Safe Prescribing — MCQs
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A 47-year-old man with type 2 diabetes is established on insulin glargine 28 units at bedtime and insulin lispro 8 units before each meal. He reports three episodes of nocturnal hypoglycaemia in the past week, with blood glucose readings of 2.8-3.2 mmol/L at 3 AM. His pre-dinner glucose averages 8.5 mmol/L and morning fasting glucose 11.2 mmol/L. What is the most appropriate adjustment to his insulin regimen?
A 54-year-old woman with deep vein thrombosis is started on low molecular weight heparin (LMWH) and warfarin. Her baseline INR is 1.1. After 3 days of overlapping therapy, her INR is 2.3. Her platelet count has dropped from 245 × 10⁹/L at baseline to 95 × 10⁹/L. She has no bleeding and feels well. What is the most appropriate immediate management?
A 35-year-old pregnant woman at 14 weeks gestation with newly diagnosed venous thromboembolism requires anticoagulation. She has normal renal function. Which anticoagulation strategy is most appropriate for the duration of her pregnancy?
A 61-year-old man is prescribed phenytoin for seizure control following neurosurgery. His phenytoin level is reported as 45 μmol/L (therapeutic range 40-80 μmol/L). However, he develops ataxia, nystagmus, and confusion. What pharmacological principle best explains this clinical scenario?
A 69-year-old man with pulmonary embolism is being treated with rivaroxaban 15mg twice daily for the first 21 days. He weighs 58kg and has eGFR 28 ml/min/1.73m². On reviewing his prescription, what is the most appropriate action?
A 66-year-old woman on warfarin for mechanical aortic valve replacement (target INR 2.5-3.5) requires urgent colonoscopy for suspected lower gastrointestinal bleeding. Her INR is 3.2. She has no active bleeding currently. What is the most appropriate anticoagulation management strategy?
A 43-year-old man with type 2 diabetes attends the emergency department having inadvertently injected 80 units of insulin glargine instead of his usual 8 units two hours ago. His current blood glucose is 6.5 mmol/L and he is asymptomatic. What is the most appropriate management?
A 78-year-old man with atrial fibrillation and CHA₂DS₂-VASc score of 5 is on dabigatran 150mg twice daily. He develops acute kidney injury with eGFR falling from 55 to 25 ml/min/1.73m². He presents with haematuria and dizziness. Blood pressure is 95/60 mmHg. What is the most appropriate immediate management?
A 52-year-old woman is started on amiodarone for recurrent atrial fibrillation. According to safe prescribing principles, which baseline investigation is most critical before initiating this medication?
A 67-year-old man taking warfarin for atrial fibrillation requires urgent dental extraction. His INR is 2.8 (target range 2-3). The dentist requests advice on anticoagulation management. What is the most appropriate recommendation?
Safe Prescribing UK Medical PG Practice Questions and MCQs
Question 211: A 47-year-old man with type 2 diabetes is established on insulin glargine 28 units at bedtime and insulin lispro 8 units before each meal. He reports three episodes of nocturnal hypoglycaemia in the past week, with blood glucose readings of 2.8-3.2 mmol/L at 3 AM. His pre-dinner glucose averages 8.5 mmol/L and morning fasting glucose 11.2 mmol/L. What is the most appropriate adjustment to his insulin regimen?
