Analgesia Opioids Flashcards
What opioids are licensed for use in dos?
Fentanyl, methadone, pethidine, buprenorphine
What opioids are unlicensed?
Morphine
alfentanil
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
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
For pethidine list the duration of action, use and routes of administration
60 minutes
Pre-medication and post-op analgesia
IM, SC
For fentanyl list the duration of action, use and routes of administration
20-30minutes
intra-op and post-op
iv(bolus, CRI), transdermal
For buprenorphine list the duration of action, use and routes of administration
6 hours
premed and post-op
IV(Bolus), IM, epidural, Oral, transdermal
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
What are the characteristics of an opioid?
Safe to give to effect
Very safe group of drugs
What are the clinical effects of opioids?
Sedation
Analgesia
Cough suppression
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
How is a drop in heart rate cause be administration of an opioid managed?
Administration of anticholinergenic
atropine
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
List the opioids in order from the most analgesic efficacy to the least
Fentanyl
methadone
buprenorphine
butorphanol
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
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
