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Medication Safety

Adverse Effect Detective

A presentation, a medication list, and a timeline you can read like evidence, because it is. Name the culprit, then walk the reasoning: temporality, known reactions, alternatives, and the monitoring that would have caught it sooner.

The confused gardener

78-year-old brought in by her daughter: three days of confusion, unsteadiness, and a fall in the garden.

No fever, no focal neurology, no head injury.

Medications

  • Hydrochlorothiazide 25 mg dailyStarted 3 weeks ago for BP
  • Sertraline 50 mg dailyStable for 2 years
  • Ramipril 5 mg dailyStable for 5 years
  • Atorvastatin 20 mg dailyStable for 5 years
Sodium
118 mmol/L
Potassium
3.4 mmol/L
eGFR
61
Glucose
6.1 mmol/L

Timeline

  1. Day -21

    Hydrochlorothiazide started

  2. Day -10

    Feeling 'a bit off', attributed to heat

  3. Day -3

    Confusion and unsteadiness begin

  4. Day 0

    Fall; presentation

Which medication is the likely culprit?

The Achilles' antibiotic

66-year-old, day 6 of ciprofloxacin for pyelonephritis, now with right heel pain climbing stairs.

On long-term prednisone 7.5 mg for polymyalgia rheumatica.

Medications

  • Ciprofloxacin 500 mg BIDDay 6 of 10
  • Prednisone 7.5 mg daily18 months
  • Amlodipine 5 mg daily3 years
  • Calcium/vitamin D18 months

Timeline

  1. Day -6

    Ciprofloxacin started

  2. Day -1

    Heel 'tightness' after walking

  3. Day 0

    Pain on stairs, tender Achilles

Most likely explanation?

The INR that never moved

71-year-old on warfarin (INR stable, 2.4 last week) with black tarry stools and lightheadedness.

Started 'something for his back' ten days ago.

Medications

  • Warfarin (INR-guided)4 years, mechanical valve
  • Naproxen 500 mg BID (OTC)Day 10, self-started
  • Bisoprolol 5 mg daily4 years
  • Pantoprazole: STOPPEDPatient stopped it himself 2 months ago: 'felt fine'
Hb
84 g/L (baseline 136)
INR
2.5
Urea
raised out of proportion to creatinine

Timeline

  1. Day -60

    Stopped his own pantoprazole

  2. Day -10

    Naproxen started for back pain

  3. Day -2

    Stools darken

  4. Day 0

    Melena and presyncope; INR today 2.5

What happened?

Restless after the prescription

34-year-old on venlafaxine, given tramadol after a wisdom-tooth extraction.

36 hours later: restlessness, tremor, sweating, diarrhea; HR 112, T 37.9, brisk reflexes with inducible ankle clonus.

Medications

  • Venlafaxine XR 150 mg daily1 year
  • Tramadol 50 mg q6h PRNStarted 2 days ago, using around the clock
  • Ibuprofen 400 mg PRNSame prescription

Timeline

  1. Day -2

    Tramadol started post-extraction

  2. Day -1

    Restless night, 'wired'

  3. Day 0

    Tremor, sweating, clonus

The diagnosis to act on?

The breathless gardener

A 63-year-old man with rheumatoid arthritis presents with six weeks of a dry cough and progressive breathlessness.

No fever, no purulent sputum, no chest pain. He can no longer manage his allotment.

Chest examination reveals fine bilateral inspiratory crackles.

He has been treated for a chest infection twice without improvement.

Medications

  • Methotrexate 20 mg weeklyStarted 14 months ago; disease well controlled
  • Folic acid 5 mg weeklyStandard co-prescription
  • Prednisone 5 mg dailyLong-standing low dose
  • Ramipril 5 mg dailyHypertension, five years, unchanged
  • Amoxicillin, then doxycyclineTwo recent courses, no response
CRP
18 mg/L
White cell count
7.2 x10^9/L
Eosinophils
0.4 x10^9/L
KCO
Reduced
HRCT
Bilateral ground-glass and reticulation

Timeline

  1. Day 0

    Methotrexate started for rheumatoid arthritis; joints improve over the following months.