- A. Reduce bedtime insulin glargine dose by 10-20% (Correct Answer)
- B. Increase bedtime insulin glargine dose by 2-4 units
- C. Reduce pre-dinner insulin lispro dose by 2 units
- D. Split insulin glargine into twice-daily dosing
- E. Add metformin 500mg at bedtime to reduce insulin requirements
Explanation: ***Reduce bedtime insulin glargine dose by 10-20%*** - The patient is experiencing the **Somogyi effect**, where nocturnal hypoglycaemia leads to a counter-regulatory hormone surge, causing **rebound fasting hyperglycaemia**. - Reducing the **basal insulin** dose is the primary safety intervention to prevent **nocturnal hypoglycaemia** and address the unsafe 3 AM glucose levels. *Increase bedtime insulin glargine dose by 2-4 units* - This would dangerously worsen the **nocturnal hypoglycaemia** levels (currently 2.8-3.2 mmol/L), leading to potential seizures or coma. - Clinicians must prioritize solving **hypoglycaemia** before attempting to lower fasting glucose levels that are caused by rebound mechanisms. *Reduce pre-dinner insulin lispro dose by 2 units* - **Insulin lispro** is rapid-acting with a peak effect at 1-2 hours and a total duration of 3-5 hours, making it unlikely to cause **3 AM hypoglycaemia**. - Reducing the pre-dinner dose would further elevate the **pre-dinner glucose** levels (currently 8.5 mmol/L) without addressing the basal insulin excess. *Split insulin glargine into twice-daily dosing* - While splitting **glargine** can stabilize glucose profiles in some, the immediate clinical priority is a **total dose reduction** to stop the hypoglycaemic episodes. - Splitting the same high total dose usually does not resolve severe **nocturnal dips** as effectively as a simple dose reduction. *Add metformin 500mg at bedtime to reduce insulin requirements* - Adding **metformin** would increase insulin sensitivity and could potentially worsen the existing **hypoglycaemic episodes** if doses are not adjusted. - Pharmacological additions are inappropriate during an **acute safety issue** involving insulin titration and hypoglycaemia risk.
Question 212: A 54-year-old woman with deep vein thrombosis is started on low molecular weight heparin (LMWH) and warfarin. Her baseline INR is 1.1. After 3 days of overlapping therapy, her INR is 2.3. Her platelet count has dropped from 245 × 10⁹/L at baseline to 95 × 10⁹/L. She has no bleeding and feels well. What is the most appropriate immediate management?
- A. Continue both LMWH and warfarin and recheck INR in 2 days
- B. Stop LMWH immediately, continue warfarin and check for heparin-induced thrombocytopenia (Correct Answer)
- C. Stop warfarin, continue LMWH and arrange haematology review
- D. Stop both medications and start a direct oral anticoagulant
- E. Continue current management and recheck platelet count in 1 week
Explanation: ***Stop LMWH immediately, continue warfarin and check for heparin-induced thrombocytopenia*** - The patient's **platelet count drop** by over 60% from baseline in 3 days while on LMWH is highly indicative of **Heparin-Induced Thrombocytopenia (HIT)**. - Immediate **cessation of all heparin products** is mandatory to prevent potentially fatal **thrombotic complications** associated with HIT. *Continue both LMWH and warfarin and recheck INR in 2 days* - Continuing LMWH in the presence of suspected **HIT** is dangerous as it can lead to paradoxical **arterial or venous thrombosis**. - A platelet drop of this magnitude requires **urgent intervention** rather than simple observation of the INR. *Stop warfarin, continue LMWH and arrange haematology review* - Continuing LMWH when **HIT** is suspected is contraindicated due to the high risk of **thromboembolism**. - While warfarin might need adjustment in HIT, the immediate priority is stopping the **heparin product**, which is the direct cause of the immune reaction. *Stop both medications and start a direct oral anticoagulant* - While DOACs are used in many DVT cases, the immediate priority is specifically identifying and managing **HIT** pathology. - Starting a DOAC may be an eventual management strategy, but the first clinical step involves the specific withdrawal of the **offending heparin agent** and formal testing. *Continue current management and recheck platelet count in 1 week* - Delaying the investigation and management of a significant **platelet drop** in suspected **HIT** could lead to rapid and catastrophic **thromboembolic events**. - Standard safety protocols require prompt diagnosis and intervention for **HIT**, making a 1-week delay unacceptable.
Question 213: A 35-year-old pregnant woman at 14 weeks gestation with newly diagnosed venous thromboembolism requires anticoagulation. She has normal renal function. Which anticoagulation strategy is most appropriate for the duration of her pregnancy?
