Clonidine 💊

💊 About: Always check the BNF link here

• An alpha-2 receptor agonist licensed for hypertension.
• Widely used in Critical Care as an additional sedative when standard sedatives are insufficient - particularly useful in agitation with tachycardia and hypertension during ventilator weaning.
• ⚠️ Must not be withdrawn suddenly ➝ wean gradually to avoid rebound hypertension and agitation.

⚙️ Mode of Action

• Stimulates central alpha-2 receptors in the vasomotor centre of the brainstem.
• ↓ Noradrenaline release + ↑ parasympathetic tone ➝ reduces peripheral vascular resistance.
• Sedative effects may relate to action at the locus coeruleus.

💉 Dose

• Hypertension: 50–100 micrograms TDS; increase every 2–3 days. Max: 1.2 mg/day.
• Migraine prevention: 50 micrograms BD × 2 weeks → increase if required to 75 micrograms BD.
• ICU sedation / hypertension management:
  • Loading dose: 75 micrograms (5 mL of 150 micrograms/mL solution) slow IV over 10 min.
  • Maintenance: 0.5–2 micrograms/kg/hr (max 4 micrograms/kg/hr).
  • Weaning: Reduce by 0.25–0.5 micrograms/kg/hr to minimise rebound hypertension & agitation.
• 📌 Used off-label for alcohol/opiate withdrawal and autonomic storm post-traumatic brain injury.

🔄 Interactions

• + Haloperidol → possible QT prolongation.
• Multiple other interactions may increase risk of hypotension (always cross-check with BNF).

⚠️ Cautions

• Hypotension, bradycardia, impaired LV function.
• Raynaud’s or other occlusive peripheral vascular disease.
• Avoid in depression and porphyria.
• 📌 Half-life: 10–20 hrs, prolonged up to 41 hrs in ESRF.

🚫 Contraindications

• Severe bradyarrhythmia due to 2nd/3rd-degree AV block or sick sinus syndrome.

❗ Side Effects

• Sedation, constipation, postural hypotension, sleep disturbance, depression, vomiting, AV block, Raynaud’s.
• Pregnancy: avoid (↓ fetal heart rate). Breastfeeding: avoid (present in milk).

📚 References

• Local Guidelines on Clonidine