MJDF Pharmacology and Therapeutics

Question 1

What is the maximum recommended dose of lidocaine with 1:80,000 adrenaline for a healthy adult weighing 70 kg, and how many 2.2 mL cartridges does this equate to?

Accepted Answer

7 cartridges (approximately 308 mg lidocaine) — based on the maximum dose of 4.4 mg/kg for lidocaine with adrenaline

Answer

1 cartridge (44 mg lidocaine)

Answer

20 cartridges (880 mg lidocaine)

Answer

3 cartridges (132 mg lidocaine)

Question 2

What is the mechanism of action of amoxicillin and why is it the first-line antibiotic for most dental infections?

Accepted Answer

Amoxicillin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (transpeptidases), preventing peptidoglycan cross-linking; it is first-line because it has a broad spectrum covering most oral pathogens, good oral bioavailability (approximately 90%), and a well-established safety profile

Answer

Amoxicillin inhibits protein synthesis at the 30S ribosomal subunit

Answer

Amoxicillin disrupts bacterial DNA replication

Answer

Amoxicillin inhibits folic acid synthesis in bacteria

Question 3

A patient allergic to penicillin requires antibiotics for an acute dental abscess. What is the recommended alternative according to FGDP/BNF guidelines?

Accepted Answer

Metronidazole 400 mg three times daily for 5 days (if the allergy is to all beta-lactams) or clarithromycin 250-500 mg twice daily for 5 days; clindamycin is reserved for severe infections due to the risk of Clostridium difficile colitis

Answer

Prescribe amoxicillin anyway as cross-reactivity is minimal

Answer

Tetracycline 250 mg four times daily for 14 days

Answer

No antibiotics can be given to penicillin-allergic patients

Question 4

What is the analgesic ceiling effect and which commonly used dental analgesic demonstrates this property?

Accepted Answer

The analgesic ceiling is the dose above which no additional pain relief is achieved despite increasing the dose; paracetamol and NSAIDs (e.g., ibuprofen) demonstrate this — increasing beyond the recommended maximum dose does not improve analgesia but does increase the risk of adverse effects

Answer

It means that analgesics become more effective at higher doses without limit

Answer

Only opioid analgesics have a ceiling effect

Answer

The ceiling effect means the drug stops working after repeated use

Question 5

What are the contraindications for using adrenaline-containing local anaesthetics in dental patients?

Accepted Answer

There are very few absolute contraindications; caution is needed with uncontrolled hyperthyroidism, phaeochromocytoma, and patients on non-selective beta-blockers (risk of hypertensive crisis); controlled cardiovascular disease is NOT a contraindication — the benefit of pain control outweighs the minimal cardiovascular risk of dental doses of adrenaline

Answer

Adrenaline-containing LA is contraindicated in all patients over 50 years old

Answer

Adrenaline is contraindicated in all patients with hypertension

Answer

Adrenaline is contraindicated whenever a patient is taking any medication

Question 6

What is the difference between bactericidal and bacteriostatic antibiotics, and give examples of each used in dental practice?

Accepted Answer

Bactericidal antibiotics kill bacteria directly (e.g., amoxicillin, metronidazole); bacteriostatic antibiotics inhibit bacterial growth and division, relying on the host immune system to eliminate the organisms (e.g., tetracycline, erythromycin/clarithromycin); in immunocompromised patients, bactericidal agents are preferred

Answer

There is no clinical difference between bactericidal and bacteriostatic antibiotics

Answer

Bacteriostatic antibiotics are always more effective than bactericidal ones

Answer

All antibiotics used in dentistry are bacteriostatic