QT Prolongation Risk Calculator
Dose Safety Checker
Check if your current dose of citalopram or escitalopram is within safe limits based on FDA/MHRA guidelines.
Why QT Prolongation Matters with Citalopram and Escitalopram
When you take an antidepressant, youâre not just treating sadness or anxiety-youâre changing how your heart beats. Citalopram and escitalopram, two commonly prescribed SSRIs, can stretch the QT interval on an ECG. Thatâs the time your heart takes to recharge between beats. When that interval gets too long, it can trigger a dangerous rhythm called Torsade de Pointes, which can lead to sudden cardiac arrest. This isnât theoretical. In 2011, the FDA and UKâs MHRA issued urgent safety warnings after data showed clear, dose-linked risks. The message was simple: higher doses = higher risk.
How Much Do These Drugs Actually Prolong the QT Interval?
The numbers donât lie. At 20mg daily, citalopram increases the QTc interval by about 8.5 milliseconds. At 40mg, that jumps to 12.6ms. At 60mg-a dose once commonly used-it adds nearly 19ms. For escitalopram, the effect is smaller but still real: 10mg adds 4.5ms, 20mg adds 6.6ms, and 30mg adds over 10ms. These arenât random fluctuations. Theyâre consistent, measurable changes seen in controlled studies.
Whatâs clinically dangerous? An absolute QTc over 500ms, or a rise of 60ms from your baseline. Most people wonât hit those numbers on standard doses. But in older adults, those with kidney or liver problems, or those taking other QT-prolonging drugs, even small increases can push them into danger zone.
Why Citalopram Is Riskier Than Escitalopram
Citalopram is a mix of two mirror-image molecules (enantiomers). Only one of them-the S-enantiomer-is responsible for the antidepressant effect. Escitalopram is just that one molecule. Thatâs why you need half the dose of escitalopram to get the same mood benefit. But hereâs the catch: the other half of citalopram-the R-enantiomer-doesnât help depression, but it does block the same heart channel (hERG) that causes QT prolongation. So youâre getting the same antidepressant effect plus extra cardiac risk.
Studies show citalopram causes about twice the QT prolongation of escitalopram at equivalent antidepressant doses. Thatâs why many clinicians now choose escitalopram when cardiac risk is a concern-even if it costs more. The trade-off is worth it: better safety, same results.
Official Dose Limits You Must Know
After the 2011 safety reviews, regulators didnât just issue warnings-they set hard limits:
- Citalopram: Max 20mg/day for patients over 65. Max 40mg/day for adults under 65. The 60mg dose was pulled from the market.
- Escitalopram: Max 10mg/day for patients over 65. Max 20mg/day for younger adults.
These arenât suggestions. Theyâre rules. Prescribing above these limits now carries legal and clinical liability. The MHRAâs 2011 update made it clear: elderly patients metabolize these drugs slower. Their bodies hold onto more of the drug, increasing exposure and risk. Thatâs why the limits are stricter for older adults.
Whoâs at Highest Risk?
Not everyone taking these drugs is in danger. But certain people need extra caution:
- Patients over 65
- Those with pre-existing long QT syndrome
- People with bradycardia (slow heart rate)
- Those whoâve had a recent heart attack
- Anyone taking other QT-prolonging drugs (like some antibiotics, antifungals, or antiarrhythmics)
- Patients with low potassium or magnesium levels
- People with liver disease-this slows drug clearance
If youâre on citalopram or escitalopram and have even one of these factors, your doctor should check your ECG before starting and again after reaching a stable dose. A simple 10-second test can catch problems before they become emergencies.
How Do Other Antidepressants Compare?
Not all antidepressants carry the same heart risk. Fluoxetine, sertraline, and paroxetine have minimal effect on QT interval. Venlafaxine (an SNRI) is mostly safe at normal doses but can be risky in overdose. Tricyclics like amitriptyline and maprotiline are worse than citalopram-especially at high doses. Thatâs why many doctors avoid them entirely in patients with heart concerns.
Escitalopram sits in a sweet spot: strong antidepressant effect, low cardiac risk, and fewer drug interactions than older options. Itâs become the go-to SSRI for patients with cardiac history, especially in the UK and Europe where regulators took a more cautious approach than the US.
What Should You Do If Youâre Already on One of These Drugs?
If youâre taking citalopram at 40mg or more, talk to your doctor. Donât stop suddenly-you could get withdrawal symptoms. But ask: Is this dose necessary? Could escitalopram at 20mg do the same job with less risk? If youâre over 65 and on citalopram at 20mg or higher, your dose should be lowered.
Get an ECG if you havenât had one in the last 6-12 months, especially if youâre on a higher dose or have other risk factors. Blood tests for potassium and magnesium are also wise. If your QTc is over 450ms (men) or 460ms (women), your doctor should reconsider your medication.
Is It Safe to Keep Taking These Medications?
Yes-for most people, theyâre still safe. The risk of sudden cardiac events from these drugs is low. But low doesnât mean zero. Thatâs why we now have clear rules: stick to the dose limits, screen for risk factors, and monitor when needed. The warnings didnât make these drugs obsolete. They made them safer to use.
Doctors now prescribe them with more awareness. Patients are better informed. And thanks to those 2011 safety reviews, fewer people are being exposed to unnecessary risk. The goal isnât to avoid these medications-itâs to use them wisely.
Final Takeaway: Safer Prescribing Is Possible
You donât have to choose between treating depression and protecting your heart. With proper dosing and screening, citalopram and escitalopram remain effective tools. But you need to know the limits. Citalopram at 40mg is the ceiling. Escitalopram at 20mg is the max. For older adults, half those amounts. If youâre unsure, ask for an ECG. If youâre on another QT-prolonging drug, check for interactions. These arenât scary drugs-theyâre manageable ones. Just donât ignore the numbers. Your heart is counting on it.
