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Diphenhydramine + Levomenthol

Allopathic
Medicines List
All Medicine
All M
Syrup
Mendil (14 mg+2 mg)/5 ml

Globe Pharmaceuticals Ltd.

Indications
  • Symptomatic relief of allergic conditions such as allergic rhinitis, urticaria, and pruritus
  • Relief of cough and throat irritation associated with upper respiratory tract infections
  • Temporary relief of nasal congestion and minor throat discomfort
  • Management of motion sickness, nausea, and vomiting (primarily diphenhydramine)
  • Adjunct therapy for cold and flu symptoms involving cough and nasal congestion
Dosage & Administration
  • Route: Oral (syrup, lozenges), topical (cream/ointment)
  • Adults and Adolescents (≥12 years):
    • Oral syrup: 10 mL every 4 to 6 hours; max 60 mL per 24 hours
    • Lozenges: 1 lozenge every 2 to 4 hours; max 6 lozenges per 24 hours
    • Topical application: Apply thin layer 3 to 4 times daily to affected area
  • Children (6–11 years):
    • Oral syrup: 5 mL every 4 to 6 hours; max 30 mL per 24 hours
    • Use under medical supervision
  • Children under 6 years:
    • Not generally recommended due to risk of sedation and toxicity
  • Elderly:
    • Use with caution; increased sensitivity to sedative and anticholinergic effects
  • Special Populations:
    • No specific dose adjustment for hepatic or renal impairment documented, but caution advised
  • Administration Notes:
    • Shake syrup well before use
    • Avoid concurrent use with other CNS depressants
    • Do not exceed recommended dosage
Mechanism of Action (MOA)
  • Diphenhydramine: A first-generation H1 antihistamine that competitively blocks histamine at H1 receptor sites, reducing allergic symptoms such as itching, swelling, and mucus secretion. It also exerts anticholinergic and sedative effects through central nervous system penetration, which suppresses cough reflex and nausea.
  • Levomenthol: Acts as a topical analgesic and mild decongestant by stimulating transient receptor potential melastatin 8 (TRPM8) cold receptors on sensory neurons, producing a cooling sensation that soothes throat irritation and nasal mucosa, providing symptomatic relief from cough and congestion.
Pharmacokinetics
  • Diphenhydramine:
    • Rapidly absorbed after oral administration, peak plasma concentration in 2–4 hours
    • Extensive hepatic metabolism mainly via CYP2D6
    • Half-life: 4–8 hours
    • Excretion primarily renal as metabolites
  • Levomenthol:
    • Minimal systemic absorption due to topical/local effects
    • Metabolized in liver; metabolites excreted renally
    • Pharmacokinetic data on systemic exposure limited due to topical use
Pregnancy Category & Lactation
  • Pregnancy:
    • Diphenhydramine: FDA Category B — no proven risk in humans, but use only if clearly needed
    • Levomenthol: Limited data; use cautiously
  • Lactation:
    • Diphenhydramine is excreted in breast milk; potential sedation in nursing infants; caution advised
    • Levomenthol: Data limited; topical use likely low risk but caution recommended
Therapeutic Class
  • Diphenhydramine: First-generation H1 antihistamine
  • Levomenthol: Topical analgesic and mild decongestant
Contraindications
  • Known hypersensitivity to diphenhydramine, levomenthol, or any formulation excipients
  • Newborns or premature infants (risk of severe CNS depression)
  • Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of MAOI therapy
  • Narrow-angle glaucoma
  • Severe urinary retention
Warnings & Precautions
  • Caution in patients with asthma, chronic obstructive pulmonary disease (COPD), or respiratory disorders due to risk of thickened bronchial secretions
  • Avoid driving or operating machinery due to sedative effects of diphenhydramine
  • Use with caution in elderly due to increased risk of confusion, sedation, and anticholinergic effects
  • Avoid concurrent CNS depressants and alcohol to reduce risk of additive sedation
  • Topical levomenthol products should not be applied to broken or irritated skin
Side Effects
  • Common:
    • Sedation, dizziness, dry mouth (diphenhydramine)
    • Local irritation or burning sensation (levomenthol topical)
    • Nausea or gastrointestinal upset (less common)
  • Serious/Rare:
    • Allergic reactions including rash, urticaria, angioedema
    • Paradoxical CNS stimulation (especially in children)
    • Respiratory depression (rare, mostly overdose)
Drug Interactions
  • CNS depressants (e.g., benzodiazepines, opioids, alcohol) — increased sedation and respiratory depression risk
  • MAO inhibitors — risk of hypertensive crisis or serotonin syndrome with diphenhydramine
  • Other anticholinergic agents — additive anticholinergic effects (e.g., urinary retention, dry mouth)
  • Cimetidine may increase diphenhydramine plasma levels by inhibiting metabolism
Recent Updates or Guidelines
  • No significant recent changes in indications or dosing recommendations
  • Increased caution in pediatric use emphasized in guidelines
  • Warnings about potential additive CNS depression with concurrent sedatives updated in safety communications
Storage Conditions
  • Store oral formulations at 20°C to 25°C (68°F to 77°F)
  • Protect from light and moisture
  • Keep topical products tightly closed, store at room temperature
  • Keep all formulations out of reach of children
  • Do not freeze