OSCE Pharmacology and Medication Administration — Questions and Answers

Question 1: What are the 'Five Rights' of medication administration?

Right patient, right drug, right dose, right route, right time (Correct answer)
Right drug, right dose, right colour, right size, right nurse
Right patient, right drug, right floor, right doctor, right chart
Right time, right place, right team, right equipment, right policy

Correct answer: Right patient, right drug, right dose, right route, right time

The Five Rights are the foundational framework for safe medication administration: confirming the correct patient receives the correct drug at the correct dose by the correct route at the correct time.

The Five Rights (also called the '5 Rs') are the minimum standard safety checks before administering any medication: (1) Right Patient — confirm identity using two identifiers (name + DOB or NHS/hospital number — never bed number alone); (2) Right Drug — match the drug name on the medication chart to the drug in hand (generic vs. brand name awareness); (3) Right Dose — calculate and verify the dose; (4) Right Route — oral, IV, IM, SC, topical, sublingual, etc.; (5) Right Time — correct timing including frequency and meal relationship. Extended versions add Right Documentation (record immediately after administration) and Right Reason. These checks are mandatory at every administration and form the basis of medication error prevention.

Question 2: A prescription reads 'paracetamol 1g PO QDS PRN.' What does 'QDS PRN' mean?

Four times daily as required (when needed) (Correct answer)
Every day as prescribed
Twice daily at regular intervals
Once daily at bedtime

Correct answer: Four times daily as required (when needed)

QDS = quater die sumendus (four times daily); PRN = pro re nata (as required/when needed). Together they mean the drug can be given up to four times per day but only when the patient requires it.

Latin prescription abbreviations remain common in clinical practice: QDS/QID = 4× daily; TDS/TID = 3× daily; BD/BID = twice daily; OD = once daily; OM = morning; ON = night; PRN = as required; STAT = immediately; AC = before meals; PC = after meals; PO = oral; IV = intravenous; IM = intramuscular; SC = subcutaneous; SL = sublingual. 'Paracetamol 1g PO QDS PRN' means: 1 gram of paracetamol by mouth, up to four times a day, but only when the patient requests or requires it for pain/fever. Maximum safe paracetamol dose for adults is 4g/24 hours (1g × 4 doses). Minimum interval between doses should be 4–6 hours.

Question 3: When preparing to administer an intramuscular (IM) injection, which site is generally preferred in adults for volumes up to 3 mL?

Ventrogluteal (gluteus medius) — preferred for most IM injections in adults (Correct answer)
Deltoid — suitable for volumes up to 1 mL only
Vastus lateralis — preferred in infants under 12 months
Dorsogluteal — preferred over all other sites

Correct answer: Ventrogluteal (gluteus medius) — preferred for most IM injections in adults

The ventrogluteal site (hand placement landmark method) is preferred for IM injection in adults due to its large muscle mass, absence of major nerves/vessels, and low complication rate.

IM injection site selection depends on patient age, muscle mass, volume, and drug viscosity: Ventrogluteal (gluteus medius): preferred for adults and children >7 months — large muscle, no major nerves or vessels nearby, accessible in multiple positions. Deltoid: suitable for small volumes (≤1 mL) including vaccinations — easy access but limited muscle mass; radial nerve risk if injection too low. Vastus lateralis (anterolateral thigh): preferred for infants and young children <2 years and in adults when other sites are unavailable. Dorsogluteal: historically used but now discouraged due to proximity to the sciatic nerve and superior gluteal artery. The Z-track technique (displacing skin laterally before injection, releasing after) minimises leakage and pain.

Question 4: Which vital sign change should trigger withholding digoxin and contacting the prescriber?

Heart rate below 60 beats per minute (bradycardia) (Correct answer)
Blood pressure above 130/80 mmHg
Temperature above 37.5°C
Respiratory rate above 18 breaths per minute

Correct answer: Heart rate below 60 beats per minute (bradycardia)

Digoxin slows heart rate via vagal effects; administration when the heart rate is already below 60 bpm risks worsening bradycardia and potentially fatal arrhythmias.

