Prescribing Safety Assessment (PSA) — Questions and Answers

Question 1: What is the principle of 'start low, go slow' in elderly prescribing?

Change medications frequently
Start with a loading dose
Begin with the lowest effective dose and increase gradually to minimize adverse effects (Correct answer)
Always use the maximum dose

Correct answer: Begin with the lowest effective dose and increase gradually to minimize adverse effects

This approach minimizes adverse drug reactions in elderly patients by starting at a reduced dose and titrating up slowly based on response and tolerability.

Question 2: A prescription reads 'amoxicillin 500 mg p.o. t.i.d. x 10 days.' What does 'p.o.' indicate?

By mouth (Correct answer)
By topical application
By injection
By rectum

Correct answer: By mouth

'P.o.' stands for 'per os,' the Latin phrase meaning 'by mouth,' indicating the oral route of administration.

Question 3: Which of the following drugs has a narrow therapeutic index that requires routine plasma level monitoring to guide dosing?

Phenytoin (Correct answer)
Amoxicillin
Omeprazole
Ibuprofen

Correct answer: Phenytoin

Phenytoin has non-linear (zero-order) pharmacokinetics and a narrow therapeutic index; plasma levels must be monitored to avoid toxicity while maintaining seizure control.

Question 4: Metformin should be withheld in patients with an eGFR below which threshold due to the risk of lactic acidosis?

45 mL/min/1.73m²
60 mL/min/1.73m²
30 mL/min/1.73m² (Correct answer)
15 mL/min/1.73m²

Correct answer: 30 mL/min/1.73m²

Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² because impaired renal clearance leads to drug accumulation and risk of potentially fatal lactic acidosis.

Question 5: A patient with severe hepatic impairment requires analgesia for moderate pain. Which approach is most appropriate?

Regular NSAIDs as they avoid hepatic metabolism
Paracetamol at full standard doses (1g QDS)
Low-dose paracetamol (500mg TDS) with careful monitoring (Correct answer)
Codeine at standard dose for reliable conversion to morphine

Correct answer: Low-dose paracetamol (500mg TDS) with careful monitoring

Low-dose paracetamol with monitoring is safer than NSAIDs (GI bleeding and renal risk in cirrhosis) or opioids (risk of precipitating hepatic encephalopathy).

Question 6: Which monitoring parameter is most important when prescribing aminoglycosides to prevent nephrotoxicity and ototoxicity?

Trough serum levels and renal function (Correct answer)
Full blood count weekly
Peak serum levels alone
Liver function tests

Correct answer: Trough serum levels and renal function

Aminoglycoside toxicity is concentration-time dependent, with sustained elevated trough levels predicting nephrotoxicity and ototoxicity; dose intervals are adjusted based on trough and eGFR.

Question 7: In a patient with renal impairment, how does decreased kidney function typically affect the TDM strategy for renally cleared drugs with narrow therapeutic indices?

Reduce the dose or extend the dosing interval to avoid accumulation (Correct answer)
No change is needed since protein binding compensates
Increase the dose to compensate for faster clearance
Double the monitoring frequency but keep the same dose

Correct answer: Reduce the dose or extend the dosing interval to avoid accumulation

Renal impairment decreases clearance of renally eliminated drugs, requiring dose reduction or interval extension to prevent toxic accumulation.

Question 8: A patient presents 4 hours after a large acetaminophen ingestion. The serum acetaminophen level is 250 mcg/mL. What is the specific antidote?

Fomepizole 15mg/kg IV loading dose
Deferoxamine infusion
N-acetylcysteine (NAC) IV (150mg/kg over 1 hour, then 50mg/kg over 4 hours, then 100mg/kg over 16 hours) (Correct answer)
Activated charcoal 1g/kg PO only

Correct answer: N-acetylcysteine (NAC) IV (150mg/kg over 1 hour, then 50mg/kg over 4 hours, then 100mg/kg over 16 hours)

N-acetylcysteine replenishes hepatic glutathione and is the antidote for acetaminophen overdose; the Rumack-Matthew nomogram guides initiation.

Question 9: Which type of drug interaction describes two drugs producing an effect greater than the sum of their individual effects?

