Fexofenadine

Fexofenadine is a Second generation Antihistaminic and Selective H1 Receptor antagonistbelonging to anti-histaminic class.

Fexofenadine is an antihistamine medication used to treat symptoms of allergies such as hay fever, hives, and itchy skin. It works by blocking the effects of histamine, a natural substance produced by the body that causes allergic symptoms.

Fexofenadine is absorbed quickly and efficiently after oral administration, with peak blood levels occurring about 1-3 hours after ingestion. It is rapidly absorbed from the small intestine, and its absorption is not significantly affected by food or the presence of other drugs. The bioavailability of fexofenadine, which is the amount of drug that enters the bloodstream and is available for use, is approximately 33-70%, depending on the formulation and dosage. fexofenadine is distributed throughout the body and is highly protein-bound in the blood, meaning that it binds strongly to proteins in the bloodstream. This protein binding can affect the extent to which the drug is distributed to different tissues in the body. Fexofenadine is metabolized in the liver by the enzyme cytochrome P450 3A4 (CYP3A4), and is primarily eliminated from the body in the urine and feces. The elimination half-life of fexofenadine is approximately 14 hours, which means that it takes about 14 hours for half of the drug to be eliminated from the body.

Tmax of Fexofenadine is approximately 1 to 3 hours after oral administration.

Cmax of Fexofenadine after a single oral dose of 5 mg is approximately 270 ng/mL

Fexofenadine shows common side effects like Headache, Drowsiness, Nausea,Dry mouth, Fatigue, Dizziness, Difficulty sleeping (insomnia), Upset stomach, Diarrhea

Fexofenadine is available in tablets, suspension and capsule.

Fexofenadine is available in India, Germany, Canada, France.

The mechanism of action of fexofenadine is to selectively antagonize H1 receptors on the surface of cells in different organ systems. It is a second-generation H1 receptor blocker. Fexofenadine also affects inflammatory mediators.

Fexofenadine is available in the form of tablets, suspension and capsule.

• Tablets: Fexofenadine tablets should be taken with or without water.

Fexofenadine is used in the treatment of Seasonal allergic rhinitis, Perennial allergic rhinitis, Chronic urticaria, Allergic conjunctivitis.

Fexofenadine is an effective medication for relieving symptoms of allergies, such as sneezing, itching, runny nose, and congestion. It works by blocking the action of histamine, a chemical that causes allergic symptoms, and can provide relief within 1 hour of taking the medication.

Fexofenadine is approved for use in the following clinical indications

1.Seasonal allergic rhinitis: Fexofenadine can be used to relieve symptoms such as sneezing, itching, runny nose, and congestion that occur in response to seasonal allergens, such as pollen, grass, and mold.

2.Perennial allergic rhinitis: Fexofenadine can be used to relieve symptoms of allergic rhinitis that occur year-round, such as those caused by dust mites, pet dander, and other indoor allergens.

3.Chronic urticaria: Fexofenadine can be used to relieve symptoms of chronic hives, such as itching, swelling, and redness, that last for more than 6 weeks and are not caused by an allergic reaction.

4.Allergic conjunctivitis: Fexofenadine can be used to relieve symptoms of allergic conjunctivitis, such as redness, itching, and watering of the eyes, that are caused by allergens such as pollen and dust.

Fexofenadine is available in the dosage strength of

• Tablets: 60mg, 120mg, 240mg.
• Suspension: 60mg/ml
• Capsule: 60mg.

Fexofenadine is available in the form of

• Tablets: Fexofenadine tablets are available in strengths of 60mg, 120mg, 240mg and are taken orally with or without food, usually once daily.
• Oral solution: Fexofenadine oral solution is available in a concentration of 60mg/mland is taken orally with or without food, usually once daily.

Dosage Adjustment in Kidney Patient

• For patients with a CrCl of 30 to 50 mL/min/1.73 m2: The recommended dose is 60 mg twice daily.

