Management of calcium channel antagonist overdose

Use of antihypertensive drugs during pregnancy and lactation

The decision to treat elevated arterial pressure in pregnancy depends on the risk and benefits imposed on the mother and the fetus. Treatment for mild-to-moderate hypertension during pregnancy may not reduce maternal or fetal risk. Severe hypertension, on the other hand, should be treated to decrease maternal risk. Methyldopa and beta-adrenoceptor antagonists have been used most extensively. In acute severe hypertension, intravenous labetalol or oral nifedipine are reasonable choices.

The poisoned child in the pediatric intensive care unit

Acutely poisoned children remain a common problem facing pediatricians working in acute care medicine in the United States and worldwide. The management of such children continues to be challenging, and their care has evolved throughout the years. The concept of gastric decontamination in acute poisoning has significantly changed over the past 10 years, and many of the previously used techniques have been abandoned or fallen out of favor for lack of evidence to their benefit or unacceptable serious risks and side effects. Supportive care continues to be the cornerstone in managing most poisoned children. Only a few patients benefit from antidotes or specific interventions.

Third-degree AV block from extended-release diltiazem ingestion in a nine-month-old

Calcium channel blocker (CCB) overdose is associated with dysrhythmias and atrioventricular (AV) block, however, experience with infant CCB overdose is limited. A 9-month-old girl was found playing with tablets of extended-release diltiazem 120 mg. The patient had two episodes of emesis, which contained pill fragments, and was brought to the Emergency Department (ED) 4.5 h after being found. Vital signs were: rectal temperature 37.1 degrees C, pulse 87 beats/min, respiratory rate 30-40 breaths/min, blood pressure 72/48 mm Hg, and oxygen saturation (SpO(2)) 99% on room air. Otherwise, the patient was well-appearing, with normal skin color and examination. The electrocardiogram revealed third-degree atrioventricular block with a ventricular rate of 90 beats/min, QRS 68 ms, and QTc 411 ms. Atropine 0.1 mg i.v. was given, which increased the heart rate to 100-110 beats/min. Calcium gluconate 500 mg was also given intravenously. Laboratory evaluation revealed bicarbonate 17 mEq/L, anion gap 16, and glucose 129 mg/dL. On hospital day 1, the patient was noted to have a junctional rhythm with a rate of 90-100, and systolic blood pressure of 80-90 mm Hg. No additional medications were given. Early on day 2, the patient converted spontaneously to a normal sinus rhythm and was discharged approximately 42 h after presentation to the ED. In addition to bradycardia and hypotension, this 9-month-old patient manifested third-degree AV block after ingesting extended-release diltiazem.

High-Dose Insulin in the Treatment of Antihypertensive Overdose

Objective

To describe a case of calcium channel blocker overdose along with an angiotensin-converting enzyme inhibitor and angiotensin receptor blocker, which was successfully treated with high-dose insulin with dextrose and potassium supplementation (HDIDK).

Case Summary

A 52-year-old woman was transferred to an admitting hospital after ingesting 14 tablets of trandolapril/verapamil SR ( Tarka)4 mg/240 mg, 15 to 16 tablets of olmesartan ( Benicar) 20 mg, and an unknown amount of (escitalopram) Lexapro combined with unknown quantities of alcohol and benzodiazepines. This combination caused hypotension and electrocardiogram changes. The patient was treated for hypotension-induced shock with epinephrine, glucagon, HDIDK, magnesium, and fluids. An insulin infusion ran for 24 hours. The patient was discharged to a psychiatric facility 3 days after admission.

Discussion

The non-dihydropyridine, verapamil, causes dilation of the coronary and peripheral vasculature by inhibiting the influx of calcium ions through L-type calcium channels. HDIDK is thought to be a useful treatment in the state of hypoinsulinemia, which prevents the uptake of glucose by myocytes and can lead to decreased inotropy and eventually shock. High-dose insulin allows glucose to be properly used for energy by the myocytes.

Conclusions

Currently HDIDK therapy is recommended as an adjunct to conventional therapy in calcium channel blocker poisoning only after fluids, high-dose calcium salts, and vasopressors. In this case, early implementation of HDIDK treatment was shown to shorten the length of therapy.

