What medical history should Fexofenadine (Allegra) be assessed for?

From the Guidelines

When prescribing fexofenadine, it is crucial to assess for a medical history of kidney disease, as this condition may require dosage adjustments due to altered drug metabolism and elimination 1.

Key Considerations

• Evaluate for a history of cardiac disease, especially conditions that may lead to QT interval prolongation, as certain antihistamines like mizolastine are contraindicated in such cases 1.
• Check for pregnancy or breastfeeding status, as safety data is limited in these populations.
• Review current medications for potential interactions, particularly with drugs that inhibit hepatic metabolism via cytochrome P450, as these can interact with certain antihistamines like mizolastine 1.
• Ask about previous allergic reactions to antihistamines, especially fexofenadine or terfenadine.
• While fexofenadine is generally well-tolerated with minimal sedation compared to older antihistamines, inquire about any history of adverse reactions to antihistamines such as drowsiness, headache, or gastrointestinal effects.

Additional Factors

• Consider the timing of medication to ensure that the highest drug levels are obtained when urticaria is anticipated, as adjustments to the timing can be helpful 1.
• Be aware that the use of sedating antihistamines as monotherapy is now less common due to concerns about reduced concentration and performance, but they can be effective and well-tolerated by some individuals 1.
• Note that the addition of an H2 antihistamine may sometimes give better control of urticaria than an H1 antihistamine taken alone, although this may be more helpful for dyspepsia that may accompany severe urticaria 1.

From the FDA Drug Label

Fexofenadine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.

The medical history of renal impairment and pregnancy should be assessed when using fexofenadine.

• Renal function should be monitored in elderly patients due to the increased risk of toxic reactions.
• Fexofenadine should be used with caution in pregnant women, only if the potential benefit justifies the potential risk to the fetus 2.

From the Research

Medical History Assessment for Fexofenadine

To assess the medical history for fexofenadine, several factors should be considered:

• Renal function: Fexofenadine is primarily excreted unchanged in the urine, and its clearance is reduced in patients with renal impairment 3, 4. Patients with end-stage renal disease (ESRD) have shown a 63% decline in oral clearance of fexofenadine 4.
• P-glycoprotein (Pgp) activity: Fexofenadine is a substrate of Pgp, and its pharmacokinetics can be affected by Pgp inhibitors 3, 5.
• Cardiovascular history: Although fexofenadine has been shown to have no significant effect on the corrected QT interval (QTc) 6, patients with a history of cardiovascular disease should be monitored closely.
• Diabetic kidney disease (DKD): Fexofenadine has been investigated as a potential treatment for DKD, and its use may be beneficial in reducing urinary albumin to creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) decline 7.
• Drug interactions: Fexofenadine can interact with other drugs, such as cyclosporin A and rifampicin, which can inhibit its hepatic uptake 5. Grapefruit juice and St John's Wort can also affect fexofenadine pharmacokinetics 4.

Key Considerations

When assessing the medical history for fexofenadine, the following key considerations should be taken into account:

• Patients with renal impairment may require dose adjustments or closer monitoring.
• Patients taking Pgp inhibitors may experience increased fexofenadine exposure.
• Patients with a history of cardiovascular disease should be monitored closely, although fexofenadine is not expected to have a significant effect on QTc.
• Patients with DKD may benefit from fexofenadine treatment, but further studies are needed to confirm its efficacy.
• Patients taking other medications that can interact with fexofenadine should be monitored closely for potential drug interactions.