• For patients with a CrCl less than 30 mL/min/1.73 m2: The recommended dose is 60 mg once daily.

• For patients on hemodialysis with a CrCl less than 10 mL/min/1.73 m2: The recommended dose is 60 mg every other day.

• It is important to note that fexofenadine should be used with caution in patients with severe kidney disease, and the dose should be adjusted based on the patient's individual needs and response to the medication. Patients with kidney disease should always consult their healthcare provider before starting or adjusting the dose of any medication.

Dosage Adjustment for Pediatric Patients

• For children aged 6 to 11 years: The recommended dose is 30 mg twice daily.
• For children aged 2 to 5 years: The recommended dose is 15 mg twice daily.

• For children under 2 years of age: Fexofenadine is not recommended as its safety and effectiveness have not been established in this age group

Take after eating and with a full glass of water to decrease gastric upset.

• Allergy: Fexofenadine should not be used in patients who have a known hypersensitivity to the medication or to any of its ingredients.
• Renal impairment: Fexofenadine should be used with caution in patients with impaired kidney function, as the medication is primarily eliminated from the body through the kidneys.
• Hepatic impairment: Fexofenadine should be used with caution in patients with impaired liver function, as the medication is metabolized in the liver.
• Pregnancy and breastfeeding: The safety of fexofenadine during pregnancy and breastfeeding has not been established, and its use in these populations should be determined by a healthcare provider.
• Concurrent use of certain medications: Fexofenadine should not be used with certain medications, such as erythromycin and ketoconazole, as these medications can increase the levels of fexofenadine in the body and increase the risk of adverse effects.

Fexofenadine is a medication that should be used with caution and under the guidance of a healthcare provider. Here are some precautions and warnings to be aware of when using Fexofenadine:

• Use only as directed: Fexofenadine should be used only as directed by a healthcare provider, and at the lowest effective dose for the shortest possible duration.
• Risk of respiratory infections: Long-term use of Fexofenadine may increase the risk of respiratory infections, such as pneumonia or tuberculosis. It is important to monitor for signs of infection and to use caution when using Fexofenadine in individuals with a history of these infections.
• Adrenal suppression: Fexofenadine may suppress the function of the adrenal glands, which can result in a variety of symptoms, including weakness, fatigue, and weight loss. Individuals who have been taking Fexofenadine for a prolonged period of time should be gradually weaned off the medication under the guidance of a healthcare provider.
• Ocular effects: Fexofenadine may cause ocular effects such as cataracts or glaucoma. It is important to have regular eye exams while taking Fexofenadine, particularly for individuals who are using high doses or have a history of eye problems.
• Growth suppression in children: Long-term use of Fexofenadine may suppress growth in children. Children who are taking Fexofenadine should be monitored regularly for growth and development.
• Use during pregnancy and breastfeeding: Fexofenadine is classified as a pregnancy category C medication, which means that it may not be safe to use during pregnancy. It is also not known whether Fexofenadine passes into breast milk. Women who are pregnant or breastfeeding should talk to their healthcare provider before using Fexofenadine.

Fexofenadine may cause liver problems, and using it with substantial quantities of ethanol may increase that risk.

Fexofenadine is present in breast milk.

Concentrations of Fexofenadine in breast milk increase with supplementation. When used as a dietary supplement, the recommended dietary allowance of Fexofenadine is increased in breastfeeding patients compared to non-breastfeeding patients. Doses of Fexofenadine for the treatment of dyslipidemias are greater than those used as a dietary supplement. Due to the potential for serious adverse reactions in the breastfed infant (including hepatoxicity), the manufacturer recommends that breastfeeding be discontinued when Fexofenadine is used for treatment of dyslipidemias.

Oral formulations should be administered on an empty stomach with water (at least 1 hour before or 2 hours after meals, milk, or other dairy products). Maintain fluid intake to ensure adequate hydration and urinary output.

