Table 1: Commonly Used Opioids for Small Animals Pre-Anesthetic Medication Opioid Type Advantages/Benefits/Indications Effects Methadone mu opioid agonist • Sedation is enhanced in combination with an alpha-2 adrenergic agent or acepromazine.
• Can be given IV without causing a histamine release • May cause vomiting or hypersalivation in cats • Can cause mydriasis in cats • Reduced tear production in dogs when combined with acepromazine • Should be administered slow IV in animals with cardiovascular disease [hypertension or bradyarrhythmias]
• Less likely to cause vomiting or excitement, thus should replace morphine or hydromorphone in animals requiring analgesia with upper airway disease (brachycephalic syndrome, laryngeal paralysis, tracheal collapse), raised intracranial or intraocular pressure, or esophageal disease • Sedative effects commonly in conjunction with dexmedetomidine or acepromazine • Remains the recommended opioid analgesic in animals scheduled for gastroduodenal endoscopy • Has a ceiling effect: despite the increase in the dosage of drug, you will not see any more effect on the patient • Effective analgesics but with a shorter duration of action • Does not cause histamine release following intravenous administration • Oxymorphone causes less vomiting than morphine and hydromorphone, so it’s a better choice for patients with head trauma, eye injury, and gastrointestinal disorders. • Short acting and may be used when short term (30 minutes to 1 hour) analgesia is desired. usually given as a constant rate infusion (CRI) due to short action • Less sedating than the other mentioned opioids when administered via the SQ or IM routes
Butorphanol
• Opioid (full mu-agonist) partial reversal • Does not cause vomiting or excitement
Mixed agonist/ antagonist
Buprenorphine
• Slow onset of action regardless of the route of administration, usually takes about 30 minutes to reach its full effect • Associated with a high incidence of vomiting (50-75%) in dogs and cats • Hyperthermia in cats
partial agonist
Hydromorphone Oxymorphone
mu-opioid receptor agonists
Meperidine
• Short acting and may be used when short term (30 minutes to 1 hour) analgesia is desired. usually given as a constant rate infusion (CRI) due to short action • Less sedating than the other mentioned opioids when administered via the SQ or IM routes • Has the potential to cause histamine release (and associated hypotension) especially when administered intravenously • Causes bradycardia and respiratory depression
mu-opioid receptor agonist
Fentanyl
mu-opioid receptor agonist
• Has a very quick onset of action, usually within 2 to 3 minutes after IV administration and lasts about 20 minutes • Is a very potent analgesic • Has a high degree of cardiovascular safety • Does not cause vomiting or histamine release
Acepromazine Acepromazine is often given in combination with opioids to provide both sedation and analgesia. Acepromazine is ideal for cats: ● Anti-arrhythmic ● Prolonged duration Contraindications: ● Not suitable for brachycephalics or epileptics.
● In Boxers, as little as 0.02 mg/kg IM can cause collapse with the animal becoming very bradycardic and hypotensive [Recommendation: acepromazine should be given with atropine or glycopyrrolate] (Lee, 2024) . ● Causes significant hypotension in animals anesthetized with isoflurane. ● Debilitated animals with severe cardiac failure.
Page 23
Book Code: VFL1526
EliteLearning.com/Veterinarian
Powered by FlippingBook