A 74-Year-Old with Knee Pain, a Raised Creatinine and Four Prescriptions
Mrs R, 74, has had hypertension for 18 years and type 2 diabetes for 15. Her regular prescriptions are enalapril 10 mg twice daily, metformin 500 mg twice daily, furosemide 40 mg each morning and aspirin 75 mg once daily. Ten days ago a private practitioner added ibuprofen 400 mg three times daily after food for right knee pain, and tramadol 50 mg at night. Today she attends the PHC complaining of dizziness and reduced urine. BP 150/90 mmHg, pulse 88/min, mild ankle oedema. She has eaten little for four days. Investigations: serum creatinine 2.1 mg/dL (baseline 1.2 three months ago), potassium 5.4 mmol/L, random glucose 180 mg/dL. The PHC pharmacy has no tramadol and no injectable iron. She asks for a 'strong painkiller' to take home because her son's wedding is in three days.
1. Identify the three most urgent medication-related problems in this patient and explain the mechanism of each. Rank them in order of immediate danger.
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1. Acute kidney injury from the 'triple whammy' - most urgent. Ibuprofen inhibits prostaglandin-mediated afferent arteriolar dilation, enalapril blocks efferent constriction, and furosemide reduces intravascular volume. Together they can collapse glomerular filtration. Her creatinine has risen from 1.2 to 2.1 mg/dL, urine output is reduced, and she is dehydrated from four days of poor intake.
2. Hyperkalaemia (K+ 5.4 mmol/L). Renal impairment, an ACE inhibitor and an NSAID all raise potassium. This is immediately dangerous because it can cause arrhythmia, even before symptoms appear.
3. Metformin at an eGFR of about 26 mL/min/1.73 m². Metformin is contraindicated below 30 because reduced clearance increases the risk of lactic acidosis, especially with AKI and dehydration.
Also important but lower immediate priority: tramadol in an elderly patient with renal impairment (confusion, seizures, respiratory depression), and the combination of aspirin plus ibuprofen (gastrointestinal bleeding). The knee pain is not the emergency; the kidney and potassium are.
2. State exactly which medicines you would stop, which you would continue, what you would give for pain, and what monitoring and referral you arrange before she leaves.
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Stop now: ibuprofen, the likely cause of the AKI, and metformin, which is contraindicated at this eGFR.
Hold and discuss with the medical officer: enalapril and furosemide. In acute kidney injury with hyperkalaemia, continuing both is unsafe. Enalapril worsens potassium retention; furosemide may worsen volume depletion. Do not simply stop all antihypertensives and send her home - the blood pressure still needs review once she is rehydrated.
Continue: aspirin 75 mg unless there is active bleeding or a clear contraindication, because it is likely secondary prevention. Note the GI risk of aspirin plus NSAID and consider gastroprotection if the medical officer agrees.
Pain: paracetamol 500-650 mg up to every 6 hours, maximum 3 g in 24 hours in an older adult, with attention to liver disease. Avoid tramadol and all NSAIDs. Do not give a 'strong painkiller' to take home.
Before she leaves: ECG for peaked T waves or arrhythmia; repeat potassium and creatinine as soon as possible; check volume status and encourage oral fluids only if she is not overloaded; arrange urgent referral to the district hospital for hyperkalaemia and AKI. Ring ahead and document the advice. The wedding is not a reason to delay.
3. The son's wedding is in three days and she wants a 'strong painkiller'. Write what you would tell her and what you would document.
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Explain in plain language: 'The painkiller you were given for your knee, together with your regular tablets, has reduced your kidney function and raised the potassium in your blood. High potassium can make the heart beat irregularly. We must stop the knee tablet and some of your regular tablets today, use paracetamol for pain, and get your blood checked at the district hospital. Please do not take any painkiller from the shop without asking us, and do not take extra tablets for the wedding.'
Also say: she should return immediately for palpitations, chest pain, severe weakness, passing very little urine, vomiting or confusion. Bring all medicine strips and prescriptions to every visit.
Document: a full medication reconciliation; the reason for stopping ibuprofen and metformin; the plan to hold enalapril and furosemide; the paracetamol dose; ECG findings; repeat potassium and creatinine; referral time and receiving facility; advice given and her understanding; the son's wedding as context but not a reason to defer care.