Cardiogenic shock triggered by verapamil and atenolol: a case report of therapeutic experience with intravenous calcium

Drug Interactions Affecting Antiarrhythmic Drug Use

Antiarrhythmic drugs (AAD) play an important role in the management of arrhythmias. Drug interactions involving AAD are common in clinical practice. As AADs have a narrow therapeutic window, both pharmacokinetic as well as pharmacodynamic interactions involving AAD can result in serious adverse drug reactions ranging from arrhythmia recurrence, failure of device-based therapy, and heart failure, to death. Pharmacokinetic drug interactions frequently involve the inhibition of key metabolic pathways, resulting in accumulation of a substrate drug. Additionally, over the past 2 decades, the P-gp (permeability glycoprotein) has been increasingly cited as a significant source of drug interactions. Pharmacodynamic drug interactions involving AADs commonly involve additive QT prolongation. Amiodarone, quinidine, and dofetilide are AADs with numerous and clinically significant drug interactions. Recent studies have also demonstrated increased morbidity and mortality with the use of digoxin and other AAD which interact with P-gp. QT prolongation is an important pharmacodynamic interaction involving mainly Vaughan-Williams class III AAD as many commonly used drug classes, such as macrolide antibiotics, fluoroquinolone antibiotics, antipsychotics, and antiemetics prolong the QT interval. Whenever possible, serious drug-drug interactions involving AAD should be avoided. If unavoidable, patients will require closer monitoring and the concomitant use of interacting agents should be minimized. Increasing awareness of drug interactions among clinicians will significantly improve patient safety for patients with arrhythmias.

Heart insufficiency after combination of verapamil and metoprolol: A fatal case report and literature review

The combination of verapamil or diltiazem with beta-blockers should be avoided because of potentially profound adverse effects on AV (atrioventricular) nodal conduction, heart rate, or cardiac contractility. This effect is unpredictable but may be enhanced due to CYP2D6 poor metabolizer status which could be a special vulnerability factor.

[Cardiogenic shock after drug therapy for atrial fibrillation with tachycardia : Case report of an 89-year-old woman]

β-Blockers and calcium channel blockers are commonly used drugs in the treatment of atrial fibrillation with tachycardia. However, in patients with high myocardial susceptibility and vulnerability, combination therapy with β-blockers and non-dihydropyridine calcium channel blockers (verapamil or diltiazem) but also individual administration can cause drug-induced cardiogenic shock. Thus, the simultaneous administration of β-blockers and non-dihydropyridine calcium channel blockers is absolutely contraindicated. In case of acute heart failure, isolated application is also contraindicated. In the treatment of a cardiogenic shock induced by β-blockers and/or non-dihydropyridine calcium channel blockers, administration of intravenous calcium, glucagon or high-dose insulin is recommended.

Polypharmacy and Possible Drug-Drug Interactions Among Diabetic Patients Receiving Home Health Care Services

OBJECTIVES

In this study, we examined the drug regimens of diabetic patients receiving home health care services to measure the prevalence of polypharmacy and to assess the likelihood of drug-drug interactions, a consequence of polypharmacy.

DESIGN

The sample consisted of 139 diabetic patients who received home health care services from one home health agency in a large mid-Atlantic city. The data were collected from March 1, 1998 to September 30, 1999. Information regarding medications was collected by the home health nurse during the initial home visit and was recorded on the medication sheet in the patient's clinical record. Any changes in medications were noted on the medication sheets.

METHODS

We identified all systemic medications prescribed for 139 home health patients. To assess drug-drug interactions, we used Micromedex formulary DRUG-REAX System.

OUTCOMES

We calculated (1) the number of systemic medications taken, and (2) the number of possible severe, moderate, and mild drug-drug interactions.

RESULTS

We found that the average number of medications taken was 8.9 (SD 3.4) prescribed medications per day. Our results show that 38.8% of the patients in the sample could potentially be subject to at least one severe drug-drug interaction. Nearly all of the patients (92.8%) were at risk for moderate drug-drug interactions, and 70.5% could have mild drug- drug interactions.

CONCLUSION

We conclude that polypharmacy is a concern for home health care patients with diabetes and the potential for drug-drug interactions is substantial. Our results indicate that the drug regimens of diabetic patients should be monitored systematically to avoid adverse events such as hospitalization. Family practitioners and home health care takers are in a unique position to identify polypharmacy and to modify drug regimens.