Page 389 - WSAVA2018
P. 389

NSAIDs
Examples include: Meloxicam, carprofen (Rimadyl ®), ketoprofen, phenylbutazone, aspirin, acetaminophen (paracetamol), robenacoxib (Onsior ®), firocoxib (Previcox ®), derocoxib (Deramaxx ®)
NSAIDs act peripherally as a group inhibiting the production of the enzyme cyclo-oxygenase and reduce the level of prostaglandins in the tissue. These actions reduce the inflammation around the injured tissue and produce direct analgesia at the site of pain.
The cyclo-oxygenase is an enzyme that is responsible for formation of inflammatory mediators, particularly prostaglandins. It can be divided into 2 groups:
• COX 1, a ‘house-keeping’ enzyme
• COX 2, an enzyme responsible for inflammation and
pain
Older NSAIDs tended to inhibit both COX-1 and COX-2. More recent drugs are being refined to only inhibit COX- 2, as COX-1 is a ‘good’ enzyme.
The prostaglandin production that is inhibited is also not ‘specific’; therefore, some ‘good’ prostaglandins are also inhibited. This includes the prostaglandins that:
• Maintain gastrointestinal mucosal integrity
• Maintain normal platelet function
• Maintain normal renal perfusion
Due to this inhibition of prostaglandins, care must be taken when administering NSAIDS. They are contraindicated in certain situations, including:
• Geriatric patients
• Trauma patients
• Patients with active bleeding or bleeding disorders
• Renal failure patients
• Patients with liver disease
NSAIDs must never be administered together with corticosteroids.
Side-effects of NSAIDS:
• Gastric irritation - This can manifest as vomiting, diarrhoea, gastric haemorrhage.
• Renal Compromise- Prostaglandins maintain and regulate the haemodynamic and blood flow of the kidneys.
• Platelet dysfunction- Prostaglandins are also involved in the induction of aggregation (unification) of platelets. Therefore, NSAIDs prolong bleeding times.
Your Singapore, the Tropical Garden City
Local anaesthetics
Examples include: Lignocaine, Bupivicaine, Marcaine and Prilocaine.
Local anaesthetics produce reversible block of nerve impulse conduction peripherally and in the spine (epidural), depending on site of administration of drug. This produces a loss of sensation and function to the blocked area.
Opioids
Opioids prevent the message from being received in the brain. All opioids have slightly different properties and the choice of drug used can be dependent upon several factors including:
• Patient presentation/disease/injury • Type of pain
• Potency of drugs
• Side effects that may occur
• Length of duration
• Route of elimination
• Veterinarian preference
Opioids bind to specific opioid receptors in the central nervous system to produce analgesia. Due to each drug having different properties some will stimulate and some will inhibit the various receptors. Therefore, combination of opioids must be used with great care as one can disrupt the effects of the other.
Types of Opioids
 Area
   Application
   Example
   Nerve/Regional Blocks
 Local anaesthetic is injected into or around the nerves of a specific area
 Thoracotomy – intercostal nerve infiltration Dental surgery Distal limb surgery
 Epidural
  Local anaesthetic is injected into the area around the spinal cord
  Stifle surgery Large animal caesarean
 Topical
   Applied directly on the skin/ area of pain
    Drug
  Use
  Duration
  Other
  Side-effects
  Morphine
 Severe pain
 ~4hrs
  Action is dose dependent Higher doses or repeated does will increase the analgesic effect
Vomiting Constipation Respiratory depression
  Methadone
 Severe pain
 ~4hrs
 Synthetic opioid Similar to morphine Quicker onset than morphine
 Less side effects than morphine No vomiting
 Fentanyl
  Severe pain
  3-5hrs
  100x potency of morphine Peak effect 5mins after I/V
  Bradycardia
  Pethidine
 Mild pain
 1-2hrs
  1/10th potency of morphine
Can cause hypotension/histamine release if given fast I/V
  Buprenorphine (E.g. temgesic ®)
  Mild – moderate pain
  8 hrs
  Slow onset of action Overdose will cause no analgesia
  Slight cardiovascular effects
  Butorphanol (E.g. torbugesic®)
  Mild, visceral or somatic pain
  ~2hrs
   Potent anti-tussive
 Slight respiratory effects
           387
            














   387   388   389   390   391