Clemastine fumarate is a first-generation antihistamine. It's used in adults and children for short-term relief of allergy symptoms, such as sneezing and runny nose. It can also help ease itchiness from chronic (long-term) hives or angioedema. Clemastine is only available by prescription, and comes as a tablet and syrup that's typically taken up to 3 times per day. Common side effects include sleepiness and dizziness. Brand name Tavist has been discontinued.
Short-term relief of allergy symptoms (sneezing, runny nose, itching, or watery eyes)
Relief of itchiness from chronic (long-term) hives or angioedema
Clemastine is a first-generation antihistamine. It blocks a natural substance in your body called histamine. In doing so, clemastine lowers inflammation and relieves runny nose, itchy nose, and sneezing.
Source: DailyMed
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
Less common or rare
Less common or rare with azatadine, cetirizine, clemastine, cyproheptadine, desloratadine, dexchlorpheniramine, diphenhydramine, or loratadine
Abdominal or stomach pain
burning
chills
clay-colored stools or dark urine
difficulty swallowing
dizziness
fast or irregular heartbeat
headache
prickly sensations
puffiness or swelling of the eyelids or around the eyes, face, lips or tongue
redness of skin
seizures
shortness of breath
skin rash
swelling
tightness in chest
tingling
unusual tiredness or weakness
Check with your doctor as soon as possible if any of the following side effects occur:
Symptoms of overdose
Clumsiness or unsteadiness
convulsions (seizures)
drowsiness (severe)
dryness of mouth, nose, or throat (severe)
feeling faint
flushing or redness of face
hallucinations (seeing, hearing, or feeling things that are not there)
shortness of breath or troubled breathing
trouble in sleeping
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
More common
Drowsiness
dry mouth, nose, or throat
gastrointestinal upset, stomach pain, or nausea
headache
increased appetite and weight gain
thickening of mucus
Less common or rare
Acid or sour stomach
belching
blurred vision or any change in vision
body aches or pain
clumsiness or unsteadiness
confusion (not with diphenhydramine)
congestion
difficult or painful urination
difficulty in moving
difficult or painful menstruation
dizziness (not with brompheniramine or hydroxyzine)
drowsiness (with high doses of desloratadine and loratadine)
dryness of mouth, nose, or throat
early menstruation
fast heartbeat
hoarseness
increased sensitivity of skin to sun
increased sweating
indigestion
loss of appetite
joint pain
muscle aching or cramping
muscle pains or stiffness
nightmares (not with azatadine, chlorpheniramine, cyproheptadine, desloratadine, hydroxyzine, or loratadine)
ringing or buzzing in ears
skin rash
swollen joints
stomach discomfort, upset or pain
tender swollen glands in neck
unusual excitement, nervousness, restlessness, or irritability
vomiting
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Taken by mouth
Comes as a tablet and liquid syrup
Available as a generic medication
Take clemastine with or without food. If it hurts your stomach, try taking it with food to help.
Clemastine might make you feel a little sleepy. Don't drive until you know how this medication affects you. Avoid drinking alcohol while taking clemastine because this raises your risk of sleepiness and dizziness. Make sure to let your healthcare professional (HCP) know if you're taking other medications that make you sleepy.
Don't start any new medications while taking clemastine, especially other antihistamines, without talking to an HCP or pharmacist first. Doing so can raise your risk of taking too much medication (overdose) and lead to severe side effects, including seizures, hallucinations (seeing things that aren't real), and even death.
Don't take clemastine with a monoamine oxidase inhibitor (MAOI), such as selegiline, phenelzine (Nardil), or tranylcypromine (Parnate). This combination can worsen side effects from clemastine, such as constipation, changes in vision, dry mouth, and fast heart rate.
If you're pregnant, don't take clemastine without talking to a healthcare professional because it's not completely clear how safe this medication is for your baby. They'll discuss the risks and benefits with you, or they might recommend a different antihistamine that has more safety data in pregnancy.
