From the Guidelines
If you suspect an Allegra (fexofenadine) overdose, seek immediate medical attention by calling poison control at 1-800-222-1222 or going to the emergency room, as fexofenadine has been reported to cause torsades de pointes (TdP) in rare cases, although the incidence is extremely low 1.
Overview of Fexofenadine Overdose
Allegra is generally considered safe, and serious overdoses are rare. Symptoms of an overdose may include drowsiness, headache, dry mouth, dizziness, or gastrointestinal upset. Most cases can be managed with supportive care and monitoring.
Mechanism of Action and Dosage
Fexofenadine is a second-generation antihistamine that works by blocking histamine receptors without significantly crossing the blood-brain barrier, which is why it causes less sedation than older antihistamines. The typical adult dose is 60mg twice daily or 180mg once daily, with lower doses for children and those with kidney problems.
Management of Overdose
If you regularly take Allegra and miss a dose, take it when you remember, but don't double up if it's almost time for your next dose. Always store medication out of reach of children to prevent accidental ingestion. In the event of an overdose, it is crucial to monitor the patient's ECG for signs of QT prolongation and TdP, as these can be life-threatening complications 1.
Key Considerations
- The risk of TdP with fexofenadine is extremely low, but it is essential to be aware of this potential complication, especially in patients with underlying heart conditions or those taking other medications that can prolong the QT interval 1.
- The Arizona Center for Education & Research on Therapeutics maintains an updated list of drugs that have a risk of causing TdP on their World Wide Web site at www.qtdrugs.org, which can be a valuable resource for healthcare professionals 1.
From the FDA Drug Label
Reports of fexofenadine hydrochloride overdose have been infrequent and contain limited information. However, dizziness, drowsiness, and dry mouth have been reported In the event of overdose, consider standard measures to remove any unabsorbed drug. Symptomatic and supportive treatment is recommended.
The effects of an overdose of Allegra (fexofenadine) may include:
- Dizziness
- Drowsiness
- Dry mouth Treatment for overdose should focus on symptomatic and supportive care, as well as measures to remove any unabsorbed drug 2.
From the Research
Effects of Allegra (Fexofenadine) Overdose
- The evidence suggests that fexofenadine is not associated with QT prolongation, TdP, or other ventricular arrhythmias 3.
- However, one case of ventricular fibrillation during fexofenadine administration has been reported in a man with a pre-existing long QT interval 4.
- In general, the management of drug overdosage involves maintaining the patient's airway, ventilation, and circulation, while the drug is excreted 5, 6.
- Fexofenadine has a high margin of safety and is well tolerated in subjects with renal or hepatic impairment, in children and the elderly 7.
- No clinically significant drug interactions have been identified, and fexofenadine is not associated with cardiotoxicity 7.
Overdose Symptoms and Treatment
- The manifestations of drug overdose can be complex and result in a variety of physiological effects, including aspiration, hypoventilation, hypoxia, hypotension, and cardiac arrhythmias 5, 6.
- Treatment options for overdose situations may involve observation alone, as the risk of treating with an additional pharmacological agent may outweigh the potential benefit 6.
- Invasive procedures such as gastric lavage and whole-bowel irrigation are not appropriate for the majority of overdose situations, and the use of oral activated charcoal may be of limited value 6.