- A. Therapeutic dose low molecular weight heparin throughout pregnancy (Correct Answer)
- B. Warfarin with target INR 2-3 after the first trimester
- C. Rivaroxaban at standard VTE treatment dose
- D. Fondaparinux at weight-adjusted dose
- E. Unfractionated heparin via continuous intravenous infusion
Explanation: ***Therapeutic dose low molecular weight heparin throughout pregnancy*** - **Low molecular weight heparin (LMWH)** is the preferred anticoagulant in pregnancy as it does not cross the **placenta** and has no known teratogenic effects. - It is preferred over other options due to its predictable pharmacokinetics and reduced risk of **heparin-induced thrombocytopenia (HIT)** and osteoporosis. *Warfarin with target INR 2-3 after the first trimester* - **Warfarin** is generally avoided because it crosses the placenta and can cause **warfarin embryopathy** (nasal hypoplasia, epiphyseal stippling) and fetal hemorrhage. - While sometimes used for mechanical heart valves in the second trimester, it is not the standard of care for **VTE** management when LMWH is available. *Rivaroxaban at standard VTE treatment dose* - **Direct oral anticoagulants (DOACs)** like rivaroxaban are **contraindicated** in pregnancy due to lack of safety data and potential placental transfer. - Current guidelines recommend against their use during pregnancy and during **breastfeeding**. *Fondaparinux at weight-adjusted dose* - **Fondaparinux** has limited safety data regarding **fetal outcomes** and is not considered a first-line treatment in pregnancy. - Its use is typically reserved for women who cannot tolerate LMWH, such as those with a history of **heparin-induced thrombocytopenia**. *Unfractionated heparin via continuous intravenous infusion* - **Unfractionated heparin (UFH)** is impractical for long-term use throughout pregnancy and requires frequent **aPTT monitoring**. - Chronic UFH use is associated with a higher risk of **osteoporosis** and heparin-induced thrombocytopenia compared to LMWH.
Question 214: A 61-year-old man is prescribed phenytoin for seizure control following neurosurgery. His phenytoin level is reported as 45 μmol/L (therapeutic range 40-80 μmol/L). However, he develops ataxia, nystagmus, and confusion. What pharmacological principle best explains this clinical scenario?
- A. Phenytoin exhibits first-order kinetics and the level will decrease predictably with dose reduction
- B. Phenytoin exhibits zero-order kinetics and small dose increases can cause disproportionate level rises
- C. The patient has developed acute phenytoin toxicity from a drug interaction reducing protein binding (Correct Answer)
- D. Laboratory error has occurred as symptoms are inconsistent with therapeutic level
- E. Phenytoin metabolites are causing toxicity despite therapeutic parent drug level
Explanation: ***The patient has developed acute phenytoin toxicity from a drug interaction reducing protein binding*** - Phenytoin is highly **protein-bound** (approx. 90%), but standard assays measure **total phenytoin**; toxicity occurs due to an increase in the **unbound (free) fraction**, which is the pharmacologically active form. - Displacement from albumin (e.g., by **valproate**, **sulfonamides**, or in **renal failure**) can cause classic signs of toxicity like **ataxia, nystagmus, and confusion** despite a **total level** appearing within the therapeutic range. *Phenytoin exhibits first-order kinetics and the level will decrease predictably with dose reduction* - Phenytoin elimination follows **Michaelis-Menten kinetics**, meaning it exhibits **dose-dependent (non-linear) kinetics**, rather than purely first-order. - At therapeutic concentrations, its metabolic enzymes become saturated, leading to a shift towards **zero-order kinetics**, where elimination rate is constant regardless of drug concentration. *Phenytoin exhibits zero-order kinetics and small dose increases can cause disproportionate level rises* - While phenytoin does exhibit **zero-order kinetics** at higher therapeutic concentrations due to enzyme saturation, this option doesn't fully explain the current scenario where the *total level is therapeutic* but toxicity is present. - The scenario points to an increase in the **free drug concentration** due to altered protein binding, rather than a disproportionate rise from a dose adjustment, which is a different aspect of its non-linear kinetics. *Laboratory error has occurred as symptoms are inconsistent with therapeutic level* - While lab errors are possible, it's less likely to be the *best explanation* when a clear pharmacological principle, like **altered protein binding** leading to increased free drug, can explain the discrepancy. - The symptoms of **ataxia, nystagmus, and confusion** are classic signs of **phenytoin toxicity**, strongly suggesting an exaggerated drug effect rather than a simple measurement error. *Phenytoin metabolites are causing toxicity despite therapeutic parent drug level* - Phenytoin is primarily metabolized to **inactive hydroxylated metabolites** (e.g., by CYP2C9 and CYP2C19), which generally do not contribute to the observed neurotoxicity. - The neurotoxic symptoms of **ataxia, nystagmus, and confusion** are directly attributable to high concentrations of the **unbound parent drug**, not its metabolites.
