FEXOFENADINE HCL

Fexofenadine HCl is an antihistamine medication that comes in a capsule or tablet form. 
Fexofenadine HCl treats and prevents symptoms of allergies like itchy eyes, sneezing and hives. 
Fexofenadine HCl works by blocking histamine in your body.

CAS Number: 138452-21-8
Molecular Formula: C32H40ClNO4
Molecular Weight: 538.12

Synonyms: FEXOFENADINE HYDROCHLORIDE, 153439-40-8, FEXOFENADINE HCL, Allegra Allergy, Allegra Hives, MDL 16,455A, Children's Allegra Hives, MDL-16455A, Children's Allegra Allergy, DTXSID5048716, 2S068B75ZU, DTXCID2028642, Benzeneacetic acid, 4-(1-hydroxy-4-(4-(hydroxydiphenylmethyl)-1-piperidinyl)butyl)-alpha,alpha-dimethyl-, hydrochloride, Allergillic, IAllergy Relief, Children Allergy, Wal-fex, basic care allergy, Fex-Allergy Relief, Dye Free Wal Fex, Telfast 30, Curist Hives Relief, Allegra Hives 24hr, Telfast 120, Telfast 180, Dg Health Aller Ease, 12HR Allergy Relief, 24HR Allergy Relief, Good Sense Aller Ease, Allergy Relief children, Childrens Allegra Allergy, Allegra Allergy 24 hour, ALLERGY 24-HR, Exchange Select Aller Ease, berkley jensen allergy relief, Kirkland Signature Aller Fex, Fexofenadine Hydrochloride Oral, Allegra Allergy, Travel BASIX, Crcle Fexofenadine Hydrochloride, Fexofenadine Hydrochloride 60 mg, Sunmark Fexofenadine Hydrochloride, Fexofenadine Hydrochloride 180 mg, Dye Free Wal Fex childrens allergy, Childrens Fexofenadine Hydrochloride, up and up non drowsy allergy relief, FEXOFENADINE HYDROCHLORIDE HIVES, FEXOFENADINE HYDROCHLORIDE ALLERGY, Childrens Fexofenadine Hydrochloride Allergy, CHILDREN'S FEXOFENADINE HYDROCHLORIDE HIVES, CHILDREN'S FEXOFENADINE HYDROCHLORIDE ALLERGY, 2-(4-((1RS)-1-Hydroxy-4-(4-(hydroxydiphenylmethyl)piperidin-1-yl)butyl)phenyl)-2-methylpropanoic acid monohydrochloride, NSC169453, NSC78248, Allegra, 138452-21-8, 2-(4-(1-Hydroxy-4-(4-(hydroxydiphenylmethyl)piperidin-1-yl)butyl)phenyl)-2-methylpropanoic acid hydrochloride, C32H40ClNO4, Fexofenadine (hydrochloride), MFCD00865710, Terfenadine carboxylate hydrochloride, Fexofenidine hydrochloride, 2-(4-{1-hydroxy-4-[4-(hydroxydiphenylmethyl)piperidin-1-yl]butyl}phenyl)-2-methylpropanoic acid hydrochloride, 153439-40-8 (HCl), 2-[4-[1-hydroxy-4-[4-[hydroxy(diphenyl)methyl]piperidin-1-yl]butyl]phenyl]-2-methylpropanoic acid, hydrochloride, MDL 16455 hydrochloride, SMR000718798, CAS-153439-40-8, Terfenidine carboxylate hydrochloride, NCGC00015453-05, Altiva, UNII-2S068B75ZU, Carboxyterfenadine hydrochloride, Allegra Flash, SR-01000075889, Allegra OD, Fexofenadine hydrochloride [USAN], Fexofenadine hydrochloride,  2-[4-[(1RS)-1-hydroxy-4-[4-(hydroxydiphenylmethyl)piperidin-1-yl]butyl]phenyl]-2-methylpropanoic acid hydrochloride,  Allegra,  MDL 16455A,  Telfast,  Telfast BD, Allegra (TN), Fexofenadine hydrochloride [USAN:USP], Fexofenadina cloridrato, Cloridrato de Fexofenadina, Clorhidrato de fexofenadina, Fexofenadine Hydrochloride?, Chlorhydrate de fexofenadine, SCHEMBL40914, MLS001306422, MLS001332493, MLS001332494, Fexofenadine Impurity Standard, SPECTRUM1504179, CHEBI:5051, HY-B0801AR, orb1308540, orb1308541, CHEMBL1200618, HY-B0801A, MSK10596A, HMS5081H08, MDL 16455A, Pharmakon1600-01504179, Tox21_113125, NSC758678, s3208, Fexofenadine