The protraction of the QT interval can be the origin of a polymorphic ventricular tachycardia call “ torque of tips ” ( TdP or Torsades de Pointes ) , which can occur through syncope , dizziness or palpitations . It usually resolves ad lib and , in some case , raise ventricular fibrillation and could be associated with sudden cardiac expiry . This adverse result that sure medication imply that , the welfare - endangerment ratio may be unfavourable and should be deliberate both in the prescription and in the authorization of a new medicine .
The mechanism by which certain medication prolong the QT interval is usually due to the block of cardiac K channel .
The incidence of TdP produced by medications is not install , although it is assumed that it is very small .
What Drugs Cause QT Prolongation?
Among the best - have it away medicinal drug that prolong the QT separation are antiarrhythmic drug . However , it has been observed that there are more drug that have this side effect such as some antihistamines , antibiotic , antivirals , fungicide , antiemetics , neuroleptics , antidepressants , among others .
The contraindication of medications such as citalopram , escitalopram , ondansetron , and domperidone has been key come to to the risk of make VD - dependent prolongation of the QT time interval .
Citalopram , escitalopram , and ondansetron are contraindicated in patients with a story of prolonged QT time interval or congenital Long QT segment , as well as with concomitant use with drugs with the ability to sustain the QT interval . cautiousness is advised in patient in whom other risk factors for develop TdP coexist , such as in those with congestive spunk nonstarter , myocardial infarction , bradyarrhythmias or predisposition to hypokalemia or hypomagnesemia ( humble levels of potassium and atomic number 12 ) due to disease or resultant medicament .
The illuminating note of domperidone resolve that it may be associated with a slight increase of the risk of serious ventricular cardiac arrhythmia or sudden cardiac dying , in special in patient role older than 60 years or in affected role who use a daily dose greater than 30 mg .
It is commend to use the lowest possible efficacious Zen , both in grownup and fry . It is recommended economic consumption with forethought in patients with a history of QT time interval prolongation , with pregnant electrolyte flutter , with underlying cardiac diseases such as congestive heart nonstarter and in elderly patients .
The absence of coherent data of azithromycin seemed to have a cardiotoxicity profile safe with respect to erythromycin and clarithromycin .
However , in March 2013 , the FDA has report the ability of azithromycin to protract the QT time interval and produce TdP.
Before doctor prescribe a medication to a affected role that has the capacity to prolong the QT musical interval is important :
Assess the possible risk of infection gene that may be present ( bradycardia , alteration electrolyte , cardiac , endocrine pathologies , etc . ) because the risk could be swell than the benefit and the prescription is contraindicate .
verify if it is going to be used in combining with other medications that prolong the QT separation or that conquer the metabolism , because the ability to prolong is heighten the QT musical interval and the risk of producing TdP.
Do not exceed the recommended window pane .
do a measurement of the QT musical interval in the electrocardiogram prior to government of the drug with the ability to protract the QT separation and nullify its prescription in patient with a slightly prolonged QT interval .
Once the medicine has been dictate with the content to prolong the QT separation is recommend :
Assess the possible occurrence of hazard factors that can potentiate the risk of proarrhythmia .
When you demand to add a medicinal drug , you have to consider if you have the capacity to prolong the QT interval , if it is an inhibitor enzymatic or if any of the agent of development endangerment of TdP.
Conclusion
For the heart specialist , there is no doubt that a patient role with retentive QT syndrome ( LQTS ) , congenitally concern to as LQTS , must be closely followed and eventually treat .
The specialist is also aware of the existence of an acquired long QT syndrome ( and the endangerment involve ) , although it is broadly considered associated with drug , most of which are blockers of atomic number 19 channels creditworthy for cardiac repolarization .
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