Safe Prescribing — MCQs

A 39-year-old woman with newly diagnosed type 2 diabetes is being considered for basal-bolus insulin therapy after failing to achieve glycaemic control with metformin and gliclazide. She works as a long-distance lorry driver. Which factor represents an absolute contraindication to her continuing this occupation while on insulin therapy?

Q103

A 73-year-old man with atrial fibrillation has been on warfarin for 18 months with consistently stable INR values between 2.2-2.8 (target 2-3). He attends for routine monitoring and his INR is 4.6. He denies any bleeding, dietary changes, or new medications. His only other medication is amlodipine 5mg daily. What is the most appropriate immediate management?

Q104

A 44-year-old man with type 1 diabetes is admitted with acute appendicitis requiring emergency surgery. His usual insulin regimen is insulin detemir 24 units at bedtime and insulin aspart 8 units before each meal. He last ate 8 hours ago and has been nil by mouth since. His current blood glucose is 11.2 mmol/L. Surgery is planned in 2 hours. What is the most appropriate insulin management?

Q105

A 67-year-old woman with atrial fibrillation on rivaroxaban 20mg once daily is admitted with acute cholecystitis requiring emergency laparoscopic cholecystectomy. Surgery is scheduled for the following morning. She took her last dose of rivaroxaban 6 hours ago. What is the most appropriate perioperative management of her anticoagulation?

Q106

A 52-year-old woman with rheumatoid arthritis is commenced on methotrexate 15mg weekly. She asks about when she should take her folic acid supplement. According to current UK prescribing guidance, when should folic acid be administered in patients taking weekly methotrexate?

Q107

A 58-year-old man with bipolar disorder is established on lithium carbonate 800mg twice daily. He presents to his GP feeling generally unwell with reduced appetite. Blood tests reveal serum lithium level of 0.9 mmol/L (therapeutic range 0.4-1.0 mmol/L), sodium 129 mmol/L, potassium 4.2 mmol/L, urea 8.2 mmol/L, and creatinine 115 µmol/L. Which monitoring parameter change would warrant immediate lithium dose reduction?

Q108

A 63-year-old man with type 2 diabetes is admitted with acute pancreatitis. He is nil by mouth with nasogastric aspiration. His usual diabetes medications are metformin 1g twice daily, gliclazide 80mg twice daily, and insulin detemir 38 units at bedtime. A variable rate intravenous insulin infusion (VRIII) is commenced. On day 3, he is improving and planning to restart oral intake. Which medication should be restarted first and when should the VRIII be discontinued?

Q109

A 72-year-old woman with non-valvular atrial fibrillation and CHA₂DS₂-VASc score of 4 has been taking apixaban 5mg twice daily for 2 years. She now requires long-term treatment with rifampicin and isoniazid for pulmonary tuberculosis. Her eGFR is 72 ml/min/1.73m², weight 68kg, and she has no other relevant medical history. What is the most appropriate management of her anticoagulation?

Q110

A 51-year-old woman with type 1 diabetes for 28 years presents to the emergency department with abdominal pain and vomiting for 12 hours. Her capillary blood glucose is 24.8 mmol/L and ketones are 4.2 mmol/L. Venous blood gas shows pH 7.28, bicarbonate 14 mmol/L. She is being treated for diabetic ketoacidosis with fixed rate intravenous insulin infusion (FRIII) at 0.1 units/kg/hour and fluid resuscitation. After 4 hours, her glucose has fallen to 13.2 mmol/L but ketones remain 3.8 mmol/L and pH is 7.31. What is the most appropriate adjustment to her management?

Safe Prescribing UK Medical PG Practice Questions and MCQs

Question 101: According to NICE guidance on anticoagulation for atrial fibrillation, which clinical scenario would require dose reduction of apixaban from the standard 5mg twice daily to 2.5mg twice daily?

