Codeine

What is this medication for?

• Oral analgesia (mild-moderate) when salicylates fail and injectable opiates not warranted; antitussive; antidiarrheal
• Analgesic (caution — CNS stimulation possible); acetaminophen combos absolutely contraindicated

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Sedation, constipation (Common)
• CNS stimulation/excitement (Documented feline response)
• Masks acute abdominal conditions (Diagnostic caution)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Respiratory depression (high doses) (Dose-ceiling effect)

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Narcotic hypersensitivity; MAOIs (selegiline, amitraz); toxin-caused diarrhea before toxin cleared; acetaminophen-containing products in cats (fatal methemoglobinemia/hepatic tissue death)
• has or has had: Hypothyroidism, severe renal insufficiency, Addison's, head trauma/↑ICP, acute abdomen, geriatric/debilitated, respiratory disease

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • MAOIs
  • Other CNS depressants
  • Anticholinergics/antidiarrheals

Storage and handling

Controlled: C-II (single-entity), C-III (combination products) — corresponding records/security.

Good to know

• The cat line bears repeating: Tylenol #3 kills cats (acetaminophen + feline glucuronidation failure) — the codeine/APAP product is a dog-only tool.
• Metabolic pharmacology nugget: analgesia depends on conversion to morphine — dogs do it variably, cats poorly (norcodeine-leaning) → thinner feline efficacy, and the human "ultrarapid metabolizer" concept doesn't translate simply.
• Oral step-down niche: when NSAIDs are insufficient/contraindicated and tramadol disappoints, plain codeine is the quiet oral opiate option (C-II logistics permitting).