Safe Prescribing — MCQs
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A 54-year-old woman attends anticoagulation clinic for routine INR monitoring. She has been on warfarin for 18 months following an unprovoked pulmonary embolism. Her INR today is 8.2. She has no signs of bleeding and is completely asymptomatic. Her previous INR results over the past 3 months have ranged between 2.3-3.1. She reports no change in medications or diet and takes no over-the-counter preparations. What is the most appropriate immediate management?
A 66-year-old man with heart failure (LVEF 30%) and chronic kidney disease stage 3b (eGFR 38 ml/min/1.73m²) is on the following medications: ramipril 10mg once daily, bisoprolol 10mg once daily, spironolactone 25mg once daily, and furosemide 40mg once daily. His latest blood results show: Na+ 138 mmol/L, K+ 5.7 mmol/L, creatinine 185 micromol/L (baseline 165 micromol/L). He is asymptomatic. Which medication adjustment represents the most appropriate initial management?
A 59-year-old man with type 2 diabetes is admitted for emergency laparotomy for perforated diverticulitis. His regular medications include metformin 1g twice daily, sitagliptin 100mg once daily, and insulin detemir 40 units at bedtime. His HbA1c 3 months ago was 58 mmol/mol (7.5%). He will be nil by mouth and commenced on a variable rate intravenous insulin infusion (VRIII). Which of his diabetes medications should be continued during the perioperative period?
A 73-year-old woman with atrial fibrillation has been stable on warfarin for 3 years with target INR 2-3. Her recent INR results have been: 2.4, 2.6, 2.3, 2.5. She is admitted with lobar pneumonia and started on clarithromycin 500mg twice daily. She has normal renal function. What is the most appropriate warfarin management during her antibiotic course?
A 47-year-old woman with type 1 diabetes on basal-bolus insulin therapy (insulin glargine 24 units at bedtime and insulin aspart 8 units with meals) is experiencing recurrent nocturnal hypoglycaemia at 3am, with morning fasting glucose readings of 12-14 mmol/L. This pattern has been consistent for 2 weeks. What is the most appropriate adjustment to her insulin regimen?
A 68-year-old man with paroxysmal atrial fibrillation (CHA₂DS₂-VASc score 4) is established on edoxaban 60mg once daily. He now requires elective inguinal hernia repair. His renal function is normal (eGFR 72 ml/min/1.73m²) and weight is 78kg. What is the most appropriate perioperative anticoagulation management?
A 52-year-old woman with newly diagnosed epilepsy is started on levetiracetam 500mg twice daily. She also takes levothyroxine 100mcg daily for hypothyroidism and the combined oral contraceptive pill. What is the most important prescribing safety consideration regarding her current medications?
A 70-year-old man with atrial fibrillation on apixaban 5mg twice daily is admitted with acute diverticulitis. He requires IV antibiotics and is made nil by mouth. His renal function shows eGFR 55 ml/min/1.73m², and he has no evidence of active bleeding. How should his anticoagulation be managed during this acute admission?
A 56-year-old woman with rheumatoid arthritis has been taking methotrexate 20mg weekly for 2 years with good disease control. She develops a severe chest infection and is started on antibiotics. Which antibiotic poses the highest risk of methotrexate toxicity due to drug interaction and should prompt consideration of temporary methotrexate dose reduction or suspension?
A 64-year-old man with type 2 diabetes is brought to hospital by ambulance after his wife found him confused at home. His capillary blood glucose is 2.1 mmol/L. He is conscious but unable to swallow safely. His current medications include metformin 1g twice daily, gliclazide 160mg twice daily, and atorvastatin 20mg once daily. What is the most appropriate immediate management?
Safe Prescribing UK Medical PG Practice Questions and MCQs
Question 171: A 54-year-old woman attends anticoagulation clinic for routine INR monitoring. She has been on warfarin for 18 months following an unprovoked pulmonary embolism. Her INR today is 8.2. She has no signs of bleeding and is completely asymptomatic. Her previous INR results over the past 3 months have ranged between 2.3-3.1. She reports no change in medications or diet and takes no over-the-counter preparations. What is the most appropriate immediate management?