Single-dose, randomized, crossover bioequivalence study of amlodipine maleate versus amlodipine besylate in healthy volunteers

Amlodipine, marketed primarily as a besylate salt, is a calcium channel blocker used for treating essential hypertension. Amlodipine maleate is another salt that is considered, in terms of pharmacokinetics and pharmacodynamics, similar to amlodipine besylate. This open, randomized, two-period crossover trial has investigated in 24 healthy volunteers over a 144 h period the bioequivalence of amlodipine maleate tablets 10 mg versus amlodipine besylate tablets (Norvasc 10 mg). Plasma amlodipine concentrations were assessed by ultra performance liquid chromatography interfaced with a double quadrupole mass spectrometer. The area under the curve total (AUC(t)) and the area under the curve to infinity (AUC(inf)) values, peak plasma concentration (C(max)), and time to attain peak (t(max)) were not statistically different between the two drugs. AUC(t) and AUC(inf) values were higher (p < 0.05) in females than in males. The tolerability profile was comparable for the two salts of amlodipine. These findings indicate that amlodipine maleate and besylate are bioequivalent and were well tolerated, which suggests that the plasma kinetics of amlodipine depend on the properties of the molecule itself. Hence, the two salts investigated could be used interchangeably in clinical practice.

Assessment of hyperglycemia after calcium channel blocker overdoses involving diltiazem or verapamil

BACKGROUND

Overdoses of calcium channel blocker agents result in hyperglycemia, primarily due to the blockade of pancreatic L-type calcium channels and insulin resistance on the cellular level. The clinical significance of the hyperglycemia in this setting has not previously been described.

METHODS

This study is a retrospective review of all adult (age, >or=15 yrs) patients with a discharge diagnosis of acute verapamil or diltiazem overdose at five university-affiliated teaching hospitals. The severity of overdose was assessed by determining whether a patient met the composite end points of in-hospital mortality, the necessity for a temporary pacemaker, or the need for vasopressors. We compared the initial and peak serum glucose concentrations with hemodynamic variables between patients who did and did not meet the composite end points.

RESULTS

A total of 40 patients met inclusion criteria, with verapamil and diltiazem accounting for 27 of 40 (67.5%) and 13 of 40 (32.5%) of the ingestions, respectively. For those patients who did and did not meet the composite end points, the median initial serum glucose concentrations were 188 (interquartile range, 143.5-270.5) mg/dL and 129 (98.5-156.5) mg/dL, respectively (p = .0058). The median peak serum glucose concentrations for these two groups were 364 (267.5-408.5) mg/dL and 145 (107.5-160.5) mg/dL, respectively (p = .0001). The median increase in blood glucose was 71.2% for those who met composite end points vs. 0% for those who did not meet composite end points (p = .0067). Neither the change in the median heart rate nor the change in systolic blood pressure was significantly different in any group.

CONCLUSION

Serum glucose concentrations correlate directly with the severity of the calcium channel blocker intoxication. The percentage increase of the peak glucose concentration is a better predictor of severity of illness than hemodynamic derangements. If validated prospectively, serum glucose concentration alone might be an indicator to begin hyperinsulinemia-euglycemia therapy.

Hyperinsulinemic Euglycemia Therapy for Verapamil Poisoning: A Review

Treatment of patients with verapamil overdose remains challenging. Traditional decontamination and supportive measures with intravenous calcium and vasopressors are the mainstays in initial care. Recently, the successful use of rescue hyperinsulinemic euglycemia therapy has been described in multiple cases. Treatment resulted in improved hemodynamic parameters and increased metabolic efficiency in patients with a low-output, myocardial shock state. Information on clinical use of hyperinsulinemic euglycemia therapy in humans is limited to case reports and small case series; no controlled clinical trials have been done. Hyperinsulinemic euglycemia therapy should be considered for patients with calcium channel blocker overdose who do not respond to initial supportive therapy.

Relative safety of hyperinsulinaemia/euglycaemia therapy in the management of calcium channel blocker overdose: a prospective observational study

OBJECTIVE

To examine the clinical safety of hyperinsulinaemia/euglycaemia therapy (HIET) in calcium channel blocker (CCB) poisoning.

DESIGN

A prospective observational study examining biochemical and clinical outcomes of a HIET protocol administered under local poisons centre guidance.

SETTING

Critical care settings.

