Codeine: veterinary dose and monograph

At a glance

Drug class

Analgesic

Also known as

Codeine phosphate, Codeine + paracetamol (Codistar/Coditard)

Species with doses

Dogs and Cats

General dose range

1–2 mg/kg PO q6–8h — check the species tables for the indication

Routes

PO

Last reviewed

1 October 2026

Indications

• Mild–moderate pain (often with paracetamol or an NSAID, multimodal)
• Antitussive — suppression of non-productive cough
• Antidiarrhoeal (reduces GI motility)

Codeine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Mild–moderate pain: Papich 5e: 0.5–1 mg/kg q4–6h PO. Plumb’s p.313: 0.5–2 mg/kg PO titrated to effect q6–12h (Mathews 2000); with acetaminophen (60 mg codeine/300 mg tablet) 1–2 mg/kg of codeine q6–8h (dogs only). Oral bioavailability in dogs is low.
• Antitussive: Papich 5e: 0.1–0.3 mg/kg q4–6h PO. Plumb’s p.313: 1–2 mg/kg PO q6–12h (Fenner 1994); start as low as 0.1–0.3 mg/kg q8–12h and increase to effect (Church 2003).
• Antidiarrhoeal: Plumb’s p.313 (Sherding & Johnson 1994): 0.25–0.5 mg/kg PO q6–8h.

Cats

• Pain (plain codeine, cautious): Papich 5e: 0.5 mg/kg q6h PO, increased as needed. Plumb’s p.313: 0.5–2 mg/kg PO q6–8h (Scherk 2003; Mathews 2000). NEVER the acetaminophen combination in cats. Antitussive (Papich): 0.1 mg/kg q6h PO.

Contraindications

Cats — avoid codeine/paracetamol combinations (feline paracetamol toxicity); plain codeine used cautiously at low dose only. Respiratory depression/severe asthma. Head trauma with raised ICP (relative). Constipation/ileus (opioid). Concurrent MAOIs/selegiline. Known opioid hypersensitivity.

Species-specific warnings

Cats: Use only plain codeine cautiously; codeine/paracetamol COMBINATION products are contraindicated (fatal feline paracetamol toxicity).

Adverse effects

• Sedation, constipation
• Respiratory depression (high dose)
• Nausea/vomiting, inappetence
• Excitation/dysphoria in cats

Drug interactions

• Other CNS depressants (sedatives, other opioids, anaesthetics): additive sedation/respiratory depression
• MAO inhibitors / selegiline: serotonergic/excitatory reaction — avoid
• Anticholinergics: additive constipation
• Paracetamol (combination): hepatotoxic to cats — dog use only

Pregnancy and lactation

Crosses the placenta; neonatal respiratory depression if used near parturition. Use only if needed.

Monitoring

• Analgesic/antitussive response
• Sedation, respiratory rate, constipation
• For combination products: ensure patient is a dog (not a cat) and watch hepatic values
• Controlled-drug accountability

Toxicity and overdose

Overdose: sedation, respiratory depression, miosis (dogs), constipation, and in cats excitation. Codeine/paracetamol combination overdose adds paracetamol hepatotoxicity (and is outright dangerous in cats). Generally a wide margin for the analgesic effect in dogs.

Management: Antidote: naloxone for opioid effects (respiratory depression). Support ventilation/oxygenation. For combination-product overdose, treat paracetamol toxicity with N-acetylcysteine and monitor liver values. Supportive care; manage constipation.

Clinical pearls

• A handy oral step for mild–moderate pain and as an antitussive — works well in multimodal protocols (with paracetamol in dogs or an NSAID)
• Dogs convert little codeine to morphine, so don't expect strong-opioid potency; titrate and add other modalities
• NEVER use codeine/paracetamol combinations in cats (paracetamol is lethal to them)
• Expect constipation on chronic dosing — anticipate and manage it

Mechanism of action

A prodrug-like opioid that acts as a relatively weak mu-opioid receptor agonist itself; in humans ~10 % is O-demethylated by CYP2D6 to morphine (the main analgesic route), but dogs have limited CYP2D6-type conversion, so canine analgesia derives more from codeine and codeine-6-glucuronide. Mu activation inhibits nociceptive transmission, suppresses the brainstem cough centre (antitussive) and slows GI motility (antidiarrhoeal/constipating).

Formulations and products

• 15 / 30 / 60 mg tablet
• Codeine linctus 3 mg/mL (15 mg/5 mL)
• Codeine + paracetamol combination tablet
• Codeine phosphate — 15 / 30 / 60 mg tablet, Tablet (human-label)
• Codeine linctus — 15 mg/5 mL syrup, Linctus (antitussive) (human-label)

Storage

Tablets/linctus: 15–30 °C, protect from light; SECURE controlled-drug storage and records.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other analgesics

• Aspirin
• Bupivacaine
• Buprenorphine
• Butorphanol
• Dipyrone (Metamizole)
• Fentanyl
• Gabapentin
• Hydromorphone

Frequently asked questions