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ATC code: R06AX13.
Pharmacology: Pharmacodynamics: Loratadine is a tricyclic antihistamine with selective peripheral H1-receptor antagonistic activity. It is a long-acting non-sedating antihistamine.
Loratadine has no clinically significant sedative or anticholinergic properties in the majority of the population and when used at the recommended dosage.
During long-term treatment there were no clinically significant changes in vital signs, laboratory test values, physical examinations or electrocardiograms.
Loratadine has no significant H2-receptor activity. It does not inhibit norepinephrine uptake and has practically no influence on cardiovascular function or on intrinsic cardiac pacemaker activity.
Pharmacokinetics: After oral administration, loratadine is rapidly and well absorbed and undergoes an extensive first pass metabolism, mainly by CYP3A4 and CYP2D6. The major metabolite-desloratadine (DL) - is pharmacologically active and responsible for a large part of the clinical effect. Loratadine and DL achieve maximum plasma concentrations (Tmax) between 1-1.5 hours and 1.5-3.7 hours after administration, respectively.
Increase in plasma concentrations of loratadine has been reported after concomitant use with ketoconazole, erythromycin and cimetidine in controlled trials, but without clinically significant changes (including electrocardiographic).
Loratadine is highly bound (97% to 99%) and its active metabolite moderately bound (73% to 76%) to plasma proteins.
In healthy subjects, plasma distribution half-lives of loratadine and its active metabolite are approximately 1 and 2 hours, respectively. Approximately 40% of the dose is excreted in the urine and 42% in the faeces over a 10 day period and mainly in the form of conjugated metabolites. Approximately 27% of the dose is eliminated in the urine during the first 24 hours. Less than 1% of the active substance is excreted unchanged in active form, as loratadine or DL.
The bioavailability parameters of loratadine and of the active metabolite are dose proportional.
The pharmacokinetic profile of loratadine and its metabolites is comparable in healthy volunteers and in healthy geriatric volunteers.
Haemodialysis does not have an effect on the pharmacokinetics of loratadine or its active metabolite in subjects with chronic renal impairment.
Concomitant ingestion of food can delay slightly the absorption of loratadine but without influencing the clinical effect.
Loratadine and its active metabolite are excreted in the breast milk of lactating women.
