fexofenadine

Action and Spectrum

Actions and Spectrum: 

• fexofenadine is a second-generation antihistamine used to treat allergic rhinitis, urticaria, and other allergic conditions. It selectively blocks the H1 histamine receptor, responsible for allergy symptoms, such as itching, sneezing, runny nose, and watery eyes. 

• Unlike first-generation antihistamines, such as diphenhydramine and chlorpheniramine, which can cause sedation and other side effects, fexofenadine is considered non-sedating due to its limited penetration into the central nervous system. 

• fexofenadine has a broad spectrum of activity against various allergic conditions, including seasonal and perennial allergic rhinitis, chronic idiopathic urticaria, and other skin conditions. It also effectively treats itching associated with eczema, atopic dermatitis, and insect bites. 

Drug Interaction

Adverse Reaction

Frequency defined 

>10% 

Vomiting (6-12%) 

1-10% 

Cough (4%) 

URTI (3%) 

Pyrexia (2%) 

Dizziness (2%) 

Pain in extremities (2%) 

Rhinorrhea (1-2%) 

Headache (5-10%) 

Diarrhea (3-4%) 

Back pain (2-3%) 

Dysmenorrhea (2%) 

Stomach discomfort (2%) 

Somnolence (1-3%)  

Post-marketing reports 

Nervousness 

Sleep disorders (insomnia, paranoia) 

Hypersensitivity reactions 

Black Box Warning

Contraindication / Caution

Contraindications/caution: 

Contraindications: 

• Hypersensitivity: fexofenadine should not be used in individuals with known hypersensitivity or allergy to the medication or its ingredients. 

• Renal impairment: The kidneys primarily eliminate fexofenadine, so it should be used cautiously in individuals with renal impairment. 

• Cardiac issues: fexofenadine may cause prolongation of the QT interval, leading to an irregular heartbeat. Therefore, it should be used cautiously in patients with a history of cardiac arrhythmias or other heart conditions. 

• Pregnancy and breast-feeding: The safety of fexofenadine during pregnancy and breastfeeding is not established, and it should only be used if the potential benefits outweigh the risks. 

• Age: fexofenadine should be used cautiously in elderly patients, as they may be more sensitive to its effects. 

Caution: 

• Central Nervous System (CNS) effects: fexofenadine may cause dizziness, drowsiness, or blurred vision. Patients should use caution when driving or operating heavy machinery until they know how the medication affects them. 

• Alcohol and sedatives: fexofenadine can increase the effects of alcohol and sedatives, increasing the risk of drowsiness and impaired coordination. 

• Other medications: fexofenadine can interact with other medications, including certain antibiotics, antifungal drugs, and drugs used to treat HIV. Patients should inform their healthcare provider of all medications before starting fexofenadine. 

• Hepatic impairment: The liver primarily metabolizes fexofenadine, so it should be used cautiously in patients with hepatic impairment. 

• Food interactions: fexofenadine can be taken with or without food, but taking it with food may delay its absorption and reduce its effectiveness. 

Pregnancy / Lactation

Pregnancy consideration: C 

Lactation: Excretion of the drug in human breast milk is unknown 

Pregnancy category: 

Category A: well-controlled and Satisfactory studies show no risk to the fetus in the first or later trimester.   

Category B: there was no evidence of risk to the fetus in animal studies, and there were not enough studies on pregnant women. 

Category C: there was evidence of risk of adverse effects in animal reproduction studies, and no adequate evidence in human studies must take care of potential risks in pregnant women.    

Category D: adequate data with sufficient evidence of human fetal risk from various platforms, but despite the potential risk, and used only in emergency cases for potential benefits.    

Category X: Drugs listed in this category outweigh the risks over benefits. Hence these categories of drugs need to be avoided by pregnant women.    

Category N: There is no data available for the drug under this category 

Pharmacology

Pharmacology: 

fexofenadine is a second-generation antihistamine that selectively blocks the H1 receptor, which is responsible for mediating the effects of histamine. Histamine is a chemical released by cells in response to an allergen that causes symptoms such as itching, sneezing, runny nose, and watery eyes. By blocking the H1 receptor, fexofenadine reduces the symptoms of allergic reactions. 

Pharmacodynamics: 

• The pharmacodynamics of fexofenadine involves its selective antagonism of histamine H1 receptors, predominantly found in smooth muscle, endothelial cells, and the central nervous system. When histamine is released in response to an allergen, it binds to these receptors, causing an increase in intracellular calcium levels and leading to various symptoms such as itching, sneezing, runny nose, and watery eyes. 
• fexofenadine binds selectively and competitively to the H1 receptor, blocking the binding of histamine and preventing the cascade of events that lead to allergic symptoms. This reduces symptoms such as itching, sneezing, runny nose, and watery eyes. 

Pharmacokinetics: 

Absorption 

fexofenadine is rapidly absorbed from the gastrointestinal tract after oral administration, with peak plasma concentrations reached within 2-3 hours for tablets and 1 hour for the suspension. The bioavailability of fexofenadine is approximately 33%, and it can be taken with or without food, although taking it with food may delay its absorption. 

Distribution 

fexofenadine is extensively distributed throughout the body, with a volume of distribution of approximately 5.8 L/kg. It is highly protein-bound (60-70%) to albumin and α1-acid glycoprotein and does not readily cross the blood-brain barrier. 

Metabolism 

The liver metabolizes fexofenadine via the cytochrome P450 (CYP) 3A4 enzyme, with only 5% metabolizing the dose. The metabolites of fexofenadine are pharmacologically inactive, and there is no evidence of accumulation of fexofenadine or its metabolites in plasma after repeated doses. 

Elimination and Excretion 

fexofenadine is excreted primarily in the feces (80%) and, to a lesser extent, in the urine (11%). The elimination half-life of fexofenadine is approximately 14.4 hours in healthy individuals and may be prolonged in patients with renal impairment. fexofenadine is not significantly removed by hemodialysis. 

Adminstartion

Administration: 

fexofenadine is available in different forms, including orally disintegrating tablets and oral suspension. Here are the general guidelines for the administration of fexofenadine: 

• fexofenadine tablets should be taken orally with a glass of water, either with or without food. The tablets should be swallowed whole without crushing or chewing. 
• Oral disintegrating tablets should be placed on the tongue and allowed to disintegrate before swallowing without needing water. 
• The oral suspension should be shaken well before each use and measured using a dosing spoon, dosing syringe, or other device provided by the manufacturer. 

Patient Information Leaflet

Patient information leaflet 

Generic Name: fexofenadine 

Pronunciation: [ FEX-oh-FEN-a-deen ] 

Why do we use fexofenadine? 

fexofenadine is a second-generation antihistamine that is used for the treatment of various allergic conditions, including: 

• Seasonal allergic rhinitis: This type of allergic reaction occurs during certain times of the year, such as during the pollen season. Sneezing, itching, a runny nose, and nasal congestion characterize it. 
• Perennial allergic rhinitis: This is a type of allergic reaction that occurs throughout the year, usually due to exposure to allergens such as dust mites, pet dander, or mold. 
• Chronic idiopathic urticaria: This condition is characterized by the appearance of hives or welts on the skin, which may be accompanied by itching.