What is fexofenadine?

Fexofenadine is a generic name for an antihistamine drug that is used for the treatment of seasonal allergy symptoms like itchy throat, runny nose, sneezing, watery eyes and chronic urticaria. This drug works by blocking the natural histamine in human body and helps to decrease allergy symptoms.

It was developed as a more efficient and safer alternative to another antihistamine drug called terfenadine. Fexofenadine belong to the group of second-generation antihistamine drugs as it is less able to pass the blood-brain barrier and cause sedation as compared to first-generation antihistamine.

The most common Brand name for this OTC drug is Allegra. Fexofenadine is available on the market in following dosage forms: oral capsule, tablet, orally disintegrating tablets and oral suspension in doses of 30 mg, 60 mg, 120 mg and 180 mg. It was first approved by the FDA in 1996 and manufactured under the Brand name Allegra.

Allegra (Fexofenadine Hcl): Side Effects, Interactions, Warning

What is fexofenadine drug class, molecular formula and weight?

Fexofenadine belongs to the class of organic compounds known as diphenylmethanes. These compounds contain a diphenylmethane moiety, which consists of methane wherein two hydrogen atoms are replaced by two phenyl groups.

Chemical name:2-[4-[1-hydroxy-4-[4-[hydroxy (diphenyl) methyl] piperidin-1-yl] butyl] phenyl]-2-methylpropanoic acid

 fexofenadine molecular formula

Molecular formula:C32H39NO4


 fexofenadine drug class

(3D molecular formula of fexofenadine)

How fexofenadine works in the body?

Fexofenadine is a second-generation, long lasting antihistamine drug that works as an antagonist of H1-receptors. It has a selective and peripheral H1-antagonist action. Fexofenadine competes for binding at H1-receptors in the GI tract, bronchial smooth muscle and large blood vessels with free body histamine.

By blocking the action of endogenous histamine, it subsequently leads to temporary relief of the histamine negative symptoms such as nasal congestion, watery eyes caused by histamine. Fexofenadine has no anticholinergic, alpha1-adrenergic or beta-adrenergic-receptor or antidopaminergic blocking effects.

Fexofenadine brand names

Fexofenadine is manufactured by various companies so never get confused with the name because it works same and you will get the fexofenadine ingredient in those medicines the only difference you will find that is the name. It is available on the market with following brand names: Allegra, Allegra allergy, Aller-ease, Mucinex allergy, Allegra 24 Hour Allergy, Allegra ODT, Children’s Allegra Allergy, Children’s Allegra ODT, Allergy Relief and Wal-Fex

What is fexofenadine used for?

Fexofenadine medication normally used for the treatment of various seasonal allergy problems like runny nose, sneezing, watery eyes, itchy throats and chronic urticaria. It also helps to treat the skin itching and hives. FDA approved indications for fexofenadine are:

  • Hay Fever
  • Seasonal Allergic Rhinitis
  • Uncomplicated Chronic idiopathic urticaria

Fexofenadine dosage forms and strengths

Fexofenadine medication is available in various brands that specially comes with three forms like tablets, oral suspension and oral disintegrating tablets. If you are going for tablets then you can find three strengths like 30 mg, 60 mg and 180 mg. If you are going for oral suspension then you will find 30mg/5ml. In the case of oral disintegrating tablets, you will get 30 mg strength.

Fexofenadine dosage for different indications

Usual Adult dose for allergic rhinitis: The usual adult dose should be 180 mg orally once per day or 60 mg two times in a day. In such case, the maximum dose is 180 mg per day.

Usual adult dose for Urticaria: In the case of urticaria the usual adult dose should be 180 mg orally once per day or 60 mg two times in a day. In such case, the maximum dose is 180mg per day.

Usual pediatric dose for allergic rhinitis: If you are giving the medicine to a child of the age between 6 months to 2 years then the dose should be 15mg orally for two times in a day. If the age is 2 years to 11 years then the dose should be 30 mg orally two times per day. If you are giving to above 12 years old age group then 180 mg orally once per day or you can give 60 mg orally two times in a day.

Oral suspension is always suitable for patients 6 months and older. Tablets and oral dissolving tablets is best for patients 6 to 11 years of age group and gel-coated tablets formulations should be for some limited patients those who are 12 years old or above.

How long can you take fexofenadine?

