FAQs for Professionals
To view frequently asked questions oriented toward consumers, click here.
For Providers: Frequently Asked Questions about drug-induced QT prolongation and torsades de pointes.
How prevalent is drug- induced LQTS (long QT syndrome) in the general population?
The incidence or prevalence of drug-induced LQT in the general medical population has not been determined. Many people might experience a prolonged QT when taking a medication, but unless they have an ECG recorded, it wouldn't be detected. A drop in serum potassium or another change in health that might affect cardiac repolarization could change a well-tolerated medicine to one that is life threatening for a person.
Do the drugs on the lists have the same effects on all patients?
No, many people take medications that may prolong QT slightly without causing any problem but unfortunately others receiving the same drug and dose, develop lethal arrhythmias. There is evidence that some of those who develop serious arrhythmias, like torsades de pointes, have predisposing genetic factors.
Are there patients without congenital LQTS who are particularly vulnerable to QT prolongation and torsades de pointes? It is important to remember that the patient's cardiac, kidney and liver function, as well as electrolyte profile, can increase vulnerability to QT prolongation and torsades de pointes, even in the absence of congenital LQTS. Genetic predisposing factors and diagnostic tests are available but they only aid in making the diagnosis in some patients.
Some people with a normal QT interval have extreme sensitivity to drugs that can prolong the QT. They may be silent carriers of genetic mutations for Long QT syndrome. Women tend to have a greater QT prolongation in response to these drugs (see comments on our lists).
Read More
Are there specific guidelines for monitoring the QTc for persons who are taking QT-prolonging drugs?
We recommend that you:
- If possible, do not prescribe QT-prolonging drugs to anyone with a QT>440ms (female) or 420ms (male).
- Do not allow QT to exceed 500ms during titration with these drugs
- Beware of drug interactions that could result in greater exposure to the QT- prolonging drugs by blocking their metabolism or delaying clearance. Beware of drugs and or dietary supplements that also prolong the QT interval.
Does female gender increase the sensitivity to QT-prolonging drugs and raise the risk of torsades de pointes with some drugs?
Yes it does. Even at equivalent blood levels of the drugs, females have an increased sensitivity to drugs that prolong the QT interval and have a higher incidence of torsades de pointes. Look for comments regarding gender for specific drugs on our lists: Please click here to view the lists. PubMed searches on this topic area are available on our site.
Is there an increased risk of developing torsades de pointes due to interactions between prescription drugs and OTC drugs or supplements? What about foods? Given the vast amount of products available, and the fact that few have been completely tested for an effect on QT, it is important for healthcare providers to keep an updated record of all prescription medications, over the counter products and supplements/vitamins/herbals and check for potential interactions. Even after many years, we often become aware of interactions with old products that are potentially harmful.
Yes, in some cases. Interactions are highly variable in their expression and sometimes difficult to predict. Some dietary supplements that contain ephedrine have been found to prolong the QT interval and would be especially dangerous if combined with prescription drugs that have this action. Some foods can cause an interaction with drugs; for example, grapefruit juice inhibits the enzyme cytochrome P450 3A4, which metabolizes approximately 50% of all medications known to prolong the QT interval.
Read More
There is a list of drugs that could potentially interact available at www.drug-interactions.org
Are the drugs on the Conditional Risk of torsades list safe for patients with Congenital Long QT Syndrome? The currently available information shows that the evidence that the risk of anyone of these drugs causing torsades de pointes is not definitive. You should remember that this statement applies only to recommended dosages and that several of these drugs have caused torsades when taken in large overdosages (e.g., diphenhydramine).
We recommend avoiding the use of these drugs in patients with long QT syndrome whenever possible. This list includes drugs that, in some reports, have been weakly associated with torsades de pointes and/or QT prolongation but, from the evidence that is available, we have concluded that they are unlikely to create a risk for torsades de pointes when used in usual recommended dosages and in patients without other risk factors, such as congenital long QT syndrome.
Read More
What criteria do you use to determine how drugs get placed on each list?
The process of assessing the risk of drugs causing QT prolongation and torsades de pointes is rigorous and complex, involving multiple data sources and contingencies.
Please click here to see a description of this process.
How often is the evidence updated? Can I register to be notified when a change is made to the lists? We regularly scan the medical literature for new reports or studies suggesting that a particular drug prolongs the QT interval and/or causes torsades de pointes. Additionally, we perform ad hoc evaluations in response to inquiries sent to our website and when cases are submitted to our International Registry for Drug-induced Arrhythmias. Once we receive a report or request, we review the FDA labeling, scan the literature and mine the FDA Adverse Event Report System (AERS) database for reports suggestive of an association between the drug(s) and prolonged QT/torsades de pointes. This process often results in the drug(s) first being placed on a "watch list." Ultimately, if we find what we believe to be a significant association, we present the evidence to our scientific advisory board, which makes a decision whether or not to add the drug, and to which list it should be added.
Our lists are monitored continually and often revised in consultation with our scientific advisory board. If you wish, we can notify you when revisions are made. Please click here to sign up.
Read More
Is there a list of drugs that prolong the QT interval available in Spanish or languages other than English?
Yes. All four lists are also available in Spanish, German and Portuguese. Contact us if you'd like a version of the QT drug lists in either of these three languages.
WARNING: brand names included on those lists apply to the US and Canada, but not necessarily to other countries.
