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Play today's Pharmacy caseFive progressive clues
These are the case findings in their original reveal order, moving from the broader presentation to the most discriminating evidence.
Clue 1
A 78-year-old is brought to the department mid-morning by her son, who cannot put his finger on what is wrong beyond saying she has not been herself since she woke. She has been unwell for the best part of a week with a urinary infection, and for three days she has eaten almost nothing — a bowl of soup she left, a slice of toast she did not touch.
Clue 2
She is not well. Her skin is cold and clammy, there is a fine tremor in her outstretched hands, and although she rouses when spoken to she drifts off again within a sentence. She does not know what day it is or which building she is in, and she cannot give any account of yesterday.
Clue 3
The answer to the immediate question takes eleven seconds and a drop of blood. Her glucose is 2.1 mmol/L (38 mg/dL). She is treated on the spot, and within minutes she is sitting up, fully oriented, asking after her son and apologising for the fuss, with no residual deficit whatsoever. The immediate problem is solved. The reason it happened is not.
Clue 4
The medicines are where the story is. She has taken glibenclamide — glyburide, in some countries — for type 2 diabetes for six years, at a dose nobody has changed. Five days ago her general practitioner started trimethoprim-sulfamethoxazole for the urinary infection. That is the only addition. Nothing else was started, stopped or adjusted; she takes no insulin, no opioids, nothing over the counter and nothing herbal. She has never drunk alcohol.
Diagnosis
Drug-Induced Hypoglycemia
Why the diagnosis fits
The immediate answer costs eleven seconds and a drop of blood — glucose 2.1 mmol/L (38 mg/dL) — and it is confirmed by the response, because she wakes fully within minutes of dextrose with no residual deficit. But hypoglycaemia is a finding, not a diagnosis, and everything that matters lies in why a woman who has taken the same tablet for six years became hypoglycaemic this week. Three things stacked up. First, the drug itself. This class binds and inhibits the ATP-sensitive potassium channels on pancreatic beta cells, depolarising the membrane, letting calcium in and releasing insulin regardless of what the blood glucose is doing — so when she stopped eating, the insulin kept coming anyway, and a missed meal is exactly the setting in which a severe episode occurs. Of the second-generation agents, hers carries the greatest hypoglycaemic risk; glipizide, glimepiride and gliclazide all sit lower. Explicit prescribing guidance advises avoiding this particular one in older adults precisely because they suffer prolonged episodes, so the prescription was already the wrong choice before anything else happened. Second, her kidneys. Risk escalates significantly once the estimated filtration rate drops below 60, and hers has fallen to 41 from 68 a year ago without anyone revisiting the dose. Third, the new antibiotic. Sulfonamides competitively displace this drug from its plasma protein binding, leaving more free drug in circulation, and one was started five days ago — the only addition to a list in which nothing else was started, stopped or adjusted. There is no competing explanation: no insulin, no opioids, nothing over the counter, and she has never drunk alcohol. The most practically important part is the last clue. Four hours after a textbook correction she is drowsy again at 2.6 mmol/L (47 mg/dL), and that recurrence is predictable rather than surprising. The low glucose can take up to 12 hours to appear in the first place, and whether it returns depends on how long the responsible agent lasts. Worse, dextrose is a double-edged treatment here: it corrects the glucose while simultaneously provoking further insulin release from beta cells the drug is still stimulating. That is what octreotide is for — it inhibits calcium influx and so blocks the insulin secretion that dextrose would otherwise trigger. The lesson is that this patient cannot be corrected and discharged; she needs admission, repeated monitoring, and a prescription that is changed rather than merely restarted.
Educational reference
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