Forty Tablets of Amlodipine, a Heart Rate of 44, and a Glucose of 340
A 58-year-old woman is brought in by her husband two hours after she swallowed approximately 40 tablets of amlodipine 10 mg along with a bottle of wine following an argument. She is drowsy but answers questions. Heart rate 44 and regular, blood pressure 72/40 mmHg, respiratory rate 22, SpO2 96% on room air. Two large-bore IVs are in place and 2 L of crystalloid have produced no change in blood pressure. Point-of-care glucose is 340 mg/dL. Venous blood gas shows pH 7.28 and lactate 6.8 mmol/L. She vomited once en route. The pill bottle is in the room.
1. Explain the hyperglycemia and the lactate. What do these two numbers tell you about how sick she is, and what they do not tell you?
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Both findings are direct consequences of L-type calcium channel blockade, and both are severity markers.
Hyperglycemia: L-type calcium channels on pancreatic beta cells are required for calcium influx and insulin granule exocytosis. Blocking them impairs glucose-stimulated insulin release. Add a catecholamine surge and developing insulin resistance, and the result is a glucose in the 300s in a non-diabetic patient who has eaten nothing. This is not stress hyperglycemia in the ordinary sense; it is a pharmacologic marker of channel blockade and correlates with overdose severity.
Lactate: two mechanisms. First, profound vasodilation and myocardial depression produce global hypoperfusion with anaerobic metabolism. Second, insulin deficiency itself impairs pyruvate dehydrogenase activity and peripheral glucose uptake, so lactate accumulates even before shock is fully established. A lactate of 6.8 with a normal-to-low blood pressure means she is already in a compensated-to-decompensated shock state.
What this does not tell you: it does not distinguish calcium channel blocker toxicity from sepsis, metformin toxicity, or another cause on its own. The bottle plus the bradycardia plus the glucose together make the diagnosis; the numbers alone do not. Nor does a single normal lactate later mean she is safe - amlodipine is a long-acting dihydropyridine, and absorption and effect can evolve over many hours.
Treat these as evidence that high-dose insulin therapy should start now rather than after the next round of labs.
2. Give your treatment sequence with doses, including what you would start before the central line is in. What are you targeting?
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Start the antidotes in parallel; do not work sequentially through a checklist.
1. Calcium, repeated. Calcium gluconate 10% 30–60 mL (3–6 g) IV peripherally now, repeated every 10–20 minutes as needed. Calcium chloride 10% 10–20 mL delivers more elemental calcium but must go through a central line - peripheral extravasation causes severe tissue injury. Give gluconate while the line is being placed.
2. Vasopressor early. Norepinephrine infusion started peripherally while central access is obtained, titrated to a mean arterial pressure of at least 65. In refractory vasodilatory shock, add epinephrine for inotropy.
3. High-dose insulin euglycemia - the definitive therapy, and it should not wait. Bolus 1 unit/kg of regular insulin, then infuse 0.5–1 unit/kg/hour, titrating up if shock persists. This is not a treatment for the glucose; it is inotropic and vasodilatory support through improved myocardial carbohydrate metabolism. Give dextrose concurrently - 25 g boluses or a 0.5 g/kg bolus followed by an infusion - and target euglycemia, not hyperglycemia. Check glucose and potassium every 15–30 minutes initially. Expect hypokalemia as insulin drives potassium intracellularly; replace as needed.
4. Glucagon 3–5 mg IV is reasonable but has limited efficacy in calcium channel blocker overdose compared with beta-blocker overdose; do not let it delay insulin.
Targets: mean arterial pressure of 65 or better, improving mental status and lactate, and a heart rate that is no longer falling. Titrate to perfusion, not to the blood pressure number alone.
3. She remains hypotensive at 90 minutes despite calcium, norepinephrine, and high-dose insulin. What are the next options, what would you avoid, and how long do you keep her?
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Escalate along two tracks: electrical and mechanical support.
- Transvenous pacing if she has high-grade atrioventricular block or a persistently inadequate rate. Capture may be poor because the myocardium is pharmacologically inexcitable, so pace while continuing pharmacologic therapy; do not use pacing as a substitute for insulin and pressors.
- Extracorporeal membrane oxygenation is the rescue for refractory calcium channel blocker shock. Call early rather than after multi-organ failure has set in - the referral conversation takes hours, and a patient who is being escalated should be discussed while she still has a salvageable window.
- Push the high-dose insulin higher (some protocols go to 10 units/kg/hour) with meticulous glucose and potassium monitoring before concluding she is refractory.
What to avoid or reconsider:
- Activated charcoal only if she is intubated or has a protected airway and presents within roughly one to two hours - she is drowsy and aspiration is the dominant risk. Decide airway first.
- Do not give repeated large fluid boluses; she has already received 2 L and further volume will worsen pulmonary edema without fixing the vasodilation.
- No role for flumazenil or naloxone. Do not use glucagon as monotherapy. Avoid peripheral calcium chloride.
Duration: extended-release amlodipine produces prolonged toxicity. Admit to intensive care for at least 24 hours, with continued monitoring after pressors are weaned, because deterioration after apparent improvement is well described. Consider whole-bowel irrigation for the sustained-release tablets if the airway is secure and presentation is early.