Clemastine Fumarate Syrup
It is used to ease allergy signs.
Drug Class
Antihistamine
Pharmacologic Class
H1-receptor antagonist, Ethanolamine derivative
Pregnancy Category
Category B
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Clemastine Fumarate Syrup is an antihistamine used to relieve symptoms of allergies like sneezing, runny nose, itchy eyes, and watery eyes. It works by blocking a natural substance (histamine) that your body makes during an allergic reaction. It can cause drowsiness.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food. If it causes stomach upset, taking it with food may help. When taking the liquid form, measure the dose accurately using the measuring device that comes with the medication. If no device is provided, ask your pharmacist for a suitable measuring tool.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs available in your area.
What to Do If You Miss a Dose
If you take this medication regularly, take the missed dose as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, do not take it more frequently than directed by your doctor.
To get the most benefit from your medication, follow your doctor's instructions carefully. Read all the information provided with your prescription and follow the instructions closely. You can take this medication with or without food. If it causes stomach upset, taking it with food may help. When taking the liquid form, measure the dose accurately using the measuring device that comes with the medication. If no device is provided, ask your pharmacist for a suitable measuring tool.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so. If you're unsure about the best way to dispose of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs available in your area.
What to Do If You Miss a Dose
If you take this medication regularly, take the missed dose as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular schedule. Do not take two doses at the same time or take extra doses. If you take this medication as needed, do not take it more frequently than directed by your doctor.
Lifestyle & Tips
- Avoid driving or operating heavy machinery until you know how this medication affects you, as it can cause significant drowsiness.
- Avoid alcohol and other sedating medications while taking clemastine, as this can increase drowsiness and other side effects.
- Drink plenty of fluids to help with dry mouth, a common side effect.
- Avoid prolonged exposure to sunlight or use sunscreen, as some antihistamines can cause photosensitivity (though less common with clemastine).
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
1.34 mg (10 mL of 0.67 mg/5 mL syrup) orally every 8 to 12 hours
Dose Range:
1.34 - 8.04 mg
Condition-Specific Dosing:
Maximum daily dose:
8.04 mg (60 mL) in 24 hours
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established
Child:
Children 6 to <12 years: 0.67 mg (5 mL of 0.67 mg/5 mL syrup) orally every 8 to 12 hours, not to exceed 4.02 mg (30 mL) in 24 hours. Not recommended for children under 6 years of age for self-medication.
Adolescent:
Adolescents âĨ12 years: Same as adult dosing
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment recommended, use with caution
Moderate:
Use with caution, consider lower end of dosing range or extended intervals
Severe:
Use with caution, consider lower end of dosing range or extended intervals due to prolonged half-life of metabolites
Dialysis:
Not well studied, use with caution. Clemastine is not significantly dialyzable.
Hepatic Impairment:
Mild:
No specific adjustment recommended, use with caution
Moderate:
Use with caution, consider lower end of dosing range or extended intervals due to extensive hepatic metabolism
Severe:
Use with caution, consider lower end of dosing range or extended intervals due to extensive hepatic metabolism
Pharmacology
Mechanism of Action
Clemastine is a first-generation antihistamine that competitively antagonizes H1 histamine receptors, thereby preventing the effects of histamine on capillaries, bronchi, and gastrointestinal smooth muscle. It also possesses significant anticholinergic and sedative properties due to its ability to cross the blood-brain barrier.
Pharmacokinetics
Absorption:
Bioavailability:
Well absorbed
Tmax:
Approximately 2-4 hours
FoodEffect:
Food may slightly delay absorption but does not significantly affect extent of absorption.
Distribution:
Vd:
Not readily available, but widely distributed throughout body tissues
ProteinBinding:
Approximately 95%
CnssPenetration:
Yes (significant, leading to sedation)
Elimination:
HalfLife:
Approximately 10-25 hours
Clearance:
Not readily available
ExcretionRoute:
Primarily via urine as metabolites, with a small amount excreted unchanged
Unchanged:
<1%
Pharmacodynamics
OnsetOfAction:
15-30 minutes
PeakEffect:
2-4 hours
DurationOfAction:
10-12 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Change in balance
Other Possible Side Effects
Like all medications, this drug can cause side effects. Although many people do not experience any side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
Feeling dizzy or sleepy
Stomach pain
* Thickening of mucus in the nose or throat
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Change in balance
Other Possible Side Effects
Like all medications, this drug can cause side effects. Although many people do not experience any side effects or only have mild ones, it is essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor for advice:
Feeling dizzy or sleepy
Stomach pain
* Thickening of mucus in the nose or throat
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- Severe drowsiness or sedation that interferes with daily activities
- Dizziness or lightheadedness
- Difficulty urinating or painful urination
- Blurred vision or changes in vision
- Signs of paradoxical excitation (especially in children): restlessness, nervousness, insomnia, tremors, seizures
- Severe dry mouth that is unmanageable
- Allergic reaction symptoms (rash, itching/swelling, severe dizziness, trouble breathing) - seek immediate medical attention
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following conditions to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the symptoms you experienced.