Synergistic (supra-additive) interaction (Correct answer)
Additive interaction
Antagonistic interaction
Competitive interaction

Correct answer: Synergistic (supra-additive) interaction

A synergistic interaction occurs when combined drug effects exceed the arithmetic sum of individual effects, as seen with some antibiotic combinations.

Question 10: A pregnant patient at 35 weeks gestation develops eclampsia with seizures and BP 175/115 mmHg. What is the drug of choice to prevent recurrent seizures?

Diazepam 10mg IV bolus as needed
Lorazepam 4mg IV followed by oral valproate
Magnesium sulfate 4–6g IV loading dose, then 1–2g/hr infusion (Correct answer)
Phenytoin 20mg/kg IV at 50mg/min

Correct answer: Magnesium sulfate 4–6g IV loading dose, then 1–2g/hr infusion

Magnesium sulfate is the drug of choice for eclampsia prophylaxis and treatment, superior to phenytoin in preventing recurrent seizures.

Question 11: A healthy 35-year-old presents with community-acquired pneumonia (CAP) requiring outpatient treatment with no comorbidities. What is the preferred first-line regimen?

Levofloxacin 750 mg once daily
Azithromycin 500 mg then 250 mg daily
Amoxicillin 500 mg three times daily (Correct answer)
Doxycycline 100 mg twice daily

Correct answer: Amoxicillin 500 mg three times daily

Current US guidelines recommend amoxicillin as first-line monotherapy for outpatient CAP in patients without comorbidities or risk factors for drug-resistant organisms.

Question 12: Clozapine requires mandatory full blood count monitoring primarily because of which serious adverse drug reaction?

Severe thrombocytopenia
Aplastic anaemia
Agranulocytosis (Correct answer)
Haemolytic anaemia

Correct answer: Agranulocytosis

Clozapine causes agranulocytosis in approximately 1% of patients, necessitating weekly FBC monitoring for the first 18 weeks then at minimum every 4 weeks thereafter.

Question 13: A patient with HFrEF previously on ramipril is being switched to sacubitril/valsartan. What is the minimum washout period required after stopping ramipril?

6 hours
12 hours
24 hours
36 hours (Correct answer)

Correct answer: 36 hours

A 36-hour washout after stopping an ACE inhibitor is required before starting sacubitril/valsartan to minimise the risk of angioedema from combined bradykinin accumulation.

Question 14: A patient stabilised on warfarin requires analgesia for headache. Which analgesic should be avoided?

Codeine 30 mg
Paracetamol 500 mg
Gabapentin 100 mg
Aspirin 600 mg (Correct answer)

Correct answer: Aspirin 600 mg

Aspirin inhibits platelet aggregation and can displace warfarin from protein binding, significantly increasing bleeding risk.

Question 15: What is a drug's half-life?

The time required for the drug's plasma concentration to decrease by 50% (Correct answer)
The time from first dose to full effect
Half of the recommended dose
The time until the drug expires

Correct answer: The time required for the drug's plasma concentration to decrease by 50%

Half-life determines dosing frequency: drugs with short half-lives need more frequent dosing, while long half-life drugs can be given less often.

Question 16: What does 'first-dose hypotension' mean?

Low blood pressure at birth
Hypotension that only occurs once
A significant drop in blood pressure occurring with the initial dose of certain medications like ACE inhibitors (Correct answer)
Blood pressure changes from standing up

Correct answer: A significant drop in blood pressure occurring with the initial dose of certain medications like ACE inhibitors

First-dose hypotension is particularly associated with ACE inhibitors, alpha-blockers, and some antihypertensives, especially in volume-depleted or elderly patients.

Question 17: Which drug combination carries the highest risk of serotonin syndrome?

Ibuprofen + codeine
Codeine + paracetamol
Tramadol + amitriptyline (Correct answer)
Morphine + diazepam

Correct answer: Tramadol + amitriptyline

Tramadol inhibits serotonin reuptake, and combined with amitriptyline (which also has serotonergic activity), the risk of serotonin syndrome is significantly increased.

