Articaine

Articaine is an amide local anaesthetic containing a thiophene ring and an ester side chain, which allows rapid hydrolysis by plasma esterases and a short elimination half-life. It is used almost exclusively for dental anaesthesia and has good tissue diffusion through bone.

Class. Amide local anaesthetic (intermediate duration, dental).

Mechanism. Reversible blockade of voltage-gated sodium channels.

Pharmacokinetics. Onset 1 to 3 minutes (infiltration), 2 to 5 minutes (block). Pulpal anaesthesia 45 to 75 minutes with adrenaline. Protein binding about 95%. Elimination half-life about 20 minutes in plasma, mainly by esterase hydrolysis to articaine acid (inactive), with renal excretion. Low systemic accumulation with repeated doses.

Indications are local, infiltration and nerve block anaesthesia in dentistry.

Adults

• 4% with adrenaline (1 in 100,000 or 1 in 200,000), 1.7 to 2.2 mL cartridges (68 to 88 mg in each cartridge). Usual dose 1 to 2 cartridges (1.7 to 5.1 mL) for infiltration and 1 to 3 for block, depending on procedure.
• Maximum 7 mg/kg, not above 500 mg, in a single session.
• Adrenaline limit: 0.04 mg in significant cardiovascular disease (about two cartridges of 1 in 100,000) and 0.2 mg in healthy adults.
• No loading dose or titration; inject slowly and give the lowest effective volume.

Children

• From 4 years in most labels: 0.5 to 2.5 mL for infiltration, depending on weight and procedure.
• Maximum 5 to 7 mg/kg depending on the label.
• Not licensed under 4 years in most regions.

Contraindications. Hypersensitivity to articaine, amide anaesthetics or sulphites (preparations with adrenaline contain sulphite); severe asthma with sulphite sensitivity; uncontrolled cardiac arrhythmia or severe uncontrolled hypertension (adrenaline-containing preparations); children under 4 years; methaemoglobinaemia.

Boxed-warning-level risks. Nerve injury (paraesthesia, mainly lingual or inferior alveolar) reported after inferior alveolar nerve block, with a higher incidence for 4% preparations that remains contested; systemic toxicity with overdose.

Adverse effects. Common: injection pain, postoperative numbness, headache, swelling. Serious: paraesthesia lasting weeks, trismus, haematoma, systemic toxicity (rare because of rapid clearance), methaemoglobinaemia (rare), anaphylaxis (sulphite).

Interactions. Adrenaline interacts with tricyclic antidepressants, monoamine oxidase inhibitors and non-selective beta blockers (hypertension, arrhythmia). Other local anaesthetics add systemic toxicity.

Common prescribing errors. Exceeding the dose in children by cartridge count; using 4% in nerve blocks near the inferior alveolar nerve without recognising the paraesthesia risk; using adrenaline in uncontrolled cardiac disease; missing a sulphite allergy.

Special groups

• Pregnancy: used in routine dental care at usual doses.
• Breastfeeding: compatible at usual doses.
• Older adults: usual doses with attention to cardiovascular status.
• Kidney impairment: no adjustment of dose for single doses.
• Liver impairment: no adjustment; clearance is largely extrahepatic.
• Regional: confirm the adrenaline concentration on the cartridge before use.

Formulations. Dental cartridges 4% with adrenaline (1 in 100,000 and 1 in 200,000).

Administration. Aspirate and inject slowly (1 mL over about 1 minute). Use dental syringes and sterile technique. Do not reuse cartridges.

Baseline. Allergy history, including sulphites, cardiac status, current medicines (especially tricyclic antidepressants and beta blockers), weight and pregnancy.

Monitoring. Observe for at least 15 to 30 minutes after injection for toxicity and allergic reactions. Review sensory recovery; check follow-up if numbness persists.

Therapeutic drug monitoring. Not used.

Dose reduction and stopping thresholds. Stop injection at any sign of toxicity or allergy. Reduce adrenaline-containing doses in cardiovascular disease.

Referral and escalation. Persistent paraesthesia beyond 8 weeks needs oral and maxillofacial surgery review. Seizures or collapse: stop injection, give oxygen and airway support, benzodiazepine, and 20% lipid emulsion 1.5 mL/kg over 1 minute then 15 mL/kg/hour. Anaphylaxis needs intramuscular adrenaline.