Histex-DM Syrup
It is used to treat nose stuffiness.It is used to ease allergy signs.It is used to relieve coughing.
Drug Class
Antihistamine, Nasal Decongestant, Antitussive
Pharmacologic Class
H1-receptor antagonist (first-generation), Alpha-1 adrenergic agonist, NMDA receptor antagonist (and sigma-1 agonist)
Pregnancy Category
Category C
FDA Approved
Jan 1970
DEA Schedule
Not Controlled
Overview
What is this medicine?
Histex-DM Syrup is an over-the-counter medicine used to relieve cold and allergy symptoms like sneezing, runny nose, watery eyes, nasal congestion, and cough. It contains an antihistamine (triprolidine) to reduce allergy symptoms, a decongestant (phenylephrine) to clear stuffy nose, and a cough suppressant (dextromethorphan) to calm your cough.
How to Use This Medicine
Taking Your Medication Correctly
To ensure you get the most benefit from 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 device.
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 have questions about disposing of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs 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 ensure you get the most benefit from 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 device.
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 have questions about disposing of your medication, consult your pharmacist. You may also want to check if there are drug take-back programs 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 medicine affects you, as it can cause drowsiness.
- Avoid alcohol and other sedating medications, as they can increase drowsiness.
- Stay hydrated by drinking plenty of fluids to help thin mucus.
- Use a humidifier to help soothe irritated airways.
- Do not exceed the recommended dose, as this can lead to serious side effects.
Available Forms & Alternatives
Available Strengths:
Dosing & Administration
Adult Dosing
Standard Dose:
10 mL (2.5 mg triprolidine, 10 mg phenylephrine, 30 mg dextromethorphan) orally every 4-6 hours as needed
Dose Range:
10 - 40 mg
Condition-Specific Dosing:
maxDailyDose:
Do not exceed 4 doses (40 mL) in 24 hours.
Pediatric Dosing
Neonatal:
Not established
Infant:
Not recommended for children under 2 years of age. Consult a physician for children under 4 years.
Child:
Children 6 to under 12 years: 5 mL orally every 4-6 hours as needed (max 4 doses in 24 hours). Children 2 to under 6 years: Consult a physician.
Adolescent:
Adolescents 12 years and older: 10 mL orally every 4-6 hours as needed (max 4 doses in 24 hours).
Dose Adjustments
Renal Impairment:
Mild:
Use with caution; consider dose reduction due to potential accumulation of triprolidine and dextromethorphan metabolites.
Moderate:
Use with caution; consider dose reduction (e.g., 50% of usual dose) and extended dosing intervals.
Severe:
Contraindicated or significant dose reduction required. Consult physician. Triprolidine and dextromethorphan are primarily renally eliminated.
Dialysis:
Not well studied; use with extreme caution. Components are not significantly dialyzable.
Hepatic Impairment:
Mild:
Use with caution; monitor for increased adverse effects.
Moderate:
Consider dose reduction (e.g., 50% of usual dose) and extended dosing intervals due to impaired metabolism of all components.
Severe:
Contraindicated or significant dose reduction required. Consult physician. All components undergo hepatic metabolism.
Pharmacology
Mechanism of Action
Triprolidine is a first-generation antihistamine that competitively antagonizes H1-receptors, leading to reduced histamine-mediated effects like sneezing, rhinorrhea, and itching. It also possesses anticholinergic properties. Phenylephrine is a direct-acting sympathomimetic amine that primarily acts as an alpha-1 adrenergic receptor agonist, causing vasoconstriction in the nasal mucosa, thereby reducing swelling and congestion. Dextromethorphan is a non-opioid antitussive that acts centrally on the cough center in the medulla to elevate the cough threshold. Its mechanism involves antagonism of NMDA receptors and agonism of sigma-1 receptors.
Pharmacokinetics
Absorption:
Bioavailability:
Triprolidine: High; Phenylephrine: ~38% (oral due to first-pass metabolism); Dextromethorphan: High
Tmax:
Triprolidine: 1-2 hours; Phenylephrine: 1-2 hours; Dextromethorphan: 1-2.5 hours
FoodEffect:
Food may slightly delay absorption but generally does not significantly affect bioavailability.