HCl - Bio-X trade mark, AKOS015907422, Tox21_113125_1, AB07499, CCG-213275, CS-4483, Fexofenadine hydrochloride (JP18/USP), FEXOFENADINE HYDROCHLORIDE [MI], FF23282, KS-1057, NC00724, NSC 758678, NSC-758678, Fexofenadine (hydrochloride) (Standard), FEXOFENADINE HYDROCHLORIDE [JAN], NCGC00015453-02, NCGC00015453-08, NCGC00092389-01, NCGC00095906-01, NCGC00095906-02, (+-)-p-(1-Hydroxy-4-(4-(hydroxydiphenylmethyl)piperidino)butyl)-alpha-methylhydratropic acid hydrochloride, AC-24745, BF164454, FEXOFENADINE HYDROCHLORIDE [MART.], FEXOFENADINE HYDROCHLORIDE [VANDF], FEXOFENADINE HYDROCHLORIDE [USP-RS], FEXOFENADINE HYDROCHLORIDE [WHO-DD], Fexofenadine hydrochloride, >98% (HPLC), DB-043190, F0698, M-016455-O, SW199568-2, EN300-52502, BIM-0050472.0001, D00671, FEXOFENADINE HYDROCHLORIDE [ORANGE BOOK], FEXOFENADINE HYDROCHLORIDE [EP MONOGRAPH], FEXOFENADINE HYDROCHLORIDE [USP IMPURITY], FEXOFENADINE HYDROCHLORIDE [USP MONOGRAPH], SR-01000075889-6, ALLEGRA-D COMPONENT FEXOFENADINE HYDROCHLORIDE, Q27255526, Fexofenadine hydrochloride 100 microg/mL in Acetonitrile, Z754918912, Fexofenadine hydrochloride, European Pharmacopoeia (EP) Reference Standard, Fexofenadine HCl, Pharmaceutical Secondary Standard,  Certified Reference Material, Fexofenadine hydrochloride, United States Pharmacopeia (USP) Reference Standard, (+/-)-P-(1-HYDROXY-4-(4-(HYDROXYDIPHENYLMETHYL)PIPERIDINO)BUTYL)-.ALPHA.-METHYLHYDRATROPIC ACID, HYDROCHLORIDE, 2-(4-{1-hydroxy-4-[4-(hydroxy-diphenyl-methyl)-piperidin-1-yl]-butyl}-phenyl)-2-methyl-propionic acid, 2-[4-[1-hydroxy-4-[4-[hydroxy(diphenyl)methyl]-1-piperidyl]butyl]phenyl]-2-methyl-propanoic acid, hydrochloride, 4-[(4-(hydroxydiphenylmethyl)-1-piperidinyl]-1-hydroxybutyl]-alpha,alpha-dimethylbenzeneacetic acid hydrochloride, 4-[1-Hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]-?,?-dimethylbenzeneacetic acid hydrochloride, Carboxyterfenadine hydro chloride, Terfenadinecarboxylate hydrochloride, 4-[1-Hydroxy-4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]butyl]-a,a-dimethylbenzeneacetic acid hydrochloride, Carboxyterfenadine hydro chloride, Terfenadinecarboxylate hydrochloride, 4-[4-[4-(Hydroxydiphenylmethyl)-1-pieridinyl]-1-hydroxybutyl]-alpha,alpha-dimethylbenzeneacetic acid hydrochloride, 4-[4-[4-(hydroxydiphenylmethyl)-1-piperidinyl]-1-hydroxybutyl]-alpha,alpha-dimethylbenzeneacetic acid hydrochloride, BENZENEACETIC ACID, 4-(1-HYDROXY-4-(4-(HYDROXYDIPHENYLMETHYL)-1-PIPERIDINYL)BUTYL)-.ALPHA.,.ALPHA.-DIMETHYL-, HYDROCHLORIDE, (+/-)-, Benzeneacetic acid, 4-(1-hydroxy-4-(4-(hydroxydiphenylmethyl)-1-piperidinyl)butyl)-alpha,alpha-dimethyl-, hydrochloride, (+-), terfenidine carboxylate hydrochloride, ALPHA,ALPHA-DIMETHYL-4-[1-HYDROXY-4-[4-(HYDROXYDIPHENYLMETHYL)-1-PIPERIDINYL]BUTYL]-BENZENEACETIC ACID HYDROCHLORIDE, 2-[4-[1-hydroxy-4-[4-(hydroxy-diphenyl-methyl)-1-piperidyl]-butyl]phenyl]-2-methyl-propanoic acid hydrochloride, FEXOFENADINE HCL, CARBOXYTERFENADINE,TERFENADINECARBOXYLATE, Fexofendine Hcl, 2-[4-[1-hydroxy-4-[4-[hydroxy(diphenyl)methyl]-1-piperidinyl]butyl]phenyl]-2-methylpropanoic acid, (+)-4-(1-HYDROXY-4-(4-HYDROXYDIPHENYLMETHYL)1-PIPERIDINYL)-BUTYL)a,a-(DIMETHYL BENZENE ACETIC ACID HYDROCHLORIDE

