Usage
Triprolidine is an antihistamine primarily used to relieve symptoms associated with allergies, hay fever, and the common cold. These symptoms include runny nose, sneezing, itchy or watery eyes, and itchy throat or skin. It is classified as a first-generation antihistamine, belonging to the alkylamine subclass. Triprolidine works by blocking the action of histamine, a substance released by the body during an allergic reaction. By blocking histamine, triprolidine reduces the symptoms caused by histamine release. It also possesses antimuscarinic activity, which contributes to drying up secretions like runny nose and watery eyes.
Alternate Names
While “triprolidine” and “triprolidine hydrochloride” are the most common names, it may be found in combination products under various brand names such as Actifed, Myidil, and Benadryl Allergy Ultratabs (in combination with other active ingredients).
How It Works
Pharmacodynamics: Triprolidine competes with histamine for binding at the H1 receptor sites. This antagonism reduces the effects of histamine, alleviating allergy symptoms. The antimuscarinic properties of triprolidine contribute to the drying of secretions, further easing symptoms such as runny nose and watery eyes.
Pharmacokinetics:
- Absorption: Triprolidine is well-absorbed after oral administration, reaching peak plasma concentrations in about 1.5 to 2 hours.
- Metabolism: It is extensively metabolized in the liver, primarily through oxidation.
- Elimination: Triprolidine is mainly eliminated through the kidneys, with a small portion excreted in feces. The elimination half-life is approximately 4 hours.
Mode of Action: Triprolidine is a competitive H1 receptor antagonist. It binds to H1 receptors, preventing histamine from binding and triggering the cascade of events that lead to allergy symptoms. The antimuscarinic effects stem from its ability to block acetylcholine at muscarinic receptors.
Receptor Binding/Enzyme Inhibition: Triprolidine primarily acts as an H1 receptor antagonist. It has negligible effects on other receptor systems or enzymes.
Dosage
Standard Dosage
Adults:
The typical adult dose is 2.5 mg every 4 to 6 hours, not exceeding 10 mg in 24 hours.
Children (6-11 years):
The usual dose is 1.25 mg every 4 to 6 hours, with a maximum daily dose of 5 mg.
Children (under 6 years):
Dosage must be determined by a doctor.
Special Cases:
- Elderly Patients: Start with lower doses and monitor closely for adverse effects. Dose adjustments may be needed based on individual patient response and tolerability.
- Patients with Renal Impairment: Dosage adjustments may be necessary depending on the degree of impairment.
- Patients with Hepatic Dysfunction: Reduce dosage as necessary due to potentially impaired metabolism.
- Patients with Comorbid Conditions: Use with caution in patients with glaucoma, urinary retention, prostatic hypertrophy, cardiovascular disease, hyperthyroidism, or bronchial asthma.
Clinical Use Cases
Triprolidine is not typically used in clinical settings such as intubation, surgical procedures, mechanical ventilation, or the ICU. Its primary use is for symptomatic relief of allergy and cold symptoms. It is also not used in emergency situations.
Dosage Adjustments
Dose adjustments should be considered based on individual patient factors, including renal or hepatic dysfunction and coexisting medical conditions.
Side Effects
Common Side Effects:
Drowsiness, dizziness, dry mouth, blurred vision, nausea, and constipation.
Rare but Serious Side Effects:
Severe allergic reactions (anaphylaxis), difficulty breathing, hallucinations, seizures, and cardiac arrhythmias.
Long-Term Effects:
Long-term use can lead to tolerance. Chronic use may also increase the risk of certain side effects, though this is less common with triprolidine compared to other first-generation antihistamines.
Adverse Drug Reactions (ADR):
Agranulocytosis, thrombocytopenia, and Stevens-Johnson syndrome are rare but potentially serious ADRs.
Contraindications
Hypersensitivity to triprolidine, narrow-angle glaucoma, urinary retention, severe asthma, and concomitant use of monoamine oxidase inhibitors (MAOIs).
Drug Interactions
Avoid alcohol and other CNS depressants. Triprolidine may interact with medications metabolized by CYP enzymes, especially CYP3A4. Monitor closely when combining with anticholinergic drugs or MAOIs.
Pregnancy and Breastfeeding
Consult a doctor before using triprolidine during pregnancy or while breastfeeding. Use only if clearly needed and the potential benefits outweigh the risks. Non-sedating antihistamines may be preferred during lactation.
Drug Profile Summary
- Mechanism of Action: H1 receptor antagonist with antimuscarinic effects.
- Side Effects: Drowsiness, dizziness, dry mouth, blurred vision, nausea, constipation.
- Contraindications: Hypersensitivity, narrow-angle glaucoma, urinary retention, severe asthma, MAOI use.
- Drug Interactions: Alcohol, CNS depressants, CYP3A4 substrates, anticholinergic drugs, MAOIs.
- Pregnancy & Breastfeeding: Consult a doctor; use with caution.
- Dosage: Adults: 2.5 mg every 4-6 hours (max 10 mg/day); Children (6-11 years): 1.25 mg every 4-6 hours (max 5 mg/day); Children (under 6): Consult a doctor.
- Monitoring Parameters: Observe for signs of CNS depression, allergic reactions, and adverse effects.
Popular Combinations
Triprolidine is often combined with pseudoephedrine (a decongestant) for enhanced relief of cold and allergy symptoms.
Precautions
Use with caution in elderly patients, children under 6, and patients with pre-existing medical conditions. Avoid driving or operating heavy machinery until the effects of the drug are known. Avoid alcohol.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Triprolidine?
A: Adults: 2.5 mg every 4-6 hours, not to exceed 10 mg/24 hours. Children (6-11 years): 1.25 mg every 4-6 hours, not to exceed 5 mg/24 hours. Children under 6: consult a doctor.
Q2: Can Triprolidine be used during pregnancy?
A: Consult a doctor before use during pregnancy. Use only if clearly needed.
Q3: What are the common side effects of Triprolidine?
A: Drowsiness, dizziness, dry mouth, blurred vision, nausea, and constipation.
Q4: Does Triprolidine interact with other medications?
A: Yes, it can interact with alcohol, CNS depressants, and certain other medications. Consult a doctor or pharmacist about potential drug interactions.
Q5: Can I operate machinery while taking Triprolidine?
A: Avoid operating machinery or driving until you know how triprolidine affects you, as it can cause drowsiness.
Q6: What should I do if I miss a dose?
A: Take the missed dose as soon as you remember, unless it’s almost time for your next dose. Do not double the dose.
Q7: How does Triprolidine work?
A: It blocks the action of histamine at H1 receptors, relieving allergy symptoms. It also possesses antimuscarinic activity, leading to the drying of secretions.
Q8: Is Triprolidine safe for children?
A: It can be used in children over 6 years old with appropriate dosing. For children under 6, consult a doctor.
Q9: What are the signs of a Triprolidine overdose?
A: Severe drowsiness, confusion, hallucinations, seizures, and difficulty breathing. Seek immediate medical attention if overdose is suspected.
Q10: Can Triprolidine be used long-term?
A: Consult a doctor for recommendations on long-term use, as tolerance may develop.
