Hydroxyzine QT Prolongation Risk Calculator
Your Risk Assessment
This tool evaluates your individual risk of QT prolongation when taking hydroxyzine based on key clinical factors. Your risk score is calculated based on the presence of specific risk factors and medication interactions.
35 years
420 ms
Risk Factors
Medication Interactions
Common examples: antibiotics (ciprofloxacin, erythromycin), antidepressants (amitriptyline), antiarrhythmics (sotalol)
Electrolyte Status
Cardiac History
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Key Risk Factors Identified
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Hydroxyzine has been used for decades to treat anxiety, itching, and nausea. It’s cheap, effective, and widely prescribed. But behind its calming reputation lies a quiet but serious danger: it can mess with your heart’s electrical rhythm and trigger a life-threatening arrhythmia called QT prolongation.
What Is QT Prolongation, and Why Does It Matter?
Your heart beats because of electrical signals that travel through muscle tissue. The QT interval on an ECG measures how long it takes for the heart’s lower chambers to recharge after each beat. If that interval stretches too long, the heart can develop a dangerous rhythm called Torsade de Pointes - a type of ventricular tachycardia that can cause fainting, seizures, or sudden death. Hydroxyzine interferes with a key ion channel in heart cells called hERG. This channel helps move potassium out of the cell during repolarization. When hydroxyzine blocks it, the heart takes longer to reset. The result? A longer QT interval. It doesn’t happen in everyone. But when it does, it can happen fast - sometimes within minutes of taking the first dose.Who’s at Risk?
Most healthy adults can take hydroxyzine without issue. But risk skyrockets if you have even one of these factors:- Age 65 or older
- Low potassium or magnesium levels
- Existing heart disease or prior QT prolongation
- Slow heart rate (below 50 bpm)
- Taking other drugs that prolong QT - like certain antibiotics, antidepressants, or antiarrhythmics
How Common Is This Risk?
It’s rare - but not rare enough to ignore. Between 1955 and 2016, global pharmacovigilance systems recorded 59 confirmed cases linking hydroxyzine to QT prolongation or Torsade de Pointes. That sounds low. But most cases go unreported. Many doctors still don’t connect a sudden fainting spell or palpitations to hydroxyzine, especially if the patient has no prior heart issues. In one Reddit thread, users reported 37 cardiac-related concerns tied to hydroxyzine between 2018 and 2023. Nearly half described dizziness or heart flutters within an hour of taking it. That’s not coincidence. That’s a red flag. The FDA added hydroxyzine to its official list of drugs with QT prolongation risk in 2019. The EMA issued a formal warning in 2015. Yet, a 2021 survey of 127 hospital pharmacists found that 63% had seen hydroxyzine prescribed to patients with two or more risk factors - even though guidelines say it’s a hard no in those cases.
How Does Hydroxyzine Compare to Other Antihistamines?
Not all antihistamines are created equal. Second-generation ones like cetirizine (Zyrtec) and loratadine (Claritin) barely touch the hERG channel. Their QT risk is negligible. That’s why they’re preferred for long-term use, especially in older adults. Among first-generation antihistamines - the sleepy ones - hydroxyzine sits near the top of the danger list. It’s slightly worse than diphenhydramine (Benadryl), which also blocks hERG but less potently. Both are far riskier than non-sedating options. Here’s a quick comparison:| Drug | Generation | QT Prolongation Risk | Typical Max Daily Dose |
|---|---|---|---|
| Hydroxyzine | First | Known Risk (CredibleMeds) | 100 mg (adults), 50 mg (elderly) |
| Diphenhydramine | First | Possible Risk | 300 mg |
| Cetirizine | Second | Minimal Risk | 10 mg |
| Loratadine | Second | Minimal Risk | 10 mg |
Hydroxyzine’s molecular structure lets it bind tightly to the hERG channel - more so than most other antihistamines. That’s why cardiologists and pharmacologists now treat it like a cardiac drug, not just a sedative.
What Should Doctors Do Before Prescribing It?
It’s not about avoiding hydroxyzine entirely. It’s about using it wisely. Before writing a prescription, a clinician should:- Check the patient’s ECG for QTc interval - it should be under 450 ms for men, under 470 ms for women.