Digoxin is a cardiac glycoside used for atrial fibrillation rate control and heart failure. It slows conduction through the AV node (negative chronotropy). Before administering digoxin, the apical pulse must be measured for a full minute. If the apical pulse is <60 bpm in adults (or <70 bpm in paediatrics), digoxin should be withheld and the prescriber contacted. Signs of digoxin toxicity include nausea, vomiting, visual disturbances (yellow-green halos, blurred vision), confusion, bradycardia, and life-threatening arrhythmias (heart block, VT, VF). Digoxin has a narrow therapeutic index (0.5–2 ng/mL); therapeutic drug monitoring is required.

Question 5: What is the purpose of a 'drug allergy alert' documentation in a patient's medication record?

To prevent the patient from receiving any drug in the same class as the allergen, preventing potentially life-threatening reactions (Correct answer)
To note drugs the patient dislikes for personal preference
To document only anaphylaxis — mild reactions are recorded elsewhere
To indicate drugs that are too expensive for the formulary

Correct answer: To prevent the patient from receiving any drug in the same class as the allergen, preventing potentially life-threatening reactions

Allergy documentation records the specific allergen and reaction type (severity) so that cross-reactive drugs and the allergen itself are avoided, preventing anaphylaxis and severe hypersensitivity reactions.

Comprehensive allergy documentation includes: the specific drug (full generic name, not class), the reaction type (anaphylaxis, urticaria, angioedema, maculopapular rash, GI intolerance), severity (mild/moderate/severe/life-threatening), and date of reaction. This information is used to: avoid the offending drug; identify cross-reactive agents (e.g., penicillin allergy — assess risk of cephalosporin); determine if desensitisation is needed; provide emergency epinephrine prescription if anaphylaxis-prone. Allergy documentation errors are a major source of medication harm. In OSCE stations, asking about allergies before any medication administration is mandatory — failure to check is a critical safety error.

Question 6: When administering IV medication, which step is essential to prevent air embolism?

Priming (flushing) the IV line to remove all air bubbles before connecting to the patient (Correct answer)
Administering the medication as rapidly as possible
Using a large-bore cannula for all IV medications
Shaking the IV bag vigorously before use

Correct answer: Priming (flushing) the IV line to remove all air bubbles before connecting to the patient

Air embolism can cause cardiac arrest; priming the IV giving set eliminates air from the line before connection to the patient, a mandatory safety step.

IV air embolism occurs when air enters the venous system, potentially causing respiratory distress, cardiac dysfunction, neurological injury, or death (venous air embolism can pass to the arterial circulation via a patent foramen ovale). Prevention requires: priming the IV giving set by running fluid through until all air is expelled; inspecting the IV line for bubbles before connection and during infusion; using air-detecting IV pumps where available; ensuring all connections are secure and closed. Additional IV safety steps include: checking infusion compatibility, calculating flow rate, verifying correct drug concentration, labelling the infusion bag with drug name/dose/date/time/rate, and checking the cannula site before and during infusion.

Question 7: A patient is prescribed warfarin. Which blood test is routinely monitored to guide dose adjustment?

INR (International Normalised Ratio) (Correct answer)
Full blood count (FBC)
Serum potassium
Creatinine kinase (CK)

Correct answer: INR (International Normalised Ratio)

The INR measures the effect of warfarin on clotting; doses are adjusted to maintain the INR within the therapeutic range (typically 2–3 for most indications).

Warfarin is a vitamin K antagonist that inhibits clotting factors II, VII, IX, and X. Its anticoagulant effect is monitored using the INR (International Normalised Ratio), derived from the prothrombin time. Therapeutic INR ranges: 2.0–3.0 for DVT/PE treatment, AF stroke prevention, and mechanical bileaflet valves in aortic position; 2.5–3.5 for mechanical mitral valves or recurrent thromboembolism. INR >3 increases haemorrhage risk; INR <2 risks thromboembolic events. INR is influenced by diet (vitamin K-rich foods — leafy greens), medications (antibiotics, NSAIDs, amiodarone), alcohol, liver disease, and intercurrent illness. Dose adjustments are made according to local anticoagulation protocols or nomograms.

Question 8: Which medication requires checking blood glucose before administration?

Insulin (Correct answer)
Amoxicillin
Furosemide
Atorvastatin

Correct answer: Insulin

Insulin lowers blood glucose; the current blood glucose level must be measured before administration to determine the correct dose and prevent hypoglycaemia.