Question 18: A 10-year-old child weighing 32 kg requires prednisolone at 1 mg/kg/day for an acute asthma exacerbation. What is the correct total daily dose?

20 mg
40 mg
50 mg
32 mg (Correct answer)

Correct answer: 32 mg

1 mg/kg/day × 32 kg = 32 mg/day; this is the calculated dose based on the child's actual body weight.

Question 19: Which patient identifier is most important to include on a prescription to prevent dispensing to the wrong individual?

Patient's email address
Patient's full name and date of birth (Correct answer)
Patient's insurance group number
Patient's pharmacy loyalty card number

Correct answer: Patient's full name and date of birth

Full name and date of birth together serve as the primary identifiers to confirm the correct patient, reducing the risk of dispensing errors when multiple patients share similar names.

Question 20: A patient develops widespread blistering with mucosal involvement and epidermal detachment affecting >30% of BSA after starting allopurinol. What is the most likely diagnosis?

Drug reaction with eosinophilia and systemic symptoms
Erythema multiforme
Toxic epidermal necrolysis (Correct answer)
Stevens-Johnson syndrome

Correct answer: Toxic epidermal necrolysis

Toxic epidermal necrolysis is defined by epidermal detachment affecting >30% of body surface area and is a life-threatening ADR most commonly triggered by allopurinol, sulfonamides, or anticonvulsants.

Question 21: NSAIDs precipitate acute kidney injury primarily through which mechanism?

Direct tubular cytotoxicity
Immune complex-mediated glomerulonephritis
Increased uric acid precipitation in renal tubules
Inhibition of prostaglandin-mediated afferent arteriolar vasodilation (Correct answer)

Correct answer: Inhibition of prostaglandin-mediated afferent arteriolar vasodilation

NSAIDs inhibit prostaglandin synthesis, abolishing the afferent arteriolar vasodilation that maintains glomerular filtration rate when renal perfusion pressure is reduced.

Question 22: Which antiepileptic drug carries the highest risk of neural tube defects when taken during the first trimester of pregnancy?

Lamotrigine
Carbamazepine
Sodium valproate (Correct answer)
Levetiracetam

Correct answer: Sodium valproate

Sodium valproate is associated with the highest risk of neural tube defects (approximately 3-4%) and major congenital malformations among antiepileptic drugs.

Question 23: A firefighter rescued from a structural fire presents with cherry-red skin, coma, and lactic acidosis with normal PaO2. What antidote should be given?

100% oxygen via non-rebreather mask only
Methylene blue 1–2mg/kg IV
Hydroxocobalamin (Cyanokit) 5g IV over 15 minutes (Correct answer)
Sodium thiosulfate 12.5g IV alone

Correct answer: Hydroxocobalamin (Cyanokit) 5g IV over 15 minutes

Hydroxocobalamin is the first-line antidote for cyanide poisoning, directly binding cyanide ions to form cyanocobalamin excreted in urine.

Question 24: For patients on warfarin, INR is used as a surrogate for TDM. A patient with atrial fibrillation has an INR of 4.8 (target 2.0–3.0). What is the most appropriate action if there is no active bleeding?

Give fresh frozen plasma immediately
Increase warfarin dose
Give IV vitamin K 10 mg
Hold warfarin and recheck INR in 1–2 days (Correct answer)

Correct answer: Hold warfarin and recheck INR in 1–2 days

For a supratherapeutic INR without active bleeding, holding warfarin and rechecking in 1–2 days is the standard approach.

Question 25: A patient on warfarin starts rifampicin for tuberculosis. What adjustment to warfarin dosing would most likely be required?

No change required — rifampicin does not affect warfarin
Dose reduction by approximately 50% due to enzyme inhibition
Immediate switch to a NOAC due to unpredictable interaction
Significant dose increase due to enzyme induction (Correct answer)

Correct answer: Significant dose increase due to enzyme induction

Rifampicin is a potent inducer of CYP2C9 and other hepatic enzymes, dramatically accelerating warfarin metabolism and requiring substantial dose increases to maintain therapeutic INR.

Question 26: A patient on warfarin has their INR rise from 2.5 to 5.8 after starting trimethoprim for a UTI. What is the primary mechanism of this interaction?