• Less Common Adverse effects

Allergic reactions, including hives, itching, or difficulty breathing Eye problems, such as cataracts or glaucoma (with long-term use) Growth suppression in children (with long-term use) High blood sugar levels Increased risk of infections, including fungal infections of the mouth or throat (thrush) Mood changes or behavioral changes, such as agitation or aggression Osteoporosis or bone fractures (with long-term use) Slow wound healing

• Rare Adverse effects

Adrenal suppression (with long-term use) Anaphylaxis (a severe and life-threatening allergic reaction) Cushing's syndrome (with long-term use) Decreased immune system function (with long-term use) Hyperglycemia (high blood sugar levels) Hypokalemia (low levels of potassium in the blood) Hypersensitivity reactions (such as rash or angioedema) Ocular toxicity (such as increased intraocular pressure, cataracts, or glaucoma with long-term use) Psychiatric effects (such as mood changes or suicidal thoughts)

Fexofenadine is generally considered to have a low potential for drug interactions due to its low affinity for cytochrome P450 enzymes and minimal plasma protein binding. However, it is still important to be aware of the following potential drug interactions: Fexofenadine may enhance the sedative effects of central nervous system (CNS) depressants, such as alcohol, benzodiazepines, and opioids. Fexofenadine may increase the plasma concentrations of drugs that are substrates of the organic cation transporter 2 (OCT2), such as metformin and dofetilide. Fexofenadine may also interact with certain antibiotics, such as erythromycin and clarithromycin, which may increase its plasma concentrations.

The common side effects of Fexofenadine include the following :

Irritation in the nose or throat (with nasal spray) Hoarseness or changes in voice (with inhalation) Headache Nausea Cough Sore throat Runny or stuffy nose Sinus pain Dry mouth or throat Skin rash or itching (with topical use)

Symptoms: Tachycardia, tremor, hyperactivity, metabolic effects (e.g. hypokalaemia, lactic acidosis), headache, nervousness, dry mouth, palpitations, dizziness, fatigue, malaise, insomnia, arrhythmias, anginal pain, seizures. Children may experience nausea, vomiting, hyperglycaemia when taken orally.

Management: Symptomatic treatment. Monitor serum K and lactate levels. May give cardioselective β-blocker with caution. May give oral or IV potassium for hypokalaemia as needed.

Pharmacodynamic

• Fexofenadine Fexofenadine is a second-generation antihistamine that works by blocking the action of histamine in the body. Histamine is a chemical released by the body in response to allergens and other triggers, and it is responsible for causing the symptoms of allergies, such as itching, sneezing, and runny nose. Fexofenadine is a selective antagonist of the histamine H1 receptor. It binds to the receptor and prevents histamine from exerting its effects, thereby reducing or eliminating allergy symptoms. Fexofenadine is also believed to have a low potential for causing sedation or other central nervous system effects, unlike some first-generation antihistamines. This is because fexofenadine does not readily cross the blood-brain barrier, which separates the bloodstream from the brain and spinal cord. Fexofenadine has a rapid onset of action, with effects observed within 1 hour of administration. The medication is also long-acting, with a duration of action of up to 24 hours.

Pharmacokinetics

• Absorption: Fexofenadine is absorbed quickly and efficiently after oral administration, with peak blood levels occurring about 1-3 hours after ingestion. It is rapidly absorbed from the small intestine, and its absorption is not significantly affected by food or the presence of other drugs
• Distribution: Fexofenadine has a relatively high distribution volume, indicating that it is widely distributed throughout the body. The medication is approximately 60-70% bound to plasma proteins.
• Metabolism: Fexofenadine is extensively metabolized in the liver by O-dealkylation to form the inactive metabolite, descarboethoxyloratadine.
• Excretion: The elimination half-life of Fexofenadine is about 8-10 hours in adults and may be prolonged in patients with impaired renal function. Fexofenadine and its metabolites are primarily eliminated in the urine, with a small amount eliminated in the feces.

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