Insulin administration requires a blood glucose measurement immediately before administration (typically <30 minutes prior). This is essential because: (1) The dose may be adjusted based on current blood glucose using a sliding scale or basal-bolus protocol; (2) If blood glucose is already low (<4 mmol/L or per local protocol), insulin administration risks severe hypoglycaemia; (3) Documentation of pre- and post-administration glucose is required for safe diabetes management. Key insulin safety checks: confirm patient identity, check glucose, confirm insulin type (short-acting vs. long-acting vs. mixed), check dose with a second nurse (required for insulin in many settings), use an insulin syringe (units not mL), and monitor for hypoglycaemia (tremor, sweating, confusion, tachycardia) within 1 hour of rapid-acting insulin.

Question 9: What does 'first-pass metabolism' mean, and which route of administration avoids it?

First-pass metabolism is the biotransformation of orally absorbed drugs by the liver before reaching systemic circulation; sublingual/intravenous routes bypass it (Correct answer)
First-pass is the initial dose given to test a patient's response to a medication
It refers to the initial absorption of a drug through the skin
First-pass metabolism enhances the bioavailability of all oral drugs

Correct answer: First-pass metabolism is the biotransformation of orally absorbed drugs by the liver before reaching systemic circulation; sublingual/intravenous routes bypass it

Oral drugs are absorbed through the GI tract and must pass through the portal circulation and liver, where they are metabolized before reaching systemic circulation — this reduces bioavailability; IV and sublingual routes bypass the liver.

First-pass metabolism (hepatic first-pass effect) is the phenomenon where orally administered drugs are absorbed from the GI tract into the portal circulation, which passes through the liver before entering systemic circulation. Hepatic enzymes (particularly CYP450) metabolise a significant fraction of the drug, reducing its bioavailability. For example, oral GTN (glyceryl trinitrate) is almost completely inactivated by first-pass metabolism — hence it is administered sublingually for angina. Other drugs with high first-pass metabolism: propranolol, morphine, lidocaine, verapamil. Routes bypassing first-pass: intravenous, sublingual, transdermal, intranasal, rectal, inhalation. Understanding first-pass pharmacokinetics explains large dose differences between oral and IV formulations.

Question 10: A patient develops a widespread urticarial rash and throat tightness 10 minutes after receiving IV amoxicillin. What is the immediate priority action?

Stop the amoxicillin infusion and administer IM adrenaline (epinephrine) 0.5 mg (1:1000) immediately — this is anaphylaxis (Correct answer)
Continue the infusion and observe whether the rash resolves spontaneously
Give oral antihistamine and continue monitoring
Apply topical hydrocortisone to the rash

Correct answer: Stop the amoxicillin infusion and administer IM adrenaline (epinephrine) 0.5 mg (1:1000) immediately — this is anaphylaxis

Throat tightness and urticaria following antibiotic administration = anaphylaxis. Immediate IM adrenaline is the first-line treatment — no other intervention takes priority.

Anaphylaxis management follows the ABCDE approach and Resuscitation Council guidelines: (1) Stop the trigger (stop IV drug immediately); (2) Call for help; (3) Lay patient flat with legs elevated (if breathing allows); (4) Administer IM adrenaline (epinephrine) 0.5 mg of 1:1000 solution (0.5 mL) into the anterolateral thigh — this is the FIRST and most important pharmacological treatment; (5) High-flow O2; (6) IV fluid challenge (500 mL crystalloid rapidly); (7) Consider IV antihistamine (chlorphenamine 10 mg) and IV hydrocortisone 200 mg as SECONDARY treatments after adrenaline. Monitoring: repeat adrenaline every 5 minutes if no improvement; admit for minimum 6 hours; prescribe EpiPen on discharge if appropriate.

Question 11: What is the correct action if a medication error (administering the wrong dose) is discovered after the medication has been given?

Immediately assess the patient for adverse effects, report to the senior clinician and prescriber, document accurately in the patient record, and complete an incident report (Correct answer)
Delete the documentation and write a corrected entry without disclosure
Wait to see if any symptoms develop before telling anyone
Administer an antidote without informing the team

Correct answer: Immediately assess the patient for adverse effects, report to the senior clinician and prescriber, document accurately in the patient record, and complete an incident report

Patient safety requires immediate assessment, transparent disclosure, escalation to the clinical team, accurate documentation, and incident reporting — concealment constitutes professional misconduct.