Fexofenadine HCl, or fexofenadine hydrochloride, is a second-generation antihistamine that is commonly used to relieve the symptoms of seasonal allergic rhinitis, such as sneezing, runny nose, itchy eyes, and nasal congestion, as well as to treat chronic idiopathic urticaria, which is characterized by persistent hives and itching. 
Fexofenadine HCl works by selectively blocking peripheral H1 histamine receptors, which are responsible for the typical allergic responses in the body, without significantly crossing the blood-brain barrier, making it less likely to cause the drowsiness commonly associated with first-generation antihistamines.

Chemically, Fexofenadine HCl is the hydrochloride salt of fexofenadine, which enhances its solubility and stability in pharmaceutical formulations, allowing it to be effectively absorbed when taken orally in tablet, capsule, or liquid form. 
Its onset of action is typically within one hour after administration, and its effects can last for 24 hours, which makes once-daily dosing convenient for patients. 
Fexofenadine HCl is also considered to have a favorable safety profile, with a low incidence of serious side effects, although some individuals may experience mild reactions such as headache, nausea, or fatigue.

The metabolite of seldane (terfenadine), fexofenadine, was launched in the USA. 
A histamine H1 receptor antagonist, Fexofenadine HCl is more effect than its parent compound without the associated side-effects.
Fexofenadine HCl, sold under the brand name Allegra among others, is an antihistamine medication used in the treatment of allergy symptoms such as allergic rhinitis and urticaria.

Therapeutically, Fexofenadine HCl is a selective peripheral H1 blocker. 
It 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.

Fexofenadine HCl was patented in 1979 and came into medical use in 1996.
Fexofenadine HCl is on the World Health Organization's List of Essential Medicines.
Fexofenadine HCl has been manufactured in generic form since 2011.

Fexofenadine HCl was the 257th most commonly prescribed medication in the United States, with more than 1 million prescriptions.
Fexofenadine HCl works selectively on histamine-1 receptors that are located in our body, but not in our central nervous system - these are called peripheral histamine receptors. 
Because it acts on these receptors, Fexofenadine HCl is much less likely to cause drowsiness compared with some older antihistamines.

Histamine is a chemical that is released by mast cells in response to an allergen, and it is responsible for many allergy symptoms, such as watery eyes, a runny nose, sneezing, and itching. 
Fexofenadine HCl binds to histamine receptors and prevents histamine from having an effect on those receptors, which reduces allergy symptoms.

Fexofenadine HCl prevents and treats allergy symptoms, such as red, itchy eyes, sneezing, a runny or stuffy nose, or hives. 
Fexofenadine HCl works by blocking histamine, a substance released by the body during an allergic reaction. 
It belongs to a group of medications called antihistamines.

The drug is widely marketed under various brand names, including Allegra, Telfast, and other regional formulations, and is often available over-the-counter in many countries for allergy relief. 
In addition to its clinical use in humans, Fexofenadine HCl has been studied in combination with other medications, such as decongestants, to provide broader symptomatic relief from allergy symptoms. 

Its pharmacokinetic properties, including minimal central nervous system penetration and renal and hepatic elimination, contribute to its effectiveness and reduced sedative effects compared with older antihistamines.
Fexofenadine HCl is an over-the-counter second-generation antihistamine used in the treatment of various allergic symptoms.