- A. Omit warfarin for 2 days, give oral vitamin K 1-5mg, and repeat INR the following day (Correct Answer)
- B. Admit for intravenous vitamin K 5mg and prothrombin complex concentrate
- C. Omit warfarin today and tomorrow, then restart at reduced dose when INR <5.0
- D. Continue warfarin at reduced dose and repeat INR in 3 days
- E. Omit warfarin for 1 day, continue at 50% dose for 2 days, then resume normal dosing
Explanation: ***Omit warfarin for 2 days, give oral vitamin K 1-5mg, and repeat INR the following day***- For an **INR of 8.2** with **no signs of bleeding**, withholding warfarin and administering **oral vitamin K (1-5 mg)** is the recommended immediate management to safely lower the INR.- Repeating the **INR the following day** is crucial to assess the effectiveness of vitamin K and guide subsequent warfarin dosing. *Admit for intravenous vitamin K 5mg and prothrombin complex concentrate*- These aggressive interventions, including **intravenous vitamin K** and **prothrombin complex concentrate (PCC)**, are reserved for **major or life-threatening bleeding** or extremely high INR values with high bleeding risk, which is not present in this asymptomatic patient.- PCC provides rapid but temporary reversal and carries its own risks, making it inappropriate for stable, asymptomatic over-anticoagulation. *Omit warfarin today and tomorrow, then restart at reduced dose when INR <5.0*- While omitting warfarin is part of the management for elevated INR, simply withholding doses without **vitamin K** is typically reserved for **INR values between 5.0 and 8.0** without bleeding.- Given an **INR > 8.0**, active reversal with vitamin K is necessary to achieve a quicker and more predictable reduction of the INR, reducing the risk of spontaneous hemorrhage. *Continue warfarin at reduced dose and repeat INR in 3 days*- Continuing warfarin at any dose with an **INR of 8.2** is extremely dangerous and significantly increases the immediate risk of **major hemorrhagic events**, such as intracranial or gastrointestinal bleeding.- Waiting **3 days** to repeat the INR is an unacceptable delay for such a critically elevated INR; more immediate monitoring is required after intervention. *Omit warfarin for 1 day, continue at 50% dose for 2 days, then resume normal dosing*- This plan is insufficient for managing an **INR of 8.2** as it does not include **oral vitamin K**, which is essential for prompt and effective reversal of significant over-anticoagulation.- Resuming warfarin, even at a reduced dose, without confirming a significant decrease in INR through **re-testing** after an acute management step is unsafe and may lead to recurrent over-anticoagulation.
Question 172: A 66-year-old man with heart failure (LVEF 30%) and chronic kidney disease stage 3b (eGFR 38 ml/min/1.73m²) is on the following medications: ramipril 10mg once daily, bisoprolol 10mg once daily, spironolactone 25mg once daily, and furosemide 40mg once daily. His latest blood results show: Na+ 138 mmol/L, K+ 5.7 mmol/L, creatinine 185 micromol/L (baseline 165 micromol/L). He is asymptomatic. Which medication adjustment represents the most appropriate initial management?
- A. Reduce spironolactone to 25mg on alternate days
- B. Add calcium resonium 15g three times daily
- C. Reduce ramipril to 5mg once daily and continue spironolactone
- D. Stop spironolactone and repeat blood tests in 5-7 days (Correct Answer)
- E. Stop ramipril and repeat blood tests in 1 week
Explanation: ***Stop spironolactone and repeat blood tests in 5-7 days*** - In a patient with **hyperkalemia (K+ 5.7 mmol/L)**, **heart failure**, and **CKD**, spironolactone, a **mineralocorticoid receptor antagonist**, is the most likely cause and should be immediately discontinued. - Stopping spironolactone is a direct and effective initial step to lower potassium, while the **ACE inhibitor (ramipril)**, which provides significant prognostic benefit, can often be maintained if hyperkalemia resolves. *Reduce spironolactone to 25mg on alternate days* - **Alternate-day dosing** is generally not recommended for managing established hyperkalemia due to insufficient control and lack of evidence for efficacy. - Complete **cessation** is a more decisive and safer initial step to prevent further rises in potassium in this clinical context. *Add calcium resonium 15g three times daily* - **Calcium resonium** is a potassium-binding resin usually reserved for more **severe hyperkalemia** (typically K+ > 6.0 mmol/L) or when other measures fail. - The initial management should focus on identifying and removing the offending drug, rather than adding another medication to excrete potassium. *Reduce ramipril to 5mg once daily and continue spironolactone* - **Ramipril (an ACE inhibitor)** is a cornerstone medication for **heart failure with reduced ejection fraction** and contributes significant mortality benefit. - Prioritizing reduction of ramipril over discontinuing spironolactone is inappropriate, as spironolactone is a more potent and direct contributor to hyperkalemia, especially in CKD. *Stop ramipril and repeat blood tests in 1 week* - Discontinuing the **ACE inhibitor** first is not recommended given its crucial role in **HFrEF management** and the relatively modest rise in creatinine (less than 25% from baseline). - **Spironolactone** is considered more "expendable" in the acute management of hyperkalemia compared to ACE inhibitors and beta-blockers, particularly when it's the primary driver of potassium elevation.