Question 215: A 69-year-old man with pulmonary embolism is being treated with rivaroxaban 15mg twice daily for the first 21 days. He weighs 58kg and has eGFR 28 ml/min/1.73m². On reviewing his prescription, what is the most appropriate action?
- A. Continue current dose as prescribed for acute VTE treatment phase
- B. Reduce dose to rivaroxaban 15mg once daily immediately
- C. Stop rivaroxaban and switch to warfarin with LMWH bridging (Correct Answer)
- D. Continue current dose but reduce to 15mg once daily after 21 days
- E. Stop rivaroxaban and switch to apixaban at standard VTE dose
Explanation: ***Stop rivaroxaban and switch to warfarin with LMWH bridging***- **Rivaroxaban** is **contraindicated** in patients with an **eGFR < 30 ml/min/1.73m²** due to its significant renal excretion (approximately two-thirds), which leads to drug accumulation and an elevated **bleeding risk**.- **Warfarin** is a safer alternative in severe renal impairment as it is primarily **hepatically metabolized** and does not rely on renal clearance, though it necessitates **LMWH bridging** until a therapeutic **INR** is achieved.*Continue current dose as prescribed for acute VTE treatment phase*- Maintaining the high initial dose of **rivaroxaban 15mg twice daily** in a patient with an **eGFR of 28 ml/min/1.73m²** dramatically increases the risk of **hemorrhage** due to drug accumulation.- The standard acute VTE treatment regimen for rivaroxaban is predicated on adequate renal function; this patient's **compromised renal function** overrides standard dosing protocols.*Reduce dose to rivaroxaban 15mg once daily immediately*- A dose reduction to **15mg once daily** is still inappropriate and unsafe for a patient with an **eGFR of 28 ml/min/1.73m²**, as it remains above the recommended **contraindication threshold**.- Clinical guidelines for **rivaroxaban** specify **discontinuation** rather than dose reduction when the **eGFR falls below 30 ml/min**, highlighting the severe risk of renal impairment.*Continue current dose but reduce to 15mg once daily after 21 days*- This approach fails to address the immediate and severe risk of **rivaroxaban accumulation** during the initial 21-day high-dose phase, which is already contraindicated with the patient's **eGFR**.- Delaying action for 21 days with a contraindicated drug could lead to **life-threatening bleeding complications** before any dose adjustment is considered.*Stop rivaroxaban and switch to apixaban at standard VTE dose*- While **apixaban** has a lower renal clearance component compared to rivaroxaban, it also requires **dose adjustment** or caution in patients with both **low body weight (≤60kg)** and **renal impairment**, which this patient has.- For severe renal impairment (**eGFR < 30 ml/min**), **warfarin** remains the generally preferred and most evidence-supported oral anticoagulant due to its non-renal metabolism.
Question 216: A 66-year-old woman on warfarin for mechanical aortic valve replacement (target INR 2.5-3.5) requires urgent colonoscopy for suspected lower gastrointestinal bleeding. Her INR is 3.2. She has no active bleeding currently. What is the most appropriate anticoagulation management strategy?
