Opiates

Related Subjects: |Analgesia and Pain management |Sedation and Analgesia on ITU |Neuropathic Pain Management |Codeine |Dihydrocodeine |Diamorphine |Morphine |Paracetamol (Acetaminophen) |Tramadol |Naloxone (Narcan) Opiate antagonist

💊 About Opiates (Opioids)

• ⚠️ IV opioids must be given slowly and titrated to effect.
• 📈 Start low and increase cautiously, especially in opioid-naïve patients.
• 🚨 Naloxone must always be immediately available where IV opioids are administered.
• 🧠 Regular reassessment of pain, sedation, and respiratory rate is essential.

🚑 Key Safety Rule: Respiratory rate < 8/min, pinpoint pupils, and reduced consciousness = suspect opioid toxicity → give naloxone and support airway.

⚙️ Mode of Action

• 🔗 Act primarily on μ-opioid (mu) receptors in the CNS and spinal cord.
• 📉 Reduce neurotransmitter release → inhibit pain transmission.
• 😊 Produce analgesia, sedation, and euphoria.
• ↩️ Effects are rapidly reversed by naloxone (opioid antagonist).

🎯 Indications

• 🩹 Pain control: Acute, chronic, post-operative, trauma.
• 😮‍💨 Persistent cough: Codeine (short-term only).
• 🌙 Palliative care: Severe cancer-related pain (no upper dose limit if titrated).
• ❤️ Acute MI: Morphine for pain and anxiety (specialist-guided use).
• 🏥 End-of-life care: Relief of pain and dyspnoea.

🚫 Contraindications & Cautions

• ⛔ Absolute Contraindications
  • Severe respiratory depression.
  • Uncontrolled cardiogenic shock (unless specialist-led).
• ⚠️ Cautions
  • Elderly or frail patients.
  • Renal or hepatic impairment.
  • Sleep apnoea.
  • Concurrent CNS depressants (alcohol, benzodiazepines, TCAs, antipsychotics).
  • History of substance misuse.

💉 Common Opioid Drugs (UK Practice)

• Morphine: Gold standard; oral, IV, SC, IM.
• Diamorphine: Highly lipid-soluble; often in palliative care and emergencies.
• Fentanyl: Very potent; IV and transdermal patches (high overdose risk).
• Oxycodone: Oral; alternative to morphine.
• Codeine: Prodrug → ~10% converted to morphine.
• Dihydrocodeine: Similar to codeine.
• Tramadol: Weak opioid + serotonin/noradrenaline effects.

⚠️ Clinical pearl: Avoid fentanyl patches in opioid-naïve patients — delayed absorption can cause fatal overdose.

⚠️ Side Effects

• 🫁 Respiratory depression – most dangerous acute toxicity.
• 📉 Hypotension – peripheral vasodilation.
• 🍽️ Gastrointestinal
  • Constipation (nearly universal).
  • Nausea and vomiting.
• 🧠 CNS
  • Sedation.
  • Euphoria or dysphoria.
  • Tolerance and dependence.
• 🔬 Other
  • Pruritus (histamine release).
  • Biliary spasm.
  • Urinary retention.
  • SIADH-like ADH release.

💡 Always prescribe laxatives with long-term opioids unless contraindicated.

🔁 Drug Interactions

• 🍺 Alcohol → ↑ sedation and respiratory depression.
• 💊 Benzodiazepines → ↑ overdose risk.
• 💊 TCAs / antipsychotics → ↑ CNS depression.
• 🌿 St John’s Wort → may reduce opioid effect.
• 🧠 SSRIs + tramadol → serotonin syndrome risk.

💉 Opioid Switching & Dose Conversion

Sometimes switching opioid or route (e.g. oral → SC) improves pain control or reduces side effects. Always reduce calculated dose by 25–50% when switching (incomplete cross-tolerance).

⚠️ After any conversion: monitor closely for 24–72 hours for toxicity or withdrawal.

🚨 Naloxone in Opioid Toxicity

• 💉 Initial IV dose: 100–200 micrograms.
• 🔁 Repeat every 2–3 minutes as needed.
• 🫁 Maintain airway and oxygenation.
• ⚠️ May precipitate acute withdrawal.
• ⏳ Shorter half-life than most opioids → re-sedation risk.

🩺 Practical Prescribing Tips

• Start low, go slow.
• Review pain, sedation, RR at every dose change.
• Prescribe antiemetic + laxative.
• Use pain scales and functional goals.
• Escalate early if pain remains uncontrolled.