Merck Manual

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Analgesics Used in Emergency Practice

Analgesics Used in Emergency Practice

Drug

Dosage

Comments

Morphine

Dogs: 0.05–0.4 mg/kg, IV, every 1–4 hr; 0.2–1 mg/kg, IM or SC, every 2–6 hr; 0.1 mg/kg diluted with 0.9% saline administered epidurally at 0.23 mL/kg, every 8–24 hr

Cats: 0.05–0.2 mg/kg, IM or SC, every 2–6 hr

Incremental IV bolus technique: dogs—increments of 0.1 mg/kg until analgesia appears adequate; cats—increments of 0.02 mg/kg. In dogs, this can be followed by CRI at 0.1 mg/kg/hr that can be increased incrementally if needed. Rapid IV injections may cause histamine release.

Oxymorphone/hydromorphone

Dogs: 0.02–0.1 mg/kg, IV, every 2–4 hr; 0.05–0.2 mg/kg, IM or SC, every 2–6 hr

Minimal cardiovascular effects; may cause panting or emesis

Cats: 0.02–0.05 mg/kg, IV, every 2–4 hr; 0.05–0.1 mg/kg, IM or SC, every 2–6 hr

Can be given as a CRI with the dose divided over 4 hr

Fentanyl

Dogs: 2–10 mcg/kg, IV, every 30–60 min; 2–20 mcg/kg/hr, IV as a CRI

With short half-life, fentanyl is best administered as a CRI.

Fentanyl transdermal patch

12.5 mcg/hr for animals <2.5 kg body wt; 25 mcg/hr for animals 2.5–10 kg body wt; 50 mcg/hr for animals 10–20 kg body wt; 75 mcg/hr for animals 20–30 kg body wt; 100 mcg/hr for animals >30 kg body wt

The patches cannot be cut. More than one patch may be used in larger animals. Injectable repository fentanyl solutions may be an alternative if available.

Butorphanol

Dogs: 0.2–0.5 mg/kg, IM, IV, or SC, every 1–3 hr

Has a ceiling effect; short duration of effect (1–2 hr) in most dogs

Cats: 0.1–0.4 mg/kg, IM, IV, or SC, every 1–6 hr

Can be given as a CRI with the dose divided over 4 hr

Buprenorphine

Dogs: 0.005–0.02 mg/kg, IM or IV, every 1–6 hr

May be more difficult to reverse

Cats: 0.005–0.01 mg/kg, IM, IV, or sublingual, every 4–8 hr

Sublingual absorption reported to be excellent in cats

Methadone

0.1–0.5 mg/kg IV, IM, or SC every 4–6 hr

Less vomiting than morphine, less panting than hydromorphone