A. Age ≥75 years with body weight 65kg and serum creatinine 110 µmol/L
B. Age 68 years with body weight 58kg and serum creatinine 145 µmol/L (Correct Answer)
C. Age 82 years alone, regardless of other parameters
D. Body weight 55kg alone, regardless of other parameters
E. Serum creatinine 150 µmol/L alone, regardless of other parameters

Explanation: ***Age 68 years with body weight 58kg and serum creatinine 145 µmol/L*** - Apixaban dose reduction (2.5mg twice daily) is required if a patient meets at least **two of the following three criteria**: age ≥80 years, body weight ≤60kg, or serum creatinine ≥133 µmol/L. - This scenario satisfies **two criteria** (body weight 58kg and serum creatinine 145 µmol/L), necessitating the lower dose to prevent excessive bleeding risk. *Age ≥75 years with body weight 65kg and serum creatinine 110 µmol/L* - This patient satisfies **zero criteria** for dose reduction; the age is below 80, weight is above 60kg, and creatinine is below the 133 µmol/L threshold. - Standard dosing of **5mg twice daily** is appropriate here to ensure adequate stroke prophylaxis while minimizing bleeding risk. *Age 82 years alone, regardless of other parameters* - Advanced **age ≥80 years** is only one of the three required criteria and does not trigger a dose reduction on its own. - Dosing remains at **5mg twice daily** unless either body weight or serum creatinine also meet their respective thresholds. *Body weight 55kg alone, regardless of other parameters* - While **body weight ≤60kg** is a risk factor, it must be accompanied by another qualifying criterion to adjust the dose. - Using the lower dose based solely on weight can lead to **under-anticoagulation** and an increased risk of ischemic stroke. *Serum creatinine 150 µmol/L alone, regardless of other parameters* - Elevated **serum creatinine ≥133 µmol/L** represents impaired renal clearance but requires a second clinical factor for dose adjustment in atrial fibrillation according to NICE. - Always calculate the **Cockcroft-Gault** clearance for renal function, but for apixaban, these specific threshold-based criteria are the primary guide for this dose reduction.

Question 102: A 39-year-old woman with newly diagnosed type 2 diabetes is being considered for basal-bolus insulin therapy after failing to achieve glycaemic control with metformin and gliclazide. She works as a long-distance lorry driver. Which factor represents an absolute contraindication to her continuing this occupation while on insulin therapy?

A. HbA1c above 58 mmol/mol despite treatment optimization
B. History of one episode of severe hypoglycaemia requiring third-party assistance
C. Presence of mild background diabetic retinopathy on screening
D. Taking insulin for less than 12 months duration
E. Impaired awareness of hypoglycaemia (Correct Answer)

Explanation: ***Impaired awareness of hypoglycaemia*** - For **Group 2 drivers** (lorry and bus), **impaired awareness of hypoglycaemia** is an absolute contraindication to driving while on insulin therapy due to the high risk of sudden incapacitation. - Safety regulations, such as those from the **DVLA**, require these drivers to demonstrate **full awareness** of hypoglycaemic symptoms and consistently monitor blood glucose levels to prevent dangerous episodes. *HbA1c above 58 mmol/mol despite treatment optimization* - While an **HbA1c** above target indicates suboptimal glycaemic control, it is not a direct legal disqualifier for heavy vehicle driving on its own. - The primary safety concern for the **DVLA** regarding insulin and driving is the **risk of hypoglycaemia**, not a specific ceiling on hyperglycemia levels, unless it's associated with acute complications affecting driving ability. *History of one episode of severe hypoglycaemia requiring third-party assistance* - For Group 2 drivers, the regulation specifies that **more than one episode** of severe hypoglycaemia in the preceding 12 months is a disqualification. - A **single episode** requires a temporary suspension and a review of control, but it is not an absolute, permanent contraindication if awareness remains intact and other conditions are met. *Presence of mild background diabetic retinopathy on screening* - **Mild background retinopathy** typically does not affect visual acuity or the visual field, which are the primary determinants for fitness to drive a heavy vehicle. - Only **advanced retinopathy** (e.g., proliferative) or laser treatment causing significant **visual field defects** would necessitate a license review or disqualification for a lorry driver. *Taking insulin for less than 12 months duration* - There is no specific **minimum duration** of insulin use (like 12 months) required before a person is allowed to drive a lorry. - Drivers can hold a **Group 2 license** while on insulin as long as they satisfy specific criteria regarding **hypoglycaemic awareness**, frequency of monitoring, and absence of recent severe episodes.

Question 103: A 73-year-old man with atrial fibrillation has been on warfarin for 18 months with consistently stable INR values between 2.2-2.8 (target 2-3). He attends for routine monitoring and his INR is 4.6. He denies any bleeding, dietary changes, or new medications. His only other medication is amlodipine 5mg daily. What is the most appropriate immediate management?