Medication error management follows a standardised process: (1) Assess the patient immediately for adverse effects and vital signs; (2) Inform the senior nurse/doctor and prescriber immediately; (3) Continue monitoring the patient; (4) Document the error accurately (what was given, when, dose, route) in the patient notes — do NOT alter previous documentation; (5) Complete a Datix/incident report (local system); (6) Disclose to the patient (duty of candour — a legal requirement under CQC Regulation 20); (7) Review and address the systems failure to prevent recurrence. Concealing a medication error violates the NMC Code of Professional Conduct, duty of candour legislation, and patient rights. OSCE stations often test candidates' professional response to errors.

Question 12: Which electrolyte abnormality potentiates digoxin toxicity?

Hypokalaemia (low potassium) (Correct answer)
Hyperkalaemia (high potassium)
Hypernatraemia (high sodium)
Hyponatraemia (low sodium)

Correct answer: Hypokalaemia (low potassium)

Low potassium increases the risk of digoxin toxicity because potassium and digoxin compete for the same binding site on the Na+/K+ ATPase pump — less potassium means more digoxin effect.

Digoxin inhibits the Na+/K+ ATPase pump on cardiomyocytes. Potassium competes with digoxin at this receptor; when serum potassium is low (hypokalaemia), more receptor sites are available for digoxin binding, increasing its pharmacological effect and toxicity risk. This interaction is clinically significant because loop diuretics (furosemide) and thiazides — commonly co-prescribed with digoxin in heart failure — cause urinary potassium loss. Hypokalaemia risk factors: diarrhoea, vomiting, diuretics, poor nutritional intake, metabolic alkalosis. Management: correct hypokalaemia before or alongside digoxin therapy; monitor K+ and digoxin levels regularly. Other electrolytes affecting digoxin: hypercalcaemia and hypomagnesaemia also increase toxicity risk.

Question 13: What is the correct injection angle for a subcutaneous (SC) injection?

45° angle in lean patients and 90° angle in patients with adequate subcutaneous tissue (Correct answer)
90° in all patients regardless of body habitus
15° angle (same as intradermal)
30° angle to ensure intramuscular placement

Correct answer: 45° angle in lean patients and 90° angle in patients with adequate subcutaneous tissue

SC injections are given at 45° in thin/lean patients to avoid hitting muscle; in patients with adequate subcutaneous tissue, 90° may be used. The needle should reach subcutaneous fat, not muscle.

Subcutaneous injection technique: clean skin with 70% alcohol swab (allow to dry to prevent skin irritation), pinch the skin fold (to elevate SC tissue away from muscle), insert needle at 45° (lean patient) or 90° (adequate SC tissue), release the skin fold after insertion, inject the drug steadily without aspiration (not required for SC drugs), withdraw the needle smoothly and apply gentle pressure (do not rub, as this can cause bruising with anticoagulants like heparin). Common SC sites: abdomen (2 inches from umbilicus), anterior thigh, upper outer arm. Rotate injection sites to prevent lipohypertrophy (especially with insulin). SC medications include insulin, low-molecular-weight heparin, morphine infusions, and some vaccines.

Question 14: Which pain scale is most appropriate for assessing pain in an unconscious or non-verbal patient?

Behavioural pain scale (BPS) or critical care pain observation tool (CPOT) — observe facial expression, limb movement, and ventilator compliance (Correct answer)
Numeric Rating Scale (NRS) 0–10
Visual Analogue Scale (VAS)
Wong-Baker FACES scale (designed for children and adults who cannot verbalise numerically)

Correct answer: Behavioural pain scale (BPS) or critical care pain observation tool (CPOT) — observe facial expression, limb movement, and ventilator compliance

Non-verbal pain scales (BPS, CPOT) use observable behavioural indicators to assess pain in patients unable to self-report — mandatory for ICU/sedated patients.

Self-report pain scales (NRS, VAS, verbal rating scale) require a conscious, communicative patient. For non-verbal patients: Behavioural Pain Scale (BPS) — used in ventilated ICU patients; assesses facial expression (1–4), upper limb movements (1–4), compliance with mechanical ventilation (1–4); score 3 (min) to 12 (max), score >6 indicates pain requiring intervention; CPOT (Critical Care Pain Observation Tool) — assesses facial expression, body movements, muscle tension, compliance with ventilator; more widely validated across ICU settings; Wong-Baker FACES scale — useful for children 3+ years or adults with cognitive impairment who can point to faces. OSCE candidates must be able to select the appropriate scale for each patient population and demonstrate its use.