Don't take clemastine if you're breastfeeding. It's unclear how this medication might affect a nursing baby, but research shows that it can get into breastmilk. Because of the possible risk of harm to newborns and babies born premature, your care team will likely ask you to avoid taking this medication if you're breastfeeding.
For the clemastine 0.5 mg/5 mL syrup:
Store clemastine syrup at room temperature and keep it in the original bottle it came in from the pharmacy.
Use a medication dose cup or an oral syringe to measure your dose of clemastine. Ask your pharmacy to provide you with one if the product doesn't include it in its packaging or if you need extras. Don't use household spoons because they might not be accurate and might cause you to take the wrong dose.
Clemastine syrup contains about 5% of alcohol. Let your prescriber know if you prefer to use a product that doesn't have alcohol in it.
Clemastine can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Risk factors: Alcohol use | Taking other medications that cause sleepiness | Age 60 or older
Clemastine can make you very sleepy, which can affect your ability to focus, think, or react. This side effect is more likely to happen or be more intense if you're 65 years or older, drink alcohol while taking this medication, or take other medications that cause sleepiness (e.g., opioids, benzodiazepines, sleep medications). Don't drive or operate machinery until you know how clemastine affects you.
People aged 65 years and older experience more side effects when taking antihistamine medications like clemastine. Watch out for changes in vision, severe dry mouth, trouble urinating, or constipation. Also, feelings of drowsiness can leave you unsteady on your feet, which can lead to accidental falls and injuries. Talk with your HCP before using clemastine.
Clemastine tablet: Each tablet contains 2.68 mg of clemastine.
Allergies and hives or angioedema:
Ages 12 years and older: The typical dose is 1 tablet by mouth up to 3 times a day if needed.
Age under 12 years old: Use the syrup.
Clemastine syrup: Each 5 mL contains 0.5 mg of clemastine.
Allergies:
Ages 6 to under 12 years old: The typical starting dose is 0.5 mg by mouth twice daily. Don't take more than 3 mg within a 24-hour period.
Ages 12 years and older: The typical dose is 1 mg by mouth twice daily. Don't take more than 6 mg within a 24-hour period.
Hives or angioedema:
Ages 6 to under 12 years old: The typical starting dose is 1 mg by mouth twice daily. Don't take more than 3 mg within a 24-hour period.
Ages 12 years and older: The typical dose is 2 mg by mouth twice daily. Don't take more than 6 mg within a 24-hour period.
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking any of these medicines, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using medicines in this class with any of the following medicines is not recommended. Your doctor may decide not to treat you with a medication in this class or change some of the other medicines you take.
Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Nursing mothers
Lower respiratory tract conditions, including asthma
Currently taking or have taken an monoamine oxidase inhibitor (MAOI) within the last 2 weeks
Short-term relief of allergy symptoms (sneezing, runny nose, itching, or watery eyes)
Relief of itchiness from chronic (long-term) hives or angioedema
Allergies
Common cold symptoms
Trouble sleeping for people 12 years and older
Short-term relief of allergy symptoms (sneezing, runny nose, itchy or watery eyes, itching of the nose or throat)
Relief of itchiness due to chronic (long-term) hives - by prescription only
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Borowy, C. S., et al. (2023). Antihistamine toxicity. StatPearls.
Drugs and Lactation Database (LactMed®). Clemastine. National Institute of Child Health and Human Development.
Gilboa, S. M., et al. (2009). Use of antihistamine medications during early pregnancy and isolated major malformations. Birth Defects Research. Part A, Clinical and Molecular Teratology.
Green, A. J., et al. (2017). Clemastine fumarate as a remyelinating therapy for multiple sclerosis (ReBUILD): A randomised, controlled, double-blind, crossover trial. Lancet.
Memon, R. J., et al. (2023). Angioedema. StatPearls.
Teva Pharmaceuticals USA, Inc. (2022). Clemastine fumarate tablet [package insert]. DailyMed.
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