Fexofenadine highest dose

180 mg per day is the highest fexofenadine dose. Never take any extra dose because it can be very dangerous for you and you may cause various side effects. In such case, go for immediate medical attention.

Fexofenadine side effects

If you are taking fexofenadine modification then you may experience some unwanted side effects.

Major side effects: Stop taking fexofenadine and call your doctor if you have fever, chills, body aches, cough, or other flu symptoms.

Minor side effects: In the case of some side effects you don’t need any medical attention because these side effects normally occur at the initial stage of medication intake, as its habituate with your body then these side effects will remove automatically. In such case, your physician may help you to reduce the effect of the side effects.

Common side effect: vomiting

Less common: In less common category you may consider side effects like back pain, chills, body aches or pain, diarrhea, coughing, dizziness, difficulty with moving, earache, ear congestion, fever, headache, joint pain, loss of voice, muscle aching or cramping, nausea, nasal congestion, pain in legs and arms, painful menstrual bleeding, sneezing, runny nose, sore throat, stomach upset, swollen joints, viral infections like flu and cold, weakness, tired and nasal congestion.

Rare side effects:

  • Feeling redness of the face, arms, neck and sometimes upper chest or feeling of warmth
  • Labored or difficulty for breathing, shortness of breath
  • Chest tightness
  • Swelling on lips, tongue, face, hands, feet, sex organs and eyelid

How to take fexofenadine?

You should take fexofenadine as per the direction on the medicine label. Never use this drug smaller or larger amount or for longer time than recommended by your physician because it can be very harmful for your body. If you are using the oral suspension of this medication then shake the liquid well before you are going for a dose and always measure the dose with a medicine measurement cup.

If you have not a measurement cup then ask your pharmacist for one. In the case, if you are using the fexofenadine orally disintegrating tablets then always keep the tablet in its pack until you are fully ready to take this drug. Never push a tablet through the foil by doing so there always a chance of damage the tablet.

Always open the pack and peel back the foil from the blister of the tablet and take it. Always use dry hand to remove the tablet and put it directly in to your mouth. It will automatically dissolve. Never shallow the tablet as a whole always allows the tablet to dissolve in your mouth without chewing.You can shallow the tablet till it dissolve completely you can also drink liquid if you have problem for the swallow and dissolve the tablet.

Another important thing always take this disintegrating tablet on empty stomach and try to take it before 1 hours of your meal or after 2 hours of your meal. If your symptoms do not get better then tell your doctor about it and never use any extra dose than the recommended dose because it can be very bad for your health.

Precautions and warnings during fexofenadine use

If you have allergic to any medicine or you have kidney disease then always take permission of your doctor for the use of fexofenadine drug. Always take this drug before 1 hour of the meal or after 2 hours of the meal. There are many other medicines with can be the cause of serious drug interactions so always use this medication cautiously.

Always tell your physician about all drugs you use. If you mark any serious side effects like swelling of your tongue, throat, lips and breathing problems or you think you have used this medication too much then immediately go for emergency medical help.

Never use this medication more than the recommendation. Always keep this medicine at room temperature and avoid sun light, heat and moisture. Never keep this medicine in your bathroom and the most important thing is always try to keep it in a safe place which is far away from the reach of children and pets.

Can fexofenadine cause arrhythmias?

Fexofenadine was made as a safer alternative to terfenadine, which was known by causing QT prolongation and life-threating arrhythmias. Animal studies on dogs didn’t show that fexofenadine prolong QT when administered at a dosage of 10 mg/kg/day orally for 5 days and also in rabbits when used in dosage producing plasma concentrations at least 28 and 63 times greater than concentrations seen after administration of 60 mg twice a day – therapeutic dosages in humans.

This lack of tendency to cause QT prolongation irregularities has been confirmed in two long-term studies in volunteers. Fexofenadine 60 mg used twice daily for 6 months or 240 mg used once daily for 12 months had no significant effect on QT prolongation compared to placebo.

Can fexofenadine cause drowsiness?

Most patients who take Allegra or Allegra D do not experience drowsiness. Unlike terdenadine and other first-generation antihistamines, fexofenadine is less likely to pass into the brain so there is a decreased chance of causing drowsiness and sedation.

However, drowsiness can still occur, especially if the drug is taken in high doses or in combination with alcohol, so it is very important that you know how fexofenadine will affect you before you drive, operate machinery, or perform other tasks that require you to be alert and focused.