Question 15: A patient is prescribed methotrexate once weekly. Why is the once-weekly schedule critical to follow exactly?

Methotrexate taken daily instead of weekly causes life-threatening bone marrow suppression and mucosal toxicity — it is one of the most dangerous prescribing errors in the UK (Correct answer)
Once-weekly dosing is purely for convenience with no safety implications
Methotrexate is ineffective if taken more frequently
The weekly schedule prevents nausea only, not serious adverse effects

Correct answer: Methotrexate taken daily instead of weekly causes life-threatening bone marrow suppression and mucosal toxicity — it is one of the most dangerous prescribing errors in the UK

Daily methotrexate (instead of weekly) causes fatal bone marrow suppression and mucositis — methotrexate prescribing errors are a persistent patient safety issue causing preventable deaths in the UK.

Methotrexate for non-oncological indications (rheumatoid arthritis, psoriasis, inflammatory bowel disease) is prescribed once weekly, not daily. This is one of the most frequently occurring serious prescribing errors in the UK, cited by the MHRA and NHS Patient Safety Agency multiple times. Patients and carers may misunderstand and take the drug daily, causing: severe bone marrow suppression (pancytopenia — potentially fatal), mucositis, hepatotoxicity, and pulmonary toxicity. All prescriptions should state 'ONCE WEEKLY on [day].' Patients must receive methotrexate treatment booklets, folic acid supplementation (to reduce toxicity), and regular FBC/LFT monitoring. OSCE stations may test recognition of this error and patient counselling skills.

Question 16: What is the correct disposal method for unused controlled drugs (CDs) in a clinical setting?

Render them irretrievable in a CD denaturing kit in the presence of two authorised witnesses, then dispose as clinical waste (Correct answer)
Pour them down the sink alone without witnesses
Return them to the patient for home use
Lock them in the CD cupboard indefinitely without documentation

Correct answer: Render them irretrievable in a CD denaturing kit in the presence of two authorised witnesses, then dispose as clinical waste

Controlled drugs must be denatured (rendered unusable) in the presence of two witnesses and documented in the CD register — strict regulations prevent diversion and misuse.

Controlled drug (CD) management is governed by the Misuse of Drugs Regulations 2001 (UK). Key requirements: Storage — in a locked CD cabinet bolted to the wall; Record-keeping — all administration, wastage, and disposal documented in a CD register (patient name, date, amount given, balance remaining, two signatures); Disposal — CDs must be denatured using an approved denaturing kit (capsules, liquid rendering them unusable) in the presence of two authorised witnesses (both must sign the CD register); CD registers must be kept for 2 years after last entry. Any discrepancy in the CD register or suspected diversion must be reported immediately to the senior pharmacist, charge nurse, and controlled drug accountable officer. Failure to comply with CD regulations has serious professional and legal consequences.

Question 17: Which patient parameter is most important to check before administering an angiotensin-converting enzyme (ACE) inhibitor such as ramipril?

Blood pressure and renal function (serum creatinine/eGFR) and serum potassium (Correct answer)
Random blood glucose
Temperature and respiratory rate
Full blood count and LFT

Correct answer: Blood pressure and renal function (serum creatinine/eGFR) and serum potassium

ACE inhibitors lower blood pressure and can cause hypotension, renal impairment, and hyperkalaemia — pre-dose BP, renal function, and potassium levels must be checked.

ACE inhibitors (ramipril, lisinopril, enalapril) block the conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone secretion. Pre-administration checks: (1) Blood pressure — do not administer if systolic BP <90 mmHg (withhold and contact prescriber); (2) Renal function (eGFR/creatinine) — baseline and regular monitoring; ACE inhibitors are contraindicated in bilateral renal artery stenosis; an initial 15–30% rise in creatinine is acceptable, but >30% rise from baseline warrants review; (3) Potassium — ACE inhibitors reduce aldosterone, causing potassium retention (risk of hyperkalaemia, especially with potassium-sparing diuretics, NSAIDs, or renal impairment). Counselling includes informing the patient about persistent dry cough (bradykinin accumulation — class effect), dizziness, and the need for regular blood monitoring.

