Ropivacaine

Ropivacaine is a long-acting amide local anaesthetic given as the pure S-enantiomer. It is less cardiotoxic and produces less motor block than bupivacaine at equal concentrations, which favours its use for labour epidural analgesia, postoperative infusions and peripheral nerve blocks.

Class. Amide local anaesthetic (long-acting, S-enantiomer).

Mechanism. Reversible blockade of voltage-gated sodium channels, with more selective blockade of sensory over motor fibres at low concentrations.

Pharmacokinetics. Onset 10 to 30 minutes for blocks, 5 to 15 minutes for epidural. Duration 2 to 6 hours for blocks, up to 8 hours for epidural. Protein binding about 94% (alpha-1 acid glycoprotein, which rises after surgery and limits free drug during prolonged infusions). Half-life about 2 hours. Hepatic metabolism by CYP1A2 (3-hydroxylation) and CYP3A4; renal excretion.

Indications are surgical anaesthesia (epidural, blocks), labour analgesia, and postoperative analgesia by infusion or intermittent bolus.

Maximum doses (adults)

• Single dose: 3 mg/kg, not above 225 mg.
• Infusion: epidural up to 28 mg/hour (14 mL/hour of 0.2%) for up to 72 hours; the 24-hour total after bolus and infusion is about 800 mg in most labels.
• Concentrations: 0.2% is 2 mg/mL, 0.5% is 5 mg/mL, 0.75% is 7.5 mg/mL and 1% is 10 mg/mL.

Techniques

• Epidural, surgical: 0.5% in 15 to 25 mL (75 to 125 mg) or 0.75% in 15 to 20 mL (113 to 150 mg), in incremental doses.
• Epidural, labour analgesia: loading 0.1 to 0.2% in 10 to 20 mL; maintenance 0.1 to 0.2% at 6 to 14 mL/hour, or programmed intermittent boluses.
• Postoperative epidural infusion: 0.2% at 6 to 14 mL/hour.
• Peripheral nerve block: 0.5% in 15 to 30 mL (75 to 150 mg), up to 0.75% for major blocks.
• Infiltration: 0.2% up to 200 mg.
• Spinal use: not licensed in many regions.
• Intravenous regional anaesthesia: not advised.

Children

• Caudal block: 0.2% at 1 mL/kg (2 mg/kg) for lumbar and thoracic levels up to 1.25 mL/kg.
• Continuous epidural infusion in infants is specialist practice, weight-based and lower in neonates, because of accumulation.

Contraindications. Hypersensitivity to amide anaesthetics; intravenous regional anaesthesia; obstetric paracervical block; infection at the site; hypovolaemia (relative for neuraxial blocks); coagulopathy or anticoagulation for neuraxial techniques.

Boxed-warning-level risks. Systemic toxicity with seizures and cardiovascular collapse after inadvertent intravascular injection or high infusion rates; rare cardiac arrest with the 0.75% concentration in obstetrics (not advised).

Adverse effects. Common: hypotension, nausea, bradycardia, back pain, motor block. Serious: local anaesthetic systemic toxicity, high spinal block, nerve injury, arrhythmias and cardiac arrest, anaphylaxis (rare).

Interactions. CYP1A2 inhibitors (fluvoxamine, ciprofloxacin, enoxacin) raise concentrations markedly; CYP3A4 inhibitors raise them modestly. Other amide anaesthetics add systemic toxicity. Beta blockers and calcium channel blockers add cardiac depression.

Common prescribing errors. Exceeding 28 mg/hour by running high-rate infusions of 0.2% with a block catheter; adding a second local anaesthetic infiltration without counting the dose; confusing concentration (2 mg/mL, 5 mg/mL, 7.5 mg/mL); extended infusions in patients with hepatic disease.

Special groups

• Pregnancy: acceptable for labour epidural and caesarean section.
• Breastfeeding: compatible.
• Older adults: reduce bolus and infusion rates by 20 to 30%.
• Kidney impairment: no dose change for single doses; consider caution for prolonged infusion.
• Liver impairment: reduce repeat dosing and infusion; avoid prolonged infusion in severe disease.
• Regional: confirm concentration and volume on the vial before drawing up.

Formulations. Solutions 0.2%, 0.75% and 1% in ampoules and infusion bags, and 0.5% in some markets.

Administration. Aspirate and inject in 3 to 5 mL increments. For infusions, use a labelled epidural line and pump, with the concentration marked. Use sterile technique.

Baseline. Allergy history, cardiac status, liver function, coagulation and anticoagulant timing, interacting drugs (especially fluvoxamine and ciprofloxacin).

Monitoring. Continuous electrocardiogram, blood pressure and oxygen saturation during blocks. Sensory and motor level every 1 to 4 hours on infusion. Watch for toxicity symptoms (perioral numbness, tinnitus, agitation) during the first 30 minutes after bolus.

Therapeutic drug monitoring. Not used.

Dose reduction and stopping thresholds. Stop infusion for toxicity symptoms, new neurological deficit, dense motor block or severe back pain. Reduce rates when plasma protein binding falls or when combined with other local anaesthetic infiltration.

Referral and escalation. Seizures or collapse: stop the injection, call for help, give oxygen and airway support, benzodiazepine for seizures, and 20% lipid emulsion 1.5 mL/kg over 1 minute then 15 mL/kg/hour (maximum cumulative 12 mL/kg). New leg weakness after an epidural infusion needs urgent imaging.