Fexofenadine HCl is selective for the H1 receptor, carries little-to-no activity at off-targets, and does not cross the blood-brain barrier - this is in contrast to previous first-generation antihistamines, such as diphenhydramine, which readily bind to off-targets that contribute to side effects such as sedation.
Fexofenadine HCl is the major active metabolite of terfenadine and is administered as a racemic mixture in which both enantiomers display approximately equivalent antihistamine activity.

Fexofenadine HCl relieves allergy symptoms by antagonizing the actions of histamine, an endogenous compound predominantly responsible for allergic symptomatology.
The relatively long duration of action of fexofenadine (approximately 24 hours)7 allows for once or twice daily dosing, and its rapid absorption allows for an onset of action within 1-3 hours. 
Fexofenadine HCl should not be taken with fruit juice, as this may impair its absorption.

The H1 histamine receptor is responsible for mediating hypersensitivity and allergic reactions. 
Exposure to an allergen results in degranulation of mast cells and basophils, which then release histamine and other inflammatory mediators. 
Histamine binds to, and activates, H1 receptors, which results in the further release of pro-inflammatory cytokines, such as interleukins, from basophils and mast cells. 

These downstream effects of histamine binding are responsible for a wide variety of allergic symptoms, such as pruritus, rhinorrhea, and watery eyes.
Fexofenadine HCl is rapidly absorbed following oral administration and its absolute bioavailability is approximately 33%.
The Tmax following oral administration is approximately 1-3 hours.

The steady-state AUCss(0-12h) and Cmax following twice daily dosing of 60mg are 1367 ng/mL.h and 299 ng/mL, respectively.
Fexofenadine HCl is decreased by >20% when coadministered with fruit juices (e.g. apple, orange, grapefruit) due to their inhibition of OATP transporters - for this reason, prescribing information recommends administering fexofenadine only with water.
Similarly, coadministration of fexofenadine with a high-fat meal appears to decrease AUC and Cmax by >20%.

Fexofenadine HCl comes as a tablet and a suspension (liquid) to take by mouth. 
It is usually taken with water once or twice a day. 
Fexofenadine HCl will work better if it is not taken with fruit juices such as orange, grapefruit, or apple juice. 

Take fexofenadine at around the same time(s) every day. 
Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. 
Take fexofenadine exactly as directed, do not take more or less of it or take it more often than prescribed by your doctor.

storage temp.: −20°C
solubility: DMSO: 32 mg/mL, soluble
form: solid
color: white

Fexofenadine HCl is a selective peripheral H1 receptor antagonist. Blockage prevents the activation of the H1 receptors by histamine, preventing the symptoms associated with allergies from occurring. 
Fexofenadine HCl does not readily cross the blood–brain barrier, so is less likely to cause drowsiness in comparison to other antihistamines that readily cross that barrier (i.e., first-generation antihistamines such as diphenhydramine). 

In general, fexofenadine takes about an hour to take effect, though this may be affected by the choice of dosage form and the presence of certain foods.
Fexofenadine HCl is used to relieve the allergy symptoms of seasonal allergic rhinitis (''hay fever''), including runny nose; sneezing; red, itchy, or watery eyes; or itching of the nose, throat, or roof of the mouth in adults and children 2 years of age and older. 

Fexofenadine HCl is also used to relieve symptoms of urticaria (hives; red, itchy raised areas of the skin), including itching and rash in adults and children 6 months of age and older. 
Fexofenadine HCl is in a class of medications called antihistamines. 
It works by blocking the effects of histamine, a substance in the body that causes allergy symptoms.

For the treatment of allergic rhinitis, fexofenadine is similarly effective to cetirizine, but is associated with less drowsiness than cetirizine.
Fexofenadine HCl was also shown to inhibit histamine-induced wheal and flare to a significantly greater degree than loratadine or desloratadine, but was slightly less effective than levocetirizine.

Fexofenadine HCl at doses above 120 mg a day does not appear to provide additional efficacy in the treatment of allergic rhinitis.
The most common side effects include headache, back and muscle pain, miosis or pinpoint pupils, nausea, drowsiness, and menstrual cramps. 
Anxiety and insomnia have also been rarely reported. 