- A. Proceed with colonoscopy without adjusting warfarin, as investigation is for bleeding
- B. Stop warfarin 5 days pre-procedure, start therapeutic low molecular weight heparin, stop heparin 24 hours pre-procedure (Correct Answer)
- C. Give 5mg oral vitamin K, proceed with colonoscopy when INR <1.5, restart warfarin immediately post-procedure
- D. Stop warfarin 3 days pre-procedure, give 2mg oral vitamin K, proceed when INR <1.5
- E. Stop warfarin, proceed with colonoscopy within 48 hours without bridging anticoagulation
Explanation: ***Stop warfarin 5 days pre-procedure, start therapeutic low molecular weight heparin, stop heparin 24 hours pre-procedure*** - Patients with **mechanical heart valves** are at high risk for **thromboembolism** and require **bridging anticoagulation** with therapeutic LMWH when warfarin is interrupted for high-bleeding-risk procedures. - **Colonoscopy** is a high-bleeding-risk procedure requiring an **INR <1.5**. Warfarin needs to be stopped 5 days prior for its effect to wear off, and LMWH (given its shorter half-life) is stopped 24 hours before to allow for coagulation to normalize for the procedure. *Proceed with colonoscopy without adjusting warfarin, as investigation is for bleeding* - Performing a colonoscopy with a therapeutic **INR of 3.2** carries a very high risk of **major hemorrhage**, especially if biopsies or polypectomy are performed during the procedure. - While the investigation is for bleeding, the priority is to ensure the procedure itself does not exacerbate the bleeding or cause new, severe bleeding complications. *Give 5mg oral vitamin K, proceed with colonoscopy when INR <1.5, restart warfarin immediately post-procedure* - Giving 5mg oral **vitamin K** is too much and will significantly reverse warfarin's effect, making re-initiation and achieving a stable therapeutic INR very difficult and unpredictable for days, without an urgent need. - Restarting warfarin immediately post-procedure without bridging leaves the patient at high risk of **thromboembolism** as warfarin takes several days to achieve a therapeutic effect. *Stop warfarin 3 days pre-procedure, give 2mg oral vitamin K, proceed when INR <1.5* - Stopping warfarin only **3 days** prior is often insufficient for the INR to drop below 1.5, particularly if the patient has a stable, therapeutic INR. - This strategy completely lacks **bridging anticoagulation** with LMWH, which is critical for a patient with a **mechanical aortic valve** due to the high risk of **thromboembolism**. *Stop warfarin, proceed with colonoscopy within 48 hours without bridging anticoagulation* - Stopping warfarin and proceeding without **bridging anticoagulation** is contraindicated for high-risk patients like those with **mechanical heart valves**. - This approach leaves the patient vulnerable to **valve thrombosis** and potentially fatal **embolic events** for the duration of warfarin's offset and prior to any restart.
Question 217: A 43-year-old man with type 2 diabetes attends the emergency department having inadvertently injected 80 units of insulin glargine instead of his usual 8 units two hours ago. His current blood glucose is 6.5 mmol/L and he is asymptomatic. What is the most appropriate management?
- A. Discharge home with advice to eat regular meals and check blood glucose 4-hourly
- B. Admit for 24-hour monitoring with intravenous 10% glucose infusion (Correct Answer)
- C. Observe for 4 hours, give oral carbohydrates, and discharge if blood glucose stable
- D. Start variable rate intravenous insulin infusion to control any rebound hyperglycaemia
- E. Admit for 12-hour observation with regular blood glucose monitoring and oral carbohydrates
Explanation: ***Admit for 24-hour monitoring with intravenous 10% glucose infusion*** - **Insulin glargine** is a **long-acting** basal insulin with a duration of action of approximately 24 hours, meaning a massive 10-fold overdose creates a prolonged risk of **severe hypoglycemia**. - Admission for **intravenous glucose** allows for precise, continuous glycemic support and the ability to adjust rates based on **hourly monitoring**, which is safer than relying on oral intake alone. *Discharge home with advice to eat regular meals and check blood glucose 4-hourly* - Discharging the patient is unsafe because the peak effect of the **overdose** may not occur for several hours, leading to potentially fatal **nocturnal hypoglycemia**. - Home monitoring every 4 hours is insufficient to detect the rapid drops in blood glucose associated with such a high dose of **exogenous insulin**. *Observe for 4 hours, give oral carbohydrates, and discharge if blood glucose stable* - A **4-hour observation** period is inadequate because it does not cover the full **pharmacodynamic profile** of long-acting glargine, which lasts up to a day. - Stability at 4 hours provides a false sense of security, as the patient remains at high risk for **delayed hypoglycemia** once the insulin reaches steady absorption. *Start variable rate intravenous insulin infusion to control any rebound hyperglycaemia* - A **variable rate intravenous insulin infusion (VRIII)** is contraindicated here because the clinical priority is treating **insulin toxicity**, not hyperglycemia. - Adding more insulin would exacerbate the existing **overdose** and significantly increase the risk of life-threatening **hypoglycemic coma**. *Admit for 12-hour observation with regular blood glucose monitoring and oral carbohydrates* - A **12-hour observation** is insufficient as it only covers half the expected duration of action of **glargine**, leaving the patient vulnerable after discharge. - Relying solely on **oral carbohydrates** is risky in the context of a 10-fold overdose, as the patient may be unable to maintain adequate intake if they become **drowsy** or symptomatic.