Trimethoprim inhibits intestinal vitamin K absorption
Trimethoprim increases gastrointestinal absorption of warfarin
Trimethoprim inhibits CYP2C9, reducing S-warfarin metabolism (Correct answer)
Trimethoprim displaces warfarin from plasma protein binding sites

Correct answer: Trimethoprim inhibits CYP2C9, reducing S-warfarin metabolism

Trimethoprim inhibits CYP2C9, the primary enzyme metabolizing the more potent S-warfarin enantiomer, leading to drug accumulation and supratherapeutic anticoagulation.

Question 27: A 72-year-old woman with heart failure on digoxin 125 mcg daily presents with nausea, vomiting, and yellow-green visual halos. Her digoxin level is 3.1 ng/mL (therapeutic range 0.5–2.0 ng/mL). What is the most appropriate immediate management?

Halve the digoxin dose and recheck levels in 48 hours
Stop digoxin, correct hypokalaemia, and administer digoxin-specific antibody fragments (DigiFab) if severe toxicity present (Correct answer)
Switch to amiodarone for rate control in heart failure
Increase loop diuretic dose to accelerate renal digoxin clearance

Correct answer: Stop digoxin, correct hypokalaemia, and administer digoxin-specific antibody fragments (DigiFab) if severe toxicity present

Symptomatic digoxin toxicity with supratherapeutic levels requires immediate cessation, electrolyte correction (especially potassium), and DigiFab in cases of severe or life-threatening toxicity.

Question 28: Which of the following best describes why TDM for tacrolimus uses whole blood rather than serum?

Tacrolimus concentrates extensively in red blood cells (Correct answer)
Tacrolimus is unstable in serum at room temperature
Tacrolimus is not detectable in serum
Serum processing destroys tacrolimus

Correct answer: Tacrolimus concentrates extensively in red blood cells

Tacrolimus binds extensively to erythrocytes, making whole blood the appropriate matrix for accurate TDM.

Question 29: Why is prescribing in children different from adults?

Children have different body composition, metabolism rates, and organ maturity affecting drug handling (Correct answer)
The same doses work for all ages
Children are just small adults
Only the route of administration changes

Correct answer: Children have different body composition, metabolism rates, and organ maturity affecting drug handling

Children are not miniature adults: their drug metabolism, body water content, organ function, and body surface area differ significantly, requiring weight-based or surface-area-based dosing.

Question 30: Stevens-Johnson syndrome is a severe mucocutaneous adverse drug reaction most classically associated with which medication?

Amoxicillin
Standard-dose ibuprofen
Carbamazepine (Correct answer)
Metformin

Correct answer: Carbamazepine

Carbamazepine and other aromatic anticonvulsants, along with allopurinol and sulfonamides, are strongly associated with Stevens-Johnson syndrome and toxic epidermal necrolysis.

Question 31: Which piece of information on a prescription protects the patient against dispensing errors at the pharmacy?

The indication (diagnosis) for the drug
Prescriber's NPI number
Insurance policy number
Drug name, strength, dosage form, and quantity (Correct answer)

Correct answer: Drug name, strength, dosage form, and quantity

Drug name, strength, dosage form (e.g., tablet, capsule), and quantity together allow the pharmacist to verify they are dispensing exactly what was intended.

Question 32: A 70-year-old woman with type 2 diabetes is prescribed metformin. Her eGFR is 30 mL/min/1.73m². What is the most appropriate action?

Discontinue metformin due to risk of lactic acidosis (Correct answer)
Continue at full dose as benefits outweigh risks
Switch to insulin immediately
Double the dose to compensate for reduced absorption

Correct answer: Discontinue metformin due to risk of lactic acidosis

Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² due to accumulation and risk of lactic acidosis.

Question 33: Which of the following best describes the goal of area under the curve (AUC)-guided vancomycin dosing compared to traditional trough-only monitoring?