A. Give oral vitamin K 1-3mg and omit warfarin for 1-2 doses, recheck INR in 24 hours
B. Omit 1 dose of warfarin, reduce maintenance dose, and recheck INR in 3-5 days (Correct Answer)
C. Continue current warfarin dose and recheck INR in 1 week
D. Give intravenous vitamin K 10mg and admit for observation
E. Withhold warfarin until INR <2.5, then restart at reduced dose

Explanation: ***Omit 1 dose of warfarin, reduce maintenance dose, and recheck INR in 3-5 days***- For an INR of 4.6 with no bleeding, a temporary reduction in warfarin's effect is needed, which is best achieved by **omitting a dose** and then **reducing the maintenance dose**.- This approach carefully brings the INR back into the therapeutic range (2.0-3.0) without causing **over-correction** or leaving the patient unprotected for too long, with re-evaluation in 3-5 days being appropriate. *Give oral vitamin K 1-3mg and omit warfarin for 1-2 doses, recheck INR in 24 hours*- Oral **Vitamin K** is generally reserved for INRs of **5.0-8.0 with minor or no bleeding**, or greater than 8.0 without bleeding, to rapidly reduce the INR.- Administering Vitamin K unnecessarily for an INR of 4.6 can cause **warfarin resistance**, making it difficult to re-establish therapeutic anticoagulation for several days. *Continue current warfarin dose and recheck INR in 1 week*- An INR of 4.6 is significantly **supra-therapeutic** for a target range of 2-3 and carries an increased risk of **hemorrhage**.- Continuing the current dose would leave the patient at an elevated bleeding risk without intervention, and waiting a full week for recheck is too long. *Give intravenous vitamin K 10mg and admit for observation*- **Intravenous Vitamin K** (especially 10mg) is reserved for **major life-threatening bleeding** or extremely high INRs (typically >10-20) requiring rapid and complete reversal.- This patient is **asymptomatic** and has no bleeding, making such an aggressive and potentially risky intervention entirely inappropriate. *Withhold warfarin until INR <2.5, then restart at reduced dose*- Completely withholding warfarin until the INR drops below 2.5 might take several days, leaving the patient **unprotected** against **thromboembolic events** (e.g., stroke) due to atrial fibrillation.- A more controlled adjustment and earlier reintroduction at a reduced dose is preferred to maintain some level of anticoagulation and prevent rebound hypercoagulability.

Question 104: A 44-year-old man with type 1 diabetes is admitted with acute appendicitis requiring emergency surgery. His usual insulin regimen is insulin detemir 24 units at bedtime and insulin aspart 8 units before each meal. He last ate 8 hours ago and has been nil by mouth since. His current blood glucose is 11.2 mmol/L. Surgery is planned in 2 hours. What is the most appropriate insulin management?

A. Continue basal insulin, omit meal-time insulin, and start variable rate intravenous insulin infusion (Correct Answer)
B. Omit all subcutaneous insulin and commence variable rate intravenous insulin infusion immediately
C. Give half the usual basal insulin dose, omit meal-time insulin, and monitor blood glucose hourly
D. Continue basal insulin at usual dose, give correction doses of rapid-acting insulin as needed
E. Switch to intravenous insulin boluses of 4 units hourly until surgery