The most common side effects demonstrated during clinical trials were cough, upper respiratory tract infection, fever, and otitis media for children ages 6 to 11 and fatigue for children ages 6 months to 5 years.
The safety profile of fexofenadine is quite favorable, as no cardiovascular or sedative effects have been shown to occur even when taking 10 times the recommended dose.

Research on humans ranges from a single 800-mg dose, to a twice-daily, 690-mg dose for a month, with no clinically significant adverse effects, when compared to a placebo. 
No deaths occurred in testing on mice, at 5000 mg/kg body weight, which is 110 times the maximum recommended dose for an adult human.
If an overdose were to occur, supportive measures are recommended. 

Theoretically, an overdose could present as dizziness, dry mouth, and/or drowsiness, consistent with an exaggeration of the usual side effects.
Hemodialysis does not appear to be an effective means of removing fexofenadine from the blood.

Taking erythromycin or ketoconazole while taking fexofenadine does increase the plasma levels of fexofenadine, but this increase does not influence the QT interval. 
The reason for this effect is likely due to transport-related effects, specifically involving p-glycoprotein (p-gp).
Both erythromycin and ketoconazole are inhibitors of p-gp, a transporter protein involved in preventing the intestinal absorption of fexofenadine. 

When p-gp is inhibited, Fexofenadine HCl may be better absorbed by the body, increasing its plasma concentration by more than intended.
Fexofenadine HCl is not to be taken with apple, orange, or grapefruit juice because they could decrease absorption of the drug. 
Therefore, it should be taken with water.

Grapefruit juice can significantly reduce the plasma concentration of Fexofenadine HCl.
The older antihistaminic agent terfenadine was found to metabolize into the related carboxylic acid, Fexofenadine HCl. 
Fexofenadine HCl was found to retain all of the biological activity of its parent while giving fewer adverse reactions in patients, so terfenadine was replaced in the market by its metabolite.

Fexofenadine HCl was originally synthesized in 1993 by Massachusetts-based biotechnology company Sepracor, which then sold the development rights to Hoechst Marion Roussel (now part of Sanofi-Aventis), and was later approved by the U.S. Food and Drug Administration (FDA) in 1996. 
Albany Molecular Research Inc. (AMRI) holds the patents to the intermediates and production of fexofenadine HCl, along with Roussel. 

Fexofenadine HCl is indicated for the relief of symptoms associated with seasonal and perennial allergic rhinitis, in adults and children 12 years of age and over. 
Symptoms treated effectively include sneezing, rhinorrhea, lacrimation, itchy, red eyes and itchy nose/palate/throat. 
Fexofenadine HCl improves health-related quality of life and work/activity productivity. 

Uses Of Fexofenadine HCl:
Fexofenadine HCl is a selective, specific H1 antagonist that is structurally related to the butyrophenone tranquilizer haloperidol. 
Fexofenadine HCl is the active carboxylic acid metabolite of terfenadine (no longer commercially available in the United States). 
Fexofenadine HCl binds mainly to the peripheral H1 receptors, with minimal crossing of the blood–brain barrier and hence minimal sedative effects. 

Fexofenadine HCl lacks the cardiotoxic effects of its parent drug, terfenadine. 
However, it has been associated with increased QT interval, syncope, and ventricular arrhythmia in at least one susceptible patient with preexisting cardiovascular risk. 
To date, no significant interactions have been demonstrated with fexofenadine when administered concomitantly with azole antifungals or macrolide antibiotics. 

Indicated for seasonal allergic rhinitis and chronic idiopathic urticaria.
Fexofenadine HCl is used for relief from physical symptoms associated with seasonal allergic rhinitis and for treatment of hives, including chronic urticaria.
Fexofenadine HCl does not cure, but rather prevents the aggravation of allergic rhinitis and chronic idiopathic urticaria, and reduces the severity of the symptoms associated with those conditions, providing relief from repeated sneezing, runny nose, itchy eyes or skin, and general body fatigue. 

In a 2018 review, Fexofenadine HCl, along with levocetirizine, desloratadine, and cetirizine, was cited to be a safe drug to use for individuals with inherited long QT syndrome.
Fexofenadine HCl is an antihistamine that may be used to treat allergy symptoms (including hay fever) in adults and children.

