAOIs (hyperthermia, seizures, death).

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Remifentanil

Chemical Properties: Piperidine-derived opioid with ester linkage, ultra-short acting. moderate lipophilic, water soluble.
Mechanism of Action: Mu-opioid receptor agonist.
Metabolism: Rapid hydrolysis by blood/tissue esterases, not dependent on liver or kidney. Small Vd
Uses: Short procedures
Dosage: Intra-op: 1 mcg/kg, Maintenance: 0.05 - 2 mcg/kg/min, post op 0.05 - 0.3 mcg/kg/min
Onset: Immediate.
Duration: Ultra-short (elimination half-life 8-20 min).
CNS Effect: No accumulation, rapid clearance.
Cardiovascular Effect: Minimal.
Respiratory Effect: Severe depression, muscle rigidity if given as bolus.
Other Notes: Not used epidurally/intrathecally due to glycine content (neurotoxic).

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Buprenorphine

Chemical Properties: Partial mu agonist, high receptor affinity.
Mechanism of Action: Partial mu agonist, kappa antagonist.
Metabolism: Liver, slow receptor dissociation.
Uses: Opioid use disorder, moderate-severe cancer pain (transdermal).
Dosage: 8-hour duration, slow dissociation.
CNS Effect: Less euphoria than full agonists.
Cardiovascular Effect: Minimal.
Respiratory Effect: Ceiling effect on depression (safer in overdose).
Other Notes: Minimal GI side effects.

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Butorphanol

Chemical Properties: Highly lipophilic opioid.
Mechanism of Action: Kappa agonist, weak mu antagonist.
Metabolism: Liver.
Uses: Migraine headaches, postop pain, epidural pain.
Dosage: Varies.
Onset: Rapid.
Duration: Moderate.
CNS Effect: Sedation.
Respiratory Effect: Ceiling effect for depression.

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Nalbuphine

Chemical Properties: Mixed agonist-antagonist.
Mechanism of Action: Kappa agonist, mu antagonist.
Metabolism: Liver.
Uses: Pain, opioid-induced pruritus, respiratory depression reversal.
Dosage: Varies.
CNS Effect: Analgesia, mild sedation.
Cardiovascular Effect: Minimal.
Respiratory Effect: Ceiling effect, not fully reversible with naloxone.

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Morphine lipophilicity

Least lipophilic of the opioids: Slow to cross the BBB, slow onset, and less accumulation in fatty tissues

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Morphine metabolism

Glucuronidation in the liver to M3G (inactive) and M6G (active, more potent than parent drug)

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Morphine in renal failure

Prolonged therapeutic effect due to M6G accumulation

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Morphine clinical uses

Moderate to severe pain, especially dull pain; can be given IV, IM, subQ, oral, intrathecal, and epidural

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Morphine dosage (IV)

0.03 - 0.15 mg/kg

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Morphine onset and duration

Onset 20 min, peak 30-60 min, duration 4-5 hrs

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Morphine respiratory effect

Dose-dependent respiratory depression; reduces responsiveness to CO₂ and O₂

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Morphine cardiovascular effect

Bradycardia from medullary vagal stimulation, minimal BP effect in healthy patients

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Fentanyl usage

Most widely used opioid analgesic in anesthesia: NO active metabolites

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Fentanyl metabolism

N-dealkylation and hydroxylation to inactive metabolites, excreted in urine and bile

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Fentanyl elimination in elderly and neonates

Prolonged due to decreased metabolism

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Fentanyl clinical uses

Profound dose-dependent analgesia, sedation; given IV, intradermal, intrathecal, epidural, and PCA

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Fentanyl intra-op dosage

2 - 50 mcg/kg

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Fentanyl post-op dosage

0.5 – 1.5 mcg/kg

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Fentanyl onset and duration

Short duration of action (20-40 min)

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Fentanyl respiratory effect

Ventilatory depression; single dose terminated by redistribution, but repeated doses require elimination

Fentanyl cardiovascular effect

Minimal BP effect in healthy patients, peripheral vasodilation (dose-dependent)

Alfentanil onset and duration

Rapid onset and shorter duration than fentanyl: NO active metabolites

Alfentanil metabolism

Liver metabolism via oxidative N-dealkylation and O-demethylation (CYP450)

