Papaveretum
Papaveretum is a mixture of the alkaloids of opium containing the equivalent of anhydrous **morphine 85.5%**, anhydrous **codeine 6.8%** and **papaverine 7.8%**. It is used for the management of moderate to severe pain in the perioperative period and incorporated into sedative and pre-anaesthetic medication protocols to provide improved sedation and analgesia. It has a similar effect to morphine with an approximate 4-hour duration of action. > **Clinical Warning:** Methadone should be used in preference to papaveretum as the licensed alternative for single or repeated bolus administration to dogs and cats. Papaveretum is not widely used for postoperative analgesia but tends to be used in combination with acepromazine to provide good sedation in aggressive dogs.
Mechanism: Papaveretum provides analgesia primarily mediated by acting as an agonist at the **mu (μ) opioid receptor** in the central nervous system. This binding inhibits the release of nociceptive neurotransmitters (such as Substance P) → altering the perception of and response to pain.
Dosing by species
- Analgesia / Sedation · 0.2-0.8 mg/kg · IV/IM/SC · PRN · Duration of action is approximately 4 hours · Use lower doses IV; only use higher doses when deep sedation is required. Often given as part of a combination for sedation.
- Analgesia / Sedation · 0.2-0.3 mg/kg · IV/IM/SC · PRN · Duration of action is approximately 4 hours · Often given as part of a combination for sedation.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- No specific contraindications available, but use with caution in patients with impaired liver function or pregnant animals near parturition.
Adverse effects
- Vomiting (common)
- Respiratory depression (especially IV during general anaesthesia)
- Constriction of gastrointestinal sphincters (e.g., pyloric sphincter)
- Reduction in gastrointestinal motility
- Sedation in neonates (crosses placenta)
Drug interactions
- Anaesthetics · Increased CNS or respiratory depression · major
- Antihistamines · Increased CNS or respiratory depression · moderate
- Barbiturates · Increased CNS or respiratory depression · major
- Phenothiazines (e.g., Acepromazine) · Increased CNS or respiratory depression; often used together intentionally for deep sedation · moderate
- Tranquillizers · Increased CNS or respiratory depression · moderate
Monitoring
- Respiratory rate and depth (especially under general anaesthesia)
- Pain scores (due to variable individual response)
- Level of sedation
- Heart rate and blood pressure
Overdose
Overdose can lead to severe **respiratory depression**, profound sedation, and potentially cardiovascular collapse. Severe adverse effects can be treated and reversed with the opioid antagonist **naloxone**.
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.