Question 18: During an OSCE medication reconciliation station, what is the primary goal of medicines reconciliation?

To create an accurate, complete list of a patient's current medications at each transition of care to prevent omissions, duplications, and errors (Correct answer)
To assess the cost of the patient's medications and suggest cheaper alternatives
To document medications the patient no longer needs
To update the formulary with new drugs the patient requests

Correct answer: To create an accurate, complete list of a patient's current medications at each transition of care to prevent omissions, duplications, and errors

Medicines reconciliation obtains a complete, accurate medication history at admission, transfer, and discharge to prevent medication errors at care transitions — a major source of preventable patient harm.

Medicines reconciliation is the process of obtaining and verifying a complete list of a patient's current medications (including OTC drugs, herbal remedies, vitamins, PRN medications, inhalers, patches) by comparing multiple information sources (patient interview, community pharmacy records, GP records, previous discharge summaries). It is performed at: hospital admission (identify what the patient was taking at home), transfer between wards or hospitals, and discharge (ensure appropriate continuation, changes, and GP communication). NICE guidance and NHS patient safety alerts identify omission of medications at admission as a leading cause of preventable patient harm. Discrepancies must be resolved by the prescribing team. OSCE stations testing this skill assess systematic information gathering, documentation, and communication with the patient about changes.

Question 19: What is 'therapeutic drug monitoring' (TDM) and for which type of drug is it most important?

Regular measurement of serum drug levels to ensure concentrations are within the therapeutic range — most critical for drugs with narrow therapeutic indices such as vancomycin, digoxin, phenytoin, and lithium (Correct answer)
Measuring drug levels after every dose of all medications
Monitoring drug levels only in neonates
Checking drug prices against formulary costs

Correct answer: Regular measurement of serum drug levels to ensure concentrations are within the therapeutic range — most critical for drugs with narrow therapeutic indices such as vancomycin, digoxin, phenytoin, and lithium

TDM is used for drugs where therapeutic efficacy and toxicity are closely related to serum concentration — narrow therapeutic index drugs require regular blood level monitoring.

Therapeutic drug monitoring (TDM) is indicated for drugs where: the relationship between dose and serum concentration is unpredictable (large pharmacokinetic variability); there is a narrow gap between therapeutic and toxic concentrations (narrow therapeutic index); clinical monitoring of effect is insufficient; and serum levels directly guide dose adjustment. Key drugs requiring TDM: Aminoglycosides (gentamicin, amikacin) — peak and trough levels; Vancomycin — AUC-guided dosing; Digoxin — check 6 hours post-dose, therapeutic range 0.5–2.0 ng/mL; Phenytoin — 10–20 mg/L; Lithium — 0.4–1.0 mmol/L (12 hours post-dose); Ciclosporin/tacrolimus — immunosuppressants in transplant patients. When to take blood samples (timing) is critical — trough levels are taken just before the next dose; peak levels at specified intervals post-dose.

Question 20: A patient's prescription states 'metformin 500 mg PO BD with food.' Why is 'with food' included in the instructions?

Metformin taken with meals reduces GI side effects (nausea, diarrhoea, abdominal discomfort) without affecting its blood glucose-lowering efficacy (Correct answer)
Taking metformin with food reduces its absorption and makes it less effective
The food is needed to activate metformin's mechanism of action
'With food' prevents a dangerous drug-food interaction causing hypoglycaemia

Correct answer: Metformin taken with meals reduces GI side effects (nausea, diarrhoea, abdominal discomfort) without affecting its blood glucose-lowering efficacy

Metformin commonly causes GI side effects; administration with or after meals significantly reduces nausea and diarrhoea without affecting its pharmacological effectiveness.

Metformin is the first-line oral antidiabetic agent for type 2 diabetes mellitus. It works primarily by reducing hepatic glucose output (decreasing gluconeogenesis) and improving insulin sensitivity. GI side effects (nausea, diarrhoea, metallic taste, abdominal cramping) occur in up to 30% of patients, especially at initiation or dose escalation. Administering metformin with or immediately after food reduces GI effects. Starting at a low dose (500 mg BD) and titrating slowly also minimizes GI intolerance. Important metformin contraindications: eGFR <30 mL/min/1.73m² (accumulation risk, lactic acidosis); hold before IV contrast (nephrotoxicity risk); severe infection/dehydration; active heart failure. Metformin does not cause hypoglycaemia when used as monotherapy.