If you have asthma.
If you have taken certain medications for depression or Parkinson's disease within the last 14 days, such as isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this may lead to very high blood pressure.
If you are currently taking linezolid or methylene blue.
If you are breastfeeding, as you should not breastfeed while taking this medication.
Special Considerations for Children:
If your child is a premature baby or a newborn, do not administer this medication, as it is not suitable for them.
Additional Important Information:
This list is not exhaustive, and it is crucial to inform your doctor and pharmacist about all your medications, including prescription and over-the-counter drugs, natural products, and vitamins, as well as any health problems you have. This will help ensure your safety while taking this medication. Never start, stop, or change the dose of any medication without consulting your doctor first.
It is essential to inform your doctor about the following conditions to ensure safe treatment:
Any allergies you have, including allergies to this medication, its components, or other substances. Be sure to describe the symptoms you experienced.
If you have asthma.
If you have taken certain medications for depression or Parkinson's disease within the last 14 days, such as isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this may lead to very high blood pressure.
If you are currently taking linezolid or methylene blue.
If you are breastfeeding, as you should not breastfeed while taking this medication.
Special Considerations for Children:
If your child is a premature baby or a newborn, do not administer this medication, as it is not suitable for them.
Additional Important Information:
This list is not exhaustive, and it is crucial to inform your doctor and pharmacist about all your medications, including prescription and over-the-counter drugs, natural products, and vitamins, as well as any health problems you have. This will help ensure your safety while taking this medication. Never start, stop, or change the dose of any medication without consulting your doctor first.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.
To minimize the risk of severe side effects, do not exceed the dosage prescribed by your doctor. Taking more than the recommended amount can increase your chance of experiencing serious adverse effects. Additionally, do not take this medication for a longer period than specified by your doctor.
Until you are aware of how this medication affects you, it is recommended that you avoid driving and other activities that require alertness. It is also advisable to refrain from consuming alcohol while taking this drug.
Before using marijuana, other forms of cannabis, or any prescription or over-the-counter (OTC) medications that may cause drowsiness, consult with your doctor. This medication may interfere with the results of allergy skin tests, so it is crucial to inform your doctor and laboratory personnel that you are taking this drug.
If you are 60 years or older, exercise caution when using this medication, as you may be more susceptible to side effects. Similarly, if the patient is a child, use this medication with caution, as children may have a higher risk of experiencing excitability.
If you are pregnant or planning to become pregnant, consult with your doctor to discuss the potential benefits and risks associated with using this medication during pregnancy.
To minimize the risk of severe side effects, do not exceed the dosage prescribed by your doctor. Taking more than the recommended amount can increase your chance of experiencing serious adverse effects. Additionally, do not take this medication for a longer period than specified by your doctor.
Until you are aware of how this medication affects you, it is recommended that you avoid driving and other activities that require alertness. It is also advisable to refrain from consuming alcohol while taking this drug.
Before using marijuana, other forms of cannabis, or any prescription or over-the-counter (OTC) medications that may cause drowsiness, consult with your doctor. This medication may interfere with the results of allergy skin tests, so it is crucial to inform your doctor and laboratory personnel that you are taking this drug.
If you are 60 years or older, exercise caution when using this medication, as you may be more susceptible to side effects. Similarly, if the patient is a child, use this medication with caution, as children may have a higher risk of experiencing excitability.
If you are pregnant or planning to become pregnant, consult with your doctor to discuss the potential benefits and risks associated with using this medication during pregnancy.
Overdose Information
Overdose Symptoms:
- Severe drowsiness or deep sleep
- Coma
- Ataxia (loss of coordination)
- Dizziness
- Blurred vision
- Dry mouth
- Flushing
- Fever
- Dilated pupils
- Urinary retention
- Tachycardia (fast heart rate)
- Hypertension (high blood pressure)
- Nausea, vomiting
- In children: paradoxical excitation, hallucinations, convulsions, respiratory depression, cardiovascular collapse, death
What to Do:
In case of overdose, seek immediate medical attention or call a Poison Control Center (1-800-222-1222). Treatment is symptomatic and supportive. Gastric lavage or activated charcoal may be considered if ingestion is recent. Do not induce vomiting.
