Histex 2.5mg/5ml Syrup
It is used to ease allergy signs.
Drug Class
Antihistamine
Pharmacologic Class
First-generation H1-receptor antagonist
Pregnancy Category
Category C
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Histex syrup contains triprolidine, an antihistamine that helps relieve symptoms like sneezing, runny nose, and watery eyes caused by allergies or the common cold. It works by blocking a natural substance called histamine that your body makes during an allergic reaction. It can also help dry up nasal secretions.
How to Use This Medicine
Taking Your Medication Correctly
To ensure you get the most out of your medication, follow your doctor's instructions carefully. Read all the information provided with your medication 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.
Missing a Dose
If you take this medication regularly, take a 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 ensure you get the most out of your medication, follow your doctor's instructions carefully. Read all the information provided with your medication 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.
Missing a Dose
If you take this medication regularly, take a 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 drowsiness.
- Avoid alcohol and other medications that can cause drowsiness (e.g., sedatives, tranquilizers, sleeping pills) while taking this medicine, as this can increase sedation.
- Drink plenty of fluids to help with dry mouth and to thin secretions.
- Avoid prolonged exposure to high temperatures, as this medication can reduce sweating and increase the risk of heatstroke.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
2.5 mg (5 mL) every 4 to 6 hours as needed
Dose Range:
2.5 - 5 mg
Condition-Specific Dosing:
maximumDailyDose:
10 mg (20 mL) in 24 hours
Pediatric Dosing
Neonatal:
Not established
Infant:
Not established (generally not recommended under 2 years without medical advice)
Child:
2 to under 6 years: 1.25 mg (2.5 mL) every 4 to 6 hours as needed (Max 5 mg/24 hours); 6 to under 12 years: 2.5 mg (5 mL) every 4 to 6 hours as needed (Max 10 mg/24 hours)
Adolescent:
12 years and older: 2.5 mg (5 mL) every 4 to 6 hours as needed (Max 10 mg/24 hours)
Dose Adjustments
Renal Impairment:
Mild:
No specific adjustment recommended, monitor for increased sedation.
Moderate:
Consider dose reduction (e.g., 50%) or extended dosing interval; monitor for increased sedation and anticholinergic effects.
Severe:
Avoid use if possible; if necessary, significant dose reduction (e.g., 75%) or extended dosing interval (e.g., every 8-12 hours) required. Monitor closely.
Dialysis:
Triprolidine is not significantly dialyzable. Dose adjustment based on residual renal function and clinical response.
Hepatic Impairment:
Mild:
No specific adjustment recommended, monitor for increased sedation.
Moderate:
Consider dose reduction (e.g., 50%) or extended dosing interval; monitor for increased sedation and anticholinergic effects.
Severe:
Avoid use if possible; if necessary, significant dose reduction (e.g., 75%) or extended dosing interval required. Monitor closely.
Pharmacology
Mechanism of Action
Triprolidine is a first-generation antihistamine that competitively antagonizes H1-receptors, thereby preventing the effects of histamine on capillaries, bronchi, and gastrointestinal smooth muscle. It also possesses significant anticholinergic (antimuscarinic) properties, contributing to its drying effects (e.g., on nasal secretions) and common side effects like drowsiness, dry mouth, and blurred vision. Its sedative effects are due to its ability to cross the blood-brain barrier and antagonize H1-receptors in the central nervous system.
Pharmacokinetics
Absorption:
Bioavailability:
Not precisely quantified, but well absorbed orally.
Tmax:
Approximately 1.5 to 2 hours
FoodEffect:
Food may slightly delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
Approximately 4.6 L/kg
ProteinBinding:
Not extensively protein bound (approximately 80% for some first-gen antihistamines, but specific for triprolidine not widely reported).
CnssPenetration:
Yes (readily crosses the blood-brain barrier, leading to sedative effects)
Elimination:
HalfLife:
Approximately 3 to 6 hours
Clearance:
Not precisely quantified, but primarily hepatic metabolism followed by renal excretion.
ExcretionRoute:
Primarily renal (as metabolites and some unchanged drug)
Unchanged:
Approximately 1% (very small amount)
Pharmacodynamics
OnsetOfAction:
Within 15-30 minutes
PeakEffect:
Approximately 1.5 to 2 hours
DurationOfAction:
Approximately 4 to 6 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate 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
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's 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:
Feeling sleepy
* Feeling nervous and excitable
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice about side effects and help you manage any concerns.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate 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
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's 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:
Feeling sleepy
* Feeling nervous and excitable
Reporting Side Effects
This list is not exhaustive, and you may experience other side effects. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice about side effects and help you manage any concerns.