PATIENTS

Seven patients with significant CCB toxicity [systolic blood pressure (BP) <90 mmHg] treated with HIET.

INTERVENTIONS

HIET was commenced after correction of any pre-existing hypoglycaemia ([blood glucose]<65 mg/dl) or hypokalaemia ([K+]<3.5mmol/l). A quantity of 50 ml of 50% intravenous dextrose was followed by a loading dose (1 unit/kg) of intravenous short-acting insulin and an insulin maintenance infusion (0.5-2.0 units/kg/h). Euglycaemia was maintained using 5-10% dextrose infusions. Potassium was maintained within low normal range (3.8-4.0 mmol/l).

MEASUREMENTS AND RESULTS

Six patients survived. All patients received fluids, calcium, and conventional inotropes. Three patients (who all ingested diltiazem) received an insulin-loading dose; all experienced a significant sustained rise in systolic BP (>10 mmHg) during the first hour of HIET. Systolic BP did not increase significantly in four patients who did not receive insulin loading. Single episodes of non-clinically significant biochemical hypoglycaemia and hypokalaemia were recorded in one and two patients respectively. Hypoglycaemia was not recorded in any patient administered HIET during the 24[Symbol: see text]h following CCB ingestion.

CONCLUSIONS

HIET used to treat CCB-induced cardiovascular toxicity is a safe intervention when administered in a critical care setting. Maximal HIET efficacy may be obtained when HIET is administered in conjunction with conventional therapy relatively early in the course of severe CCB poisoning when insulin resistance is high.

A case of amlodipine overdose

A case of severe amlodipine overdose with only mild symptoms is described. Plasma concentrations of amlodipine were measured in serial samples by gas chromatography. There was no concomitant overdose. The present case is compared with previous reported cases of amlodipine overdose where patients all developed severe symptoms. We conclude that amlodipine overdose does not always cause severe symptoms.

Treatment of poisoning caused by β-adrenergic and calcium-channel blockers

PURPOSE

The toxic effects and treatment of beta-adrenergic blocker and calcium-channel blocker (CCB) overdose are reviewed.

SUMMARY

Overdoses with cardiovascular drugs are associated with significant morbidity and mortality. Beta-blockers and CCBs represent the most important classes of cardiovascular drugs. In overdose, beta-blockers and CCBs have similar presentation and treatment overlaps and are often refractory to standard resuscitation measures. The common feature of beta-blocker toxicity is excessive blockade of the beta-receptors resulting in bradycardia and hypotension. Poisoning by CCBs is characterized by cardiovascular toxicity with hypotension and conduction disturbances, including sinus bradycardia and varying degrees of atrioventricular block. Therapies include beta-agonists, glucagon, and phosphodiesterase inhibitors. However, in beta-blocker poisoning where symptomatic bradycardia and hypotension are present, high-dose glucagon is considered the first-line antidote. Traditionally, antidotes for CCB overdose have included calcium, glucagon, adrenergic drugs, and amrinone. For cases of CCB poisoning where cardiotoxicity is evident, first-line therapy is a combination of calcium and epinephrine; high-dose insulin with supplemental dextrose and potassium therapy (HDIDK) is reserved for refractory cases. Health-system pharmacists should be aware that when these drugs are used as antidotes, higher than normal dosing is needed.

CONCLUSION

Poisoning by beta-blockers or CCBs usually produces hypotension and bradycardia, which may be refractory to standard resuscitation measures. For cases of beta-blocker poisoning where symptomatic bradycardia and hypotension are present, high-dose glucagon is considered the first-line antidote. For cases of CCB poisoning where cardiotoxicity is evident, a combination of calcium and epinephrine should be used initially, reserving HDIDK for refractory cases.

