What should I do if I accidentally take an extra dose of amlodipine?

Reports of intentional and accidental amlodipine overdose have resulted in adverse side effects and death.^1-3 According to Micromedex, while a specific dose for amlodipine toxicity has not been established, patients who ingest greater than 10 mg may develop toxicity and should seek medical attention.¹ The lowest reported oral dose that led to toxicity and death in an adult was 30 mg and 100 mg, respectively.¹

There are several reports that illustrate the different effects of an amlodipine overdose. For instance, a patient who ingested 250 mg of amlodipine was asymptomatic and did not require hospitalization.⁴ In a another instance, a patient who ingested 120 mg remained normotensive, underwent gastric lavage, and required hospitalization.⁴ Another patient ingested 105 mg, experienced hypotension (90/50 mm Hg), and was hospitalized.⁴ These reports suggest that the effects of amlodipine overdose vary among individuals.   

The early effects of an amlodipine overdose are reflex tachycardia and hypotension, though hypotension may not develop until several hours after exposure and may come on precipitously.¹ Additional side effects include drowsiness, nausea, vomiting, peripheral vasodilation, shock, metabolic acidosis, acute renal failure, respiratory failure and/or hypoxemia.^1,4,5 If toxicity is severe, the consequent hypotension may be more profound and refractory to inotropic therapies.¹ Moreover, among the calcium channel blockers, amlodipine overdose is of serious concern because of the drug’s long half-life, which may lead to periods of tissue hypoperfusion.³

If admitted to the hospital for massive overdose, a patient may require cardiac, respiratory, and blood pressure monitoring.⁴ Intravenous calcium gluconate can be utilized to help reverse the effects of calcium entry blockade.⁴

^References 

1. Amlodipine Besylate. Truven Health Analytics. https://www.micromedexsolutions.com/. Accessed 6/13/17.
2. Sen S. Chronic self-medication with amlodipine for headache in a young adult with depression. International Journal of Green Pharmacy. 2016;10(3).
3. Reuter-Rice KE, Peterson BM. Conventional and Unconventional Lifesaving Therapies in an Adolescent With Amlodipine Ingestion. Critical care nurse. 2016;36(4):64-69.
4. Amlodipine Besylate Tablets. Drugs@FDA. https://www.accessdata.fda.gov. Accessed 6/13/17.
5. Shivakumar B, Hareesh R, Agte A. Amlodipine intoxication: a different presentation of overdose of a commonly prescribed anti-hypertensive. Journal of Evolution of Medical and Dental Sciences. 2013;2(50):9801-9806.