Question 21: When administering medications through a nasogastric (NG) tube, what must be confirmed before each administration?

Correct NG tube position (gastric placement confirmed by pH testing of aspirate ≤5.5 and/or X-ray) and tube patency before medication administration (Correct answer)
That the patient is nil by mouth before giving NG medications
That all medications are in tablet form for NG administration
That the patient is in the upright position only if awake

Correct answer: Correct NG tube position (gastric placement confirmed by pH testing of aspirate ≤5.5 and/or X-ray) and tube patency before medication administration

NG tube position must be confirmed before every administration — displacement into the lungs can cause aspiration of medications, which is potentially fatal.

NG tube misplacement into the respiratory tract causing pulmonary administration of feeds or medications is a Never Event (preventable serious patient safety incident) in the UK. NPSA guidance (2011) requires: primary confirmation by pH testing of gastric aspirate (pH ≤5.5 confirms gastric placement — aspirate turns yellow indicator strips); if pH >5.5 (or no aspirate), chest/abdominal X-ray to confirm placement before first use and after suspected displacement. The 'whoosh' test (air injection and auscultation) is unreliable and MUST NOT be used. Tube position should be checked: before each feed or medication administration; after coughing, vomiting, or suctioning; if there are concerns about displacement. Document the pH result and aspirate volume before each use.

Question 22: Which of the following drugs carries the highest risk of causing hypoglycaemia when used as monotherapy?

Sulphonylureas (e.g., gliclazide, glibenclamide) (Correct answer)
Metformin
SGLT2 inhibitors (dapagliflozin, empagliflozin)
DPP-4 inhibitors (sitagliptin, saxagliptin)

Correct answer: Sulphonylureas (e.g., gliclazide, glibenclamide)

Sulphonylureas stimulate insulin secretion regardless of blood glucose level, so they can cause hypoglycaemia even when blood glucose is normal — unlike metformin and DPP-4 inhibitors.

Antidiabetic drug hypoglycaemia risk: High risk: Sulphonylureas (gliclazide, glibenclamide, glipizide) — stimulate pancreatic beta cells to release insulin constitutively, independent of blood glucose; risk is highest with glibenclamide (long-acting) and in elderly, renal impairment, or irregular meals; Insulin (all types). Low/no risk (as monotherapy): Metformin — reduces hepatic glucose production, does not stimulate insulin; SGLT2 inhibitors — renal glucose excretion, no insulin stimulation; DPP-4 inhibitors — enhance incretin effect only in response to eating; GLP-1 agonists — glucose-dependent mechanism. For OSCE medication safety stations, recognising high-risk hypoglycaemic drugs informs monitoring frequency and patient counselling (carry glucose tablets, recognise symptoms: sweating, tremor, confusion, tachycardia, hunger).

Question 23: What is the correct process for verifying patient identity before medication administration?

Ask the patient to state their full name and date of birth, check against the medication chart and wristband — use two patient identifiers (Correct answer)
Ask nearby staff to confirm who the patient is
Check only the bed number against the medication chart
Ask the patient if they want their medication without further verification

Correct answer: Ask the patient to state their full name and date of birth, check against the medication chart and wristband — use two patient identifiers

Two independent patient identifiers (name + date of birth, or name + hospital number) directly verified with the patient AND against the medication chart/wristband prevents wrong-patient medication errors.

Wrong-patient medication errors are preventable Never Events. Safe identification process: (1) Approach the patient and ask them to state their full name — never say the name and ask 'Are you John Smith?' (leading question — confused patients may agree regardless); (2) Ask the patient to state their date of birth; (3) Check both identifiers against the patient's wristband (place of safety); (4) Check both identifiers against the medication administration record (MAR) chart; (5) If identifiers match on all three (patient, wristband, MAR), proceed with administration. For unconscious patients, verify via wristband and MAR only; involve a second nurse. Bed number is NOT a safe identifier. This process applies to every medication administration regardless of familiarity with the patient.

Question 24: What is 'polypharmacy' and what risk does it present for patients?

