MFDS Human Disease and Pharmacology 2 — Questions and Answers
Question 1: A patient with chronic kidney disease (eGFR 20 mL/min) requires a dental prescription for pain relief. Which analgesic is contraindicated and what is the recommended alternative?
- Paracetamol is contraindicated; use ibuprofen instead
- NSAIDs (e.g., ibuprofen) are contraindicated as they reduce renal blood flow and can precipitate acute kidney injury; paracetamol is the recommended first-line analgesic (Correct answer)
- Codeine is contraindicated; use diclofenac instead
- All analgesics are safe in renal impairment
Correct answer: NSAIDs (e.g., ibuprofen) are contraindicated as they reduce renal blood flow and can precipitate acute kidney injury; paracetamol is the recommended first-line analgesic
NSAIDs are contraindicated in patients with significant renal impairment (eGFR <30 mL/min) because they inhibit prostaglandin-mediated renal blood flow regulation, which can precipitate acute kidney injury, fluid retention, and hyperkalaemia. Paracetamol is the first-line analgesic in renal impairment as it is hepatically metabolised. If stronger analgesia is needed, codeine can be used with caution (reduced doses) as its metabolites accumulate in renal failure.
Question 2: What is the significance of an INR result for a patient taking warfarin, and what is the generally accepted safe range for dental extractions?
- INR measures liver function; no range is relevant for dentistry
- INR measures the degree of anticoagulation; dental extractions can generally be performed safely if the INR is 4.0 or below, with local haemostatic measures (Correct answer)
- INR must be below 1.0 for any dental procedure
- INR is only relevant for patients on heparin, not warfarin
Correct answer: INR measures the degree of anticoagulation; dental extractions can generally be performed safely if the INR is 4.0 or below, with local haemostatic measures
The INR (International Normalised Ratio) measures the degree of anticoagulation with warfarin, with a normal value of approximately 1.0. For dental extractions, current UK guidelines recommend that procedures can be performed in primary care if the INR is stable and ≤4.0, checked within 24-72 hours before the procedure. Local haemostatic measures (suturing, oxidised cellulose, tranexamic acid mouthwash) should be used. Warfarin should NOT be stopped or reduced for dental procedures due to thromboembolic risk.
Question 3: A patient with a history of asthma experiences an acute asthma attack during dental treatment. What is the appropriate emergency management in the dental surgery?
- Administer intramuscular adrenaline immediately
- Sit the patient upright, administer salbutamol 100 mcg via spacer (2-10 puffs), give high-flow oxygen, and call 999 if not responding (Correct answer)
- Lay the patient flat and administer oral prednisolone
- Give intravenous aminophylline and prepare for intubation
Correct answer: Sit the patient upright, administer salbutamol 100 mcg via spacer (2-10 puffs), give high-flow oxygen, and call 999 if not responding
For acute asthma in the dental surgery: sit the patient upright (improves ventilation); administer salbutamol via a metered dose inhaler with a large-volume spacer (2 puffs initially, up to 10 puffs); give high-flow oxygen (15 L/min via face mask); and call 999 if there is no improvement, signs of severe/life-threatening attack (inability to complete sentences, SpO2 <92%, silent chest, cyanosis). Nebulised salbutamol 5 mg should be administered if available.
Question 4: Which hepatitis virus is most commonly transmitted through needlestick injuries in dental practice, and what is the post-exposure prophylaxis protocol?
- Hepatitis A — no prophylaxis needed
- Hepatitis B — post-exposure prophylaxis includes hepatitis B immunoglobulin (HBIG) and/or accelerated hepatitis B vaccination course if the recipient is not immune (Correct answer)
- Hepatitis C — immediate interferon treatment
- Hepatitis E — oral ribavirin prophylaxis
Correct answer: Hepatitis B — post-exposure prophylaxis includes hepatitis B immunoglobulin (HBIG) and/or accelerated hepatitis B vaccination course if the recipient is not immune
Hepatitis B virus (HBV) is the most transmissible bloodborne virus through needlestick injury, with a transmission rate of approximately 6-30% from HBeAg-positive sources (compared to 1.8% for HCV and 0.3% for HIV). Post-exposure management includes immediate wound care, risk assessment, and for non-immune recipients: hepatitis B immunoglobulin (HBIG) ideally within 48 hours plus an accelerated vaccination course. All dental healthcare workers should be vaccinated and have confirmed immunity (anti-HBs ≥10 mIU/mL).
Question 5: A patient taking a selective serotonin reuptake inhibitor (SSRI) antidepressant requires dental treatment. What is the most clinically significant drug interaction to be aware of?
- SSRIs potentiate the effect of local anaesthetics, causing prolonged numbness
- SSRIs inhibit platelet aggregation, increasing the risk of post-operative bleeding, and there is a potential interaction with tramadol increasing the risk of serotonin syndrome (Correct answer)
- SSRIs cause severe hypertension when combined with adrenaline-containing local anaesthetics
- SSRIs have no clinically significant interactions relevant to dentistry
Correct answer: SSRIs inhibit platelet aggregation, increasing the risk of post-operative bleeding, and there is a potential interaction with tramadol increasing the risk of serotonin syndrome
SSRIs (e.g., fluoxetine, sertraline, citalopram) inhibit serotonin reuptake in platelets, impairing platelet aggregation and increasing bleeding risk, particularly when combined with NSAIDs or aspirin. Additionally, tramadol (sometimes prescribed for dental pain) combined with SSRIs can precipitate serotonin syndrome — a potentially life-threatening condition with agitation, hyperthermia, and muscle rigidity. Paracetamol with codeine is a safer analgesic choice for these patients.
Question 6: What are the oral manifestations of iron deficiency anaemia?
- Gingival hyperplasia and excessive bleeding
- Angular cheilitis, glossitis (smooth depapillated tongue), recurrent aphthous ulceration, and generalised oral mucosal pallor and atrophy (Correct answer)
- Blue-black pigmentation of the gingivae
- Bilateral parotid gland enlargement
Correct answer: Angular cheilitis, glossitis (smooth depapillated tongue), recurrent aphthous ulceration, and generalised oral mucosal pallor and atrophy
Iron deficiency anaemia produces characteristic oral manifestations: angular cheilitis (fissuring and erythema at the commissures), glossitis (the tongue becomes smooth, red, and depapillated — sometimes described as 'bald tongue'), recurrent aphthous ulceration, generalised pallor and atrophy of the oral mucosa, dysphagia (in severe cases, Plummer-Vinson syndrome with pharyngeal web), and burning mouth symptoms. These occur because rapidly dividing epithelial cells are particularly sensitive to iron deficiency.
MFDS Human Disease and Pharmacology 2
A patient with chronic kidney disease (eGFR 20 mL/min) requires a dental prescription for pain relief.
Which analgesic is contraindicated and what is the recommended alternative?