- Review all medications using the CredibleMeds database. If the patient is on any drug marked "Known Risk," hydroxyzine is off the table.
- Test potassium and magnesium levels. If either is low, correct it first.
- Ask about heart disease, syncope, or family history of sudden cardiac death.
- Use the lowest effective dose for the shortest time possible.
What About Alternatives?
If you’re taking hydroxyzine for anxiety or itching, there are safer options. For anxiety: Buspirone, low-dose SSRIs like sertraline, or even cognitive behavioral therapy (CBT) are better long-term choices. For itching: gabapentin, naltrexone, or topical capsaicin have proven effective with no cardiac risk. In dermatology, hydroxyzine is still listed as a second-line option for chronic pruritus - but only if cardiac screening is done. Many dermatologists now skip it entirely and go straight to gabapentin, which has seen a 62% rise in prescriptions since 2015. For insomnia or sedation in the elderly: mirtazapine, trazodone, or non-pharmacological sleep hygiene are safer. The American Geriatrics Society Beers Criteria now lists hydroxyzine as a "Potentially Inappropriate Medication" for older adults.The Future of Hydroxyzine
Research is moving fast. A 2023 study found that people with a genetic variant called CYP2D6 poor metabolizer status are over three times more likely to experience QT prolongation on hydroxyzine. That means future prescribing might involve genetic testing. A new compound called VH-01 is in early trials. It keeps the antihistamine effect but cuts hERG binding by 87%. If it works, it could replace hydroxyzine entirely. The 2025 European Society of Cardiology guidelines are expected to ban chronic hydroxyzine use entirely. It may only be allowed as a single dose for procedural anxiety - like before a dental appointment.What Should You Do If You’re Taking Hydroxyzine?
If you’re on hydroxyzine and have no heart issues, no electrolyte imbalances, and aren’t on other risky meds - you’re probably fine. But don’t assume safety. Ask your doctor:- "Have you checked my QT interval?"
- "Am I on any other meds that could interact?"
- "Is there a safer alternative for my condition?"
Use it with eyes wide open. Or don’t use it at all.
Mussin Machhour
December 24, 2025 AT 07:18Man, I took hydroxyzine for years for sleep and never thought twice. Guess I got lucky. But now I’m gonna ask my doc to check my QT before refilling. Better safe than sorry.
Sophie Stallkind
December 24, 2025 AT 07:42It is imperative that clinicians exercise due diligence when prescribing hydroxyzine, particularly in elderly populations. The pharmacokinetic alterations associated with aging necessitate a heightened awareness of cardiac risk, as evidenced by the EMA’s revised dosage guidelines.
Bailey Adkison
December 25, 2025 AT 07:24So let me get this straight. You’re saying a $5 pill that’s been around since the 50s is suddenly dangerous because some fancy charts say so? My grandma took this for 30 years and still beats me at chess. You’re overcomplicating things
Carlos Narvaez
December 26, 2025 AT 17:49hERG blockade. QTc >450. CredibleMeds Category 2. That’s it. Stop prescribing it like it’s melatonin.
Justin James
December 28, 2025 AT 06:50They’re hiding the truth. Hydroxyzine is just the tip. The FDA, Big Pharma, and the AMA all know this causes sudden cardiac death in young people. They keep it on the shelf because it’s cheap and keeps people docile. Look at the timeline - right after the 2019 warning, prescriptions went up. Coincidence? Or are they profiting off silent deaths?
I know a guy who collapsed after one dose. Hospital said it was ‘idiopathic’ - yeah right. His ECG was never checked. They don’t want you to know this stuff. Your doctor’s been trained to ignore it.
They even ban it in Europe but sell it here? That’s not policy. That’s corporate negligence. They’re using our bodies as test subjects. And you’re just gonna take it because your doctor said so?
Check your meds. Cross-reference with CredibleMeds. If you’re on anything else - antipsychotics, antibiotics, SSRIs - you’re playing Russian roulette with your heart.
I’m not scared. I’m informed. And I’m warning you.
Rick Kimberly
December 28, 2025 AT 22:29This is a well-structured and deeply informative overview. I appreciate the inclusion of both clinical guidelines and real-world data from pharmacovigilance systems. The comparison table is particularly helpful for prescribers navigating alternatives.