Explanation: ***Continue basal insulin, omit meal-time insulin, and start variable rate intravenous insulin infusion*** - In **Type 1 Diabetes**, **basal insulin** must never be omitted to prevent **ketogenesis** and progression to **Diabetic Ketoacidosis (DKA)**. - For emergency surgery and fasting patients, a **Variable Rate Intravenous Insulin Infusion (VRIII)** is the gold standard to provide precise glycemic control during the perioperative stress response. *Omit all subcutaneous insulin and commence variable rate intravenous insulin infusion immediately* - Stopping **basal insulin** increases the risk of **rebound hyperglycemia** and ketosis if the VRIII is briefly interrupted or when the patient transitions back to subcutaneous injections. - Current guidelines recommend continuing **long-acting analogues** (like **insulin detemir**) at their usual dose to maintain a background level of insulin. *Give half the usual basal insulin dose, omit meal-time insulin, and monitor blood glucose hourly* - Reducing the **basal dose** by half is often recommended for elective surgery if the patient is expected to miss only one meal, but it is insufficient for **emergency surgery** with high metabolic stress. - This approach does not offer the same level of flexibility or safety as a **VRIII** for managing blood glucose fluctuations during general anesthesia. *Continue basal insulin at usual dose, give correction doses of rapid-acting insulin as needed* - Correction doses of **subcutaneous rapid-acting insulin** have a slow onset and long duration, making them unpredictable for a patient who is **nil by mouth (NBM)** and undergoing surgery. - The **VRIII** is preferred because it allows for immediate adjustments based on real-time blood glucose monitoring, ensuring a tighter target range of **6–10 mmol/L**. *Switch to intravenous insulin boluses of 4 units hourly until surgery* - **Intravenous boluses** have a very short half-life and cause significant fluctuations in blood glucose levels, leading to unstable control. - A **continuous infusion** (VRIII) is the only appropriate intravenous method to ensure a steady state and prevent **iatrogenic hypoglycemia** or hyperglycemia.

Question 105: A 67-year-old woman with atrial fibrillation on rivaroxaban 20mg once daily is admitted with acute cholecystitis requiring emergency laparoscopic cholecystectomy. Surgery is scheduled for the following morning. She took her last dose of rivaroxaban 6 hours ago. What is the most appropriate perioperative management of her anticoagulation?

A. Proceed with surgery and omit rivaroxaban for 48 hours postoperatively
B. Delay surgery for 24 hours, omit next rivaroxaban dose, then proceed (Correct Answer)
C. Administer prothrombin complex concentrate and proceed immediately
D. Switch to unfractionated heparin infusion and proceed when APTT normalizes
E. Bridge with therapeutic dose LMWH and proceed when anti-Xa level is <0.4 IU/ml

Explanation: ***Delay surgery for 24 hours, omit next rivaroxaban dose, then proceed*** - **Rivaroxaban** has a half-life of 5–9 hours in healthy individuals but can be longer in the elderly; delaying surgery for **24 hours** after the last dose allows sufficient drug clearance for intermediate-risk procedures like laparoscopic cholecystectomy. - Monitoring is generally not required, and **omitting the next dose** provides a safe window for the emergency procedure while balancing the risk of thrombosis and surgical hemorrhage. *Proceed with surgery and omit rivaroxaban for 48 hours postoperatively* - Since the patient took her last dose only **6 hours ago**, the anticoagulant effect is near **peak levels**, making immediate surgery unsafe due to high intraoperative bleeding risk. - Omission postoperatively is necessary for recovery, but the primary concern is the **active anticoagulation** present at the time of the proposed incision. *Administer prothrombin complex concentrate and proceed immediately* - **Prothrombin complex concentrate (PCC)** or andexanet alfa is indicated for **life-threatening bleeding** or truly emergent surgery that cannot wait even a few hours. - Acute cholecystitis is urgent but typically allows for a **24-hour stabilization period**, making the use of expensive/risky reversal agents unnecessary. *Switch to unfractionated heparin infusion and proceed when APTT normalizes* - **Bridging** with unfractionated heparin (UFH) is not indicated for patients on **DOACs** and would inappropriately maintain a high level of anticoagulation when the goal is to clear the drug. - Rivaroxaban does not have a reliable relationship with **APTT**, so using this marker to guide surgical timing would be clinically inaccurate. *Bridge with therapeutic dose LMWH and proceed when anti-Xa level is <0.4 IU/ml* - **LMWH bridging** is generally contraindicated in DOAC patients as it increases **bleeding complications** without clear benefit in the perioperative period. - While rivaroxaban does affect **anti-Xa levels**, delaying the surgery is a more standard and practical approach than serial laboratory monitoring for an urgent case.

Question 106: A 52-year-old woman with rheumatoid arthritis is commenced on methotrexate 15mg weekly. She asks about when she should take her folic acid supplement. According to current UK prescribing guidance, when should folic acid be administered in patients taking weekly methotrexate?