Drug Interactions
Contraindicated Interactions
- Monoamine Oxidase Inhibitors (MAOIs) - concurrent use or within 14 days of MAOI therapy
Major Interactions
Moderate Interactions
- Beta-2 agonists (may have additive cardiovascular effects)
- Potassium chloride (wax-matrix formulations - increased risk of GI lesions due to anticholinergic effects)
Minor Interactions
- None specifically noted as minor, but general caution with drugs affecting gastric motility
Monitoring
Baseline Monitoring
Allergy symptoms (e.g., sneezing, runny nose, itching)
Rationale: To establish baseline severity and assess treatment efficacy.
Timing: Prior to initiation of therapy
Concomitant medications
Rationale: To identify potential drug interactions, especially with CNS depressants or anticholinergics.
Timing: Prior to initiation of therapy
Routine Monitoring
Symptom relief (e.g., reduction in sneezing, rhinorrhea, pruritus)
Frequency: Daily or as needed
Target: Significant reduction in symptoms
Action Threshold: Lack of efficacy may require dose adjustment or alternative therapy
Adverse effects (e.g., drowsiness, dry mouth, blurred vision, urinary retention, dizziness)
Frequency: Daily or as needed
Target: Minimal to no adverse effects
Action Threshold: Significant or bothersome adverse effects may require dose reduction or discontinuation
Mental status (especially in elderly or children)
Frequency: As needed, particularly during initial therapy
Target: Normal alertness for age
Action Threshold: Excessive sedation, confusion, or paradoxical excitation (in children) requires immediate evaluation and dose adjustment/discontinuation
Symptom Monitoring
- Drowsiness
- Sedation
- Dry mouth
- Blurred vision
- Urinary retention
- Dizziness
- Constipation
- Nervousness (paradoxical effect, especially in children)
- Excitability (paradoxical effect, especially in children)
Special Patient Groups
Pregnancy
Clemastine is classified as Pregnancy Category B. Studies in animals have not shown a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women. Use only if clearly needed and the potential benefits outweigh the potential risks.
Trimester-Specific Risks:
First Trimester:
Generally considered low risk based on animal data, but human data are limited.
Second Trimester:
No specific increased risk identified.
Third Trimester:
Use with caution near term, as antihistamines may cause adverse effects in the newborn (e.g., irritability, tremors, respiratory depression), especially if used in high doses or for prolonged periods.
Lactation
Clemastine is excreted into breast milk. Due to the potential for sedation, irritability, and anticholinergic effects (e.g., dry mouth, decreased milk supply) in the nursing infant, and the theoretical risk of decreased milk production, use is generally not recommended during breastfeeding. If use is necessary, monitor the infant closely for adverse effects.
Infant Risk:
Moderate to high risk (L3-L4). Potential for infant drowsiness, irritability, paradoxical excitation, and theoretical risk of decreased milk supply.
Pediatric Use
Clemastine is not recommended for children under 6 years of age for self-medication due to increased susceptibility to adverse effects, including paradoxical excitation (restlessness, nervousness, insomnia, tremors, seizures) and respiratory depression. Use in children should be under medical supervision, with careful dosing and monitoring. Infants and neonates are particularly sensitive to the anticholinergic effects.
Geriatric Use
Elderly patients are more susceptible to the sedative and anticholinergic effects of clemastine (e.g., dizziness, sedation, hypotension, confusion, urinary retention, constipation). Lower doses may be required, and alternative, less sedating antihistamines are generally preferred in this population. Use with extreme caution in elderly patients with prostatic hypertrophy or glaucoma.
Clinical Information
Clinical Pearls
- Clemastine is a first-generation antihistamine with significant sedative and anticholinergic properties, making it less suitable for daytime use or in situations requiring alertness.
- It has a relatively long half-life compared to some other first-generation antihistamines, allowing for less frequent dosing.
- Due to its anticholinergic effects, it should be used with caution in patients with glaucoma, prostatic hypertrophy, bladder neck obstruction, or pyloroduodenal obstruction.
- Paradoxical excitation (restlessness, nervousness, insomnia) can occur, especially in young children, rather than sedation.
- Avoid concurrent use with alcohol or other CNS depressants due to additive sedative effects.
Alternative Therapies
- Second-generation antihistamines (e.g., loratadine, cetirizine, fexofenadine) for less sedating allergy relief.
- Other first-generation antihistamines (e.g., diphenhydramine, chlorpheniramine, brompheniramine) for similar sedative and anticholinergic profiles.
- Nasal corticosteroids (e.g., fluticasone, mometasone) for allergic rhinitis.
- Mast cell stabilizers (e.g., cromolyn sodium) for allergy prevention.
Cost & Coverage
Average Cost:
Low price range per 120 mL syrup
Generic Available:
Yes
Insurance Coverage:
Tier 1 (preferred generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to check with your pharmacist for more information. If you have any questions or concerns about your medication, do not hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.