Allegra and Relistor drug interactions - a phase IV clinical study of FDA data

Summary:

Drug interactions are reported among people who take Allegra (fexofenadine hydrochloride) and Relistor (methylnaltrexone bromide). Common drug interactions include swelling among females and nausea among males.

The phase IV clinical study analyzes what interactions people have when they take Allegra and Relistor. It is created by eHealthMe based on reports of 40 people who take the same drugs from the FDA, and is updated regularly.

What is Allegra?

Allegra has active ingredients of fexofenadine hydrochloride. It is often used in allergies. eHealthMe is studying from 75,498 Allegra users. Check the latest studies of Allegra.

What is Relistor?

Relistor has active ingredients of methylnaltrexone bromide. eHealthMe is studying from 1,659 Relistor users. Check the latest studies of Relistor.

eHealthMe: drug outcomes in the real world

eHealthMe runs one of the largest post-marketing drug safety studies in the world. We study millions of patients and 5,000 more each day. Our data-driven phase IV clinical trials have been referenced on 800+ peer-reviewed medical publications including The Lancet, Mayo Clinic Proceedings, and Nature. Tools to study our phase IV findings are available to the public, anonymous and free >>>.

On Aug, 20, 2026

40 people who take Allegra and Relistor together, and have interactions are studied.

What are the common drug interactions of Allegra and Relistor, by gender? *:

female:

Swelling
Thrombosis (formation of a blood clot inside a blood vessel)
Tremor (trembling or shaking movements in one or more parts of your body)
Abdominal pain
Hangover
Migraine (headache)
Vomiting
Abnormal sleep-related event
Depression
Muscular weakness (muscle weakness)

male:

Nausea (feeling of having an urge to vomit)
Abdominal pain
Infection
Muscle spasticity (tight or stiff muscles and an inability to control those muscles)
Muscular weakness (muscle weakness)
Pollakiuria (abnormally frequent passage of relatively small quantities or urine)
Pulmonary function test decreased
Anxiety
Asthma
Benign prostatic hyperplasia (benign enlargement of the prostate)

What are the common drug interactions of Allegra and Relistor, by age (0-1 to 60+)? *:

0-1:

n/a

2-9:

n/a

10-19:

n/a

20-29:

n/a

30-39:

n/a

40-49:

Chronic kidney disease
Dyspnoea (difficult or laboured respiration)
Metabolic acidosis (body produces too much acid, or when the kidneys are not removing enough acid from the body)
Renal failure (kidney dysfunction)
Respiratory acidosis (respiratory failure or ventilatory failure, causes the ph of blood and other bodily fluids to decrease)
Ventricular extrasystoles (premature cardiac contraction)
Drug ineffective
Injection site oedema
Injection site pain
Weight increased

50-59:

Abdominal pain
Drug ineffective
Hangover
Migraine (headache)
Vomiting
Muscle tightness
Muscular weakness (muscle weakness)
Oral disorder (mouth disease)
Lipoma (a growth of fatty tissue that slowly develops just under your skin)
Activities of daily living impaired

60+:

Cataplexy (loss of muscle tone accompanied by full conscious awareness)
Cystitis (inflammation of the wall of the bladder)
Diarrhoea
Dry skin
Dyspnoea (difficult or laboured respiration)
Ear infection
Fluid retention (an abnormal accumulation of fluid in the blood)
Kidney infection
Nasopharyngitis (inflammation of the nasopharynx)
Nausea (feeling of having an urge to vomit)

What are the existing conditions these people have? *

Narcolepsy (brain's inability to regulate sleep-wake cycles normally): 20 people, 50.00%
Constipation: 13 people, 32.50%
Pain: 12 people, 30.00%
Cataplexy (loss of muscle tone accompanied by full conscious awareness): 11 people, 27.50%
High Blood Pressure: 10 people, 25.00%
Hypersensitivity: 7 people, 17.50%
Ill-Defined Disorder: 6 people, 15.00%
Thrombosis (formation of a blood clot inside a blood vessel): 6 people, 15.00%
Stress And Anxiety: 6 people, 15.00%
Neck Pain: 3 people, 7.50%

* Approximation only. Some reports may have incomplete information.

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