Question 173: A 59-year-old man with type 2 diabetes is admitted for emergency laparotomy for perforated diverticulitis. His regular medications include metformin 1g twice daily, sitagliptin 100mg once daily, and insulin detemir 40 units at bedtime. His HbA1c 3 months ago was 58 mmol/mol (7.5%). He will be nil by mouth and commenced on a variable rate intravenous insulin infusion (VRIII). Which of his diabetes medications should be continued during the perioperative period?
- A. Continue all diabetes medications at normal doses
- B. Continue insulin detemir only; stop metformin and sitagliptin (Correct Answer)
- C. Continue metformin only; stop insulin detemir and sitagliptin
- D. Stop all diabetes medications while on VRIII
- E. Continue sitagliptin and insulin detemir; stop metformin
Explanation: ***Continue insulin detemir only; stop metformin and sitagliptin*** - **Insulin detemir**, a **long-acting basal insulin**, should be continued (often at a reduced dose) to provide background glycemic control, preventing **insulin deficiency**, hyperglycemia, and **diabetic ketoacidosis (DKA)** in **nil by mouth (NBM)** patients. - Continuing basal insulin alongside a **variable rate intravenous insulin infusion (VRIII)** helps stabilize blood glucose levels, reduces the total insulin requirement from the VRIII, and facilitates a smoother transition back to subcutaneous insulin post-surgery. *Continue all diabetes medications at normal doses* - **Metformin** must be withheld perioperatively due to the risk of **lactic acidosis**, especially in emergency surgery where **acute kidney injury (AKI)** and hypoperfusion are concerns. - Oral hypoglycemics like **sitagliptin** are inappropriate for **NBM** patients as their effect depends on food intake and they can increase the risk of **hypoglycemia**, while a VRIII is managing acute glucose. *Continue metformin only; stop insulin detemir and sitagliptin* - Continuing **metformin** is contraindicated in this perioperative setting due to the significant risk of **lactic acidosis**, exacerbated by surgical stress and potential organ dysfunction. - Stopping **basal insulin (detemir)** entirely for an insulin-requiring patient who is **NBM** significantly increases the risk of **DKA** and severe hyperglycemia, even with a VRIII running concurrently. *Stop all diabetes medications while on VRIII* - While the **VRIII** provides acute glycemic control, completely stopping **basal insulin** in patients who are normally on it can lead to **insulin deficiency**, rebound hyperglycemia, and **DKA** once the VRIII is weaned or discontinued. - Current guidelines recommend continuing a portion of the patient's usual **basal insulin dose** (e.g., 50-80%) to maintain physiological insulin levels and prevent metabolic decompensation. *Continue sitagliptin and insulin detemir; stop metformin* - **Sitagliptin** (a DPP-4 inhibitor) should be withheld because the patient is **NBM** and its mechanism of action relies on the **incretin effect** stimulated by food. It offers no benefit and carries a potential risk of **hypoglycemia**. - Although continuing **insulin detemir** is correct, the inclusion of **sitagliptin** makes this option incorrect, as oral hypoglycemic agents are generally stopped during the perioperative period with VRIII.
Question 174: A 73-year-old woman with atrial fibrillation has been stable on warfarin for 3 years with target INR 2-3. Her recent INR results have been: 2.4, 2.6, 2.3, 2.5. She is admitted with lobar pneumonia and started on clarithromycin 500mg twice daily. She has normal renal function. What is the most appropriate warfarin management during her antibiotic course?
