Nifedipine overdose

Are vasopressors useful in toxin-induced cardiogenic shock?

OBJECTIVE

Overdoses with cardio-depressive medications can result in toxin-induced cardiogenic shock (TICS), a life-threatening condition characterized by severe hypotension and ineffective tissue perfusion. Vasopressors are often employed in the treatment of shock to increase heart rate and blood pressure. We sought to conduct a systematic review of the literature to evaluate the effectiveness of vasopressors in improving hemodynamic function and survival in the treatment of TICS.

DATA SOURCES

We searched PubMed, EMBASE, TOXLINE, and International Pharmaceutical Abstracts.

STUDY SELECTION

We included studies evaluating the use of vasopressors in humans or animals with TICS. We limited human study types to randomized controlled trials, clinical trials, observational studies, and case reports.

DATA EXTRACTION

Our search yielded 913 citations and 144 of these met our inclusion criteria. 130 were human case reports and 14 were animal studies.

DATA SYNTHESIS

Human case report data showed vasopressors were ineffective more often than they were partially or fully effective. In the majority of animal studies, vasopressor treatment failed to improve hemodynamic parameters and resulted in decreased survival.

CONCLUSIONS

Human case reports and controlled animal experiments lead to different conclusions about vasopressors in TICS. Most animal studies indicate that vasopressors impair hemodynamic function and increase mortality. In contrast, human case reports suggest that vasopressors are often ineffective but not necessarily harmful.

Calcium Channel Blocker Ingestion: An Evidence-Based Consensus Guideline for Out-of-Hospital Management

In 2003, U.S. poison control centers were consulted after 9650 ingestions of calcium channel blockers (CCBs), including 57 deaths. This represents more than one-third of the deaths reported to the American Association of Poison Control Centers' Toxic Exposure Surveillance System database that were associated with cardiovascular drugs and emphasizes the importance of developing a guideline for the out-of-hospital management of calcium channel blocker poisoning. The objective of this guideline is to assist poison center personnel in the appropriate out-of-hospital triage and initial management of patients with suspected ingestions of calcium channel blockers. An evidence-based expert consensus process was used to create this guideline. This guideline applies to ingestion of calcium channel blockers alone and is based on an assessment of current scientific and clinical information. The expert consensus panel recognizes that specific patient care decisions may be at variance with this guideline and are the prerogative of the patient and the health professionals providing care, considering all of the circumstances involved. The panel's recommendations follow. The grade of recommendation is in parentheses. 1) All patients with stated or suspected self-harm or the recipient of a potentially malicious administration of a CCB should be referred to an emergency department immediately regardless of the amount ingested (Grade D). 2) Asymptomatic patients are unlikely to develop symptoms if the interval between the ingestion and the call is greater than 6 hours for immediate-release products, 18 hours for modified-release products other than verapamil, and 24 hours for modified-release verapamil. These patients do not need referral or prolonged observation (Grade D). 3) Patients without evidence of self-harm should have further evaluation, including determination of the precise dose ingested, history of other medical conditions, and the presence of co-ingestants. Ingestion of either an amount that exceeds the usual maximum single therapeutic dose or an amount equal to or greater than the lowest reported toxic dose, whichever is lower (see Table 5), would warrant consideration of referral to an emergency department (Grade D). 4) Do not induce emesis (Grade D). 5) Consider the administration of activated charcoal orally if available and no contraindications are present. However, do not delay transportation in order to administer charcoal (Grade D). 6) For patients who merit evaluation in an emergency department, ambulance transportation is recommended because of the potential for life-threatening complications. Provide usual supportive care en route to the hospital, including intravenous fluids for hypotension. Consider use of intravenous calcium, glucagon, and epinephrine for severe hypotension during transport, if available (Grade D). 7) Depending on the specific circumstances, follow-up calls should be made to determine outcome at appropriate intervals based on the clinical judgment of the poison center staff (Grade D).

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.

Calcium channel blocker overdose

A case of diltiazem overdose with significant hemodynamic compromise is presented. Multiple therapeutic modalities were attempted with limited results. Control was finally achieved with a combination of norepinephrine, dobutamine, and cardiac pacing. Invasive pulmonary monitoring parameters are reported and were important in the management of this patient. The management of calcium channel blocker overdose and the various available therapeutic modalities are discussed.

