Clonidine (Catapres, Duraclon, Kapvay)

Premedication - 2–4 mcg/kg PO 60–90 min before induction reduces preoperative anxiety, minimum alveolar concentration (MAC), and intraoperative opioid requirement; particularly useful in pediatric premedication at 4 mcg/kg PO.

Regional anesthesia adjunct - 1–2 mcg/kg added to local anesthetic in spinal, epidural, or peripheral nerve block prolongs analgesia and motor block; typical neuraxial dose 30–100 mcg.

Intraoperative sympatholysis - 1–2 mcg/kg IV over 10 min blunts the hemodynamic response to laryngoscopy and surgical stimulation, and reduces volatile MAC.

Pediatric emergence delirium - 1–2 mcg/kg IV at the end of a sevoflurane-based anesthetic reduces the incidence and severity of emergence agitation.

Postoperative shivering - 0.5–1 mcg/kg IV terminates shivering rapidly.

Withdrawal management - Opioid withdrawal: 0.1–0.3 mg PO every 6–8 hr titrated to symptoms; alcohol withdrawal as adjunct to benzodiazepines.

Continue chronic clonidine perioperatively - Abrupt discontinuation produces severe rebound hypertension; if patient cannot take PO, bridge with the transdermal patch (allow 2–3 days for steady-state) or IV infusion.

Bradycardia and hypotension - Treat with atropine, glycopyrrolate, fluids, and direct vasopressors (phenylephrine, norepinephrine); hemodynamic effect lasts hours, not minutes.

Drug Interactions - Additive sedation with benzodiazepines, opioids, and volatile anesthetics; additive bradycardia with beta-blockers and dexmedetomidine; tricyclic antidepressants may blunt antihypertensive effect.

Pediatric Implications - Premedication 2–5 mcg/kg PO; caudal or epidural 1–2 mcg/kg (max 50–100 mcg). Avoid in neonates and infants under 3 months because of apnea risk; expect prolonged sedation in younger children.

Obstetric Implications - Used as an epidural labor-analgesia adjunct (75–150 mcg neuraxial). Crosses placenta but typical doses produce minimal neonatal sedation. Compatible with breastfeeding.

Absolute: severe sinus-node dysfunction or symptomatic bradyarrhythmia, second- or third-degree atrioventricular (AV) block without a pacemaker, cardiogenic shock.

Relative: severe coronary insufficiency, recent myocardial infarction, severe hepatic disease, depression history, polysubstance abuse.

Caution: elderly (prolonged sedation), volume-depleted patients, concurrent high-dose beta-blocker therapy, infants under 3 months.

Adult sympatholysis or sedation: 1–2 mcg/kg IV over 10 min.

Postoperative shivering: 0.5–1 mcg/kg IV.

Pediatric emergence delirium: 1–2 mcg/kg IV at end of case.

0.1–2 mcg/kg/hr for ICU sedation, withdrawal management, or postoperative analgesia.

75–150 mcg (1–2 mcg/kg) added to local anesthetic in single-shot or initial-dose epidural.

20–40 mcg/hr added to a continuous epidural infusion.

15–150 mcg added intrathecally; 30–75 mcg typical for prolongation of bupivacaine spinal.

0.5–1 mcg/kg added to peripheral nerve block local anesthetic, maximum 150 mcg.

Central alpha-2 adrenergic agonist in the locus coeruleus and dorsal horn, decreasing sympathetic outflow and producing sedation and analgesia partly through release of endogenous opioids; less alpha-2 selective than dexmedetomidine.

Hepatic (about 50%); remainder excreted unchanged.

Renal.

Available formulations: oral tablet 0.1, 0.2, 0.3 mg; transdermal patch (Catapres-TTS) 0.1, 0.2, 0.3 mg per 24 hr; preservative-free injection (Duraclon) for neuraxial use.

Patch reaches steady state in 2–3 days; do not initiate intraoperatively to control acute hemodynamics.

Less alpha-2 selective than dexmedetomidine (about 200:1 versus 1620:1 for alpha-2:alpha-1) but cheaper and available in oral and transdermal forms.

Avoid abrupt discontinuation in patients on chronic therapy — taper or use the patch as a bridge to prevent rebound hypertension.

Mark and protect any in-place transdermal patch during prepping and draping.