Usage
- Medical Conditions: Diphenylpyraline is prescribed for the symptomatic relief of allergic conditions such as allergic rhinitis (hay fever), allergic conjunctivitis, allergic dermatoses, pruritus (itching), urticaria (hives), and insect bites and stings. It may also be present in cough syrups to provide relief from cough.
- Pharmacological Classification: Antihistamine (H1 receptor antagonist). Also possesses anticholinergic and sedative properties.
- Mechanism of Action: Diphenylpyraline competes with histamine for H1 receptor sites on effector cells, thus reducing the effects of histamine and providing temporary relief from allergy symptoms. Its anticholinergic activity contributes to a drying effect on the nasal mucosa.
Alternate Names
- International/Regional Variations: Piprinhydrinate (as diphenylpyraline teoclate).
- Brand Names: Solphyllex, Actophlem Cough Syrup (India); various other combination cold and cough medications internationally.
How It Works
- Pharmacodynamics: Diphenylpyraline binds to and blocks the H1 histamine receptors, preventing histamine from exerting its effects. This leads to a reduction in vascular permeability, smooth muscle contraction, and mucus secretion. The anticholinergic effect contributes to drying of secretions.
- Pharmacokinetics: Diphenylpyraline is readily absorbed after oral administration. Onset of action is typically within 15-30 minutes, with peak effects within 1-2 hours. Duration of action can last up to 6 hours. Metabolism is primarily hepatic, and elimination is mainly through renal excretion.
- Mode of Action: Competitive antagonism at the H1 histamine receptor.
- Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Binds to H1 histamine receptors, indirectly affecting levels of dopamine and acetylcholine.
- Elimination Pathways: Primarily hepatic metabolism, followed by renal excretion.
Dosage
Standard Dosage
Adults:
- 10-20 mg, two to four times daily (up to a maximum of 6 mg per day in some regions).
Children:
- Dose adjusted according to body weight (e.g., 1.25 mg per kg of body weight daily in divided doses). Use with caution, as children may be more sensitive to the effects of this drug.
Special Cases:
- Elderly Patients: Start with lower doses due to increased risk of side effects, especially drowsiness and confusion.
- Patients with Renal Impairment: Dose adjustment necessary based on creatinine clearance.
- Patients with Hepatic Dysfunction: Dose reduction required.
- Patients with Comorbid Conditions: Use with caution in patients with cardiovascular disease, asthma, or thyroid disorders.
Clinical Use Cases:
Dosing information for specific clinical use cases such as intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations is not available in the provided sources.
Dosage Adjustments:
Modify dosage based on patient-specific factors like renal/hepatic dysfunction, age, and other comorbid conditions.
Side Effects
Common Side Effects:
- Drowsiness
- Dizziness
- Dry mouth
- Blurred vision
- Constipation
- Urinary retention
- Headache
- Fatigue
Rare but Serious Side Effects:
- Confusion
- Seizures
- Allergic reactions (rash, itching, swelling)
- Tachycardia or palpitations
- Hypotension
Long-Term Effects:
Information about potential long-term effects with chronic use is not readily available.
Adverse Drug Reactions (ADR):
Severe allergic reactions, seizures, significant cardiovascular effects (tachycardia, hypotension).
Contraindications
- Hypersensitivity to diphenylpyraline
- Severe liver disease
- Narrow-angle glaucoma
- Urinary retention
- Prostatic hypertrophy
- Pyloroduodenal obstruction
- Epilepsy
Drug Interactions
- CNS depressants: (alcohol, barbiturates, benzodiazepines, opioid analgesics): Enhanced sedation.
- Anticholinergic drugs: (antidepressants, antipsychotics, gastrointestinal medications): Increased anticholinergic effects.
- MAOIs: Intensified anticholinergic and CNS depressant effects.
- Other: Aminoglycosides (masking of ototoxicity), betahistine (antagonism), bupropion (increased seizure risk), mefloquine (QT prolongation).
Pregnancy and Breastfeeding
Use only if clearly needed and under close medical supervision, as safety during pregnancy and lactation hasn’t been fully established. Potential for fetal risks and excretion in breast milk.
Drug Profile Summary
- Mechanism of Action: H1 receptor antagonist.
- Side Effects: Drowsiness, dry mouth, blurred vision, constipation.
- Contraindications: Hypersensitivity, severe liver disease, narrow-angle glaucoma, urinary retention.
- Drug Interactions: CNS depressants, anticholinergics, MAOIs.
- Pregnancy & Breastfeeding: Use with caution.
- Dosage: Adults: 10-20 mg 2-4 times/day (max. 6 mg/day in some areas). Children: Weight-based dosing.
- Monitoring Parameters: Observe for adverse reactions, especially CNS depression, anticholinergic effects, and allergic reactions.
Popular Combinations:
Often included in combination cold and cough medications with other active ingredients like theophylline, etofylline, ammonium chloride, and sodium citrate.
Precautions
- Pre-existing conditions: Screen for contraindications.
- Pregnant/Breastfeeding: Use with caution.
- Children/Elderly: Age-specific dosing and monitoring.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Diphenylpyraline?
A: Adults: 10-20 mg, 2-4 times daily (max. 6 mg/day in some regions), Children: Dose adjusted according to weight.
Q2: What are the common side effects?
A: Drowsiness, dry mouth, blurred vision, constipation, urinary retention.
Q3: What are the contraindications for Diphenylpyraline?
A: Hypersensitivity, severe liver disease, narrow-angle glaucoma, urinary retention, prostatic hypertrophy.
Q4: Can Diphenylpyraline be used during pregnancy or breastfeeding?
A: Use only if clearly needed and under close medical supervision due to limited safety data.
Q5: What are the major drug interactions with Diphenylpyraline?
A: CNS depressants, anticholinergics, MAOIs, certain other medications like aminoglycosides, betahistine, bupropion, and mefloquine.
Q6: How does Diphenylpyraline work?
A: It is an H1 receptor antagonist, blocking the effects of histamine in the body.
Q7: What conditions is Diphenylpyraline used to treat?
A: Allergic conditions like rhinitis, conjunctivitis, dermatoses, pruritus, urticaria, and insect bites. It is also used to provide relief from cough.
Q8: Are there any special precautions for elderly patients?
A: Yes, start with a lower dose due to increased risk of side effects.
Q9: How long does it take for Diphenylpyraline to start working?
A: Typically within 15-30 minutes.
Q10: What should I do if I experience side effects?
A: Contact your healthcare provider, especially if the side effects are severe or persistent.