AUC dosing is only used in pediatric patients
AUC dosing better balances efficacy and nephrotoxicity risk (Correct answer)
AUC dosing simplifies monitoring by requiring fewer blood draws
AUC dosing eliminates the need for renal function monitoring

Correct answer: AUC dosing better balances efficacy and nephrotoxicity risk

AUC-guided dosing optimizes the AUC/MIC ratio for efficacy while minimizing nephrotoxicity risk compared to trough-only monitoring.

Question 34: A patient on digoxin has a serum level of 2.8 ng/mL. The therapeutic range is 0.5–2.0 ng/mL. What is the most appropriate next step?

Switch to a different cardiac glycoside
Increase the digoxin dose
Continue the current dose
Hold digoxin and reassess (Correct answer)

Correct answer: Hold digoxin and reassess

A digoxin level above the therapeutic range indicates toxicity risk; the dose should be held and the patient reassessed for signs of toxicity.

Question 35: A patient on simvastatin 40 mg daily is prescribed clarithromycin for a respiratory infection. What is the primary concern?

Hepatotoxicity from the antibiotic alone
Myopathy or rhabdomyolysis due to elevated simvastatin levels (Correct answer)
Reduced statin efficacy due to enzyme induction
QT interval prolongation from both drugs combined

Correct answer: Myopathy or rhabdomyolysis due to elevated simvastatin levels

Clarithromycin is a potent CYP3A4 inhibitor that dramatically increases simvastatin plasma levels, raising the risk of myopathy and rhabdomyolysis.

Question 36: A patient on simvastatin 40 mg starts clarithromycin for a chest infection and develops severe myalgia with dark urine. What is the most likely mechanism?

Clarithromycin inhibits CYP3A4, raising simvastatin plasma levels (Correct answer)
Clarithromycin directly damages skeletal muscle
The simvastatin dose was independently too high
Clarithromycin induces CYP3A4, increasing statin conversion to toxic metabolites

Correct answer: Clarithromycin inhibits CYP3A4, raising simvastatin plasma levels

Clarithromycin is a potent CYP3A4 inhibitor that markedly increases simvastatin exposure, precipitating statin-induced myopathy and potentially rhabdomyolysis.

Question 37: A pregnant patient requires an antibiotic. Which class is avoided due to risk of dental discolouration and inhibited bone development in the fetus?

Penicillins
Cephalosporins
Macrolides
Tetracyclines (Correct answer)

Correct answer: Tetracyclines

Tetracyclines cross the placenta and chelate calcium in developing fetal bones and teeth, causing permanent yellow-brown dental staining and impaired skeletal development.

Question 38: What is a good medicine for sleep?

Zopiclone 15.75mg On Prn
Zopiclone 3.75mg On PRN (Correct answer)
Zopiclone 4.75mg On Prn
Zopiclone 97.75mg On Prn

Correct answer: Zopiclone 3.75mg On PRN

Zopiclone 3.75mg is a common starting dose for insomnia, particularly in elderly patients or those sensitive to sedatives, and is often prescribed 'as needed' (PRN). This lower dose helps minimize side effects such as excessive sedation, dizziness, and dependence. It is typically used as a short-term treatment for insomnia.

Question 39: A patient with Child-Pugh B hepatic cirrhosis requires regular analgesia. What is the maximum recommended daily paracetamol dose?

2 g (Correct answer)
4 g
3 g
500 mg

Correct answer: 2 g

In significant hepatic impairment, the maximum paracetamol dose is reduced to 2 g per day to avoid hepatotoxicity.

Question 40: Initial blood cultures grow gram-negative rods and the patient is started on broad-spectrum coverage. Sensitivities return showing susceptibility to ceftriaxone. What should be done?

De-escalate to ceftriaxone based on susceptibilities (Correct answer)
Continue broad-spectrum antibiotics to ensure coverage
Add vancomycin for additional gram-positive coverage
Discontinue all antibiotics since the organism is identified

Correct answer: De-escalate to ceftriaxone based on susceptibilities

De-escalation to the narrowest effective agent once culture sensitivities are available is a fundamental antibiotic stewardship principle that reduces resistance and adverse effects.

Question 41: A patient starts rituximab infusion and develops fever, rigors, and bronchospasm within the first hour. What is the most likely cause?