Can children use fexofenadine?

Fexofenadine (Allegra) is approved as effective and safe medicine for allergy symptoms in children as young as 2 years old. In the treatment of urticaria, fexofenadine may be administered to infants who are at least 6 months of age. Fexofenadine oral suspension is also recommended for children under 12, while tablets can be taken by patients 12 and over.

However, children under the age of 4 may experience serious or potentially fatal Allegra D side effects because this medicine contains a combination of fexofenadine and pseudoephedrine. Products containing pseudoephedrine and similar stimulants should not be given to children under 4.

Can patients with liver disease take fexofenadine safely?

Yes, you can take fexofenadine if you have liver disease but always keep it the lowest dose. It’s always better if you are using this for allergy. Always use the nasal spray to control the allergy symptoms. As fexofenadine medication is metabolized mostly through the liver, It’s always depends on your present condition like how serious is your liver problem, if the liver condition is critical then just ask your doctor about it.

Can patients with renal disease take fexofenadine safely?

No, patients with renal disease can’t take fexofenadine safely as this medication is mostly eliminated by the kidney and there is always a risk of toxic reaction to the patients those who have renal disease because of the low drug clearance. In such case, you need to ask your doctor for the best dose and need to monitor your renal function on regular intervals for the safety purpose.

How long does fexofenadine take to work?

According to the medical experiment fexofenadine medication normally takes 1 to 2 hours to experience the full benefit of this medication. If you are taking this medicine for some days and not finding any good result then you need to ask your doctor about it because you may need any dose adjustment.

How long does fexofenadine stay in your system, urine, blood, saliva?

The elimination half-life of fexofenadine medication is around 14 to 15 hours. So this drug will take around 4 cycles which is almost 2 to 3 days for the complete remove from your system, blood and saliva.

What is Allegra D?

Allegra-D is a Brand name for a medicine that contains a combination of fexofenadine and pseudoephedrine. So the only difference compared to Allegra is that this product except fexofenadine also contains pseudoephedrine.

Pseudoephedrine is a decongestant that shrinks blood vessels in the nasal passages and relieves the symptoms of congestion (stuffy nose). Allegra D is contraindicated for use in children younger than 4 years of age, as it may cause serious side effects.

Who should avoid Allegra and Allegra D?

Fexofenadine may cause serious complications in patients with kidney disease. Pseudoephedrine that can be found in some Allegra products can also cause adverse reactions in patients with other conditions as well. Before taking Allegra or Allegra D products, tell your doctor if you have ever been diagnosed with any of the following conditions. Doctor may need to adjust your dosage of the medicine or choose an alternative treatment:

  • Kidney disease
  • Urination difficulties
  • High blood pressure
  • Heart disease
  • Glaucoma
  • Thyroid disorders
  • Diabetes
  • An enlarged prostate

Fexofenadine use during pregnancy

Fexofenadine is classified in pregnancy category C by the FDA pregnancy list of drugs which means that: Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

In animal models studies have failed to reveal evidence of teratogenicity. Decreased dose-related pup weight gain and survival occurred at 3 times the maximum recommended human dose. There are no controlled data in human pregnancy.

Fexofenadine use during breastfeeding

Fexofenadine may pass into breast milk; however in low amounts so only use this drug after getting approval from your physician. If you are using this medication during breastfeeding then always monitor your baby if any side effects occur then immediately take medical help.

Can geriatric patients use fexofenadine safely?

Geriatric patients seem to be more sensitive to fexofenadine than younger adults. Dose adjustment may be needed in geriatric population while taking fexofenadine in order to minimize the risk of side effects to happen.

Fexofenadine overdosage

If you take extra dose or too much fexofenadine then immediately call your local poison center or call your healthcare provider. Symptoms of overdosage may include unusual or severe drowsiness, dizziness, or dry mouth.

In such case go for medical attention as soon as possible because it can be very serious. In the event of overdose, consider standard measures to remove any unabsorbed drug. Symptomatic and supportive treatment is recommended.

Fexofenadine absorption, metabolism and elimination


Fexofenadine medication normally absorb of a single dose of two 60mg capsules to a healthy human with a mean time to extreme plasma concentration happening at 2.6 hours after the dose. The maximum plasma concentration settles around 131ng/mL after the administration of a 60 mg capsule to a healthy adult.

