Claritin is the one of the brand names of Loratadine and is used to treat allergies including urticaria (hives), chronic idiopathic urticaria, Kimura's disease and allergic rhinitis (hay fever). Claritin works well against both the eye and nose symptoms of allergic rhinitis like sneezing, itching or burning of eyes and runny nose. The drug belongs to 2nd generation antihistamine family. The drug is also available in combination with pseudoephedrine, a decongestant. The drug is taken by mouth and comes in various forms like tablets, syrups and oral suspension. Claritin was discovered in 1981, came to market in 1993 and is on the World Health Organization's List of Essential Medicines. As of 2015, Claritin is available as an OTC in many countries.
Common side effects of the drug includes dry mouth, blurred vision, liver problems, gastrointestinal problems, sleepiness, urinary retention, psychomotor retardation allergic reactions, seizures and headache. Sedation is very uncommon. The drug is safe in pregnancy and breast feeding but not recommended in children below 2 years of age.
Contraindications- severe hepatic (liver) disorders, renal disorders of elderly patients
Brands- As of 2017 claritin was available under many brand names, dosage forms and combinations drug formulations with betamethasone, dexamethasone, paracetamol, phenylephrine, ambroxol, salbutamol, pseudoephedrine etc.
Mechanism of action- Claritin is a tricyclic antihistamine and acts by being selective inverse agonist of peripheral histamine H1-receptors.
Pharmacokinetics- Claritin is absorbed well from the gastrointestinal tract and possess rapid first-pass hepatic metabolism; it is metabolized by isoenzymes of the cytochrome P450 system such as CYP2D6, CYP3A4. The drug is almost totally (97–99%) bound to plasma proteins. The metabolite of Claritin- desloratadine is mainly responsible for the antihistaminergic effects. The peak effect of the drug occurs after 1 to 2 hours after intake and its biological half-life is approximately 8 hours (ranges between 3 to 20 hours). The half life of desloratadine is around 27 hours (ranges between 9 to 92 hours) and is responsible for Claritin’s long lasting effect. About 40% of it is excreted through urine as conjugated metabolites; traces amount can be found in stool.
Interactions- substances like erythromycin, cimetidine, ketoconazole and furanocoumarin derivatives act as inhibitors of the CYP3A4 enzyme can cause increased plasma level of Claritin (loratadine). This is clinically significant in controlled trials.
Precautions- Antihistamines like Claritin should be discontinued about 48 hr before skin allergy tests, since the drugs may prevent or reduce otherwise-positive result of skin/dermal activity indicators.