Sepsis unmasked by rituximab-induced immunosuppression
Direct complement activation by rituximab
IgE-mediated anaphylaxis to murine antibody components
Cytokine release from rituximab binding CD20 on circulating B cells (Correct answer)

Correct answer: Cytokine release from rituximab binding CD20 on circulating B cells

Rituximab binds CD20 on circulating B cells triggering cytokine release; this infusion reaction is most severe during the first infusion when circulating B-cell burden is highest.

Question 42: A patient with a documented penicillin allergy (rash) requires a beta-lactam antibiotic for a serious infection. What is the safest approach?

Penicillin allergy means only monobactams and vancomycin can be used
All beta-lactams are absolutely contraindicated in any penicillin allergy
Carbapenems have the highest cross-reactivity with penicillins and must be avoided
Cross-reactivity between penicillins and cephalosporins is primarily due to the R1 side chain; structural dissimilarity makes most cephalosporins safe (Correct answer)

Correct answer: Cross-reactivity between penicillins and cephalosporins is primarily due to the R1 side chain; structural dissimilarity makes most cephalosporins safe

Cross-reactivity between penicillins and cephalosporins is due to similar R1 side chains; for non-anaphylactic penicillin allergy, structurally dissimilar cephalosporins can often be used safely.

Question 43: A patient with severe alcohol use disorder has a CIWA-Ar score of 22 and is experiencing visual hallucinations and tremor. What is the most appropriate treatment?

Haloperidol 5mg IM for hallucinations
Clonidine 0.1mg PO for autonomic symptoms alone
Propranolol 20mg PO for tremor and tachycardia
Diazepam 10–20mg IV/PO titrated to CIWA score every 1–2 hours (Correct answer)

Correct answer: Diazepam 10–20mg IV/PO titrated to CIWA score every 1–2 hours

Benzodiazepines (symptom-triggered diazepam dosing) are first-line for alcohol withdrawal with a high CIWA score, preventing seizures and delirium tremens.

Question 44: A patient with a severe penicillin allergy (anaphylaxis) develops a skin and soft tissue infection caused by Staphylococcus aureus (MSSA). Which antibiotic is most appropriate?

Vancomycin (Correct answer)
Cephalexin
Amoxicillin-clavulanate
Cefazolin

Correct answer: Vancomycin

Vancomycin is the safest option in true penicillin anaphylaxis, as cross-reactivity with beta-lactams remains a concern despite being low with cephalosporins.

Question 45: What is neuropathic pain and how is it treated differently?

Pain that responds well to paracetamol
Pain only in the feet
Pain that does not require treatment
Pain caused by nerve damage, often treated with antidepressants or anticonvulsants rather than standard analgesics (Correct answer)

Correct answer: Pain caused by nerve damage, often treated with antidepressants or anticonvulsants rather than standard analgesics

Neuropathic pain (burning, shooting, tingling) results from nerve damage and responds poorly to standard painkillers but often improves with amitriptyline, gabapentin, or pregabalin.

Question 46: A patient on theophylline for COPD has a level of 22 mcg/mL (therapeutic 10–20 mcg/mL). Which symptom is most consistent with theophylline toxicity?

Seizures (Correct answer)
Hypoglycemia
Bradycardia
Hypotension

Correct answer: Seizures

Theophylline toxicity can cause seizures, tachycardia, and arrhythmias, with seizures being a serious manifestation at supratherapeutic levels.

Question 47: In what unit is the effective dosage measured?

Sievert (Sv) (Correct answer)
Roentgen (r)
Gray (gy)
Becquerel (bq)

Correct answer: Sievert (Sv)

The Sievert (Sv) is the unit used to measure the effective dose of radiation, which accounts for the biological effects of different types of radiation on human tissue. It quantifies the health risk from exposure to ionizing radiation. This differs from Gray (Gy), which measures absorbed dose, and Becquerel (Bq), which measures radioactivity.

Question 48: A 74-year-old man with HFrEF has a BP of 88/60 mmHg at clinic. He is on ramipril 10mg, bisoprolol 10mg, furosemide 80mg, and spironolactone 25mg daily. Which medication should be reduced first?