- A. Continue warfarin at the same dose and check INR after completing the antibiotic course
- B. Temporarily switch to a prophylactic dose DOAC for the duration of antibiotic treatment
- C. Continue warfarin at the same dose but check INR after 3-5 days of concurrent antibiotic use (Correct Answer)
- D. Reduce warfarin dose by 50% for the duration of antibiotic treatment
- E. Withhold warfarin until antibiotic course is completed then restart
Explanation: ***Continue warfarin at the same dose but check INR after 3-5 days of concurrent antibiotic use***- **Clarithromycin** is a potent inhibitor of the **CYP450 system** (specifically **CYP3A4**), which reduces the metabolism of **warfarin** and significantly increases the risk of **bleeding**.- Regular monitoring of the **INR** within **3-5 days** allows for precise dose adjustments based on individual patient response, preventing over-anticoagulation while maintaining therapeutic levels.*Continue warfarin at the same dose and check INR after completing the antibiotic course*- Waiting until the antibiotic course is finished is dangerous because the **INR** can rise rapidly within days of starting **clarithromycin**, significantly increasing the risk of **major hemorrhage**.- Drug interactions with **macrolides** typically manifest early due to their effect on **warfarin metabolism**, making delayed monitoring an unsafe clinical practice.*Temporarily switch to a prophylactic dose DOAC for the duration of antibiotic treatment*- Switching to a **DOAC** is not indicated for managing short-term drug interactions and complicates anticoagulation in a patient stable on **warfarin**.- Furthermore, **clarithromycin** also interacts with most **DOACs** (like rivaroxaban and apixaban) via **P-glycoprotein** and **CYP3A4** inhibition, potentially increasing their levels and bleeding risk as well.*Reduce warfarin dose by 50% for the duration of antibiotic treatment*- A preemptive, fixed dose reduction is not recommended because the degree of **enzyme inhibition** and individual patient response to the interaction varies significantly.- This approach risks making the patient **subtherapeutic**, thereby increasing the risk of **thromboembolic events** like stroke in the setting of atrial fibrillation.*Withhold warfarin until antibiotic course is completed then restart*- Completely withholding **warfarin** leaves the patient without **anticoagulation**, placing them at a high risk for an **ischemic stroke** due to atrial fibrillation.- Warfarin has a long **half-life**, and stopping it abruptly without a clear clinical indication (e.g., active bleeding, very high INR) is inappropriate for managing a drug interaction, as the risk of thrombosis outweighs the risk of managed interaction.
Question 175: A 47-year-old woman with type 1 diabetes on basal-bolus insulin therapy (insulin glargine 24 units at bedtime and insulin aspart 8 units with meals) is experiencing recurrent nocturnal hypoglycaemia at 3am, with morning fasting glucose readings of 12-14 mmol/L. This pattern has been consistent for 2 weeks. What is the most appropriate adjustment to her insulin regimen?
- A. Increase insulin glargine to 28 units at bedtime
- B. Reduce insulin glargine to 20 units at bedtime (Correct Answer)
- C. Add a bedtime snack without adjusting insulin doses
- D. Switch insulin glargine administration from bedtime to morning
- E. Reduce the evening meal insulin aspart dose
Explanation: ***Reduce insulin glargine to 20 units at bedtime*** - The patient's pattern of **recurrent nocturnal hypoglycemia** at 3 am followed by **rebound hyperglycemia** in the morning (12-14 mmol/L) is classic for the **Somogyi effect**. - Reducing the bedtime **basal insulin (glargine)** dose will prevent the nocturnal hypoglycemia, thus eliminating the counter-regulatory hormone response that causes the high morning blood glucose. *Increase insulin glargine to 28 units at bedtime* - Increasing the **basal insulin** dose would exacerbate the already existing **nocturnal hypoglycemia**, making it more severe and potentially dangerous for the patient. - The high morning fasting glucose is a rebound phenomenon, not a sign of insufficient basal insulin; therefore, an increase would worsen the underlying problem. *Add a bedtime snack without adjusting insulin doses* - While a bedtime snack might temporarily prevent hypoglycemia, it does not address the fundamental issue of **excessive basal insulin** dose throughout the night. - This approach may lead to **unintended weight gain** and could still result in hypoglycemia later in the night if the insulin dose remains too high. *Switch insulin glargine administration from bedtime to morning* - Changing the administration time of **insulin glargine** (a long-acting basal insulin) may alter its peak action slightly, but it does not resolve the problem of an **overall high basal dose**. - The primary concern is the total amount of basal insulin, not just its timing, especially with documented recurrent nocturnal lows. *Reduce the evening meal insulin aspart dose* - **Insulin aspart** is a rapid-acting insulin with a duration of action typically 3-5 hours, meaning its effect would have worn off well before 3 am. - Reducing the evening meal bolus would primarily lead to **post-prandial hyperglycemia** after dinner, without addressing the specific issue of nocturnal hypoglycemia.
