A 'triple whammy' prescription in a patient with worsening renal function

1. Acute kidney injury from the 'triple whammy'. Diclofenac inhibits prostaglandin-mediated afferent arteriolar dilatation, ramipril removes efferent arteriolar tone, and the combination - especially with a diuretic (spironolactone) and possible volume depletion from nausea - collapses glomerular filtration pressure. Creatinine has risen from 1.4 to 2.4 mg/dL in a few months and eGFR has fallen from 52 to 34; this is not a slow diabetic decline, it is an acute-on-chronic hit.

2. Hyperkalaemia (K 5.9 mmol/L). Three potassium-retaining drugs are stacked: ramipril reduces aldosterone, spironolactone blocks the mineralocorticoid receptor directly, and trimethoprim in cotrimoxazole blocks the epithelial sodium channel in the distal nephron in exactly the same way as amiloride, an effect clinicians routinely forget. Add the AKI itself and 5.9 mmol/L is entirely predictable, and dangerous.

3. Metformin at eGFR 34. Metformin is contraindicated below eGFR 30 and should be dose-reduced between 30 and 45; with an acute kidney injury on top, continuing 2 g daily risks lactic acidosis. It must be stopped now.

4. Undiagnosed anaemia with NSAID exposure. Haemoglobin 10.8 g/dL in a man on long-term diclofenac raises the possibility of occult gastrointestinal blood loss, which the NSAID also masks symptomatically.

5. Symptom masking. His relief is exactly why the prescription is dangerous: analgesia has hidden the progression of joint disease and encouraged continued use.

Today, in order of urgency:

1. Stop diclofenac - this is the single highest-yield action for the kidneys and the gut.
2. Stop cotrimoxazole and send urine for culture; if treatment is still needed, choose according to sensitivity and renal function (for example fosfomycin or a cephalosporin at an adjusted dose). Trimethoprim-containing regimens should be avoided in this patient.
3. Stop spironolactone while potassium is 5.9 mmol/L.
4. Stop metformin for now and apply sick-day rules.
5. Review ramipril - in true volume depletion with AKI it is reasonable to hold it until creatinine and potassium settle, then restart at a lower dose if there is no renal artery disease. Do not simply abandon it permanently; the diabetes needs renoprotection once stable.
6. Assess for hyperkalaemia: ECG, and treat if there are changes or if potassium is confirmed high - a potassium binder plus review of intake, with insulin–dextrose and salbutamol reserved for ECG changes or a rapidly rising potassium.
7. Check for volume depletion and replace fluid cautiously; in an elderly diabetic, assess for urinary obstruction too.

Monitoring. Creatinine, urea, electrolytes and potassium daily while in the acute phase, then at 48–72 hours after any change, and again a week later; urine output and weight; full blood count and stool occult blood for the anaemia; glucose, since stopping metformin will worsen control.

Communication. Speak to the prescriber the same day, naming the four interacting drugs and the numbers (K 5.9, creatinine 2.4, eGFR 34) rather than simply listing them; document the advice, the time and the response, including the prescriber's decision if it differs from your recommendation.

Analgesia for osteoarthritis. Paracetamol 1 g up to three times daily (maximum 3 g/day in this patient, given age and comorbidity) is the systemic first choice. Add topical diclofenac gel to the knees - systemic absorption is low, so it is a reasonable compromise - plus physiotherapy, quadriceps strengthening, weight reduction and a walking aid. Explain plainly that no oral NSAID is safe for him now, and that this is not a temporary caution: with an eGFR of 34 and diabetes, an oral NSAID carries a high risk of another kidney injury and of gastrointestinal bleeding.

What to watch for. Passing much less urine, ankle or facial swelling, nausea, vomiting, diarrhoea or any illness that causes dehydration - in any of these, stop metformin and contact the clinic. Black or tarry stools, vomiting blood or unusual breathlessness need urgent review. Fever or loin pain suggesting another urinary infection should be assessed rather than self-treated.

Restart thresholds and rules.

• Metformin: restart at a reduced dose only when eGFR is stable above 30 mL/min/1.73 m² (and reduced between 30 and 45); do not restart during any acute illness.
• Spironolactone: restart only if potassium is consistently below about 5.0 mmol/L and renal function has recovered, and preferably not alongside trimethoprim or another potassium-retaining drug.
• Ramipril: restart once creatinine and potassium are stable, with a check at 1–2 weeks.

Record all of this in a written medicines list for the patient and in a discharge note that the next prescriber will actually read.