A. On the same day as methotrexate to enhance absorption
B. At least 24 hours after the methotrexate dose (Correct Answer)
C. Daily including on the day of methotrexate administration
D. Only on the three days immediately following methotrexate
E. On alternate days throughout the week

Explanation: ***At least 24 hours after the methotrexate dose*** - According to **BNF and BSR guidelines**, folic acid is administered at least **24 hours after** methotrexate to reduce side effects like **mucosal and hematological toxicity**. - Typically, a 5mg dose is given **once weekly** on a specific day that does not coincide with the methotrexate dose to maintain its **therapeutic efficacy**. *On the same day as methotrexate to enhance absorption* - Taking folic acid on the **same day** as methotrexate is avoided because it may competitively inhibit the **dihydrofolate reductase** enzyme, potentially reducing the drug's effectiveness. - It does not enhance absorption; rather, it interferes with the **antifolate mechanism** of methotrexate. *Daily including on the day of methotrexate administration* - While some localized protocols allow daily use, standard UK guidance advises against administration on the **day of the methotrexate dose**. - Consistent daily use including the methotrexate day increases the risk of **diminishing the clinical response** of the arthritis treatment. *Only on the three days immediately following methotrexate* - This regimen is not supported by standard **UK prescribing guidance** and adds unnecessary **complexity** for the patient. - Most clinical outcomes are better managed with a **single weekly dose** or a consistent strategy that avoids the 24-hour window around methotrexate. *On alternate days throughout the week* - **Alternate day dosing** is not a recommended or conventional approach in rheumatology for folic acid supplementation. - Following a **simple weekly schedule** improves patient **compliance** and ensures the safest pharmacodynamic interaction between the two medications.

Question 107: A 58-year-old man with bipolar disorder is established on lithium carbonate 800mg twice daily. He presents to his GP feeling generally unwell with reduced appetite. Blood tests reveal serum lithium level of 0.9 mmol/L (therapeutic range 0.4-1.0 mmol/L), sodium 129 mmol/L, potassium 4.2 mmol/L, urea 8.2 mmol/L, and creatinine 115 µmol/L. Which monitoring parameter change would warrant immediate lithium dose reduction?

A. Development of fine hand tremor
B. Serum sodium falling to 125 mmol/L
C. Thyroid-stimulating hormone rising from 2.5 to 4.8 mU/L
D. eGFR declining from 65 to 58 ml/min/1.73m²
E. Serum lithium level rising to 1.15 mmol/L (Correct Answer)

Explanation: ***Serum lithium level rising to 1.15 mmol/L***- **Lithium** has a very **narrow therapeutic index** (typically 0.4–1.0 mmol/L), and a level of 1.15 mmol/L exceeds the safe range, significantly increasing the risk of **toxicity**.- Urgent dose adjustment is required as toxicity can lead to severe **neurological symptoms**, renal impairment, and cardiac arrhythmias.*Development of fine hand tremor*- A **fine hand tremor** is a common **side effect** of lithium therapy that can occur even when serum levels are within the therapeutic range.- While bothersome, it is not an immediate indication for dose reduction unless it progresses to a **coarse tremor**, which is a sign of more severe toxicity.*Serum sodium falling to 125 mmol/L*- **Hyponatremia** increases the risk of lithium toxicity because the kidneys conserve lithium in an attempt to reabsorb sodium.- While significant and requiring attention, the priority for immediate dose reduction is the **actual serum lithium level** exceeding the therapeutic range.*Thyroid-stimulating hormone rising from 2.5 to 4.8 mU/L*- Lithium can cause **hypothyroidism** or a rise in **TSH**, but this is typically managed by adding **levothyroxine** rather than immediately reducing the lithium dose.- A mild rise in TSH, even into the subclinical hypothyroid range, does not indicate acute lithium toxicity and does not warrant an immediate reduction in psychiatric maintenance therapy.*eGFR declining from 65 to 58 ml/min/1.73m²*- A mild decline in **eGFR** warrants close monitoring of renal function, as lithium is **renally excreted**, but this specific drop is relatively minor.- Immediate action for a dose reduction is usually triggered by a more significant drop or if the eGFR falls below 45 ml/min/1.73m².

Question 108: A 63-year-old man with type 2 diabetes is admitted with acute pancreatitis. He is nil by mouth with nasogastric aspiration. His usual diabetes medications are metformin 1g twice daily, gliclazide 80mg twice daily, and insulin detemir 38 units at bedtime. A variable rate intravenous insulin infusion (VRIII) is commenced. On day 3, he is improving and planning to restart oral intake. Which medication should be restarted first and when should the VRIII be discontinued?