Bench-to-bedside review: hyperinsulinaemia/euglycaemia therapy in the management of overdose of calcium-channel blockers

Hyperinsulinaemia/euglycaemia therapy (HIET) consists of the infusion of high-dose regular insulin (usually 0.5 to 1 IU/kg per hour) combined with glucose to maintain euglycaemia. HIET has been proposed as an adjunctive approach in the management of overdose of calcium-channel blockers (CCBs). Indeed, experimental data and clinical experience, although limited, suggest that it could be superior to conventional pharmacological treatments including calcium salts, adrenaline (epinephrine) or glucagon. This paper reviews the patho-physiological principles underlying HIET. Insulin administration seems to allow the switch of the cell metabolism from fatty acids to carbohydrates that is required in stress conditions, especially in the myocardium and vascular smooth muscle, resulting in an improvement in cardiac contractility and restored peripheral resistances. Studies in experimental verapamil poisoning in dogs have shown that HIET significantly improves metabolism, haemodynamics and survival in comparison with conventional therapies. Clinical experience currently consists only of a few isolated cases or short series in which the administration of HIET substantially improved cardiovascular conditions in life-threatening CCB poisonings, allowing the progressive discontinuation of vasoactive agents. While we await further well-designed clinical trials, some rational recommendations are made about the use of HIET in severe CBB overdose. Although the mechanism of action is less well understood in this condition, some experimental data suggesting a potential benefit of HIET in β-adrenergic blocker toxicity are discussed; clinical data are currently lacking.

Unusual ECG findings mimicking complete heart block in an unrecognised calcium antagonist overdose

We present a case of severe cardiovascular instability which required intensive care management after a myocardial infarction had been diagnosed incorrectly. Unusual ECG findings were diagnostic of calcium antagonist toxicity as the cause of the cardiovascular collapse. A discussion of the potential pitfalls in the management of patients intoxicated with these agents is undertaken. Of particular interest is the prolonged period of supportive therapy required prior to the return of an unsupported circulation. The physiological variables encountered with this type of poisoning were confirmed by the use of a PiCCO device.

Cardiovascular challenges in toxicology

The diagnoses and subsequent treatment of poisoned patients manifesting cardiovascular compromise challenges the most experienced emergency physician. Numerous drugs and chemicals cause cardiac and vascular disorders. Despite widely varying indications for therapeutic use, many agents share a common cardiovascular pharmacologic effect if taken in overdose. Standard advanced cardiac life support protocol care of these patients may not apply and may even result in harm if followed. This chapter discusses com-mon cardiovascular toxins and groups them into their common mechanisms of toxicity. Multiple agents exist that result in human cardiovascular toxicity. The management of the toxicity of each agent should follow a rationale approach. The first step in the care of all poisoned patients focuses on good supportive care.

Fatal unintentional overdose of diltiazem with antemortem and postmortem values

BACKGROUND

Therapeutic errors involving calcium channel antagonists (CCA) resulting in death rarely have been reported in detail. We report a fatality from an unintentional overdose of sustained-release (SR) diltiazem including antemortem and postmortem blood concentrations.

CASE REPORT

A 65-year-old man with aortic stenosis mistakenly took six tablets of diltiazem 360 mg SR. He developed symptoms of toxicity by 7 hours after ingestion. By 10 hours, he went to the emergency department. Despite a prolonged resuscitative attempt, the patient died 17 hours postingestion. An antemortem blood sample drawn 11.5 hours after ingestion was 2.9 mcg/mL. Postmortem gas chromatography of central blood revealed a diltiazem level of 6 mcg/mL and the peripheral blood sample measured 5 mcg/ mL.

CONCLUSION

This case suggests that an unintentional overdose with a CCA may be lethal if the patient's cardiovascular ability to compensate for the toxic effects is compromised.

Metaraminol (Aramine) in the management of a significant amlodipine overdose

OBJECTIVE

To report a patient with a significant amlodipine self-poisoning who failed to clinically respond to conventional treatment and was managed with metaraminol (Aramine).

PATIENT

A 43-year old male presenting after ingestion of 560 mg amlodipine, who failed to respond clinically to treatment with fluid resuscitation, calcium salts, glucagon and norepinephrine/epinephrine inotropic support.

MAIN RESULTS

Following a loading bolus of 2 mg and intravenous infusion (83 microg/min) of metaraminol (Aramine) there was improvement in his blood pressure, cardiac output and urine output.

CONCLUSIONS

This is the first case report of the beneficial use of metaraminol (aramine) in the management of significant amlodipine poisoning unresponsive to conventional therapy.