May I have permission to use or translate information on your site (www.QTdrugs.org, www.torsades.org) in my lecture/ paper/ book/ presentation/publication/ business report/ etc.? Although the QT Drug List information is free to anyone who visits our site, we do not encourage that it be published separately from ArizonaCERT because it could rapidly become outdated. Circulation of out-of-date lists could be very dangerous for some patients. We welcome all interested parties to use or link to the lists on our website to assure they have the most recent information.
We welcome anyone to use the information on our website in any way they find useful. However, we do not recommend printing and distributing the information because it changes frequently, and using outdated lists could be dangerous. To ensure that you have the most up-to-date information we suggest that you use the hyperlink: www.azcert.org/medical-pros/drug-lists/drug-lists.htm.
Read More
Are your drug lists for prolonged QT- torsades de pointes available in an updatable PDA format?
Yes, the drug lists for risk of QT prolongation and torsades de pointes can be accessed in a PDA format at www.QTdrugs.org/m
How can I be informed about updates and how can I get them?
Anyone can receive notice that the lists have been updated by registering with us.
For Providers: Frequently Asked Questions about drug therapy in patients with Congenital Long QT Syndrome.
Which drugs can be used to prevent arrhythmias in patients with congenital Long QT Syndrome (LQTS)? There has been a focus on understanding the genetics of LQTS in the last few years, in order to make rational choices for therapy. Potassium supplementation for patients with a specific HERG mutation shortens the QT and has shown promise, as well as mexiletine for patients with a defective SCN5A sodium channel. However there is insufficient evidence to recommend routine use of these therapies at this time.
Beta-blockers, especially long acting agents like atenolol and nadolol, remain the mainstay of pharmacologic therapy.
Read More
What antibiotics are safe in patients with congenital LQTS? The choice of antibiotic depends on the type and seriousness of the infection, infection site, resistance profile of the organism and patient's condition, so we cannot suggest a universally safe solution. Our CLQTS list contains drugs that should be avoided in patients with congenital LQTS, including some antibiotics. However, even if a certain product is not listed, it can NOT automatically be assumed to be safe. We always recommend that patients with congenital LQTS take medications only under the supervision of their physician who knows their drug therapy, their complete medical history and current medical condition. We recommend that when prescribing any medication to a patient with congenital LQTS, physicians consider potential interactions with other medications the patient is taking, their general health, including electrolyte profile, and careful observation when introducing or changing any medication.
Because these drugs are not tested in LQTS patients and because there are multiple forms of LQTS, it is not possible to say that any antibiotic is "absolutely safe". There are some that clearly have been found to be dangerous and we include them on the CLQTS List. However, even if a drug is not on this list, you cannot assume that it will be safe. Use caution when administering any medication to patients with LQTS.
Read More
What types of antidepressants are safe in patients with congenital LQTS? Our CLQTS List contains drugs that should be avoided in patients with congenital LQTS, including some antidepressants. However, this does not mean that a given product is automatically safe, even if it is NOT listed. We always recommend that patients with congenital LQTS take medications only under the supervision of a physician who knows the patient's drug therapy, their complete history and their current medical condition. We recommend that when prescribing any medication to a patient with congenital LQTS, physicians consider potential interactions with other medications the patient is taking, their general health, including electrolyte profile, and careful observation when introducing or changing any medication.
Prescribing for patients with congenital LQTS is a challenge. Because these drugs are not tested in LQTS patients and because there are multiple forms of LQTS with different sensitivities, it is not possible to say that any antidepressant is "absolutely safe."
Read More
What types of therapies for ADHD are safe in patients with congenital LQTS? Our CLQTS List includes drugs that should be avoided in patients with congenital LQTS, including stimulants that have the ability to increase heart rate and blood pressure, because some patients with LQTS can develop sudden death in the presence of adrenergic stimulation. However, this does not mean that a certain product is automatically safe if it is NOT on the CLQTS list. We always recommend that patients with congenital LQTS take medications only under the supervision of their physician who knows their drug therapy, complete history and current medical condition. We recommend that when prescribing any medication to a patient with congenital LQTS, physicians consider potential interactions with other medications the patient is taking, their general health, including electrolyte profile, and careful observation when introducing or changing any medication.
Because these drugs are not tested in LQTS patients and because there are multiple forms of LQTS, it is not possible to say that any drug is "absolutely safe." There is no evidence to suggest that any of the current pharmaceutical therapies for ADHD are risk-free for patients with congenital LQTS. Many of these agents are adrenergic stimulants and are presumed to be potentially dangerous.
Read More
Which anesthetics are safe for patients with congenital LQTS? Drug use in anesthesiology is a special case, since dose titration can be achieved very rapidly. We always recommend that patients with congenital LQTS take medications only under the supervision of their physician who knows their drug therapy, complete history and current medical condition. We recommend that when prescribing any medication to a patient with congenital LQTS, physicians consider potential interactions with other medications the patient is taking, their general health, including electrolyte profile, and careful observation when introducing or changing any medication.
Many anesthetics stimulate the sympathetic nervous system and can be dangerous for those with congenital Long QT, especially Long QT1 or 2. Some anesthetics directly prolong the QT interval and are especially dangerous. It is essential that patients with congenital Long QT be treated by highly trained anesthesiologists who are familiar with this illness and the drugs that are known to prolong QT.
Read More