A. Restart all oral diabetes medications together, then stop VRIII 30 minutes later
B. Restart subcutaneous insulin first, continue VRIII for 30-60 minutes, then restart oral medications once eating normally (Correct Answer)
C. Stop VRIII when oral intake commences, then restart all medications immediately
D. Restart metformin and gliclazide with first meal, then stop VRIII 2 hours later
E. Continue VRIII until full diet established, then restart all medications and stop VRIII 6 hours later

Explanation: ***Restart subcutaneous insulin first, continue VRIII for 30-60 minutes, then restart oral medications once eating normally***- For patients already on **subcutaneous basal insulin**, it should be continued or restarted first to provide a stable background level before transitioning off the **VRIII**.- A **30-60 minute overlap** between the subcutaneous dose and stopping the VRIII is essential to prevent **rebound hyperglycemia**, as intravenous insulin has an extremely short half-life.*Restart all oral diabetes medications together, then stop VRIII 30 minutes later*- **Metformin** should be withheld until **renal function** (eGFR) and clinical stability are confirmed, especially after an acute episode like pancreatitis and nil-by-mouth status.- Oral medications do not provide the immediate basal glycemic control needed to safely discontinue an insulin infusion in a patient who requires insulin.*Stop VRIII when oral intake commences, then restart all medications immediately*- Stopping VRIII immediately upon caloric intake without a **priming dose** of subcutaneous insulin leads to a rapid drop in circulating insulin levels.- This approach carries a high risk of **ketosis** or severe hyperglycemia because oral medications have a slower onset than the rapidly cleared IV insulin.*Restart metformin and gliclazide with first meal, then stop VRIII 2 hours later*- **Gliclazide** (a sulfonylurea) increases the risk of **hypoglycemia** if the patient's oral intake remains inconsistent or low during the recovery phase.- Reintroducing oral agents without first establishing the **basal insulin** requirement ignores the patient's pre-existing need for insulin detemir.*Continue VRIII until full diet established, then restart all medications and stop VRIII 6 hours later*- A **6-hour overlap** is unnecessarily long and significantly increases the risk of **iatrogenic hypoglycemia** due to excessive insulin stacking.- Standard clinical guidelines recommend a much shorter transition period (typically **30-60 minutes**) once the subcutaneous insulin has been administered.

Question 109: A 72-year-old woman with non-valvular atrial fibrillation and CHA₂DS₂-VASc score of 4 has been taking apixaban 5mg twice daily for 2 years. She now requires long-term treatment with rifampicin and isoniazid for pulmonary tuberculosis. Her eGFR is 72 ml/min/1.73m², weight 68kg, and she has no other relevant medical history. What is the most appropriate management of her anticoagulation?

A. Continue apixaban 5mg twice daily as rifampicin does not significantly interact
B. Increase apixaban dose to 7.5mg twice daily to compensate for enzyme induction
C. Switch to rivaroxaban 20mg once daily as it has fewer interactions with rifampicin
D. Switch to warfarin with target INR 2-3 and monitor INR more frequently (Correct Answer)
E. Discontinue anticoagulation during tuberculosis treatment and restart afterwards