It raises an important question: why do so many providers still overlook cardiac screening when prescribing first-gen antihistamines? Is it lack of awareness, time constraints, or simply the inertia of habit?
Perhaps integrating automated EHR alerts with CredibleMeds data could reduce preventable harm. Systemic change, not just individual caution, is needed.
Terry Free
December 29, 2025 AT 05:02Oh wow, hydroxyzine? The same stuff you give to your dog for allergies? Guess it’s not just for itching anymore. Next they’ll tell us Benadryl is a heart assassin too. Chill out. People aren’t dropping dead from this every day. It’s not a war crime.
Lindsay Hensel
December 30, 2025 AT 16:25I’m a nurse. I’ve seen it. A sweet 72-year-old woman, no history, just took hydroxyzine for anxiety before her chemo. Two hours later - syncope. Code blue. She survived. But her ECG? QTc 580. We almost lost her. This isn’t theoretical. It’s happening in our units every week. Please, if you’re prescribing this - check the ECG. Just once.
Michael Dillon
December 31, 2025 AT 03:04Look, I get the risk. But let’s not turn every antihistamine into a villain. Hydroxyzine’s not poison. It’s just not for everyone. I’ve got a cousin on it for anxiety and he’s fine. He’s 40, no meds, potassium normal. So chill. Not everyone’s gonna drop dead. But yeah - if you’re old or on 12 other pills? Maybe skip it.
Gary Hartung
December 31, 2025 AT 08:34And yet… they still sell it. Like it’s candy. At CVS. Next to the ibuprofen. No warning label. No pharmacist consultation. No ‘do not use if you have a heartbeat.’ It’s absurd. They’re selling cardiac time bombs on the same shelf as toothpaste. And we’re supposed to trust ‘the system’? Ha. I’ll take my chances with gabapentin - at least it doesn’t pretend to be harmless.
Ben Harris
January 2, 2026 AT 04:28Why do we even still use this drug? It’s a relic. A dinosaur. We’ve got better options. Why keep a ticking time bomb in the medicine cabinet just because it’s cheap? Someone’s making money off this. And it’s not us. It’s the pharmacy benefit managers. The manufacturers. The insurance companies who don’t cover gabapentin unless you’ve tried and nearly died on hydroxyzine first
It’s a scam. And you’re all just part of the machine
Oluwatosin Ayodele
January 3, 2026 AT 12:39Back home in Nigeria we use hydroxyzine for everything - allergies, sleep, anxiety. No ECG. No labs. No problem. People live to 80. You Americans overthink everything. You check your heart every time you sneeze. This is why you have so many mental health issues - you’re scared of your own bodies
Jason Jasper
January 4, 2026 AT 07:36I’ve been on hydroxyzine for chronic hives for 5 years. No issues. But after reading this, I’m getting an ECG next week. Better to be safe. Thanks for the detailed breakdown - it made me think. Not scared. Just aware.
Zabihullah Saleh
January 6, 2026 AT 01:25It’s funny how we treat drugs like they’re either saints or sinners. Hydroxyzine isn’t evil. It’s a tool. Like a hammer. You can use it to build a house or smash a window. The problem isn’t the tool - it’s who’s holding it and whether they know how to use it. We’ve turned prescribing into a checklist instead of a conversation. That’s the real danger.
It’s not about banning it. It’s about restoring clinical judgment. About seeing the person, not just the lab values. About asking: why are they taking this? What are they really struggling with? Anxiety? Insomnia? Loneliness?
Maybe the real QT prolongation isn’t in their heart - it’s in our healthcare system. We’re so busy checking boxes we’ve forgotten how to listen.
And that’s the thing no algorithm can fix.
Harbans Singh
January 6, 2026 AT 13:23As someone who’s worked in rural India with limited resources, I’ve seen how hard it is to get even basic cardiac screening. But that doesn’t mean we ignore the risk - it means we adapt. Maybe we start with simple questions: ‘Have you ever fainted?’ ‘Any family history of sudden death?’ ‘Are you on other meds?’
We don’t need fancy ECGs everywhere. We need awareness. And we need to teach patients: if your heart feels weird after this pill - stop. Don’t wait. Walk to the clinic. Call someone.
Knowledge doesn’t need expensive tech. It just needs to be shared.