The concurrent use of multiple medications (typically ≥5), increasing the risk of drug-drug interactions, adverse effects, non-adherence, and medication errors (Correct answer)
Using only one drug to treat all conditions simultaneously
Taking medications with alcohol
Using only generic medications to reduce cost

Correct answer: The concurrent use of multiple medications (typically ≥5), increasing the risk of drug-drug interactions, adverse effects, non-adherence, and medication errors

Polypharmacy (commonly defined as ≥5 regular medications) is associated with increased adverse drug reactions, drug interactions, falls, hospitalisation, and non-adherence — medication reviews are essential.

Polypharmacy is defined as the routine use of ≥5 regular medications. It is increasingly prevalent in elderly and multimorbid patients. Risks include: Drug-drug interactions (increasing as exponential combinations); Adverse drug reactions (ADRs — responsible for 6.5% of UK hospital admissions); Decreased adherence (pill burden, complex regimes, side effects); Prescribing cascade (new drug prescribed for the side effect of another); Falls risk (antihypertensives, sedatives, diuretics); Increased cognitive impairment (anticholinergics). Management: regular structured medication reviews (especially at transitions of care); application of validated deprescribing tools (STOPP/START criteria for older adults); patient-centred shared decision-making about which medications are essential vs. providing marginal benefit; pharmacist-led medication reconciliation. OSCE candidates should flag polypharmacy concerns and advocate for medication review.

Question 25: A patient is prescribed gentamicin. What two key parameters must be monitored to guide dosing and prevent toxicity?

Serum drug levels (peak and trough or AUC) and renal function (eGFR/creatinine) (Correct answer)
Blood pressure and heart rate
Liver function tests and INR
Full blood count and CRP

Correct answer: Serum drug levels (peak and trough or AUC) and renal function (eGFR/creatinine)

Gentamicin is an aminoglycoside antibiotic with nephrotoxic and ototoxic potential; serum drug levels and renal function guide dosing to maintain efficacy and avoid toxicity.

Gentamicin is an aminoglycoside antibiotic used for serious Gram-negative infections. It has a narrow therapeutic index with two major dose-dependent toxicities: nephrotoxicity (tubular damage — manifests as rising creatinine, reduced urine output — usually reversible with dose adjustment) and ototoxicity (cochlear and vestibular damage — may be irreversible — manifests as tinnitus, hearing loss, vertigo). Monitoring: (1) Serum gentamicin levels — trough (before next dose, should be <1 mg/L for once-daily dosing), or peak/trough for multiple daily dosing regimens; (2) Renal function — eGFR, creatinine, and urine output checked at least every 48 hours (more frequently if renal impairment develops). Hydration status is also important — dehydration potentiates nephrotoxicity. Gentamicin should be used with caution in patients with pre-existing renal impairment, elderly patients, and those on other nephrotoxic drugs.

Question 26: What is the 'prescribing cascade' in pharmacology, and why is it clinically important?

When a side effect of one drug is misidentified as a new condition and treated with another drug, creating a chain of unnecessary medications (Correct answer)
A method of safely increasing a drug dose in small increments
The correct method for prescribing drugs in a stepped-care protocol
Cascading prescriptions across multiple specialties for the same indication

Correct answer: When a side effect of one drug is misidentified as a new condition and treated with another drug, creating a chain of unnecessary medications

The prescribing cascade occurs when adverse drug effects are mistakenly treated as new conditions, leading to additional medications, more side effects, and further medications — a major driver of polypharmacy.

The prescribing cascade is a common and underrecognised iatrogenic harm cycle first described by Rochon and Gurwitz. Classic examples: Antipsychotic drug → drug-induced Parkinsonism → levodopa/carbidopa prescribed (thinking it is new Parkinson's disease) → dopaminergic excess side effects; ACE inhibitor → cough → codeine linctus prescribed for cough; NSAID → elevated blood pressure → antihypertensive added; Calcium channel blocker → ankle oedema → diuretic added. Prevention requires systematic ADR assessment at every prescribing decision — asking 'Could this new symptom be a side effect of a current medication?' Structured medication reviews (STOPP/START criteria) and pharmacist input are key prevention strategies.

OSCE Pharmacology and Medication Administration

What are the 'Five Rights' of medication administration?

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