1. close voltage gated Ca2+ channels on presynaptic terminals 2. open K+ channels on postsynaptic neurons both reduce NT release

- euphoria - analgesia - sedation - miosis

- hypotension - constipation - contraction of biliary SM - pruritus

Opioid Analgesics Flashcards by winta gheb

What do opioid agonists do?

produce analgesia by activating receptors located in brain and spinal cord

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Opioid receptor types:

3 main classes (mu, delta, and kappa) and are G protein linked couple to Gi

majority of opioid act on the mu receptor

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2 actions on neurons

close voltage gated Ca2+ channels on presynaptic terminals
open K+ channels on postsynaptic neurons

both reduce NT release

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Analgesic effects of opioids are due to ability to

inhibit ascending pain transmission

2. activate descending pain-inhibitory circuits

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Spinal analgesia

inhibit ascending pain transmission

all 3 receptor types

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Supraspinal analgesia

inhibitory descending neurons inhibit pain transmission

all 3 receptor types

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Descending pain inhibitory neurons are inhibited by

GABA**

meaning theres a transmission of pain

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Opioids and supraspinal analgesia

Opioids inhibit GABA neurons –> activate pain inhibitory descending neurons –> inhibition of pain transmission

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Opioid analgesics are classified into

Pure agonists- high affinity for mu receptors
Mixed agonists and antagonists
Antagonists

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Agonists and receptors

My Father & My Mothers Children (MFMMC)

Morphine (mu, weak delta/Kappa)
Fentanyl (mu)
Meperidine (mu)
Methadone (mu)
Codeine (weak at mu/delta)

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Mixed A/As and receptors

Peanut Butter, No Butter (PBNB)

Pentazocine (mu ant, k ago)
Butorphanol (mu ant, k ago)
Nalbuphine (mu ant, k ago)
Buprenorphine (mu ago, k ant)

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Antagonists and receptors

Naloxone
Naltrexone

Ant at all receptors

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CNS effects

euphoria
analgesia
sedation
miosis

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Peripheral effects

hypotension
constipation
contraction of biliary SM
pruritus

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Opioids are converted to?

glucuronides

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Morphine is conjugated to?

M3G

M6G

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Heroin is hydrolyzed to?

Monoacetylmorphine and morphine

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Codeine is converted to?

Morphine

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What is metabolized by CYP2D?

Codeine, oxycodone, and hydrocodone

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Merperidine is converted to?

Normeperidine

increase in normeperidine can occur in pt with decreased renal function and high conc can cause seizures

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Fentanyl is metabolized by ___ to inactivate ___

CYP3A4, metabolites

Methadone is metabolized by ____

P450

OA use:

analgesia
acute pulmonary edema
cough
diarrhea
anesthesia

OA AE:

nausea
vomiting
sedation
itching
constipation

Contraindications

- use of pure agonist with weak partial agonists - pt with head injuries - pt with impaired pulmonary function - impaired hepatic funtion - impaired renal function - pregnancy - children and breastfeeding moms (codeine and tramadol --> CYP2D6)

Drug interactions

1. Sedative hypnotics- increase CNS depression | 2. MAO inhibitors --> serotonin syndrome

Which opioids inhibit serotonin reuptake?

- methadone - meperidine - tramadol - fentanyl

What is serotonin syndrome?

when opioids are taken with MAO inhibitor - delirium - hyperthermia - headache - coma - death

Properties of specific agents

``` Agonists Mixed agonist-antagonists Antagonists Antitussives Antimotility ```

Agonists

- Morphine, hydromorphone, oxymorphone - Heroin - Meperidine - Fentanyl - Methadone - Levophanol - Codeine, oxycodone, hydrocodone

Morphine, hydromorphone, oxymorphone

severe pain treatment DOC mu high affinity d/k low affinity

Heroin

rapid hydrolization to 6-MAM --> morphine heroin and 6-MAM enter brain quick

Meperidine

mu agonist - short term treatment of acute pain - half life 3 hrs - normeperidine has longgg half life so be careful of use of meperidine cause it can accumulate normeperidine leading to tremors, twitches, and seizures

Fentanyl

mu agonist - severe pain - rapid and potent

Methadone

- long duration - severe pain - mu agonist - NMDA antagonist - serotonin and NE reuptake inhibitor

Methadone use and AE

managing opioid withdrawal for addicted pt bc long half life and less euphoria AE- long QT, torsades de pointes and death

Levorphanol

all receptor agonist serotonin and NE reuptake inhibitor NMDA antagonist severe pain

Oxycodone and Hydrocodone

Oxy- moderate and severe pain, alone or used with nonopioid Hydro- moderate and severe pain, only with NSAID and Acetaminophen

Codeine

mild to moderate pain low affinity for opioid receptors effect due to conversion to morphine by CYP2D6

Mixed A/As

``` Peanut butter no butter (PBNB) PENTAZOCINE BUTORPHANOL NALBUPHINE BUPRENORPHINE ```

PENTAZOCINE BUTORPHANOL NALBUPHINE cause?

psychotomimetic effects

BUPRENORPHINE

approved for management of opioid addiction

Mixed A/As are not recommended bc?

ceiling effect

Tramadol

metabolized by CYP2D and CYP3A4 mu agonist NE and 5HT reuptake inhibitor mild to moderate pain treatment

Naloxone

acute opioid overdose

Naltrexone

opioid and alcohol addiction

High efficacy opioids

Everything except oxycodone, hydrocodone, pentazocine, and codeine (lowest)

Antitussives

- Dextrometorphan and codeine | - suppression of cough

Antimotility

Diphenoxylate and Loperamide - treatment of diarrhea - usual doses lack analgesic effects

Diphenoxylate

contain atropine to discourage overdose | - high doses have CNS effects