Spironolactone
Bisoprolol
Ramipril
Furosemide (Correct answer)

Correct answer: Furosemide

In symptomatic hypotension in HFrEF, the diuretic is typically reduced first as it contributes to low filling pressures without direct survival benefit.

Question 49: A 68-year-old man with AF and CKD (eGFR 25 mL/min) needs anticoagulation. Which DOAC is most problematic at this level of renal impairment?

Edoxaban
Dabigatran (Correct answer)
Apixaban
Rivaroxaban

Correct answer: Dabigatran

Dabigatran is approximately 80% renally eliminated and is contraindicated when eGFR < 30 mL/min, making it the most problematic DOAC in severe CKD.

Question 50: A breastfeeding mother needs analgesia following a Caesarean section. Which analgesic should be used with the greatest caution?

Codeine (Correct answer)
Diclofenac
Paracetamol
Ibuprofen

Correct answer: Codeine

Codeine is converted to morphine by CYP2D6; in ultra-rapid metabolizers, excessive morphine passes into breast milk and can cause neonatal respiratory depression.

Question 51: A patient with CrCl 30 mL/min is prescribed digoxin. Compared to a patient with normal renal function, the expected pharmacokinetic change is:

Unchanged half-life as digoxin is hepatically metabolized
Reduced volume of distribution requiring a smaller loading dose
Prolonged half-life, requiring dose reduction (Correct answer)
Shorter half-life, requiring more frequent dosing

Correct answer: Prolonged half-life, requiring dose reduction

Digoxin is 70% renally excreted; in renal impairment, its half-life is prolonged significantly, requiring maintenance dose reduction to prevent toxicity.

Question 52: A patient receiving gentamicin for gram-negative bacteremia has a creatinine clearance of 30 mL/min. Which pharmacokinetic adjustment is most appropriate?

Increase the dose, keep the interval the same
Keep the dose the same, extend the dosing interval (Correct answer)
Switch to a different aminoglycoside
No adjustment needed as aminoglycosides are hepatically cleared

Correct answer: Keep the dose the same, extend the dosing interval

Aminoglycosides are renally eliminated; in renal impairment, extending the dosing interval (not reducing the dose) maintains adequate peak concentrations while allowing drug clearance.

Question 53: Which prescription abbreviation is considered most dangerous and should always be written in full to prevent a medication error?

'tab' for tablet
'PO' for by mouth
'mg' for milligrams
'U' for units, which can be misread as a zero causing a tenfold overdose (Correct answer)

Correct answer: 'U' for units, which can be misread as a zero causing a tenfold overdose

Writing 'U' for units is dangerous because it can be misread as '0', turning '10U of insulin' into '100 units' — a potentially fatal tenfold overdose.

Question 54: A 68-year-old woman with type 2 diabetes and CKD stage 3b (eGFR 32) on lisinopril develops hyperkalaemia with K+ 6.2 mmol/L. What is the most appropriate immediate action?

Add spironolactone for additional renal and cardiovascular protection
Increase the lisinopril dose to improve renal protection
Continue lisinopril and add a potassium-binding resin
Stop lisinopril immediately and manage the hyperkalaemia (Correct answer)

Correct answer: Stop lisinopril immediately and manage the hyperkalaemia

ACE inhibitors can cause dangerous hyperkalaemia in CKD; with K+ 6.2 mmol/L, lisinopril must be stopped immediately to prevent life-threatening cardiac arrhythmias.

Question 55: Which condition would most likely increase cyclosporine blood levels and require downward dose adjustment?

Co-administration of rifampin
High-fiber diet
Increased physical activity
Co-administration of fluconazole (Correct answer)

Correct answer: Co-administration of fluconazole

Fluconazole inhibits CYP3A4, reducing cyclosporine metabolism and increasing blood levels, necessitating dose reduction.

Question 56: A 77-year-old man with HFrEF is considered for spironolactone 25mg daily. His eGFR is 26 mL/min. What is the primary prescribing concern?