Distribution:
Vd:
Triprolidine: ~4 L/kg; Phenylephrine: Not well established; Dextromethorphan: ~5-6 L/kg
ProteinBinding:
Triprolidine: ~80%; Phenylephrine: Not well established; Dextromethorphan: ~60-70%
CnssPenetration:
Triprolidine: Yes (significant); Phenylephrine: Limited; Dextromethorphan: Yes
Elimination:
HalfLife:
Triprolidine: 3-5 hours; Phenylephrine: 2-3 hours; Dextromethorphan: 2-4 hours (parent), 10-20 hours (dextrorphan)
Clearance:
Not precisely quantified for combination; primarily hepatic metabolism and renal excretion.
ExcretionRoute:
Renal (urine)
Unchanged:
Triprolidine: ~1%; Phenylephrine: <1%; Dextromethorphan: <1%
Pharmacodynamics
OnsetOfAction:
Triprolidine: 15-60 minutes; Phenylephrine: 15-30 minutes; Dextromethorphan: 15-60 minutes
PeakEffect:
Triprolidine: 1-2 hours; Phenylephrine: 1-2 hours; Dextromethorphan: 1-2.5 hours
DurationOfAction:
Triprolidine: 4-6 hours; Phenylephrine: 4-6 hours; Dextromethorphan: 4-6 hours
Confidence:
Medium
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention. Although rare, some people may have severe and potentially life-threatening side effects when taking this medication. Be aware of the following signs of a serious allergic reaction:
- 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 have mild 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 for advice:
- Feeling dizzy or sleepy
- Feeling nervous and excitable
- Trouble sleeping
Reporting Side Effects
This list does not include all possible side effects. If you have questions or concerns about side effects, consult your doctor. For medical advice about side effects, call your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
If you experience any of the following symptoms, call your doctor immediately or seek emergency medical attention. Although rare, some people may have severe and potentially life-threatening side effects when taking this medication. Be aware of the following signs of a serious allergic reaction:
- 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 have mild 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 for advice:
- Feeling dizzy or sleepy
- Feeling nervous and excitable
- Trouble sleeping
Reporting Side Effects
This list does not include all possible side effects. If you have questions or concerns about side effects, consult your doctor. For medical advice about side effects, call 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 dizziness or drowsiness
- Nervousness, restlessness, or trouble sleeping
- Fast, pounding, or irregular heartbeat
- Significant increase in blood pressure
- Difficulty urinating
- Blurred vision
- Hallucinations or confusion (especially with overdose)
- Symptoms that worsen or last more than 7 days (5 days for children), or are accompanied by high fever, rash, or persistent headache.
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, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you have a cough that produces a significant amount of mucus, a chronic cough caused by smoking or exposure to smoke, or lung conditions like asthma or emphysema.
If you have taken certain medications for depression or Parkinson's disease within the last 14 days, including isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this may increase the risk of severely high blood pressure.
If you are currently taking linezolid or methylene blue, as these medications can interact with this drug.
Additionally, it is crucial to provide your doctor and pharmacist with a comprehensive list of all your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
You should also inform them about any existing health problems. This information will help your doctor determine whether it is safe for you to take this medication with your other medications and health conditions. Do not start, stop, or change the dosage 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, its components, or other substances, such as foods or drugs. Be sure to describe the allergic reaction you experienced, including any symptoms that occurred.
If you have a cough that produces a significant amount of mucus, a chronic cough caused by smoking or exposure to smoke, or lung conditions like asthma or emphysema.
If you have taken certain medications for depression or Parkinson's disease within the last 14 days, including isocarboxazid, phenelzine, tranylcypromine, selegiline, or rasagiline, as this may increase the risk of severely high blood pressure.
If you are currently taking linezolid or methylene blue, as these medications can interact with this drug.