The role of insulin and glucose (hyperinsulinaemia/euglycaemia) therapy in acute calcium channel antagonist and beta-blocker poisoning

The inotropic effect of insulin has been long established. High-dose (0.5-1 IU/kg/hour) insulin, in combination with a glucose infusion to maintain euglycaemia (hyperinsulinaemia/euglycaemia therapy), has been proposed as a treatment for calcium channel antagonist (CCA) and beta-adrenoceptor antagonist (beta-blocker) poisonings. However, the basis for its beneficial effect is poorly understood.CCAs inhibit insulin secretion, resulting in hyperglycaemia and alteration of myocardial fatty acid oxidation. Similarly, blockade of beta(2)-adrenoceptors in beta-blocker poisoning results in impaired lipolysis, glycogenolysis and insulin release. Insulin administration switches cell metabolism from fatty acids to carbohydrates and restores calcium fluxes, resulting in improvement in cardiac contractility. Experimental studies in verapamil poisoning have shown that high-dose insulin significantly improved survival compared with calcium salts, epinephrine or glucagon. In several life-threatening poisonings in humans, the administration of high-dose insulin produced cardiovascular stabilisation, decreased the catecholamine vasopressor infusion rate and improved the survival rate. In a canine model of propranolol intoxication, high-dose insulin provided a sustained increase in systemic blood pressure, cardiac performance and survival rate compared with glucagon or epinephrine. In contrast, insulin had no effect on heart rate and electrical conduction in the myocardium. In another study, high-dose insulin reversed the negative inotropic effect of propranolol to 80% of control function and normalised heart rate. High-dose insulin produced a significant decrease in the left ventricular end-diastolic pressure and a significant increase in the stroke volume and cardiac output. The vasodilator effect was explained by an enhanced cardiac output leading to withdrawal of compensatory vasoconstriction. No clinical studies have yet been performed. Although not effective in all cases, we recommend hyperinsulinaemia/euglycaemia therapy in patients with severe CCA poisoning who present with hypotension and respond poorly to fluid, calcium salts, glucagon and catecholamine infusion. However, careful monitoring of blood glucose and serum potassium concentrations is required to avoid serious adverse effects. More clinical data are needed before this therapy can be recommended in beta-blocker poisoning. There is a need for large prospective clinical trials to confirm safety and efficacy of hyperinsulinaemia/euglycaemia therapy in both CCA and beta-blocker poisoning.

High-Dose Insulin Therapy for Calcium-Channel Blocker Overdose

OBJECTIVE:

To evaluate the evidence for using high-dose insulin therapy with supplemental dextrose and potassium in calcium-channel blocker (CCB) overdose.

DATA SOURCES:

Evidence of efficacy for high-dose insulin therapy with supplemental dextrose and potassium was sought by performing a search of MEDLINE and Toxline between 1966 and July 2004 using combinations of the terms calcium-channel blocker, overdose, poisoning, antidote, and insulin. Abstracts from the North American Congress of Clinical Toxicology for the years 1996–2003 were also reviewed.

STUDY SELECTION AND DATA EXTRACTION:

Identified articles, including animal studies, case reports, and case series, were evaluated for this review. No clinical trials were available.

DATA SYNTHESIS:

Animal models of CCB overdose demonstrate that high-dose insulin with supplemental dextrose and potassium was a more effective therapy than calcium, glucagon, or catecholamines. High-dose insulin appears to enhance cardiac carbohydrate metabolism and has direct inotropic effects. Published clinical experience is limited to 13 case reports where insulin was used after other therapies were failing; 12 of these patients survived. High-dose insulin therapy was beneficial for CCB-induced hypotension, hyperglycemia, and metabolic acidosis. Bradycardia and heart block resolved in some patients, but persisted in others.

CONCLUSIONS:

Based on animal data and limited human experience, as well as the inadequacies of available alternatives for patients with significant poisoning, high-dose insulin therapy warrants further study and judicious use in patients with life-threatening CCB poisoning.

Deadly pediatric poisons: nine common agents that kill at low doses

More than 97% of pediatric exposures reported to the AAPCC in 2001 had either no effect or mild clinical effects. Despite the large number of exposures, only 26 of the 1074 reported fatalities occurred in children younger than age 6. These findings reflect the fact that, in contrast to adolescent or adult ingestions, pediatric ingestions are unintentional events secondary to development of exploration behaviors and the tendency to place objects in the mouth. Ingested substances typically are nontoxic or ingested in such small quantities that toxicity would not be expected. As a result, it commonly is believed that ingestion of one or two tablets by a toddler is a benign act and not expected to produce any consequential toxicity. Select agents have the potential to produce profound toxicity and death, however, despite the ingestion of only one or two tablets or sips. Although proven antidotes are a valuable resource, their value is diminished if risk after ingestion is not adequately appreciated and assessed. Future research into low-dose, high-risk exposures should be directed toward further clarification of risk, improvements in overall management strategies,and, perhaps most importantly, prevention of toxic exposure through parental education and appropriate safety legislation.