Explanation: ***Switch to warfarin with target INR 2-3 and monitor INR more frequently*** - **Rifampicin** is a potent inducer of **P-glycoprotein (P-gp)** and **CYP3A4**, which significantly reduces the plasma concentration of **apixaban**, increasing the risk of **thromboembolic stroke**. - Unlike DOACs, the anticoagulant effect of **warfarin** can be reliably monitored and adjusted using the **International Normalized Ratio (INR)**, making it suitable for co-administration with **enzyme inducers** like rifampicin. *Continue apixaban 5mg twice daily as rifampicin does not significantly interact* - This is incorrect because **rifampicin** is a strong **CYP3A4** and **P-gp inducer**, leading to a significant **reduction in apixaban plasma concentrations** (up to 50% decrease in AUC). - Maintaining the same dose would result in **subtherapeutic anticoagulation**, leaving a high-risk patient (**CHA₂DS₂-VASc of 4**) vulnerable to **stroke** and other thromboembolic events. *Increase apixaban dose to 7.5mg twice daily to compensate for enzyme induction* - There are **no established clinical guidelines** or evidence to support increasing the apixaban dose beyond its standard therapeutic range (2.5mg or 5mg twice daily) to counteract **enzyme induction** by rifampicin. - **Non-standard dosing** strategies for DOACs are not validated and carry unknown risks regarding both efficacy and safety, making this an inappropriate management strategy. *Switch to rivaroxaban 20mg once daily as it has fewer interactions with rifampicin* - **Rivaroxaban** is also a substrate of **CYP3A4** and **P-gp**, meaning its plasma levels would similarly be significantly reduced by co-administration with **rifampicin**. - Current guidelines generally recommend **avoiding all Direct Oral Anticoagulants (DOACs)** when a patient requires concomitant treatment with potent **CYP3A4 and P-gp inducers**. *Discontinue anticoagulation during tuberculosis treatment and restart afterwards* - With a high **CHA₂DS₂-VASc score of 4**, this patient has a significantly elevated annual risk of **stroke**, making discontinuation of **anticoagulation** medically unsafe. - **Tuberculosis treatment** typically lasts for many months (e.g., 6 months), and discontinuing **thromboprophylaxis** for such a prolonged period would expose the patient to an unacceptably high risk of **thromboembolic events**.

Question 110: A 51-year-old woman with type 1 diabetes for 28 years presents to the emergency department with abdominal pain and vomiting for 12 hours. Her capillary blood glucose is 24.8 mmol/L and ketones are 4.2 mmol/L. Venous blood gas shows pH 7.28, bicarbonate 14 mmol/L. She is being treated for diabetic ketoacidosis with fixed rate intravenous insulin infusion (FRIII) at 0.1 units/kg/hour and fluid resuscitation. After 4 hours, her glucose has fallen to 13.2 mmol/L but ketones remain 3.8 mmol/L and pH is 7.31. What is the most appropriate adjustment to her management?

A. Stop the insulin infusion as glucose is adequately controlled
B. Reduce the insulin infusion rate to 0.05 units/kg/hour to prevent hypoglycaemia
C. Continue the same insulin infusion rate and commence 10% glucose infusion (Correct Answer)
D. Increase the insulin infusion rate to 0.15 units/kg/hour
E. Switch from intravenous insulin to subcutaneous rapid-acting insulin

Explanation: ***Continue the same insulin infusion rate and commence 10% glucose infusion*** - In **Diabetic Ketoacidosis (DKA)**, the primary goal is to suppress **ketogenesis** and resolve acidosis; therefore, the weight-based **Fixed Rate Intravenous Insulin Infusion (FRIII)** must be maintained at 0.1 units/kg/h. - When blood glucose drops below **14 mmol/L** but ketones remain high (>0.6 mmol/L), **10% glucose** must be started as a substrate to prevent hypoglycemia while allowing the insulin to continue clearing the ketones. *Stop the insulin infusion as glucose is adequately controlled* - Stopping insulin before the **anion gap** closes and ketones are cleared will lead to a rebound of **ketoacidosis** and clinical deterioration. - Insulin should only be discontinued once the patient is eating/drinking and has transitioned to **subcutaneous insulin**. *Reduce the insulin infusion rate to 0.05 units/kg/hour to prevent hypoglycaemia* - Reducing the insulin rate is inappropriate because lower doses may not be sufficient to switch off **ketone production** at the required rate. - The correct approach to avoid hypoglycemia is to supplement with **intravenous glucose** rather than compromising the insulin infusion. *Increase the insulin infusion rate to 0.15 units/kg/hour* - Increasing the rate is unnecessary as the blood glucose has already shown a significant drop from **24.8 to 13.2 mmol/L**, indicating an adequate response to the current dose. - Adjusting the insulin rate upwards is usually reserved for cases where the **ketone level** fails to fall by at least 0.5 mmol/L per hour. *Switch from intravenous insulin to subcutaneous rapid-acting insulin* - Switching to **subcutaneous insulin** is premature because the patient still has significant **ketonemia (3.8 mmol/L)** and the acidosis has not fully resolved (bicarbonate is still low at 14 mmol/L). - Criteria for resolution usually include **ketones < 0.6 mmol/L**, pH > 7.3, and the patient being able to tolerate oral intake.

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