Seek Immediate Medical Attention If You Experience:
- Severe drowsiness or dizziness that interferes with daily activities
- Difficulty urinating or inability to urinate
- Blurred vision or changes in vision
- Severe dry mouth that is bothersome
- Unusual excitement, nervousness, or restlessness (especially in children)
- Signs of an allergic reaction (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:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
Potential interactions with other medications or health conditions. This medication may interact with other drugs or exacerbate certain health problems.
To ensure safe treatment, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are currently taking
Any natural products or vitamins you are using
* Existing health problems or conditions
Before making any changes to your medication regimen, consult with your doctor to confirm that it is safe to take this medication in conjunction with your other drugs and health conditions. Do not initiate, discontinue, or modify the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, any of its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced as a result of the allergy.
Potential interactions with other medications or health conditions. This medication may interact with other drugs or exacerbate certain health problems.
To ensure safe treatment, provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are currently taking
Any natural products or vitamins you are using
* Existing health problems or conditions
Before making any changes to your medication regimen, consult with your doctor to confirm that it is safe to take this medication in conjunction with your other drugs and health conditions. Do not initiate, discontinue, or modify the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Adhere strictly to the dosage instructions provided by your doctor, as taking more than prescribed may increase your risk of experiencing severe side effects. Do not exceed the recommended treatment duration, and only take this medication for the length of time specified by your doctor.
Until you are familiar with how this medication affects you, exercise caution when engaging in activities that require alertness, such as driving. Additionally, refrain from consuming alcohol while taking this drug, as it may exacerbate its effects.
Before using marijuana, other forms of cannabis, or any prescription or over-the-counter (OTC) medications that may cause drowsiness or slow your reactions, consult with your doctor to discuss potential interactions. If the patient is a child, this medication should be used with caution, as children may be at a higher risk of experiencing excitability.
If you are pregnant, planning to become pregnant, or are breast-feeding, it is crucial to discuss the benefits and risks of this medication with your doctor, as this will help you make an informed decision about its use and potential impact on you and your baby.
Until you are familiar with how this medication affects you, exercise caution when engaging in activities that require alertness, such as driving. Additionally, refrain from consuming alcohol while taking this drug, as it may exacerbate its effects.
Before using marijuana, other forms of cannabis, or any prescription or over-the-counter (OTC) medications that may cause drowsiness or slow your reactions, consult with your doctor to discuss potential interactions. If the patient is a child, this medication should be used with caution, as children may be at a higher risk of experiencing excitability.
If you are pregnant, planning to become pregnant, or are breast-feeding, it is crucial to discuss the benefits and risks of this medication with your doctor, as this will help you make an informed decision about its use and potential impact on you and your baby.
Overdose Information
Overdose Symptoms:
- Severe drowsiness or deep sleep
- Severe dry mouth, nose, or throat
- Flushing or redness of the face
- Dilated pupils
- Blurred vision
- Fast or irregular heartbeat
- Confusion, hallucinations, or delirium
- Seizures
- Loss of consciousness
- Difficulty breathing
What to Do:
In case of overdose, seek immediate medical attention or call a Poison Control Center (1-800-222-1222). Bring the medication bottle with you. Treatment is supportive and symptomatic.
Drug Interactions
Contraindicated Interactions
- Monoamine Oxidase Inhibitors (MAOIs) (concurrent use or within 14 days of MAOI discontinuation)
Major Interactions
- CNS depressants (e.g., alcohol, opioids, benzodiazepines, sedatives, hypnotics, anxiolytics, tricyclic antidepressants, antipsychotics) - increased sedation and CNS depression.
- Other anticholinergic drugs (e.g., atropine, scopolamine, some antipsychotics, tricyclic antidepressants) - increased risk of anticholinergic side effects (dry mouth, urinary retention, blurred vision, constipation).
Moderate Interactions
- Potassium chloride (oral forms) - increased risk of GI lesions due to decreased GI motility.
- Betahistine - may reduce the effect of betahistine.
Minor Interactions
- None specifically noted as minor, most interactions are moderate to major due to additive effects.
Monitoring
Baseline Monitoring
Baseline CNS status (alertness, orientation)
Rationale: To assess for pre-existing conditions that may be exacerbated by sedation and to establish a baseline for monitoring drug effects.
