Calcium channel blocker toxicity | |
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Other names | Calcium channel blocker poisoning, calcium channel blocker overdose |
A 20% lipid emulsion commonly used for calcium channel blocker toxicity | |
Specialty | Emergency medicine |
Symptoms | Slow heart rate, low blood pressure, nausea, vomiting, sleepiness[1][2] |
Complications | Cardiac arrest[2] |
Usual onset | Within 6 hours[2] |
Causes | Too much calcium channel blockers either by accident or on purpose[3] |
Differential diagnosis | Beta blocker toxicity[1] |
Treatment | Activated charcoal, whole bowel irrigation, intravenous fluids, calcium gluconate, glucagon, high dose insulin, vasopressors, lipid emulsion[1][2] |
Prognosis | High risk of death[2] |
Frequency | > 10,000 (US)[2] |
Calcium channel blocker toxicity is the taking of too much of the medications known as calcium channel blockers (CCBs), either by accident or on purpose.[3] This often causes a slow heart rate and low blood pressure.[1] This can progress to the heart stopping altogether.[2] Some CCBs can also cause a fast heart rate as a result of the low blood pressure.[4] Other symptoms may include nausea, vomiting, sleepiness, and shortness of breath.[2] Symptoms usually occur in the first six hours but with some forms of the medication may not start until 24 after hours.[2]
There are a number of treatments that may be useful.[1] These include efforts to reduce absorption of the drug including: activated charcoal taken by mouth if given shortly after the ingestion or whole bowel irrigation if an extended release formula was taken.[1] Efforts to bring about vomiting are not recommended.[1] Medications to treat the toxic effects include: intravenous fluids, calcium gluconate, glucagon, high dose insulin, vasopressors and lipid emulsion.[1][2] Extracorporeal membrane oxygenation may also be an option.[1]
More than ten thousand cases of calcium channel blocker toxicity were reported in the United States in 2010.[2] Along with beta blockers and digoxin, calcium channel blockers have one of the highest rates of death in overdose.[2] These medications first became available in the 1970s and 1980s.[2] They are one of the few types of medication in which one pill can result in the death of a child.[2]
Most people who have taken too much of a calcium channel blocker, especially diltiazem, get slow heart rate and low blood pressure (vasodilatory shock).[1] This can progress to the heart stopping altogether.[2] CCBs of the dihydropyridine group, as well as flunarizine, predominantly cause reflex tachycardia as a reaction to the low blood pressure.[4][5][6]
Other potential symptoms include: nausea and vomiting, a decreased level of consciousness, and breathing difficulties.[2] Symptoms usually begin within 6 hours of taking the medication by mouth.[2] With extended release formulations symptoms may not occur for up to a day.[2] Seizures are rare in adults but in children occur more often.[2] Hypocalcaemia may also occur.[7]
Calcium channel blockers, also known as calcium channel antagonists, are widely used for a number of health conditions.[8] Thus they are commonly present in many people's homes. In young children one pill may cause serious health problems and potentially death.[8] The calcium channel blocker that caused the greatest number of deaths in 2010 in the United States was verapamil.[2] This agent is believed to cause more heart problems than many of the others.[2]
A blood or urine test to diagnose overdose is not generally available.[2] CCB overdose may cause high blood sugar levels, and this is often a sign of how severe the problem will become.[1]
CCB toxicity can cause a number of electrocardiogram abnormalities with a low sinus rhythm being the most common.[1] Others include: QT prolongation, bundle branch block, first-degree atrioventricular block, and even sinus tachycardia.[1]
It may not be possible to tell the difference between beta blocker toxicity and calcium channel blocker overdose based on signs and symptoms.[1]
The medical management of CCB toxicity may be difficult.[1] It may not improve with the usual treatments used for a low blood pressure and a slow heart rate.[9] Those who have no symptoms or signs six hours following taking an immediate release formulation and 24 hours after taking an extended release formulation generally need no further medical treatment.[2]
Activated charcoal is recommended if it can be given within an hour or two of taking the calcium channel blockers.[1] In those who have taken an extended release formulation of a CCB but are otherwise doing fine, whole bowel irrigation with polyethylene glycol may be useful.[1] Causing vomiting by the use of medications such as ipecac is not recommended.[1]
High doses of intravenous insulin with glucose may be useful and are a first line treatment in overdoses.[1][10] As this treatment may cause a drop in blood sugar and blood potassium levels, these should be monitored closely.[11]
Intravenous calcium gluconate or calcium chloride is considered a specific antidote.[12] Slow heart rate can be treated with atropine and sympathomimetics. Low blood pressure is treated with vasopressors such as adrenaline.[6][13]
There is tentative clinical evidence and good theoretical evidence of the benefit of lipid emulsion in severe overdoses of CCBs.[14] Methylene blue may also be used for those with low blood pressure that does not respond to other treatments.[10]
More than 10,000 cases of potential calcium channel blocker toxicity occurred in the United States in 2010.[2] When death occurs in medicine overdose, heart medications are the cause more than 10% of time.[2] The three most common types of heart medications that result in this outcome are calcium channel blockers along with beta blockers and digoxin.[2]