The tablet formulations are quite bioequivalent to the capsule when you are taking equal dose like if you are taking 60 or 180 mg tablet then the Cmax (maximum plasma concentration) will stay 142 and 494 ng/mL. The fexofenadine pharmacokinetics is linear for 240 mg oral doses on regular basis.

The mixed combination of applesauce and 60 mg capsule administration did not have a major effect on the pharmacokinetics of fexofenadine in adults. If you are taking 180 mg fexofenadine tablet with a high fat meal then it decrease the AUC (mean area under the curve) and maximum plasma concentration of fexofenadine by twenty one and 20% correspondingly.


Around five percent of the total dose of fexofenadine medication was eliminated by hepatic metabolism.


According to the medical research the mean elimination half-life time period of fexofenadine is around 14.4 hours and it’s for administration of 60mg twice daily in the case of ahealthy adult.

According to human mass balance study, recovery of approximately 11% and 80% of the fexofenadine medication dose in the urine and feces respectively. The bioavailability of fexofenadine is unidentified if the fecal module represents mainly unabsorbed medicine or in the case of biliary excretion or unabsorbed medicine.

Can I drink alcohol while taking fexofenadine?

According to the health expert there is no such contradiction to drinking moderate amount of alcohol while taking fexofenadine, since this drug doesn’t pass into CNS in high amounts.

But that does mean that its totally safe, so patients who are taking this medication should avoid alcohol until they get clear idea about this medication it is not showing any side effects to them. If the patient have kidney and liver problem then it can be dangerous so always ask about this to your health expert.

Can I take fexofenadine and Advil together?

According to medical research there is no such interaction between these two medications. So yes, you can take fexofenadine and Advil together if you mark any side effects then go for medical help immediately.

Can I take benedryl with allegra?

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Can I take fexofenadine with antacids?

No, you can’t take fexofenadine with antacids because using these two medications together at the same time can decrease the effect of fexofenadine. The general recommendation is to take them at least 2 hours one after another.  Fexofenadine should not be taken closely in time with aluminum and magnesium containing antacids. Studies showed that aluminium and magnesium can decrease concentrations of fexofenadine in blood.

Can I take fexofenadine and Viagra together?

Drug interaction found in between Viagra and fexofenadine so never take these two medications together. However the true mechanism of interaction has not been described yet.

Can I take fexofenadine and erythromycin together?

Coadministration of fexofenadine and erythromycin has been shown to increase blood concentrations of fexofenadine. The proposed mechanism is erythromycin inhibition of the fexofenadine intestinal efflux through the P-glycoprotein transporter. Furthermore, erythromycin may decrease biliary excretion of fexofenadine. However, no increases of adverse effects or QT prolongation interval were noted.

Can I take fexofenadine and antifungal drugs together?

Fexofenadine should not be taken together in combination with antifungal drugs such as: ketoconazole, itraconazole, fluconazole, clotrimazole, miconazole etc. Coadministration of fexofenadine and mentioned antifungal drugs has been shown to increase blood concentrations of fexofenadine.

The proposed mechanism is erythromycin inhibition of the fexofenadine intestinal efflux through the P-glycoprotein transporter. Furthermore, erythromycin may decrease biliary excretion of fexofenadine. However, no increases of adverse effects or QT prolongation interval were noted.

Can I take fexofenadine and St. John’s Wort together?

Fexofenadine should not be taken together with St. John’s Wort products. Acute administration of St. John’s wort may increase blood concentrations of fexofenadine, while long-term use reverses the effects and may actually reduce the fexofenadine bioavailability.

At the beginning, St. John’s wort appears to first inhibit and then subsequently induce intestinal P-glycoprotein following multiple doses, resulting in enhanced fexofenadine secretion and absorption. Otherwise, large single doses may inhibit P-glycoprotein, whereas smaller, multiple daily doses are likely to induce P-glycoprotein.

Can I take fexofenadine with Quinapril together?

No, you can’t take fexofenadine and quinapril together. If you take these medicines together then quinapril will interact with fexofenadine in the gastrointestinal tract as a result the absorption into bloodstream of fexofenadine may be ineffective which cause less fexofenadine medication effectiveness.

In such case, if you want to evade the interaction then you have to take these two medicines at least two to three hour gap. If you mark any side effects then don’t just abrupt the medication suddenly just takes the help of your physician.

Can I take fexofenadine with Cabometyx?