Timing: Prior to initiation of therapy, especially in elderly or those on other CNS depressants.
History of urinary retention, glaucoma, or prostatic hypertrophy
Rationale: Anticholinergic effects can worsen these conditions.
Timing: Prior to initiation of therapy.
Routine Monitoring
Level of consciousness/sedation
Frequency: Regularly, especially during initial therapy and dose adjustments.
Target: Patient should remain alert enough for daily activities; excessive drowsiness is a sign of over-sedation.
Action Threshold: If excessive drowsiness, confusion, or impaired coordination occurs, reduce dose or discontinue.
Anticholinergic side effects (dry mouth, blurred vision, urinary hesitancy/retention, constipation)
Frequency: Regularly, as reported by patient.
Target: Minimal to tolerable side effects.
Action Threshold: If severe or intolerable, consider dose reduction or alternative therapy.
Symptom relief (e.g., sneezing, runny nose)
Frequency: As needed, based on patient report.
Target: Adequate symptom control.
Action Threshold: If symptoms persist or worsen, re-evaluate diagnosis or consider alternative therapy.
Symptom Monitoring
- Excessive drowsiness or sedation
- Dizziness
- Blurred vision
- Dry mouth
- Nasal dryness
- Urinary retention or difficulty urinating
- Constipation
- Nervousness or restlessness (paradoxical excitation, especially in children)
- Confusion (especially in elderly)
Special Patient Groups
Pregnancy
Triprolidine is classified as Pregnancy Category C. Animal studies have shown adverse effects, but there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Avoid use in the third trimester due to potential for adverse effects in the neonate (e.g., irritability, tremors).
Trimester-Specific Risks:
First Trimester:
Limited human data. Animal studies suggest potential for adverse effects. Use only if clearly needed.
Second Trimester:
Limited human data. Generally considered safer than first trimester, but still use with caution.
Third Trimester:
Avoid use, especially close to term, due to potential for neonatal irritability, tremors, and respiratory depression, and theoretical risk of retrolental fibroplasia in premature infants.
Lactation
Triprolidine is excreted into breast milk. Due to its sedative and anticholinergic effects, and the potential for decreased milk supply, it is generally not recommended for use during breastfeeding, especially in newborns or premature infants. The American Academy of Pediatrics considers antihistamines to be of concern during lactation.
Infant Risk:
Moderate risk (L3). Potential for infant sedation, irritability, and anticholinergic effects (e.g., dry mouth, constipation). May also decrease milk supply, particularly in the early postpartum period.
Pediatric Use
Use with caution in children, especially those under 2 years of age, as they may be more susceptible to adverse effects, including paradoxical excitation (nervousness, restlessness, insomnia) or increased sensitivity to anticholinergic effects. Dosing must be precise based on age/weight. Not recommended for infants under 6 months.
Geriatric Use
Elderly patients are more susceptible to the sedative and anticholinergic effects (e.g., confusion, dizziness, dry mouth, urinary retention, constipation) of triprolidine. Use with caution, starting with the lowest effective dose and monitoring closely for adverse effects. Avoid in elderly patients with cognitive impairment, glaucoma, or prostatic hypertrophy.
Clinical Information
Clinical Pearls
- Triprolidine is a first-generation antihistamine known for its significant sedative and anticholinergic properties. Counsel patients about these effects.
- Due to its short half-life, frequent dosing (every 4-6 hours) is required for continuous symptom relief.
- Advise patients to avoid activities requiring mental alertness (e.g., driving, operating machinery) until they know how the medication affects them.
- Warn patients about additive CNS depression when combined with alcohol or other sedatives.
- Consider alternative, less sedating antihistamines (second-generation) for patients who require daytime allergy relief or have occupations requiring alertness.
- Monitor elderly patients closely for confusion, falls, and urinary retention.
Alternative Therapies
- Second-generation antihistamines (e.g., Loratadine, Cetirizine, Fexofenadine, Desloratadine, Levocetirizine) for allergy symptoms with less sedation and anticholinergic effects.
- Nasal corticosteroids (e.g., Fluticasone, Mometasone) for allergic rhinitis.
- Cromolyn sodium nasal spray for allergy prevention.
- Decongestants (e.g., Pseudoephedrine, Phenylephrine) for nasal congestion (often combined with antihistamines).
Cost & Coverage
Average Cost:
Typically low cost per 120 mL bottle
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (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 use, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it's a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't 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.