Alpha-2 Adrenergic Agonist
Pregnancy: Caution — limited data; used for hypertension in pregnancy (labetalol/nifedipine preferred)
Clonidine
Brand names: Catapres
Adult dose
Dose: Anaesthetic adjunct: 150 mcg IV over 10 min. Hypertensive crisis: 150 mcg IV slowly. Opioid/alcohol withdrawal: 75–150 mcg TDS oral. Pain adjunct: 150 mcg epidural (single dose).
Route: IV, oral, or epidural
Frequency: Single dose IV; TDS oral
Max: 300 mcg IV; 900 mcg/day oral
Central alpha-2 agonist — reduces anaesthetic requirements (reduces MAC of volatile agents), provides perioperative analgesia, reduces opioid consumption. Causes bradycardia and hypotension. Sudden discontinuation after prolonged use: rebound hypertension.
Paediatric dose
Dose: 1 mcg/kg
Route: IV or oral
Frequency: Single dose IV; TDS oral
Max: 4 mcg/kg
Concentration: 150 mcg/mL mcg/ml
Paediatric sedation: 1–2 mcg/kg IV or oral. Also used for ADHD (off-label) and withdrawal management in neonatal opioid withdrawal syndrome.
Dose adjustments
Renal
Reduce dose in severe renal impairment (renally excreted)
Hepatic
Caution in severe hepatic impairment
Paediatric weight-based calculator
Paediatric sedation: 1–2 mcg/kg IV or oral. Also used for ADHD (off-label) and withdrawal management in neonatal opioid withdrawal syndrome.
Clinical pearls
- Reduces MAC of volatile agents by 20–30% — useful for opioid-sparing anaesthesia
- Epidural clonidine: excellent adjunct for postoperative pain (reduces opioid requirements)
- Neonatal opioid withdrawal (NAS): clonidine used as adjunct to morphine for symptom control
- Do NOT stop abruptly after >2 weeks oral therapy — rebound hypertensive crisis; taper dose over 1–2 weeks
Contraindications
- Sick sinus syndrome or severe bradycardia
- Second/third degree AV block (without pacemaker)
- Severe peripheral vascular disease (relative)
Side effects
- Sedation (useful perioperatively)
- Bradycardia
- Hypotension
- Dry mouth
- Constipation
- Rebound hypertension on sudden discontinuation (long-term oral use)
Interactions
- Beta-blockers — additive bradycardia/AV block; enhanced rebound hypertension if both stopped simultaneously
- Ciclosporin — clonidine inhibits tubular secretion; increased ciclosporin toxicity
- TCAs — reduce antihypertensive effect of clonidine
Monitoring
- Heart rate (bradycardia risk)
- Blood pressure
- Sedation level
- Signs of rebound hypertension on discontinuation
Reference: BNFc; BNF; BNF for Children; Miller's Anaesthesia; Eisenach JC (Anesthesiology review). Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.