Question 176: A 68-year-old man with paroxysmal atrial fibrillation (CHA₂DS₂-VASc score 4) is established on edoxaban 60mg once daily. He now requires elective inguinal hernia repair. His renal function is normal (eGFR 72 ml/min/1.73m²) and weight is 78kg. What is the most appropriate perioperative anticoagulation management?
- A. Stop edoxaban 24 hours before surgery and restart 6 hours post-operatively if haemostasis achieved (Correct Answer)
- B. Stop edoxaban 48 hours before surgery and restart 48-72 hours post-operatively
- C. Continue edoxaban throughout the perioperative period without interruption
- D. Stop edoxaban 24 hours before surgery, bridge with low molecular weight heparin, restart edoxaban 24 hours post-operatively
- E. Stop edoxaban 72 hours before surgery and restart 24 hours post-operatively
Explanation: ***Stop edoxaban 24 hours before surgery and restart 6 hours post-operatively if haemostasis achieved*** - For procedures with **standard bleeding risk** (like inguinal hernia repair) and normal renal function (eGFR >50 mL/min), omitting **edoxaban** for **24 hours** (one dose) is sufficient due to its 10-14 hour half-life, ensuring adequate drug clearance before surgery. - **Direct Oral Anticoagulants (DOACs)** have a rapid onset of action, allowing them to be restarted relatively quickly, typically **6-24 hours** post-operatively, once primary haemostasis is secured and the risk of bleeding is minimized. *Stop edoxaban 48 hours before surgery and restart 48-72 hours post-operatively* - A **48-hour interruption** for edoxaban is generally reserved for procedures with **high bleeding risk** or in patients with moderate renal impairment (eGFR 15-50 mL/min), neither of which applies to this patient. - Delaying the restart of anticoagulation for **48-72 hours** post-operatively significantly increases the patient's risk of **thromboembolic events** given his CHA₂DS₂-VASc score of 4, without providing additional safety benefits for a standard-risk procedure. *Continue edoxaban throughout the perioperative period without interruption* - While some very minor procedures (e.g., minor dental work, superficial skin procedures) might allow uninterrupted anticoagulation, an **inguinal hernia repair** carries a sufficient bleeding risk to warrant a temporary cessation of anticoagulation. - Continuing **edoxaban** without interruption for this type of surgery would significantly increase the risk of **perioperative bleeding** and associated complications. *Stop edoxaban 24 hours before surgery, bridge with low molecular weight heparin, restart edoxaban 24 hours post-operatively* - **Bridging anticoagulation** with low molecular weight heparin (LMWH) is generally **not recommended** for patients on DOACs because they have predictable pharmacokinetics with a rapid offset and onset of action, unlike warfarin. - Studies have shown that **LMWH bridging** in DOAC patients significantly increases the risk of **major bleeding** without providing additional protection against stroke or other thromboembolic events. *Stop edoxaban 72 hours before surgery and restart 24 hours post-operatively* - An interruption of **72 hours** is excessive for a patient with normal renal function and a standard bleeding risk procedure, leading to an unnecessarily prolonged period of vulnerability to **thromboembolic events**. - Guideline-directed management for **standard risk** elective surgery aims to minimize the "off-drug" window to the shortest safe duration, which for edoxaban with normal renal function is typically 24 hours pre-operatively.
Question 177: A 52-year-old woman with newly diagnosed epilepsy is started on levetiracetam 500mg twice daily. She also takes levothyroxine 100mcg daily for hypothyroidism and the combined oral contraceptive pill. What is the most important prescribing safety consideration regarding her current medications?
