Acute And Chronic Analgesic Drugs Flashcards
Opioid receptos sub-types
μ (mu)
k (kappa)
δ (delta)
Examples of opioids
Morphine Pethidine Methadone Buprenorphine Butorphanol Fentanyl Alfentianil
pure μ agonists
Morphone, methadone and pethidine
partial μ agonist
Buprenorphine
k agonist and a μ antagonist
Butorphanol
Opioid that can’t be given IV
Pethidine
Requirements of an opioid drug to enable it to be given epidutally
Preservative-free or preservatives are not neurotoxic
Opioid metabolism and excretion
Metabolised by the liver and excreted in the urine
Opioids commonly used for pre-medication
Buprenorphine, methadone and butorphanol
How NSAIDs work
Blocking Cyclo-oxygenase enzymes (COX)
COX enzymes convert arachidonic acid to:
Prostoglandins
Accumulation of prostoglandins reaction
Red, swollen, warm and painful tissues
Uses for NSAIDs other than analgesia
Anti-inflamatory
Anti-pyretic (decreases body temperature)
Anti-endotoxaemic
NSAIDs should not be used in these cases
- When a sterioid has been used
- In renal failure
- In cases of hypovolaemia
- When an animal is hypotensive
- Evidence of gastro-intenstinal ulceration, vomiting or diarrhoea
- Animals with a clotting dysfunction
Why do NSAIDs have an effect on clotting?
Thromboxane A2 a factor which helps in clotting is blocked by NSAID administration
Which part of the pain pathway to NASIDs affect?
Transduction
Which part of the pain pathway do Alpha 2 adrenergic agonists affect?
Modulation and Perception
How Alpha 2 adrenergic agonists are handled by the body
Metabolised in the liver and excreted in the urine
Routes of administration for Alpha 2 Adrenergic agonists
IV, IM, SC
Epidural route
Can be absorbed by mucous membranes
Ketamine mode of action to produce analgesia
An antagonist at NMDA (N-methyl D-aspartate) receptors which are involved in the development of central sensitisation
Type of pain Ketamine is most useful against.
Somatic pain
Analgesic drugs that can produce a total absence of pain
Local anaesthetics
Local anaesthetics work on which part of the pain pathway
Transmission
How do local anaesthetics work?
To stop the transmission of electrical impulses along nerves by blocking the sodium channels in the nerve fibres
Examples of local anaesthetic drugs
- Lidocaine
- Bupivicaine
- Ropivacaine
- Mepivacaine
- Procaine
Two subdivisions of local anaesthetics
Amide Linked group
Ester Linked Group
Local anaesthetics belonging to the Amide Linked Group
- Lidocaine
- Bupivacaine
- Mepivacaine
- Ropivacaine
How are Amide Linked local anaesthetics handled by the body?
Metabolised by the liver
The only local anaesthetic that can be administered intravenously
Lidocaine
Local anaesthetics belonging to the Ester linked group
Procaine
How are Ester linked group local anaesthetics managed by the body?
Broken down in the blood by enzymes
Duration and onset of action for lidocaine
5-10 minutes onset
Last up to 1 hour
Duration and onset of action for Bupivacaine
30 minute onset
6-8 hour duration
Local anaesthetic that produces less motor blockade than others
Ropivacaine
How can maropitant produce analgesia?
Creates visceral analgesia by antagonising the NK1 receptors
Non pharmaceutical methods of pain management
- Providing a comfortable environment - correct temperature, quiet, comfortable bedding
- Adequate nutritional support to aid wound healing
- encourage normal sleeping patterns with light and dark times
- grooming, TLC and quality time
- Gentle physiotherapy - massage, hot and cold packs, passive range of motion exercises
- support of fracture with bandages/sprints and wound dressings
- ensuring an empty bladder and bowels
What does galliprant target
Works as an antagonist at the EP4 receptor for PGE2
- can provide analgesia for osteoarthritis without affecting other enzymes
What does bedvetinmab (librealla & Solensia) target?
Contains monoclonal antibody (mAb) which targets nerve growth factor (NGF)
Paracetamol action
Non-acidic NSAID which acts at the level of the spinal chord COX enzymes, the opioid, serotoninergic and cannabinoid systems
Dose rate for paracetamol
10mg/kg IV
Up to 30mg/kg PO BID or TID
Mechanism of Gabapentin and Pregabalin
Binding to calcium channels in the CNS, reducing the production of pro-nociceptive inputs and facilitating descending inhibitory pathways
Tramadol mechanism
works at the µ opioid receptors, 5HT receptors and noradrenaline receptors.
NMDA Antagonist
Amantadine
Additional therapies added to pain management plans
Acupuncture
Physiotherapy
