“Hydroxyzine has been associated with prolongation of the QT interval and may precipitate torsades de pointes, especially when used in high doses, in overdose, or in combination with other agents that prolong the QT interval. Hydroxyzine should be used with caution in patients who have a history of congenital long‑QT syndrome, other cardiac disease, or who are taking other medications known to prolong the QT interval. Electrolyte abnormalities (e.g., hypokalemia, hypomagnesemia), severe hepatic impairment, and renal impairment may also increase the risk. A thorough cardiac evaluation and ECG monitoring should be considered before and during treatment in high‑risk patients.”
Key Points
| Issue | Details |
|-------|---------|
| Mechanism | Hydroxyzine is a first‑generation H1 antihistamine that can block cardiac potassium channels, leading to delayed ventricular repolarization. |
| Population at Risk | • Congenital long‑QT syndrome
• Structural heart disease (e.g., heart failure, ischemia)
• Electrolyte disturbances (low potassium or magnesium)
• Severe hepatic or renal impairment
• Elderly patients
• Patients on other QT‑prolonging drugs (e.g., macrolide antibiotics, fluoroquinolones, certain anti‑arrhythmics, antipsychotics, antidepressants, some anti‑emetics) |
| Clinical Red Flags | • New or worsening palpitations, syncope, or arrhythmia symptoms
• QT interval > 450 ms in men or > 460 ms in women (baseline or during therapy) |
| Monitoring Recommendations | • Baseline ECG if risk factors present
• Repeat ECG if dose increased or if combined with other QT‑prolonging agents
• Check serum electrolytes (K⁺, Mg²⁺) before and during therapy in high‑risk patients |
| Management | • Reduce or discontinue hydroxyzine if QT prolongation occurs
• Treat electrolyte abnormalities promptly
• Avoid co‑administration of other QT‑prolonging drugs when possible |
| Contraindications | Hydroxyzine is contraindicated in patients with a known hypersensitivity to the drug or in those with known prolonged QT interval due to other causes. |
Practical Take‑Away
- Use at the lowest effective dose and avoid exceeding the recommended daily limit (commonly 100 mg/day for anxiety, up to 200 mg/day for severe itch).
- Check the patient’s medication list for other QT‑prolonging agents and counsel them on the risks.
- If you are treating a patient with significant cardiac history, consider an alternative antihistamine (e.g., cetirizine, loratadine) that carries a lower QT‑prolongation risk.
- For high‑risk patients (e.g., congenital long‑QT, heart failure), an ECG before initiation and periodically thereafter is advised.
Bottom Line
Hydroxyzine can prolong the QT interval and potentially cause torsades de pointes. The Daily Med label advises careful patient selection, ECG monitoring, and avoidance of concomitant QT‑prolonging drugs in susceptible individuals.