  2. Day 380

    Insidious dry cough begins. No systemic upset.

  3. Day 400

    Treated as a chest infection with amoxicillin. No change.

  4. Day 415

    Second course, doxycycline. Still no change; breathlessness now on flat ground.

  5. Day 425

    Presents to clinic. Bilateral fine crackles; oxygen saturation 92 percent on air.

Which explanation best fits this picture?

Acidotic with a normal glucose

A 52-year-old woman is admitted 36 hours after an elective hernia repair with nausea, vomiting and abdominal pain.

She has been fasted before surgery and has eaten little since.

She looks unwell and is breathing deeply.

Capillary glucose is 9.8 mmol/L, and the surgical team have been reassured by it.

Medications

  • Dapagliflozin 10 mg dailyType 2 diabetes and CKD; not held before surgery
  • Metformin 1000 mg BIDHeld on admission
  • Ramipril 5 mg dailyContinued
  • Acetaminophen and oxycodonePost-operative analgesia
pH
7.19
Bicarbonate
12 mmol/L
Anion gap
24
Glucose
9.8 mmol/L
Beta-hydroxybutyrate
5.2 mmol/L
Creatinine
118 umol/L

Timeline

  1. Day 0

    Fasted from midnight for elective surgery. Dapagliflozin taken as usual that morning.

  2. Day 1

    Uneventful hernia repair. Eating very little; nauseated.

  3. Day 2

    Vomiting, abdominal pain, deep sighing respiration. Glucose 9.8, so hyperglycemic emergency considered unlikely.

  4. Day 2

    Venous gas: pH 7.19, bicarbonate 12, anion gap 24. Ketones strongly positive.

What is the most likely diagnosis?

Agitated, sweating, and jerking at the ankles

A 46-year-old man is brought in agitated, tremulous and drenched in sweat.

Onset over about eight hours. He is anxious and confused, with dilated pupils.

Examination shows hyperreflexia and inducible clonus, most marked at the ankles.

Temperature 38.6 C, heart rate 122, blood pressure 156/94.

Medications

  • Sertraline 100 mg dailyDepression, taken for two years, unchanged
  • Tramadol 50 mg QIDStarted three days ago by a walk-in clinic for back pain
  • Ondansetron 4 mgTaken twice yesterday for nausea
  • Atorvastatin 20 mg nightlyUnchanged
Temperature
38.6 C
Creatine kinase
640 U/L
White cell count
11.2 x10^9/L
Creatinine
96 umol/L
Lactate
2.1 mmol/L

Timeline

  1. Day 0

    Sertraline in steady use for two years without problems.

  2. Day 730

    Attends a walk-in clinic with back pain. Tramadol started; the antidepressant is not mentioned.

  3. Day 732

    Nausea; takes ondansetron left over from a previous prescription.

  4. Day 733

    Agitation, sweating, tremor and confusion develop over hours. Brought to the emergency department.

Which diagnosis best explains this presentation?

A potassium that will not stay up

A 71-year-old woman is admitted with palpitations and cramps.

She has had three episodes of hypokalemia in six months, each corrected and each recurring.

ECG shows frequent ventricular ectopics and a prolonged QT interval.

She has no diarrhoea, no vomiting, and is on no diuretic.

Medications

  • Omeprazole 40 mg dailyReflux; taken continuously for nine years without review
  • Amlodipine 5 mg dailyHypertension
  • Potassium chloride supplementsPrescribed after each hypokalemic episode
  • Alendronate weeklyOsteoporosis
Potassium
2.9 mmol/L
Magnesium
0.42 mmol/L
Calcium
2.05 mmol/L
Creatinine
84 umol/L
QTc
498 ms

Timeline

  1. Day 0

    Omeprazole started for reflux nine years ago; never formally reviewed.

  2. Day 3000

    First episode of hypokalemia. Corrected with oral potassium; no cause identified.

  3. Day 3090

    Second episode. Potassium supplements continued.

  4. Day 3180

    Third episode, now with cramps, palpitations and a prolonged QT.

  5. Day 3181

    Magnesium finally checked: 0.42 mmol/L.

Why does her potassium keep falling despite supplementation?