Verapamil intoxication: a literature review of overdoses and discussion of therapeutic options

Calcium channel antagonists can be quite toxic. In the management of poisoning, early recognition is critical. Calcium channel antagonists are frequently prescribed, and the potential for serious morbidity and mortality with overdosage is significant. Ingestion of these agents should be suspected in any patient who presents in an overdose situation with unexplained hypotension and conduction abnormalities. The potential for toxicity should be noted in patients with underlying hepatic or renal dysfunction who are receiving therapeutic doses. Because there is no specific antidote, decontamination of the gastrointestinal tract is crucial. Intravenous calcium should be administered to symptomatic patients because it is relatively innocuous and may be beneficial. Volume expansion should be the initial approach to hypotension unrelated to bradycardia. Patients who have had a verapamil overdose should be observed in intensive care units where Swan-Ganz catheterization and ventricular pacing are routinely available. The choice of sympathomimetic agents for treatment remains controversial. According to the published literature, isoproterenol, epinephrine, and norepinephrine may be more effective in improving bradycardia and the resultant hypotension than dopamine. However, none of these agents is universally effective. A more logical approach may be to improve cardiac output with agents like amrinone. Bay K 8644 and 4-aminopyridine show promise as potential antidotes but at present are still experimental.

Poisoning caused by the combined ingestion of nifedipine and metoprolol

Poisonings due to ingestion of a calcium channel or beta-adrenergic blocker have been the subject of several previous reports, but reports of poisoning due to combined ingestion of these drugs are infrequent. This is a report of suicidal ingestion of nifedipine 600 mg, metoprolol 200 mg, and etizolam 20 mg. Intravenous dopamine, norepinephrine, and calcium chloride had little effect but the administration of methylprednisolone and glucagon were associated with an increase in systolic blood pressure above 100 mm Hg.

Two deaths from intravenous nifedipine abuse

An incident is reported in which 2 intravenous drug abusers died as the result of uncontrolled experimentation with intravenous injection of the common anti-hypertensive and anti-anginal drug Nifedipine (Adalat t.m. Bayer), probably in mistake for the commonly abused short-acting benzodiazepine drug Temazepam. Large quantities of Nifedipine were identified in the blood of both decreased men by gas chromatography. Apart from intense gastric mucosal congestion, pulmonary oedema and general visceral congestion, the autopsy findings were entirely nonspecific. The similarity in colour, shape and texture between capsules of Nifedipine and those of Temazepam is likely to have prompted the mistake.

Survival following severe overdose with mexiletene, nifedipine, and nitroglycerine

Survival following attempted suicide in a 50-year-old man by ingestion of 12.4 g of mexiletine, 620 mg of nifedipine and 50 to 100 tablets of sublingual nitroglycerine 1:150 is reported. Initial presentation was that of mental obtundation, vomiting, tonic-clonic seizure, high-degree atrioventricular block, profound vasodilation and cardiovascular collapse. Treatment consisted of intravenous calcium gluconate and aggressive fluid management. Maintenance of cardiovascular stability required continuous infusion phenylephrine, dopamine and epinephrine. The patient made a full recovery and was medically discharged on the fourth hospital day. This case represents the largest overdose of mexiletine to date to end in patient survival.

Pharmacokinetics and toxic effects of nifedipine in massive overdose

A 57-year-old man took 30 x 20 mg nifedipine retarded release tablets. He developed hypotension, tachycardia and flushing, but remained in sinus rhythm. The concentration of nifedipine 10 h after overdose was 604 micrograms 1-1, and of the M-I metabolite 110 micrograms 1-1. Log concentration time curves were linear from 10-72 h for nifedipine, with a half-life of 7.5 h; and for M-I with a half-life of 8.2 h. On this evidence, oral absorption of nifedipine retarded release is complete by 10 h. There was no evidence of saturation of nifedipine or M-I metabolism, even at concentrations ten times above the therapeutic concentration.

Nifedipine overdose accompanied by ethanol intoxication in a patient with congenital heart disease

A 34-year-old female was brought to the emergency department after taking 200 to 250 mg of nifedipine and drinking an unknown amount of ethanol in a suicide attempt. She was hypotensive, acidotic, mildly hyperglycemic, and exhibited a conduction abnormality on the ECG. The patient was treated with IV fluids, thiamine, and calcium infusion. The patient was later found to have an endocardial cushion defect with a patched ventricular septal defect and an atrial septal defect of the ostium primum type. We did not observe any untoward effects due to the combination of drugs and congenital abnormalities that could be explained on an individual basis. Nifedipine overdose associated with alcohol intoxication, to our knowledge, has not been previously reported.