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Drug & therapeutic level monitoring flashcards

15 high-yield MRCP Part 1 cards from the Intellect Medicos Clinical Pharmacology & Toxicology course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.

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1. What does a high trough level of gentamicin or vancomycin indicate, and how should the regimen be changed?

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   The drug is accumulating (reduced clearance). Extend the dosing interval rather than simply lowering the dose.

   Why? A high trough means the level has not fallen enough before the next dose, which raises the risk of nephrotoxicity and ototoxicity.

2. When should blood be taken for a ciclosporin or phenytoin level?

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   A trough level — immediately before the next dose.

   Why? For these drugs the pre-dose level best reflects exposure and toxicity risk. Phenytoin levels are checked if toxicity or non-adherence is suspected.

3. When should liver function be checked after starting a statin?

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   Baseline, then at 2–3 months and at 12 months (not again unless clinically indicated).

   Why? Statins can raise transaminases; routine checks after the first year are not needed unless clinically indicated.

4. Above what ALT level should a statin not be started (or be stopped)?

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   ALT more than 3 times the upper limit of normal.

   Why? Mildly raised transaminases (under 3 times normal) are not a reason to withhold a statin.

5. After starting an ACE inhibitor, what change in renal function should prompt review?

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   A rise in creatinine of 30% or more (or a fall in eGFR of 25% or more), or potassium of 6.0 mmol/L or more.

   Why? A small rise in creatinine is expected. Larger rises suggest renal artery stenosis or another cause, so look for causes and reduce or stop the drug.

6. Name four baseline investigations before starting amiodarone.

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   Any four: TFTs, LFTs, U&Es with potassium and magnesium, ECG, chest X-ray.

   Why? Amiodarone affects the thyroid, liver, lungs and QT interval, so baseline values are needed for later comparison.

7. How often are TFTs and LFTs checked in a patient stable on amiodarone?

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   Every 6 months.

   Why? Thyroid dysfunction and hepatotoxicity can appear at any time, even after stopping, because of the very long half-life.

8. Which blood tests are monitored on methotrexate, and how often once the dose is stable?

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   FBC, LFTs and creatinine/eGFR — at least every 12 weeks once stable (every 2 weeks at first, then monthly).

   Why? Methotrexate can cause myelosuppression, hepatotoxicity and accumulates in renal impairment.

9. What is the antidote ('rescue') for methotrexate toxicity?

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   Folinic acid (calcium folinate).

   Why? Folinic acid bypasses the dihydrofolate reductase block, so cells can make DNA again.

10. Which enzyme activity must be measured before starting azathioprine?

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    Thiopurine methyltransferase (TPMT).

    Why? Patients with absent TPMT activity should not receive thiopurines; reduced activity needs a lower dose because of the risk of severe myelosuppression.

11. Which blood test is particularly monitored in the first 6 months of sodium valproate treatment?

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    Liver function tests (with FBC).

    Why? Valproate can cause severe hepatotoxicity, usually in the first 6 months; thrombocytopenia is the main FBC concern.

12. Name four baseline tests before starting lithium.

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    Any four: U&Es/eGFR, thyroid function, calcium, weight/BMI, FBC; ECG if cardiovascular risk.

    Why? Lithium can cause renal impairment, hypothyroidism, hyperparathyroidism (hypercalcaemia) and weight gain.

13. How often is the serum lithium level checked after starting or changing the dose?

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    Weekly until stable, then every 3 months for the first year (then usually every 6 months).

    Why? Levels can change with dose, fluid status and interacting drugs; lithium has a narrow therapeutic range.

14. How long after the last dose should a serum lithium sample be taken?

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    12 hours post-dose.

    Why? A standardised 12-hour level is what the target ranges are based on; a sample taken sooner after a dose reads falsely high.

15. How long after a dose should a digoxin level be taken?

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    At least 6 hours post-dose.

    Why? Digoxin takes about 6 hours to distribute into tissues; an earlier sample overestimates the level at its site of action.