Mebidal

Approved Indications:

• Allergic Rhinitis: Relief of sneezing, nasal itching, rhinorrhoea associated with seasonal and perennial allergic rhinitis.
• Urticaria (Hives): Adjunctive symptomatic control of pruritus and wheals in acute and chronic urticaria.
• Allergic Conjunctivitis: Relief of ocular pruritus and tearing associated with allergic conjunctivitis.
• Dermal Pruritus: Used for symptomatic relief of itching from allergic dermatoses like atopic dermatitis.

Clinically Accepted Off‑Label Uses:

• Allergic Rhinoconjunctivitis: Combined nasal and ocular allergic symptoms.
• Mild Food or Drug-Induced Allergies: Adjunct for non-life-threatening allergic reactions (not for anaphylaxis).

Route: Oral; tablets swallowed whole, syrup measured carefully.

Adults and Adolescents (≥12 years):

• Standard Dose: 10 mg (1–2 tablets or 2 tsp) once daily at bedtime.
• May adjust to 5 mg overnight if sedation is problematic.

Children (6–11 years):

• Pediatric Dose: 5 mg once daily at bedtime (1 tsp syrup or ½ tablet).

Children (<6 years):

• Not routinely recommended due to insufficient safety data.

Geriatric Patients:

• Same as adults; initiate at 5 mg nightly if at risk of CNS effects.

Renal or Hepatic Impairment:

• Use with caution; no formal dose adjustment, but monitor for prolonged effects.

Mebhydrolin is a first-generation antihistamine that acts as a potent H1 receptor antagonist. By blocking histamine binding at H1 receptors, it prevents vasodilation, increased vascular permeability, and sensory nerve stimulation that underlie classic allergy symptoms (itching, nasal discharge, swelling). Its mild anticholinergic effects contribute to drying of nasal secretions and reduce tissue edema. It crosses the blood–brain barrier, leading to its sedative effects.

• Absorption: Well absorbed after oral dosing; peak plasma levels in 1–2 hours.
• Distribution: Widely distributed; crosses into CNS.
• Protein Binding: Moderate, ~70–80%.
• Metabolism: Primarily hepatic via CYP450 enzymes to inactive metabolites.
• Half-Life: Approximately 6–9 hours.
• Elimination: Excreted in urine and feces both as metabolites and unchanged drug.

• Pregnancy:
  No formal FDA category; animal studies show no clear teratogenic effects. Limited human data; use only if symptomatic benefit outweighs theoretical risks.
• Lactation:
  Excreted in breast milk; may cause sedation or irritability in the infant. Use with caution and monitor breastfed infants closely for drowsiness or feeding difficulties.

• Primary Class: Antihistamine
• Subclass: First-generation, H1 receptor antagonist

• Known hypersensitivity to mebhydrolin or any tablet/syrup excipient
• Acute asthma exacerbations
• Acute angle‑closure glaucoma
• Bladder outflow obstruction
• Severe urinary retention

• CNS Depression: Causes sedation—avoid driving or operating machinery until individual response is known.
• Elderly and Children: Increased sensitivity; risk of sedation and anticholinergic effects—start with low dose.
• Caution with Co‑medications: Especially those that inhibit CYP450 or have sedating potential (e.g., opioids, benzodiazepines, alcohol).
• Anticholinergic Effects: Risk of dry mouth, urinary retention; caution in prostatic hypertrophy and glaucoma.
• Overdose Risk: May cause severe central excitatory or depressive effects—keep out of reach of children.

Common:

• Drowsiness, sedation
• Headache, dizziness
• Dry mouth
• Mild gastrointestinal upset

Less Common:

• Blurred vision
• Urinary retention
• Constipation

Rare but Serious:

• Paradoxical CNS stimulation (e.g., excitation, insomnia in children)
• Tachycardia or palpitations
• Allergic reactions (angioedema, rash)

Onset typically within hours of dosing and dose-dependent (especially sedation).

• CNS Depressants (e.g., alcohol, opioids, benzodiazepines): Additive sedation, respiratory depression.
• Anticholinergics: Enhanced dry-mouth, urinary retention, constipation.
• CYP450 Inhibitors/Inducers: May alter plasma levels—monitor efficacy and side effects.
• MAO Inhibitors: May potentiate antihistamine side effects (especially sedation and anticholinergic effects).

• Immunotherapy Guidelines: First-generation antihistamines like mebhydrolin are now considered second-line due to sedation risk; non-sedating alternatives (e.g., cetirizine) are preferred.
• EMA/FDA: No recent safety alerts; labeling increasingly emphasizes sedation risk and driving precautions.
• Allergy Management Updates: Counsel patients on how sedative effects may impact quality of life and daily activities.

• Temperature: Store between 20 °C and 25 °C (68 °F‑77 °F); excursions permitted to 15–30 °C.
• Humidity: Keep in a dry place.
• Light: Store in original container away from direct sunlight.
• Handling: Keep tightly closed; keep out of children’s reach.
• Syrup Forms: Shake well before use; observe shelf-life after opening.