- A. Levetiracetam reduces the effectiveness of the combined oral contraceptive pill
- B. Levetiracetam may cause psychiatric adverse effects and requires monitoring for mood changes (Correct Answer)
- C. The dose of levothyroxine should be increased due to enzyme induction by levetiracetam
- D. Levetiracetam levels need regular therapeutic drug monitoring
- E. Combined oral contraceptive increases seizure frequency and should be stopped
Explanation: ***Levetiracetam may cause psychiatric adverse effects and requires monitoring for mood changes*** - **Levetiracetam** is well-known for causing **behavioral side effects** such as irritability, aggression, anxiety, and depression, which can affect a significant proportion of patients. - Given these potential **psychiatric symptoms**, especially in the initial phase of treatment, close monitoring for **mood changes** and behavioral disturbances is crucial to ensure patient safety and well-being. *Levetiracetam reduces the effectiveness of the combined oral contraceptive pill* - **Levetiracetam** is not a **hepatic enzyme inducer**, unlike many older antiepileptic drugs (e.g., carbamazepine, phenytoin). - Therefore, it does not significantly interact with or reduce the effectiveness of the **combined oral contraceptive pill** (COCP), making it a safer option for women of childbearing potential requiring contraception. *The dose of levothyroxine should be increased due to enzyme induction by levetiracetam* - **Levetiracetam** has minimal hepatic metabolism and does not induce **cytochrome P450 enzymes**, which are primarily responsible for drug interactions. - Consequently, it does not typically affect the metabolism or require dose adjustments of **levothyroxine**; routine TSH monitoring would continue as per standard hypothyroidism management. *Levetiracetam levels need regular therapeutic drug monitoring* - Routine **therapeutic drug monitoring (TDM)** for **levetiracetam** is generally not recommended because there is no strong correlation between its plasma concentration and **clinical efficacy** or toxicity. - Dosing adjustments for **levetiracetam** are primarily based on the patient's clinical response (seizure control) and renal function, rather than measured drug levels. *Combined oral contraceptive increases seizure frequency and should be stopped* - The **combined oral contraceptive pill** does not commonly affect the **seizure threshold** or significantly increase seizure frequency in most individuals with epilepsy. - Therefore, there is no general recommendation to stop the **COCP** in patients with epilepsy, provided there are no other contraindications or specific drug interactions with the antiepileptic medication.
Question 178: A 70-year-old man with atrial fibrillation on apixaban 5mg twice daily is admitted with acute diverticulitis. He requires IV antibiotics and is made nil by mouth. His renal function shows eGFR 55 ml/min/1.73m², and he has no evidence of active bleeding. How should his anticoagulation be managed during this acute admission?
- A. Continue apixaban at current dose as it has good bioavailability and can be given with small sips of water (Correct Answer)
- B. Stop apixaban and switch to therapeutic dose low molecular weight heparin
- C. Stop apixaban and switch to intravenous unfractionated heparin infusion
- D. Reduce apixaban dose to 2.5mg twice daily until oral intake resumes
- E. Stop apixaban temporarily until oral intake is re-established, then restart
Explanation: ***Continue apixaban at current dose as it has good bioavailability and can be given with small sips of water*** - **Apixaban** has high oral **bioavailability** and can be safely administered with small sips of water in patients who are **nil by mouth (NBM)** for non-surgical reasons. - The patient has no **active bleeding** and his **eGFR of 55** supports the maintenance of the standard **5mg twice daily** dose for stroke prophylaxis in **atrial fibrillation**. *Stop apixaban and switch to therapeutic dose low molecular weight heparin* - **Bridging therapy** with **LMWH** is unnecessary and increases the risk of **hematoma** or bleeding complications when oral administration is still feasible. - **LMWH** is generally reserved for patients who are strictly prohibited from swallowing or have **severe malabsorption** syndromes. *Stop apixaban and switch to intravenous unfractionated heparin infusion* - **Unfractionated heparin** is typically indicated for patients at very high risk of bleeding who may need **rapid reversal** for urgent surgery, which is not indicated here. - This approach is unnecessarily invasive and requires intensive **aPTT monitoring**, adding complexity to the management of simple **diverticulitis**. *Reduce apixaban dose to 2.5mg twice daily until oral intake resumes* - Dose reduction targets specific criteria: **age ">=80"**, **weight " - Under-dosing **DOACs** without clinical indication increases the risk of **thromboembolic events** like stroke. *Stop apixaban temporarily until oral intake is re-established, then restart* - Temporary cessation without a parenteral bridge leaves the patient unprotected against **atrial fibrillation-related stroke**. - Since **diverticulitis** management allows for medication with small sips of water, there is no clinical rationale to hold **anticoagulation**.