Fexofenadine HCl is also used to treat skin itching and hives caused by a condition called chronic idiopathic urticaria in adults and children who are at least 6 years old.
Fexofenadine HCl is primarily used for the treatment of allergic conditions, particularly seasonal allergic rhinitis, which is commonly known as hay fever, where it helps alleviate symptoms such as sneezing, runny nose, nasal congestion, itchy or watery eyes, and general irritation caused by exposure to pollen, dust, or other allergens. 

By blocking peripheral H1 histamine receptors, it prevents the histamine-mediated inflammatory response, which reduces the severity and frequency of these allergic symptoms, providing patients with relief that allows them to maintain daily activities without interruption.
In addition to seasonal allergies, Fexofenadine HCl is widely prescribed for chronic idiopathic urticaria, a condition characterized by persistent hives, redness, and itching of the skin with no identifiable trigger. 

Its antihistamine action helps suppress the appearance of hives and decreases the sensation of itchiness, improving quality of life and allowing patients to sleep and function more comfortably. 
Because Fexofenadine HCl is a second-generation antihistamine, it is particularly favored in both conditions for its non-sedating properties, meaning that it does not cross the blood-brain barrier significantly and therefore does not cause drowsiness or impair mental alertness, unlike many first-generation antihistamines.

Fexofenadine HCl is also sometimes used in combination with other medications, such as decongestants, to provide broader relief from allergy symptoms, including nasal congestion or sinus pressure. 
Beyond these primary uses, it has occasionally been used off-label in certain allergic skin disorders or mild drug-induced allergies under medical supervision, where histamine plays a central role in symptom development.
 
Its versatility in oral formulations, such as tablets, orally disintegrating tablets, or suspension for children, makes it suitable for patients of different ages, including adults and children above a certain age, ensuring consistent therapeutic effects while maintaining safety.
Fexofenadine HCl’s uses extend beyond just the treatment of seasonal allergies and chronic hives because its mechanism of selectively blocking H1 histamine receptors makes it effective in any condition where histamine release is a major contributor to symptoms. 

Fexofenadine HCl is sometimes prescribed for perennial allergic rhinitis, which occurs year-round due to exposure to indoor allergens such as dust mites, pet dander, or mold, helping patients reduce continuous nasal congestion, sneezing, and itching without causing sedation that could interfere with work or school performance.
In pediatric medicine, Fexofenadine HCl is formulated as oral suspensions or chewable tablets, allowing children to safely manage symptoms of allergic rhinitis and hives while minimizing the risk of drowsiness that is more concerning in younger patients. 
The non-sedating nature of Fexofenadine HCl also makes it particularly suitable for individuals who need to remain alert during daily activities, such as driving, operating machinery, or attending school, which is a significant advantage over first-generation antihistamines that often induce lethargy.

Safety Profile Of Fexofenadine HCl:
Fexofenadine HCl is generally considered to have a low risk of serious adverse effects, especially compared with first-generation antihistamines, but like all medications, it can still cause some side effects and requires careful use under certain conditions. 
The most commonly reported side effects are relatively mild and include headache, dizziness, fatigue, nausea, and dry mouth, which usually resolve without the need for discontinuing the medication. 

Some individuals may also experience mild gastrointestinal disturbances, such as diarrhea or stomach discomfort, particularly when the drug is taken on an empty stomach.
Unlike many older antihistamines, Fexofenadine HCl has minimal sedative effects because it does not significantly cross the blood-brain barrier, but rare cases of drowsiness or sleepiness have been reported, especially at higher doses or when combined with alcohol or other central nervous system depressants. 

Hypersensitivity reactions, though uncommon, can occur in some patients and may include rash, itching, swelling, or in very rare cases, severe allergic reactions (anaphylaxis), requiring immediate medical attention. 
Patients with renal or hepatic impairment should use Fexofenadine HCl cautiously and under medical supervision, as altered metabolism or excretion may increase the risk of accumulation and side effects.

Drug interactions are generally limited, but co-administration with aluminum or magnesium-containing antacids can reduce the absorption of Fexofenadine HCl, decreasing its effectiveness if taken simultaneously. 
Similarly, fruit juices, especially grapefruit, apple, or orange juice, can slightly lower the drug’s absorption, which may reduce its therapeutic effect if consumed around the time of dosing. 
Overdose is rare but can result in extreme drowsiness, rapid heartbeat, or other cardiovascular symptoms, though serious outcomes are uncommon due to its relatively safe pharmacological profile.