Fexofenadine: uses, side effects and cautions

Fexofenadine is an antihistamine for hay fever, conjunctivitis with itchy red eyes, eczema, hives, reactions to bites and stings and some food allergies. It comes only as tablets. The NHS notes it is less likely to cause sleepiness than the older sedating antihistamines, and slightly less likely than other non-drowsy ones.

It blocks the effect of histamine released during allergic reactions. The NHS says to expect relief within 1 to 2 hours. Acrivastine, cetirizine, loratadine, desloratadine and levocetirizine seem to work as well. If one non-drowsy antihistamine has not worked for you, trying another is reasonable.

It is compatible with steroid nasal sprays such as beclometasone, budesonide or fluticasone, and with eye drops, which doctors often combine for hay fever.

For hay fever the NHS gives 120mg once a day for adults and children aged 12 and over, and 30mg twice a day, 10 to 12 hours apart, for ages 6 to 11. For hives the usual dose is 180mg once a day from age 12. Your own dose comes from your prescriber or the pack.

The 30mg tablets can be taken with or without food. The 120mg and 180mg tablets should be taken before a meal. Always use water, and swallow tablets whole. Apple, orange and grapefruit juice can reduce how well fexofenadine works, so avoid them around the time of the dose. If a child on twice-daily doses misses one, it can be given within 4 hours; after that, skip it. Adults on once-daily dosing take a forgotten dose when remembered unless the next is nearly due.

Some people only need it for a day or two after a sting; others take it regularly during high pollen counts.

Common effects, in more than 1 in 100 people, are nausea, sleepiness, headache and dizziness. If sleepy or dizzy, do not drive, cycle or use tools; if dizzy, sit or lie down and then get up slowly. If you are taking it for the first time, see how it affects you before driving. A fast or irregular heartbeat should prompt you to tell a doctor or call 111 straight away.

Anaphylaxis is rare but possible; swelling of the lips, mouth, throat or tongue, struggling to breathe, a tight throat, blue or pale skin, confusion or collapse need a 999 call. Taking more than usual is unlikely to harm, but call 111 if you get a headache, a fast heartbeat or sleepiness, or are concerned. Suspected side effects can be reported through the Yellow Card scheme.

The NHS names leflunomide for arthritis, teriflunomide for multiple sclerosis, velpatasvir for hepatitis C and apalutamide for prostate cancer. Indigestion remedies containing aluminium or magnesium should be separated from fexofenadine by about 2 hours. It also asks about anything that causes drowsiness, dry mouth or difficulty passing urine. Paracetamol and ibuprofen can be taken together with it.

Tell your doctor or pharmacist if you have ever had an allergic reaction to fexofenadine or another medicine, have liver or kidney problems, have or have had heart problems, are due to have an allergy test (which it may affect, so you may need to stop it a few days earlier) or are pregnant, trying to get pregnant or breastfeeding.

Fexofenadine is not usually recommended in pregnancy because there is little information, and other antihistamines with better safety data may be more suitable. Speak to a doctor or pharmacist who can help decide. You can take it while breastfeeding if you need to, as only tiny amounts reach milk, but other antihistamines might be better, so ask first. It does not affect contraception.

It is best not to drink alcohol with it, as it can add to sleepiness. Eat and drink normally apart from the fruit juices mentioned above.