Pharmacology: Antihistamines (loratadine) diminish or abolish the main actions of histamine in the body by competitive, reversible blockade of histamine receptor sites on tissues. Histamines H1 receptors are responsible for vasodilatation, increased capillary permeability, flare and itch reactions in the skin, and to some extent for contraction of smooth muscle in the bronchi and gastrointestinal tract.
Loratadine is a long-acting tricyclic antihistamine with selective peripheral histamine H1-receptor antagonistic activity. Studies have been shown that neither loratadine nor its metabolites readily cross the blood-brain barrier. It has higher affinity for the pheripheral rather than the central nervous system H1-receptors. Hence, less problem of daytime sedation for those who have to drive or operate machinery.
It is rapidly absorbed from the gastrointestinal tract after oral administration. The peak plasma concentration is being attained at about one hour. Loratadine undergoes extensive metabolism. Descarboethoxyloratadine, which is the major metabolite has potent histamine H1-receptor blocking activity. Reported half-lives for loratadine and descarboethoxyloratadine are about 12 and 18 hours respectively.
Loratadine is about 98% bound to plasma proteins while its major metabolite, descarboethoxyloratadine is less extensively bound. Loratadine and its metabolite have been detected in breast milk, but do not appear to cross the blood-brain barrier to a significant extent. Loratadine and its metabolites are excreted in the urine and faeces.
Loratadine is indicated for the relief of nasal as well as non-nasal symptoms of seasonal allergic rhinitis, chronic urticaria and other allergic dermatological disorders.
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The use of loratadine in children under the age of 2 have not yet been established.
In adults, somnolence, tachycardia and headache have been reported with doses greater than 10mg (40-180mg). In children, extrapyramidal side effects and palpitations have been reported in doses greater than 10mg.
General symptomatic and supportive measures should be instituted in the event of overdosage. The treatment should consist of emesis, preferably by administration of ipecac syrup except in patients with impaired consciousness. Following emesis, activated charcoal should be administered to absorb any remaining drug. However, if emesis is unsuccessful or contraindicated, gastric lavage should be performed using normal saline. Saline cathartics may be of value as it draw water into the bowel by osmosis, hence rapidly diluting the bowel content. Hemodialysis is of no value as loratadine is not eliminated by hemodialysis.
Contraindicated in patients with known hypersensitivity or idiosyncrasy to loratadine or other components in the product.
Dose should be lowered (5 mg daily or 10mg every other day) in patients with liver impairment or renal impairment (GFR < 30mL/min). It should also be used with caution in patients with prostatic hyperthrophy, urinary retention, glaucoma and epilepsy. Children and elderly are more susceptible to side effects.
Safety and efficacy of loratadine in children younger than 2 years of age have not yet been established.
There are no well-controlled studies in pregnant women. Loratadine and its metabolite, descarboethoxyloratadine have been detected in breast milk. Hence, loratadine should only be used when the potential benefit outweighs the potential risk.
Gastritis, alopecia, anaphylaxis, abnormal hepatic function, tachycardia, palpitation, fatigue, headache, somnolence, dry mouth, nervousness, wheezing, abdominal pain, hyperkinesia, malaise, nausea and rash has been reported.
Loratadine has no potentiating effect when administered concurrently with alcohol. Increase in plasma concentrations of loratadine has been reported with concomitant use of ketoconazole, erythromycin or cimetidine in healthy individuals but without clinically significant changes. Caution should be exercised when coadministering drugs known to inhibit hepatic metabolism.
Drug/lab test: Loratadine should be discontinued approximately 48 hours prior to skin testing procedures. Since antihistamines may prevent or diminish otherwise positive reactions to dermal reactivity indicators.
Store at or below 30°C. Protect from light.
Shelf-Life: Tablet: 3 years.
Syrup: 1.5 years.
R06AX13 - loratadine ; Belongs to the class of other antihistamines for systemic use.
Tab (oval, white, convex, film-coated tablet with single score on one side only) 10 mg x 50 x 10's. Syr (clear, colourless with peach flavour) 5 mg/5 mL x 120 mL x 50's.