Alfentanil drug interaction

Erythromycin prolongs metabolism, increasing respiratory depression and sedation

Alfentanil clinical use

Limited due to prolonged respiratory depression and sedation

Alfentanil intra-op anesthesia dosage

8 - 100 mcg/kg

Alfentanil maintenance infusion dosage

0.5 – 3 mcg/kg/min

Alfentanil respiratory effect

Profound respiratory depression, risk of prolonged apnea

Hydromorphone origin

Semisynthetic opioid derived from morphine: NO active metabolites

Hydromorphone metabolism

No active metabolites: Preferred opioid in renal failure patients

Hydromorphone clinical uses

Management of pain

Hydromorphone IV dosage

0.01 – 0.02 mg/kg

Hydromorphone IM dosage

0.02 – 0.04 mg/kg

Hydromorphone onset and duration

Onset 15-30 min, peak 30-90 min, duration 4-5 hrs

Meperidine classification

Synthetic mu receptor agonist with declining use: ACTIVE metabolite (normeperidine)

Meperidine metabolism

Demethylation in the liver to normeperidine, which lowers seizure threshold and induces CNS excitability

Meperidine clinical uses

Analgesia, antispasmodic effect, and postoperative shivering reduction via kappa receptor stimulation

Meperidine contraindications

Avoid in renal failure, elderly, and chronic cancer patients due to normeperidine accumulation

Meperidine drug interaction

Significant interactions with first-generation MAO inhibitors → Risk of hyperthermia, seizures, and death

Remifentanil classification

Piperidine-derived opioid with ester link: NO active metabolites

Remifentanil metabolism

Rapidly hydrolyzed by blood and tissue esterases to a less active compound

Remifentanil elimination half-life

8-20 min

Remifentanil clinical uses

Ultra-short duration and titratability make it ideal for intra-op use

Remifentanil intra-op anesthesia dosage

1 mcg/kg

Remifentanil maintenance infusion dosage

0.05 - 2 mcg/kg/min

Remifentanil respiratory effect

Profound respiratory depression; bolus dosing not recommended due to muscle rigidity risk

Remifentanil epidural use

Contraindicated due to potential glycine neurotoxicity

Buprenorphine classification

Potent partial agonist at mu receptors, kappa antagonist

Buprenorphine clinical uses

Opioid use disorder treatment, moderate to severe cancer pain (transdermal system)

Buprenorphine duration

Long duration (~8 hrs) due to slow receptor dissociation

Buprenorphine respiratory effect

Ceiling effect prevents respiratory depression at high doses

Buprenorphine GI effect

Minimal constipation compared to full mu agonists

Butorphanol classification

Highly lipophilic opioid: Kappa agonist, weak mu antagonist

Butorphanol clinical uses

Migraine headaches, postoperative pain, epidural pain (under study)

Butorphanol analgesic effect

More potent than morphine but has a ceiling effect

Butorphanol respiratory effect

Ceiling effect prevents severe respiratory depression

Butorphanol side effects

Significant sedation

Nalbuphine classification

Mixed opioid agonist-antagonist (kappa agonist, mu antagonist)

Nalbuphine clinical uses

Pain treatment, opioid-induced pruritus, opioid-induced respiratory depression

Nalbuphine respiratory effect

No respiratory depression even with increased dose (ceiling effect)

Nalbuphine cardiovascular effect

No adverse circulatory changes

Nalbuphine reversal with naloxone

Difficult to reverse with naloxone

Naloxone classification

Pure opioid antagonist: Competitive antagonism at mu, kappa, and delta receptors

Naloxone clinical uses

Reversal of opioid-induced respiratory depression and analgesia

Naloxone duration

Shorter than most opioid agonists → Risk of respiratory depression recurrence

Naltrexone classification

Opioid antagonist similar to naloxone, but with higher oral efficacy and longer duration

Naltrexone clinical uses

Alcohol use disorder, prevention of opioid euphoria

Naltrexone duration

~24 hrs → Used for long-term opioid addiction management

Naltrexone metabolism

ACTIVE metabolite → Longer half-life than naloxone

Nalmefene classification

Long-acting parenteral opioid antagonist

Nalmefene clinical uses

Opioid overdose reversal, alcohol use disorder treatment

Nalmefene IV dosage

0.5 – 1.6 mg

Nalmefene elimination half-life

10 hrs

Nalmefene duration

8 hrs → Suitable for long-term overdose management

Opioids Flashcards

(79 cards)