Question 179: A 56-year-old woman with rheumatoid arthritis has been taking methotrexate 20mg weekly for 2 years with good disease control. She develops a severe chest infection and is started on antibiotics. Which antibiotic poses the highest risk of methotrexate toxicity due to drug interaction and should prompt consideration of temporary methotrexate dose reduction or suspension?
- A. Amoxicillin
- B. Doxycycline
- C. Trimethoprim (Correct Answer)
- D. Clarithromycin
- E. Azithromycin
Explanation: ***Trimethoprim*** - Both methotrexate and trimethoprim inhibit **dihydrofolate reductase**, leading to a synergistic antifolate effect that can result in life-threatening **bone marrow suppression**. - Clinical guidelines specifically advise avoiding this combination because it drastically increases the risk of **pancytopenia** and mucosal toxicity.*Amoxicillin* - Penicillins can potentially reduce the **renal clearance** of methotrexate by competing for secretion in the renal tubules, but this interaction is generally less clinically significant than with antifolates. - While monitoring is advised, it does not pose the same high-level risk of direct **metabolic synergy** seen with trimethoprim.*Doxycycline* - This tetracycline antibiotic has **minimal interaction** with methotrexate and is generally considered safe to use for respiratory infections in this context. - It does not significantly affect the **folate metabolic pathway** or the renal excretion of methotrexate.*Clarithromycin* - As a macrolide, it can potentially increase methotrexate levels, but this interaction is **infrequent** and rarely leads to severe toxicity in patients with normal renal function. - It is more commonly associated with interactions involving drugs metabolized by **CYP3A4**, which is not the primary metabolic pathway for methotrexate.*Azithromycin* - Similar to other macrolides, it lacks a significant mechanism for interfering with **methotrexate excretion** or its action on folate metabolism. - It is considered a **safer alternative** for chest infections when compared to the high-risk profiles of antifolate or highly nephrotoxic agents.
Question 180: A 64-year-old man with type 2 diabetes is brought to hospital by ambulance after his wife found him confused at home. His capillary blood glucose is 2.1 mmol/L. He is conscious but unable to swallow safely. His current medications include metformin 1g twice daily, gliclazide 160mg twice daily, and atorvastatin 20mg once daily. What is the most appropriate immediate management?
- A. Administer 100ml of 20% glucose intravenously over 15 minutes
- B. Administer 1mg glucagon intramuscularly
- C. Give 200ml orange juice orally with supervision
- D. Administer 200ml of 10% glucose intravenously over 15 minutes (Correct Answer)
- E. Give glucose gel 1.5-2 tubes squeezed into buccal cavity
Explanation: ***Administer 200ml of 10% glucose intravenously over 15 minutes*** - This patient presents with **severe hypoglycaemia** (2.1 mmol/L) and an **unsafe swallow** due to confusion, necessitating rapid parenteral treatment. - **200ml of 10% glucose** is the standard and safest initial intravenous treatment, providing adequate carbohydrate replacement with a lower risk of **vein irritation** compared to higher concentrations. *Administer 100ml of 20% glucose intravenously over 15 minutes* - While this provides a similar amount of glucose, **20% glucose** is highly hypertonic and carries a significant risk of **thrombophlebitis** and tissue damage if extravasation occurs. - National guidelines typically recommend **10% glucose** for routine management unless there are specific concerns about fluid overload. *Administer 1mg glucagon intramuscularly* - **Glucagon** relies on sufficient **hepatic glycogen stores** and may be less effective in patients on **sulfonylureas** like gliclazide, which can deplete these stores. - Its onset of action is slower than intravenous glucose, making it less suitable for immediate management in this critically hypoglycemic patient who has intravenous access established. *Give 200ml orange juice orally with supervision* - This is **contraindicated** as the patient is confused and has an **unsafe swallow**, which significantly increases the risk of **aspiration pneumonia**. - Oral fluids should only be given to conscious patients who can swallow safely. *Give glucose gel 1.5-2 tubes squeezed into buccal cavity* - While buccal glucose can be used, **intravenous glucose** is the most rapid and definitive treatment for **severe hypoglycaemia** with altered consciousness, especially when IV access is available. - Buccal absorption can be inconsistent and may not provide as quick or reliable a response as direct intravenous administration in this acute setting.
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