No, you can’t use fexofenadine with cabometyx medication together because interactions found between these two medicines. By using these two drugs together the cabometyx may boost the effect of fexofenadine and the blood levels. Sometimes you may need dose adjustment so if you mark any side effects then ask your physician and another important think you should say all the drugs you are using even if you are taking any kind of herbs.

Can I take fexofenadine with aluminum hydroxide?

No, you can’t take aluminum hydroxide with fexofenadine because if you use these two medications together then effect of fexofenadine may decrease. Remember always take fexofenadine at least two hours before the aluminum hydroxide for the best result. Never stop this medication immediately if you mark any side effects first go for a medical checkup.

Fexofenadine and weight gain?

According to the medical research, there is no such weight gain effect those who are using fexofenadine but rare people reported about weight gain. In such case, you may or may not require any medical attention. If you are gaining weight suddenly then it may be serious in such case go for the immediate medical checkup.

Can I take fexofenadine with coffee?

Fexofenadine should not be taken together with coffee. Generally the patient with gastric hyper-secretory, GERD and esophagitis should always avoid coffee as it can be very serious for you or increase the side effects.

Can I take fexofenadine with milk?

Fexofenadine should not be taken with milk as it slower the effects of the fexofenadine medication so always waits for around one to two hours after taking the fexofenadine before consuming milk for the better result.

Can I take fexofenadine with fruit juice?

Consuming large amounts of certain fruit juices, including grapefruit, apple or orange, may decrease the levels of fexofenadine in your body. Pharmacokinetics analysis showed that the bioavailability of Fexofenadine was reduced by 36%. Fexofenadine should be taken with water and refrain from drinking large amounts of grapefruit, orange, or apple juice. This will make it easier for your body to absorb the medication.

Can I take fexofenadine with Tums?

Since there are no interactions between fexofenadine and tums ingredients, the patient can combine these two medicines during a short-term period. It is especially good at the beginning of fexofenadine therapy, because fexofenadine full effects are expected at least 1 day, while Tums are working immediately in relieving heartburn, but only for a short-time.

Ideally, you would take a chewable antacid such are tums at least a half hour after taking fexofenadine because you should give your body a little time to get the fexofenadine in before taking tums that work by coating the stomach.

Can you take fexofenadine with Pepto Bismol?

There is no such drug interaction between fexofenadine with Pepto Bismol according to the medical data base that doesn’t mean that there is no interactions exists in between them so take these two medications cautiously. If you mark any side effect then go for medical attention immediately.

Can you take fexofenadine with Zantac?

Yes, you can take fexofenadine with Zantac safely. According to medical science there is no such interactions found between these two drugs.

Can you take fexofenadine and alendronic acid together?

You can’t use fexofenadine and alendronic acid together because medical interaction found in between these drugs. Alendronic acid is normally used in women for the avoidance and treatment of osteoporosis which is mostly caused by menopause and in men and women to treat osteoporosis caused by taking steroids.

Alendronic acid is also used in order to increase bone mass in men with diagnosed osteoporosis, and to treat Paget’s disease of bone in men and women. Using these two medications together can increase the side effects which can put bad effects on your body so normally these drugs are not recommended to use together.

Can I take fexofenadine and metoprolol together?

Yes, you can take fexofenadine and metoprolol together as till the date there is no such interactions found according to the medical data base.fexofenadine is an antihistamine and it has no such interaction with metoprolol so don’t worry you can take it safely.

Can I take the fexofenadine and ulipristal together?

No, you can’t take ulipristal and fexofenadine together because using these two drugs together can be serious and drug interactions happen. Ulipristal may augment the blood levels and also increase the effects of fexofenadine, in such condition you may need regular monitor of your health or dose adjustment so it’s too risky.

Can you use fexofenadine before skin tests?

No, you can’t use fexofenadine before skin tests antigens because the fexofenadine may interfere with your response to skin test antigens, multiple. If you are using fexofenadine then you need to tell it to your physician before you get tested with skin test antigens, multiple.   

Proper storage and disposal information of fexofenadine

Always store fexofenadine drug in between 68 to 77 degrees F. Always keepthis medicine away from sun light, heat and moisture. Keep these medicines in the original packaging until you use these medicines. Most important thing is always keep these medicines away from the pets and children. Never keep the expired medicine and to know about the perfect disposal method you can ask your pharmacists.

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