Makindo Medical Notes

Related Subjects: |Drug Toxicity - clinical assessment |Sedation and Analgesia on ITU |Neuropathic Pain Management |Codeine |Dihydrocodeine |Diamorphine |Morphine |Paracetamol (Acetaminophen) |Tramadol |Toxin elimination by dialysis |Drug Toxicity with Specific Antidotes |Naloxone (Narcan) Opiate antagonist

Opiate reversal can cause myalgia, vomiting, yawning, chills, and diarrhoea. In end-of-life care, if concerned about opiate toxicity, administer very small doses of naloxone.

About

• Commonly used both medically and illegally for pain management, but accidental overdose is common, often due to increasing tolerance and required doses.
• Naloxone is an essential opiate antagonist to manage overdose symptoms and should be used with knowledge of dosing.
• Overdose can be accidental or intentional.

Aetiology

• Opioids bind to kappa and Mu CNS opioid receptors, producing analgesia, sedation, and respiratory depression.

Common Opiates

• Heroin
• Methadone
• Codeine
• Oxycodone
• Pethidine
• Dihydrocodeine
• Coproxamol
• Diamorphine
• Morphine
• Dextropropoxyphene

Clinical Presentation

• Drowsiness and depressed level of consciousness and respiration.
• Constricted (pinpoint) pupils.
• Visible signs of drug abuse, such as needle marks in habitual users.
• Co-ingestion with alcohol can exacerbate effects, increasing sedation and respiratory depression.
• Additional symptoms may include mild hypotension, agitation, and, rarely, seizures.
• Specific cardiac effects like arrhythmias may occur with certain opioids, e.g., dextropropoxyphene.

Investigations

• U&E, FBC, ABG, LFTs, and lactate to assess metabolic state and organ function.
• ECG: QRS widening, arrhythmias, and potential heart block, especially with dextropropoxyphene.
• CXR if signs of sepsis or respiratory infection are present.
• CT head if the cause of reduced consciousness (GCS) remains unclear.
• Screen for other potential co-ingested substances, including paracetamol and salicylates.

Management

• ABCs: Ensure airway, breathing, and circulation are stable; initiate resuscitation if necessary. Administer high-flow oxygen at 15 L/min as needed.
• For pulmonary oedema, consider diuretics and CPAP in non-cardiogenic cases.
• Administer naloxone: Initial dose: 0.4 mg (400 mcg) to 2 mg (2000 mcg) IV or IM.
• Naloxone has a shorter half-life than many opioids, so repeated doses or a continuous IV infusion may be needed.
• Monitor closely, particularly respiratory rate and coma depth. Adjust infusion rate according to vital signs.
• Note: Naloxone may cause hypertension, arrhythmias, pulmonary oedema, or cardiac arrest, especially in high doses.
• In cases where IV access is difficult or the patient may abscond, IM naloxone is an alternative.

References

• Opiate toxicity online reference