Attenuated Inhibition of L-type Calcium Currents by Troglitazone in Fructose–Fed Rat Cardiac Ventricular Myocytes

We recently reported that troglitazone, an insulin-sensitizing agent, inhibited l-type Ca current (ICa,L) more effectively in streptozotocin (STZ)-induced diabetic ventricular myocytes than in age-matched control myocytes. However, whether this agent would effectively inhibit ICa,L in an animal model of hyperinsulinemia is unknown. Using whole-cell voltage-clamp techniques, ICa,L was measured in ventricular myocytes isolated from 12 to 16 weeks on fructose-enriched feeding and age-matched control rats. Under control conditions, fructose-fed myocytes did not differ from control myocytes in membrane capacitance, current density, or voltage-dependent properties of ICa,L. Troglitazone inhibited ICa,L in both control and fructose-fed myocytes in a concentration-dependent manner. However, this inhibition was less in fructose-fed than in control myocytes; the half-maximum inhibitory concentrations of troglitazone measured at a holding potential of -50 mV were 16.9 and 9.8 micromol/L, respectively. Contrary to the STZ-induced diabetic rat, the suppressive effect of troglitazone on cardiac ventricular ICa,L was attenuated in fructose-fed rats. Persistent elevation of plasma insulin concentration may play a role in these processes.

Pharmacology, Pathophysiology and Management of Calcium Channel Blocker and ??-Blocker Toxicity

Calcium channel blockers (CCB) and beta-blockers (BB) account for approximately 40% of cardiovascular drug exposures reported to the American Association of Poison Centers. However, these drugs represent >65% of deaths from cardiovascular medications. Yet, caring for patients poisoned with these medications can be extremely difficult. Severely poisoned patients may have profound bradycardia and hypotension that is refractory to standard medications used for circulatory support.Calcium plays a pivotal role in cardiovascular function. The flow of calcium across cell membranes is necessary for cardiac automaticity, conduction and contraction, as well as maintenance of vascular tone. Through differing mechanisms, CCB and BB interfere with calcium fluxes across cell membranes. CCB directly block calcium flow through L-type calcium channels found in the heart, vasculature and pancreas, whereas BB decrease calcium flow by modifying the channels via second messenger systems. Interruption of calcium fluxes leads to decreased intracellular calcium producing cardiovascular dysfunction that, in the most severe situations, results in cardiovascular collapse.Although, CCB and BB have different mechanisms of action, their physiological and toxic effects are similar. However, differences exist between these drug classes and between drugs in each class. Diltiazem and especially verapamil tend to produce the most hypotension, bradycardia, conduction disturbances and deaths of the CCB. Nifedipine and other dihydropyridines are generally less lethal and tend to produce sinus tachycardia instead of bradycardia with fewer conduction disturbances.BB have a wider array of properties influencing their toxicity compared with CCB. BB possessing membrane stabilising activity are associated with the largest proportion of fatalities from BB overdose. Sotalol overdoses, in addition to bradycardia and hypotension, can cause torsade de pointes. Although BB and CCB poisoning can present in a similar fashion with hypotension and bradycardia, CCB toxicity is often associated with significant hyperglycaemia and acidosis because of complex metabolic derangements related to these medications. Despite differences, treatment of poisoning is nearly identical for BB and CCB, with some additional considerations given to specific BB. Initial management of critically ill patients consists of supporting airway, breathing and circulation. However, maintenance of adequate circulation in poisoned patients often requires a multitude of simultaneous therapies including intravenous fluids, vasopressors, calcium, glucagon, phosphodiesterase inhibitors, high-dose insulin, a relatively new therapy, and mechanical devices. This article provides a detailed review of the pharmacology, pathophysiology, clinical presentation and treatment strategies for CCB and BB overdoses.