MFDS Human Disease and Pharmacology — Questions and Answers
Question 1: A patient with a prosthetic heart valve presents for a dental extraction. According to current NICE guidelines (2016 update), what antibiotic prophylaxis is recommended?
- Amoxicillin 3g orally one hour before the procedure
- Antibiotic prophylaxis is NOT routinely recommended by NICE for dental procedures, even in patients with prosthetic heart valves (Correct answer)
- Clindamycin 600mg intravenously at induction
- Erythromycin 1g orally two hours before the procedure
Correct answer: Antibiotic prophylaxis is NOT routinely recommended by NICE for dental procedures, even in patients with prosthetic heart valves
NICE Clinical Guideline CG64 (updated 2016) recommends that antibiotic prophylaxis against infective endocarditis should NOT be routinely offered for dental procedures in the UK, including for patients with prosthetic heart valves. This differs from American Heart Association guidelines which still recommend prophylaxis for high-risk patients. The NICE position emphasises that the evidence does not show a clear link between dental procedures and infective endocarditis development.
Question 2: A diabetic patient taking metformin presents for dental treatment. Their HbA1c is 75 mmol/mol (9.0%). What is the clinical significance of this result?
- The diabetes is well controlled and routine treatment can proceed without concern
- The diabetes is poorly controlled (target <48 mmol/mol), indicating increased risk of delayed healing, infection, and the need for medical liaison before elective surgical procedures (Correct answer)
- The result is within the pre-diabetic range and has no relevance to dental treatment
- The HbA1c indicates hypoglycaemia risk only
Correct answer: The diabetes is poorly controlled (target <48 mmol/mol), indicating increased risk of delayed healing, infection, and the need for medical liaison before elective surgical procedures
An HbA1c of 75 mmol/mol (9.0%) indicates poor glycaemic control. The NICE target for type 2 diabetes is generally 48 mmol/mol (6.5%) or 53 mmol/mol (7.0%). Poor control increases the risk of impaired wound healing, susceptibility to infection (including periodontal disease progression), dry mouth, candidiasis, and delayed recovery from surgical procedures. Medical liaison is advisable before elective invasive dental treatment.
Question 3: What is the mechanism of action of adrenaline (epinephrine) when used in a dental local anaesthetic cartridge?
- It acts as a direct analgesic to enhance pain relief
- It is a sympathomimetic amine that causes local vasoconstriction via alpha-1 adrenergic receptors, reducing local anaesthetic absorption and prolonging the duration and depth of anaesthesia (Correct answer)
- It acts as an anticoagulant to reduce surgical bleeding
- It directly blocks sodium channels in nerve fibres
Correct answer: It is a sympathomimetic amine that causes local vasoconstriction via alpha-1 adrenergic receptors, reducing local anaesthetic absorption and prolonging the duration and depth of anaesthesia
Adrenaline acts on alpha-1 adrenergic receptors in blood vessel smooth muscle, causing vasoconstriction at the injection site. This reduces blood flow, which slows systemic absorption of the local anaesthetic agent, prolongs its duration of action, increases the depth of anaesthesia, reduces bleeding at the surgical site, and lowers the risk of systemic toxicity by reducing peak plasma levels. The typical concentration in dental cartridges is 1:80,000.
Question 4: A patient presents for emergency dental treatment and reports taking clopidogrel and aspirin (dual antiplatelet therapy) following coronary stent insertion six months ago. How should this be managed?
- Stop both drugs 7 days before extraction
- Do NOT stop either drug — perform the extraction with local haemostatic measures such as suturing, oxidised cellulose, and tranexamic acid mouthwash (Correct answer)
- Stop aspirin but continue clopidogrel
- Postpone all dental treatment until the antiplatelet therapy is completed
Correct answer: Do NOT stop either drug — perform the extraction with local haemostatic measures such as suturing, oxidised cellulose, and tranexamic acid mouthwash
Current guidelines recommend NOT stopping dual antiplatelet therapy for dental extractions due to the risk of stent thrombosis, which carries a mortality rate of up to 40%. Local haemostatic measures are sufficient to manage post-extraction bleeding: suturing, oxidised cellulose (Surgicel) or collagen sponge in the socket, and tranexamic acid 5% mouthwash (held for 2 minutes, four times daily for 2 days). The bleeding risk from dental procedures on antiplatelet therapy is low and manageable.
Question 5: What is the initial emergency management of anaphylaxis in the dental surgery according to the UK Resuscitation Council guidelines?
- Administer oral antihistamines and observe for 30 minutes
- Administer intramuscular adrenaline 1:1000 (500 micrograms for an adult) into the anterolateral thigh, call 999, and position the patient supine with legs elevated (Correct answer)
- Administer intravenous hydrocortisone only
- Apply oxygen via nasal cannula and wait for the ambulance
Correct answer: Administer intramuscular adrenaline 1:1000 (500 micrograms for an adult) into the anterolateral thigh, call 999, and position the patient supine with legs elevated
The UK Resuscitation Council guidelines for anaphylaxis in the dental practice: 1) Call for help and dial 999; 2) Administer IM adrenaline 1:1000 (500 mcg/0.5 mL for adults) into the anterolateral thigh — repeat at 5-minute intervals if no improvement; 3) Position supine with legs elevated (sitting up if breathing difficulty); 4) High-flow oxygen 15 L/min; 5) IV access and fluids if trained; 6) Chlorphenamine 10 mg IM and hydrocortisone 200 mg IM as second-line treatments.
Question 6: Which class of antihypertensive drugs is most commonly associated with drug-induced gingival enlargement?
- ACE inhibitors (e.g., ramipril)
- Beta-blockers (e.g., atenolol)
- Calcium channel blockers (e.g., nifedipine, amlodipine) (Correct answer)
- Angiotensin II receptor blockers (e.g., losartan)
Correct answer: Calcium channel blockers (e.g., nifedipine, amlodipine)
Calcium channel blockers, particularly nifedipine and amlodipine, are the antihypertensive drugs most commonly associated with gingival enlargement (overgrowth). The mechanism involves inhibition of calcium-dependent collagenase, reducing collagen breakdown in the gingival tissues. The prevalence is approximately 6-15% for nifedipine. Other drugs causing gingival enlargement include ciclosporin (immunosuppressant) and phenytoin (anticonvulsant). Management includes meticulous oral hygiene, and drug substitution if possible.
MFDS Human Disease and Pharmacology
A patient with a prosthetic heart valve presents for a dental extraction.
According to current NICE guidelines (2016 update), what antibiotic prophylaxis is recommended?