Question 218: A 78-year-old man with atrial fibrillation and CHA₂DS₂-VASc score of 5 is on dabigatran 150mg twice daily. He develops acute kidney injury with eGFR falling from 55 to 25 ml/min/1.73m². He presents with haematuria and dizziness. Blood pressure is 95/60 mmHg. What is the most appropriate immediate management?
- A. Stop dabigatran and give idarucizumab 5g intravenously (Correct Answer)
- B. Reduce dabigatran dose to 110mg twice daily and monitor
- C. Stop dabigatran, give tranexamic acid, and observe
- D. Switch from dabigatran to apixaban at reduced dose
- E. Continue dabigatran but increase monitoring frequency
Explanation: ***Stop dabigatran and give idarucizumab 5g intravenously*** - The patient presents with **life-threatening bleeding** (haematuria, dizziness, hypotension) exacerbated by **dabigatran accumulation** due to acute kidney injury (eGFR 25 ml/min/1.73m²), where dabigatran is contraindicated. - **Idarucizumab** is the specific and immediate reversal agent for dabigatran, rapidly neutralizing its anticoagulant effect, which is critical in an emergency with **hemodynamic instability**. *Reduce dabigatran dose to 110mg twice daily and monitor* - Reducing the dose is insufficient and dangerous in the context of **active, significant bleeding** with **hemodynamic compromise**. - Dabigatran is largely renally cleared, and its use is **contraindicated** with an eGFR below 30 ml/min/1.73m², making a dose reduction inappropriate and ineffective for managing the current crisis. *Stop dabigatran, give tranexamic acid, and observe* - While stopping dabigatran is correct, **tranexamic acid** is an antifibrinolytic and does not directly reverse the **thrombin inhibition** caused by dabigatran. - **Observation** is unsafe given the patient's **hypotension** and potential for ongoing severe bleeding due to the accumulated dabigatran, which requires immediate and specific reversal. *Switch from dabigatran to apixaban at reduced dose* - Switching to another anticoagulant, even at a reduced dose, is absolutely **contraindicated** during an episode of **active bleeding** with hemodynamic instability. - The immediate priority is to stop the bleeding and reverse the existing anticoagulation, not to introduce a different anticoagulant. *Continue dabigatran but increase monitoring frequency* - Continuing dabigatran is medically **negligent** as the patient is actively bleeding, hypotensive, and has severe renal impairment leading to drug accumulation. - Increasing monitoring frequency does not address the **active bleeding** or the **toxic accumulation** of the drug and would delay critical intervention.
Question 219: A 52-year-old woman is started on amiodarone for recurrent atrial fibrillation. According to safe prescribing principles, which baseline investigation is most critical before initiating this medication?