Additionally, it is crucial to provide your doctor and pharmacist with a comprehensive list of all your medications, including:
Prescription and over-the-counter (OTC) drugs
Natural products
* Vitamins
You should also inform them about any existing health problems. This information will help your doctor determine whether it is safe for you to take this medication with your other medications and health conditions. Do not start, stop, or change the dosage 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.
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 chances of experiencing adverse effects. Additionally, do not take this medication for a longer duration than specified by your doctor.
Until you understand how this medication affects you, it is crucial to avoid operating a vehicle, performing tasks that require alertness, or engaging in activities that demand your full attention. It is also recommended 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 or slow your reactions, consult with your doctor to discuss potential interactions.
When administering this medication to children, exercise caution, as they may be at a higher risk of experiencing excitability.
If you are pregnant, planning to become pregnant, or are breast-feeding, inform your doctor. It is necessary to discuss the potential benefits and risks of this medication to both you and your baby to make an informed decision.
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 chances of experiencing adverse effects. Additionally, do not take this medication for a longer duration than specified by your doctor.
Until you understand how this medication affects you, it is crucial to avoid operating a vehicle, performing tasks that require alertness, or engaging in activities that demand your full attention. It is also recommended 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 or slow your reactions, consult with your doctor to discuss potential interactions.
When administering this medication to children, exercise caution, as they may be at a higher risk of experiencing excitability.
If you are pregnant, planning to become pregnant, or are breast-feeding, inform your doctor. It is necessary to discuss the potential benefits and risks of this medication to both you and your baby to make an informed decision.
Overdose Information
Overdose Symptoms:
- Severe drowsiness or sedation
- Dizziness, confusion, hallucinations
- Nervousness, restlessness, tremors, seizures
- Rapid heartbeat, high blood pressure
- Dilated pupils
- Nausea, vomiting
- Difficulty breathing
- Urinary retention
What to Do:
In case of overdose, seek immediate medical attention or call a Poison Control Center at 1-800-222-1222. Be prepared to provide the name of the product, the amount taken, and the time it was taken.
Drug Interactions
Contraindicated Interactions
- Monoamine Oxidase Inhibitors (MAOIs) (e.g., phenelzine, selegiline, tranylcypromine, isocarboxazid, linezolid, methylene blue) - concurrent use or within 14 days of MAOI discontinuation due to risk of hypertensive crisis (phenylephrine) and serotonin syndrome (dextromethorphan).
Major Interactions
- Other sympathomimetics (e.g., pseudoephedrine, ephedrine, amphetamines) - increased risk of cardiovascular effects (hypertension, tachycardia).
- Serotonergic drugs (e.g., SSRIs, SNRIs, TCAs, triptans, tramadol, St. John's Wort) - increased risk of serotonin syndrome with dextromethorphan.
- CNS depressants (e.g., alcohol, benzodiazepines, opioids, sedatives, hypnotics) - additive CNS depression with triprolidine.
- Anticholinergic drugs (e.g., tricyclic antidepressants, atropine, some antipsychotics) - additive anticholinergic effects with triprolidine (e.g., dry mouth, urinary retention, blurred vision).
Moderate Interactions
- Beta-blockers (non-selective) - may enhance the pressor effect of phenylephrine.
- Digoxin - increased risk of arrhythmias with phenylephrine.
- CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, quinidine, amiodarone) - may increase dextromethorphan levels and risk of toxicity.
- Antihypertensive medications - phenylephrine may reduce the effectiveness of antihypertensive drugs.
Minor Interactions
- Potassium-sparing diuretics - phenylephrine may increase potassium loss.
Monitoring
Baseline Monitoring
Blood Pressure and Heart Rate
Rationale: Phenylephrine can cause increases in blood pressure and heart rate, especially in susceptible individuals.
Timing: Prior to initiation, especially in patients with pre-existing cardiovascular conditions.
Medical History Review
Rationale: Identify conditions like hypertension, heart disease, diabetes, thyroid disorders, glaucoma, prostate enlargement, or concurrent MAOI use that contraindicate or require caution.
