Fexofenadine is a second generation, long-lasting selective histamine H1 receptor antagonist with the anti-inflammatory property. Fexofenadine is a highly selective and reversible competitor at peripheral H1 histamine receptors in the gastrointestinal (GI) tract, blood vessels, and bronchial smooth muscle. This agent interferes with mediators release from mast cells either by inhibiting calcium ion influx across mast cell/basophil plasma membrane or by inhibiting intracellular calcium ion release within the cells. In addition, fexofenadine may also inhibit the late-phase allergic reaction by acting on leukotrienes or prostaglandins, or by producing an anti-platelet activating factor effect. Overall, this agent blocks the actions of endogenous histamine, thereby leads to temporary relief of the negative symptoms associated with histamine and achieve effects such as decreased vascular permeability, reduction of pruritus and localized smooth muscle relaxation.
Fexofenadine hydrochloride (Allegra) is an antihistamine drug used in the treatment of hayfever and similar allergy symptoms. It was developed as a successor of an alternative to terfenadine. Fexofenadine, like other second and third-generation antihistamines, does not readily pass through the blood-brain barrier, and so causes less drowsiness than first-generation histamine-receptor antagonists.
Fexofenadine is classified as a second-generation antihistamine because it is less able to pass the blood-brain barrier and cause sedation, compared to first-generation antihistamines.
Mechanism of Action of Fexofenadine
Fexofenadine competes with free histamine for binding at H1-receptors in the GI tract, large blood vessels, and bronchial smooth muscle. This blocks the action of endogenous histamine, which subsequently leads to temporary relief of the negative symptoms (eg. nasal congestion, watery eyes) brought on by histamine. Fexofenadine exhibits no anticholinergic, antidopaminergic, alpha1-adrenergic or beta-adrenergic-receptor blocking effects. Fexofenadine is a second-generation, long lasting H1-receptor antagonist (antihistamine) which has a selective and peripheral H1-antagonist action. Histamine is a chemical that causes many of the signs that are part of allergic reactions, such as the swelling of tissues. Histamine is released from histamine-storing cells (mast cells) and attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cell to be “activated,” releasing other chemicals which produce the effects that we associate with allergy. Fexofenadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of cells by histamine. Unlike most other antihistamines, Fexofenadine does not enter the brain from the blood and, therefore, does not cause drowsiness. Fexofenadine lacks the cardiotoxic potential of terfenadine since it does not block the potassium channel involved in repolarization of cardiac cells.
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Indications of Fexofenadine
- Pollen allergy
- Seasonal allergic rhinitis
- Uncomplicated chronic idiopathic urticaria
- Runny nose
- Sneezing
- Itchy, watery eyes
- Itching of the nose or throat
- Treating hay fever (seasonal allergic rhinitis) in adults and children aged six years and over.
- Treating a long-term itchy nettle-type rash or hives (chronic idiopathic urticaria) in adults and adolescents aged 12 years and over.
Contra Indications of Fexofenadine
- kidney disease with reduction in kidney function
Allergies
- Antihistamines
- Antihistamines – Piperidine
Dosages of Fexofenadine
Strengths : 30mg, 60mg ,180mg Tablets
Oral suspension : 30mg/5mL
Allergic Rhinitis
- 180 mg orally once a day OR 60 mg orally 2 times a day
- Maximum dose: 180 mg/day.
Urticaria
- 180 mg orally once a day OR 60 mg orally 2 times a day
- Maximum dose: 180 mg/day.
Pediatric dosage
Allergic Rhinitis
- 6 months to 2 years: 15 mg orally 2 times a day
- 2 years to 11 years: 30 mg orally 2 times a day
- 12 years and older: 180 mg orally once a day OR 60 mg orally 2 times a day
Urticaria
- 6 months to 2 years: 15 mg orally 2 times a day
- 2 years to 11 years: 30 mg orally 2 times a day
- 12 years and older: 180 mg orally once a day OR 60 mg orally 2 times a day
Side Effects of Fexofenadine
The most common
- Fatigue
- Dry mouth
- Headache
- Drowsiness
- Dizziness
- Weakness
- dry mouth, sore throat, cough;
- muscle pain;
- drowsiness, tired feeling;
- nausea, diarrhea; or
- headache.
- fast, pounding, or uneven heartbeat;
More common
- headache
- fast, pounding, or uneven heartbeat;
- fever, flu symptoms;
- seizure (convulsions); or
- jaundice (yellowing of the skin or eyes).
- dry mouth, sore throat, cough;
- muscle pain;
- drowsiness, tired feeling;
- nausea,
- fever, flu symptoms;
- seizure (convulsions); or
- jaundice (yellowing of the skin or eyes).
Less common
- Dizziness
- dry mouth
- dysmenorrhea, such as, difficult or painful menstruation
- dyspepsia, such as, acid or sour stomach, belching, heartburn, indigestion, stomach discomfort , upset or pain,
- fatigue, such as, unusual tiredness or weakness
- myalgia, such as, joint pain, swollen joints, muscle aching or cramping, muscle pains or stiffness, difficulty in moving
- pharyngitis, such as, body aches or pain, congestion, cough, dryness or soreness ofthroat, fever, hoarseness, runny nose, tender swollen glands in neck, trouble in swallowing, voice changes.
- somnolence, such as, sleepiness or unusual drowsiness
- nausea
Drug Interactions of Fexofenadine
Fexofenadine may interact with following drugs, supplements & may change the efficacy of drugs
- antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
- “azole” antifungals (e.g., itraconazole, ketoconazole, voriconazole)
- benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
- diltiazem
- domperidone
- macrolide antibiotics (e.g., clarithromycin, erythromycin)
- mifepristone
- other antihistamines (e.g., cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine)
- selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, fluoxetine, paroxetine, sertraline)
- sotalol
- “statin” anti-cholesterol medications (e.g., atorvastatin, lovastatin, simvastatin)
- zopiclone
Antacids containing aluminum or magnesium should not be taken within 15 minutes of fexofenadine as they reduce the absorption of fexofenadine by almost 50%. This is not thought to be due to a change in pH (in fact, absorption can actually increase under increasingly alkaline pH), but rather due to the formation of metal complexes with charged/polar moieties on fexofenadine. As suggested by Shehnaza et al (2014), various sites of the molecule are thought to be responsible for this interaction, including the piperidine nitrogen, the carboxylic acid (-COOH) group, and both hydroxyl (-OH) groups. Meals with high amounts of fat decrease the absorption of fexofenadine by about 50%.
Pregnancy & Lactation of Fexofenadine
FDA pregnancy category C
Pregnancy
This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.
Lactation
Fexofenadine passes into breast milk. This medication should not be used by breastfeeding women.
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