Hydrocodone
Hydrocodone is a phenanthrene-derivative **opiate agonist** used primarily in veterinary medicine as a potent **antitussive** (cough suppressant) for dogs. * **Primary Indications:** Management of harsh, dry, non-productive coughs associated with conditions like collapsing trachea, bronchitis, or canine infectious tracheobronchitis (kennel cough). * **Behavioral Use:** Occasionally used to treat opioid-related behavioral problems (e.g., lick granulomas, stereotypies) by providing an exogenous opioid source to reduce self-stimulating behaviors. * **Analgesia:** Combination products containing acetaminophen can be used for moderate oral analgesia in dogs. > **CRITICAL WARNING:** Combination products containing acetaminophen (e.g., Vicodin®, Lortab®) are **STRICTLY CONTRAINDICATED IN CATS** due to fatal acetaminophen toxicity.
Mechanism: Hydrocodone acts primarily by binding to **mu-opioid receptors** in the central nervous system. * **Antitussive Effect:** Direct suppression of the cough reflex at the **cough center** in the **medulla oblongata**. * **Analgesic Effect:** Binds to pre- and post-synaptic **mu-receptors** in the brain and spinal cord → inhibits release of nociceptive neurotransmitters (like Substance P) → hyperpolarizes neurons → decreases excitability and pain transmission. * **Respiratory Effects:** Tends to have a drying effect on respiratory mucosa, increasing the viscosity of secretions. The addition of homatropine methylbromide (an anticholinergic) in some formulations enhances this drying effect.
Dosing by species
- For adjunctive treatment of opioid-related stereotypies · 1.25-5 mg per cat PO q12h · PO · q12h · Do NOT use any product that contains acetaminophen.
- For cough · 0.22 mg/kg PO q6-12h · PO · q6-12h · Goal is to suppress coughing without causing excessive sedation
- As an analgesic using fixed dose combination products with acetaminophen · 0.22-0.5 mg/kg of the hydrocodone component PO q8-12h · PO · q8-12h · Do not exceed 15 mg/kg of the acetaminophen component q8h.
- For cough using Hycodan (or equivalent) · ¼ to 1 tablet (5 mg) once to 4 times daily · PO · q6-24h · In small and medium sized dogs.
- For lick granulomas · 5-10 mg (1-2 tablets) per 20 kg of body weight PO three times daily · PO · TID
- For adjunctive treatment of opioid-related stereotypies, lick granuloma · 0.22-0.25 mg/kg PO q8-12h · PO · q8-12h · Supplies exogenous opioids to decrease the need for self-stimulation.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hypersensitivity to narcotic analgesics
- Patients receiving monoamine oxidase inhibitors (MAOIs, e.g., selegiline)
- Diarrhea caused by toxic ingestion (until toxin is eliminated)
- Acetaminophen-containing products MUST NOT be used in cats
Adverse effects
- Sedation
- Constipation (especially with chronic therapy)
- Vomiting
- Gastrointestinal disturbances
- Masking of clinical signs of underlying respiratory disease
Drug interactions
- Acepromazine · May cause additive hypotension in dogs with collapsing trachea
- Anticholinergic Drugs · May cause additive anticholinergic effects
- Antidepressants (Tricyclic & MAOIs) · May potentiate the adverse effects associated with the antidepressant
- CNS Depressants (anesthetics, antihistamines, phenothiazines, barbiturates, tranquilizers) · May cause increased CNS or respiratory depression
Monitoring
- Clinical efficacy (reduction in cough frequency/severity, pain relief)
- Adverse effects (excessive sedation, constipation, respiratory depression)
Overdose
Massive overdose primarily causes **CNS, cardiovascular, and respiratory depression** secondary to opiate effects. * **Treatment:** If ingestion was recent, empty the gut using standard protocols. Administer **naloxone** to reverse opioid effects as necessary. * **Note on Homatropine:** The homatropine ingredient in some formulations may cause anticholinergic effects, but its relatively low toxicity usually does not require specific treatment.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.