Spironolactone causes metabolic alkalosis in renal impairment
High risk of gynaecomastia in elderly men
Spironolactone will be ineffective below eGFR 30
Severe hyperkalaemia risk due to reduced renal potassium excretion (Correct answer)

Correct answer: Severe hyperkalaemia risk due to reduced renal potassium excretion

Spironolactone is generally avoided when eGFR < 30 mL/min because impaired renal potassium excretion combined with aldosterone antagonism markedly increases hyperkalaemia risk.

Question 57: A patient develops serotonin syndrome after starting tramadol while already prescribed sertraline. Which symptom triad is most characteristic?

Somnolence, respiratory depression, and miosis
Hypotension, urinary retention, and constipation
Agitation, hyperthermia, and clonus (Correct answer)
Bradycardia, hypothermia, and miosis

Correct answer: Agitation, hyperthermia, and clonus

Serotonin syndrome presents with the classic triad of neuromuscular excitability (clonus, hyperreflexia), autonomic instability, and altered mental status including agitation and hyperthermia.

Question 58: A patient with chronic pain and an eGFR of 25 ml/min is prescribed gabapentin. What dosing adjustment is required?

Dose reduction required as gabapentin is renally excreted (Correct answer)
Increase the dose to compensate for reduced absorption
Switch to pregabalin which requires no adjustment
No adjustment needed as gabapentin is hepatically metabolized

Correct answer: Dose reduction required as gabapentin is renally excreted

Gabapentin is almost entirely excreted unchanged by the kidneys; dose reduction is mandatory in renal impairment to prevent toxicity.

Question 59: Under the 2015 FDA Pregnancy and Lactation Labeling Rule (PLLR), the old letter-category system (A/B/C/D/X) was replaced. What do the new labeling sections require?

Narrative summaries of human and animal data for pregnancy, lactation, and reproductive potential (Correct answer)
Only a black box warning if any risk is identified
A single pregnancy risk score from 0 to 10
Color-coded risk tiers (green/yellow/red) standardized across all drugs

Correct answer: Narrative summaries of human and animal data for pregnancy, lactation, and reproductive potential

The PLLR requires narrative text describing available human and animal data about risks in the subsections for Pregnancy, Lactation, and Females and Males of Reproductive Potential, replacing the simple A-X letter grades.

Question 60: A cancer patient on regular modified-release morphine reports breakthrough pain. How should PRN morphine be administered?

On a fixed 8-hourly schedule only
Only before physiotherapy sessions
Only at nighttime when pain worsens
As needed, up to every 4 hours (Correct answer)

Correct answer: As needed, up to every 4 hours

Breakthrough (PRN) morphine can be administered as needed, typically up to every 4 hours, in addition to the background modified-release dose.

Question 61: In hepatic impairment, what change occurs to the first-pass effect of orally administered drugs with high hepatic extraction ratios?

It increases bioavailability only for acidic drugs
It is decreased, increasing oral bioavailability (Correct answer)
It is increased, reducing oral bioavailability
It is unchanged as hepatocyte number remains constant

Correct answer: It is decreased, increasing oral bioavailability

Hepatic impairment reduces first-pass metabolism, allowing more of an orally administered high-extraction drug to reach systemic circulation, increasing bioavailability.

Question 62: In hepatic impairment, which plasma protein is most significantly reduced, leading to increased free drug fractions of highly protein-bound medications?

Alpha-1 acid glycoprotein
Transferrin
Albumin (Correct answer)
Fibrinogen

Correct answer: Albumin

Albumin, synthesized by the liver, is reduced in hepatic impairment, increasing the free fraction of acidic drugs like phenytoin, warfarin, and furosemide.

Prescribing Safety Assessment (PSA)

The PSA is a UK national exam for final-year medical students that assesses safe and effective prescribing skills across eight domains. It is jointly owned by the Medical Schools Council and NHS England and must be passed to progress to foundation training.

Questions

120 min

Time Limit

62%

To Pass

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Exam Rules

You can skip questions and return to them later
Flag questions for review before submitting
No feedback shown until you submit the entire exam
Unanswered questions count as wrong — answer everything
10 pretest questions are mixed in and don't affect your score
Timer auto-submits when time runs out
Your progress is auto-saved every 30 seconds