- A. Echocardiography to assess left ventricular function
- B. Thyroid function tests, liver function tests, and chest radiograph (Correct Answer)
- C. 24-hour Holter monitor to assess arrhythmia burden
- D. Serum electrolytes including calcium and magnesium
- E. Full blood count and coagulation screen
Explanation: ***Thyroid function tests, liver function tests, and chest radiograph*** - **Amiodarone** is known for its wide range of **extra-cardiac toxicities**, notably affecting the **thyroid** (due to high iodine content), **liver** (hepatotoxicity), and **lungs** (pulmonary fibrosis). - Baseline **thyroid function tests (TFTs)**, **liver function tests (LFTs)**, and a **chest radiograph (CXR)** are crucial to establish a baseline for monitoring these potential adverse effects throughout treatment. *Echocardiography to assess left ventricular function* - While an **echocardiogram** is valuable for diagnosing and assessing the underlying **cardiac pathology** contributing to atrial fibrillation, it is not primarily a *safety monitoring* test for amiodarone's *side effects*. - Amiodarone is considered a relatively **cardiac-safe antiarrhythmic**, especially in patients with **structural heart disease** or **heart failure**, making baseline LV function assessment less critical for drug safety *monitoring* compared to other organ systems. *24-hour Holter monitor to assess arrhythmia burden* - A **24-hour Holter monitor** is used to quantify the frequency and type of **arrhythmia**, which helps in assessing treatment efficacy, not for pre-treatment safety screening for amiodarone's known **toxicities**. - This investigation evaluates the *disease state* rather than the *patient's physiological readiness* for the drug's specific side effect profile. *Serum electrolytes including calcium and magnesium* - **Electrolyte imbalances** like **hypokalemia** and **hypomagnesemia** are important to correct before initiating *any* antiarrhythmic, as they can predispose to **proarrhythmia**, particularly **Torsades de Pointes**. - However, amiodarone's primary and most critical baseline monitoring targets its unique **multi-organ toxicity** (thyroid, liver, lung), making TFTs, LFTs, and CXR more specifically critical as *baseline safety investigations* for *this particular drug*. *Full blood count and coagulation screen* - **Amiodarone** does not typically cause **bone marrow suppression** or have direct, significant effects on the **coagulation cascade** that would necessitate a baseline **full blood count (FBC)** or **coagulation screen** as a primary safety measure. - While amiodarone can **potentiate oral anticoagulants** like **warfarin**, requiring closer **INR monitoring**, a baseline coagulation screen is not a specific safety requirement for amiodarone *itself* but rather for the **drug interaction** with other medications.
Question 220: A 67-year-old man taking warfarin for atrial fibrillation requires urgent dental extraction. His INR is 2.8 (target range 2-3). The dentist requests advice on anticoagulation management. What is the most appropriate recommendation?
- A. Stop warfarin 5 days before procedure and restart immediately after
- B. Continue warfarin and proceed with dental extraction (Correct Answer)
- C. Stop warfarin 2 days before procedure and use bridging low molecular weight heparin
- D. Reduce warfarin dose by 50% for 3 days before procedure
- E. Stop warfarin and give 2mg oral vitamin K the day before procedure
Explanation: ***Continue warfarin and proceed with dental extraction*** - For minor surgical procedures with low bleeding risk, such as **dental extractions**, current guidelines recommend continuing **warfarin** if the **INR is < 4.0**. - The risk of **thromboembolic events** (e.g., stroke) from stopping anticoagulation outweighs the risk of local bleeding, which can be managed with **tranexamic acid mouthwash** or sutures. *Stop warfarin 5 days before procedure and restart immediately after* - Stopping warfarin for 5 days is unnecessary for **minor dentistry** and significantly increases the risk of **thromboembolism** in a patient with atrial fibrillation. - This approach is typically reserved for major surgeries with **high bleeding risk** where the INR must be < 1.5. *Stop warfarin 2 days before procedure and use bridging low molecular weight heparin* - **Bridging therapy** is not indicated for minor dental procedures and unnecessarily increases the cost and patient discomfort. - Bridging is usually reserved for patients with a very high **thromboembolic risk** (e.g., mechanical heart valves) undergoing major elective surgery. *Reduce warfarin dose by 50% for 3 days before procedure* - Reducing the dose is unpredictable and may lead to a **sub-therapeutic INR**, leaving the patient unprotected against **embolic stroke**. - There is no clinical evidence to support simple dose reduction for managing perioperative bleeding risk in **simple extractions**. *Stop warfarin and give 2mg oral vitamin K the day before procedure* - **Vitamin K** is used for reversing over-anticoagulation in cases of **excessive INR** or major bleeding, not for routine preoperative management. - Administering Vitamin K makes it difficult to re-establish a **therapeutic INR** postoperatively, extending the period of stroke risk.
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