Pharmacology and Therapeutics
Scope
Tests dose calculation and patient selection for local anaesthetics, the choice and limits of antibiotics and analgesics, and the interactions and pregnancy considerations that shape dental prescribing.
Local anaesthetics
- Amides (lidocaine, articaine, mepivacaine, bupivacaine, prilocaine) are metabolised hepatically; esters are hydrolysed by plasma pseudocholinesterase.
- pKa drives onset, lipid solubility drives potency, protein binding drives duration.
- Lidocaine 2% = 20 mg/mL; articaine 4% = 40 mg/mL. Maximum lidocaine 7 mg/kg (absolute 500 mg); articaine 7 mg/kg (500 mg).
Antibiotics and analgesics
- Odontogenic infection: amoxicillin 500 mg every 8 hours; penicillin allergy - clindamycin (with Clostridioides difficile risk) or azithromycin; metronidazole 400 mg every 8 hours for anaerobes.
- Ibuprofen 400–600 mg every 6–8 hours is first-line after extraction; avoid aspirin in children.
Worked example
A 60 kg patient is to receive 2% lidocaine with 1:100,000 epinephrine. Lidocaine limit: 7 × 60 = 420 mg = 21 mL, about 11.6 cartridges of 1.8 mL. But epinephrine 1:100,000 is 0.018 mg/mL, and the cardiac cap of 0.2 mg allows only 11.1 mL, about 6 cartridges. The vasoconstrictor cap, not the anaesthetic cap, governs the maximum volume here.
Traps
- Believing epinephrine raises the maximum anaesthetic dose - it lowers the usable volume in cardiac patients.
- Quoting cartridge counts rather than mg/kg, when cartridge volume and concentration vary.
- Prescribing antibiotics for a drained, localised abscess with no systemic signs; drainage is the treatment.