Timing: Before prescribing/recommending.
Routine Monitoring
Symptom Resolution (cough, congestion, sneezing)
Frequency: Daily
Target: Improvement or resolution of symptoms within 7 days.
Action Threshold: If symptoms worsen or persist for more than 7 days (or 5 days for children), or are accompanied by fever, rash, or persistent headache, discontinue and seek medical attention.
Adverse Effects (e.g., drowsiness, dizziness, nervousness, insomnia, dry mouth, urinary retention)
Frequency: Daily
Target: Absence or mild, tolerable adverse effects.
Action Threshold: If severe or persistent adverse effects occur, discontinue use and seek medical advice.
Blood Pressure and Heart Rate (in susceptible patients)
Frequency: As needed, if concerns arise
Target: Within patient's normal range.
Action Threshold: Significant elevation (e.g., >20 mmHg systolic or >10 mmHg diastolic from baseline, or new onset tachycardia) warrants discontinuation and medical evaluation.
Symptom Monitoring
- Cough frequency and severity
- Nasal congestion
- Sneezing
- Rhinorrhea
- Sore throat (if present)
- Drowsiness/Sedation
- Dizziness
- Nervousness/Restlessness
- Insomnia
- Dry mouth
- Blurred vision
- Urinary difficulty
- Palpitations/Tachycardia
- Headache
Special Patient Groups
Pregnancy
Category C. Use only if the potential benefit justifies the potential risk to the fetus. Consult a healthcare provider before use.
Trimester-Specific Risks:
First Trimester:
Limited data; potential for cardiovascular effects with phenylephrine. Triprolidine and dextromethorphan generally not associated with major malformations.
Second Trimester:
Generally considered safer than first trimester, but still use with caution.
Third Trimester:
Avoid phenylephrine in the third trimester due to potential for uterine vasoconstriction and fetal hypoxia. Antihistamines may cause irritability in the neonate if used close to delivery.
Lactation
L3 (Moderate Concern). Components are excreted into breast milk. Use with caution and monitor the infant for adverse effects.
Infant Risk:
Triprolidine: May cause drowsiness, irritability, or anticholinergic effects in the infant; may decrease milk supply. Phenylephrine: May cause irritability or vasoconstriction in the infant. Dextromethorphan: Generally considered low risk, but monitor for sedation.
Pediatric Use
Not recommended for children under 2 years of age. For children 2 to under 6 years, consult a physician. Use with caution in children due to potential for paradoxical excitation with antihistamines and risk of overdose with cough/cold products.
Geriatric Use
Use with caution. Elderly patients are more susceptible to the anticholinergic effects (e.g., dry mouth, urinary retention, constipation, confusion) of triprolidine and the cardiovascular effects (e.g., hypertension, tachycardia) of phenylephrine. Start with the lowest effective dose and monitor closely.
Clinical Information
Clinical Pearls
- This product is for symptomatic relief of cold/allergy symptoms and does not treat the underlying cause.
- Advise patients to read the label carefully and not to exceed the recommended dose, as overdose can lead to serious side effects, especially in children.
- Counsel patients on the potential for drowsiness and to avoid activities requiring mental alertness.
- Warn about the critical interaction with MAOIs; ensure patients understand the 14-day washout period.
- Patients with underlying conditions such as hypertension, heart disease, diabetes, thyroid disease, glaucoma, or prostate enlargement should consult a doctor before use.
Alternative Therapies
- Single-ingredient antihistamines (e.g., loratadine, cetirizine for non-drowsy relief)
- Single-ingredient decongestants (e.g., pseudoephedrine, oxymetazoline nasal spray)
- Single-ingredient antitussives (e.g., guaifenesin, benzonatate)
- Saline nasal sprays for congestion
- Honey for cough relief
Cost & Coverage
Average Cost:
$10 - $30 per 120 mL or 473 mL bottle
Generic Available:
Yes
Insurance Coverage:
Typically OTC, not covered by prescription insurance. May be eligible for FSA/HSA.
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to 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.