Analgesia Opioids Flashcards by Larissa May

What opioids are licensed for use in dos?

Fentanyl, methadone, pethidine, buprenorphine

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What opioids are unlicensed?

Morphine

alfentanil

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For Morphine list the duration of action, use and routes of administration

3-4hours
pre-medication and post-op analgesia
IV(bolus and CRI), IM, SC, epidural

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For methadone list the duration of action, use and routes of administration

3-4hours
Premedication and post-op analgesia
iv(CRI bolus), IM, SC epidural

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For pethidine list the duration of action, use and routes of administration

60 minutes
Pre-medication and post-op analgesia
IM, SC

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For fentanyl list the duration of action, use and routes of administration

20-30minutes
intra-op and post-op
iv(bolus, CRI), transdermal

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For buprenorphine list the duration of action, use and routes of administration

6 hours
premed and post-op
IV(Bolus), IM, epidural, Oral, transdermal

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For butorphanol list the duration of action, use and routes of administration

60 minutes 
premed and post op analgesia and sedation 
IV (bolus), IM, SC
kappa agonist 
mu antagonist

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What are the characteristics of an opioid?

Safe to give to effect

Very safe group of drugs

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What are the clinical effects of opioids?

Sedation
Analgesia
Cough suppression

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What are the undesirable effects of opioids?

Respiratory depression 
-when opioids administered during anaesthesia makes respiratory centre less responsive to a rise in CO2
Cardiovascular effects 
-reduction in hear rate
-dose and drug dependent
Excitation 
-rare when given im 
-don't worry about excitation in cats
Euphoria (inappropriately high doses 
Gut stasis 
Nausea and vomiting-Morphine before they are in pain
Ocular effects 
(pupillary constriction

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How is a drop in heart rate cause be administration of an opioid managed?

Administration of anticholinergenic

atropine

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What factors should you consider before administering atropine?

low doses iv might promote bradycardia
high doses iv can stimulate tachycardia
Try to give im
if bradycardia develops on injection IV give more atropine
If tachycardia develops on iv injection wait

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List the opioids in order from the most analgesic efficacy to the least

Fentanyl
methadone
buprenorphine
butorphanol

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List the characteristics of methadone

More efficacious than morphine
reduced nausea and vomiting than morphine
no concern over histamine release if given IV
Minimal CVS and respiratory side effects
licensed in cats and dogs

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List the characteristics of pethidine

Very short acting
large volumes (painful on IM)
histamine release if given IV
Licensed in UK

List the characteristics of fentanyl

Some respiratory depression when given during anaesthesia
induces bradycardia
useful by CRI
short acting boluses useful during surgery

List the characteristics of Buprenorphine

Long acting
Good evidence to support use in cats
may not be effective via sc
delayed onset of action

List the characteristics of butorphanol

Poor analgesia
Can confound subsequent full mu agonist administration
good sedation

What premed opioid should you select for moderate to severe pain (fracture repair)

Methadone

What pre-med opiod should you select for moderate pain? (ex lap)

Pethidine
methadone
buprenorphine

What pre-med opioid would you select for mild pain (castration)

Buprenorphine

What opioid would you select for sedation?

Butorphanol

What other factors may influence the choice of opioid?

Use of alpha 2

Temperament of the animal (Light or heavy sedation)

During intra-operative period what opioid would you give for severe pain?

Methadone Fentanyl bolus/CRI Epidural morphine

During the intra-operative period what opioid would you give for moderate pain?

Methadone | Fentanyl bolue or CRI

During the intra-operative period what opioid would you give for mild pain?

Unnecessary

What else should you consider during the intra-operative period when administering analgesia?

Use of regional techniques cardiovascular stability (greater reliance on intra-operative opiods to spare inhalant agent) Adjunctive drugs Alpha 2 ketamine

How should you start analgesia in the post-operative patient?

``` Assess the patient make a plan assess the patient for pain and adjust the plan accordingly Assess the patient for pain Make a new analgesia plan ```

During the post-operative period what are the intervals of dosing for methadone, buprenorphine?

Methadone 4-5 hours (may need extending if repeatedly administered) Buprenorphine 6 hours

What is the average dose for burenorphine?

20mcg/kg im/iv

What is the average dosage for methadone?

0.3-0.5mg/kg 4 hourly intervals IV

What is the average dose for morphine and how is it administered?

CRI 0.2-0.25 mg/kg/hr

How is fentanyl administered post-operatively?

CRI low dose | gives better analgesia than morphine

What is naloxone and what is it used for?

``` Reverses effect of Mu receptor opioid Reverse opioid induced dysphoria Will antagonise the analgesic effect short acting 20-30 minutes 0.01-0.04 mg/kg iv ```

What is potency?

The concentration of the drug required to elicit half of the maximum biological response of the agonist. Buprenorphine is more potent than methadone or morphine

What is efficacy?

The maximum biological effect that the drug or receptor ligand can achieve following binding of the drug to the receptor

What must you consider when administering a fentanyl CRI during surgery?

May require ventilation of IPPV | Stop infusion 10-15 minutes before the end of the surgery

When using a transdermal fentanyl patch what are important factors to consider?

Low bioavailability use another drug alongside it | take 12-18hours to be full effective