An Outpatient Approach to Nausea and Vomiting
Prolongation of the QT may be a result of a medication's mechanism of action, drug interactions, alteration of metabolism or elimination, or augmentation of concomitant QT prolongation effects from other agents. Many commonly prescribed antiemetics carry specific warnings regarding QT prolongation. For example, the FDA recently placed a warning for QT prolongation with ondansetron. Ondansetron's QT prolongation is exhibited in a dose-dependent manner; hence, the FDA has advised to cease using the 32-mg single IV dosage. Domperidone may also significantly prolong the QT interval. For this reason, a baseline ECG is recommended with a corrected QT interval assessed prior to starting therapy.
The manner in which pharmacists handle general QT prolongation warnings is dependent on the tools available to them. Most outpatient pharmacies will not have a patient laboratory or ECG capability, but should have the patient's medication record. Watching for high-risk drug-drug and drug-disease state interactions, as well as educating patients on the risks of torsade de pointes, is necessary. Targeting patients with heart disease and individuals on medications that can increase the risk of potassium and magnesium abnormalities should help the pharmacist identify the appropriate counseling.
QT Prolongation Concerns
Prolongation of the QT may be a result of a medication's mechanism of action, drug interactions, alteration of metabolism or elimination, or augmentation of concomitant QT prolongation effects from other agents. Many commonly prescribed antiemetics carry specific warnings regarding QT prolongation. For example, the FDA recently placed a warning for QT prolongation with ondansetron. Ondansetron's QT prolongation is exhibited in a dose-dependent manner; hence, the FDA has advised to cease using the 32-mg single IV dosage. Domperidone may also significantly prolong the QT interval. For this reason, a baseline ECG is recommended with a corrected QT interval assessed prior to starting therapy.
The manner in which pharmacists handle general QT prolongation warnings is dependent on the tools available to them. Most outpatient pharmacies will not have a patient laboratory or ECG capability, but should have the patient's medication record. Watching for high-risk drug-drug and drug-disease state interactions, as well as educating patients on the risks of torsade de pointes, is necessary. Targeting patients with heart disease and individuals on medications that can increase the risk of potassium and magnesium abnormalities should help the pharmacist identify the appropriate counseling.