Chemical name and CAS number
Ethyl 4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene)piperidine-1-carboxylate; 79794-75-5.
Pharmacokinetics
Loratadine is rapidly absorbed from the gastrointestinal tract after oral administration, peak plasma concentrations being attained in about 1 hour. Bioavailability is increased and time to peak plasma concentrations is delayed when taken with food. Loratadine undergoes extensive metabolism. The major metabolite, desloratadine, has potent antihistaminic activity. Reported mean elimination half-lives for loratadine and desloratadine are 8.4 and 28 hours, respectively. Loratadine is about 98% bound to plasma proteins; desloratadine is less extensively bound. Loratadine and its metabolites have been detected in breast milk, but do not appear to cross the blood-brain barrier to a significant extent. Most of a dose is excreted equally in the urine and faeces, mainly in the form of metabolites. The disposition of loratadine does not appear to be significantly altered in patients with severe renal impairment and haemodialysis does not appear to be an effective means of removing loratadine or its metabolite desloratadine from the body.
Adverse effects
A major advantage of the non-sedating antihistamines is that they generally cause little or no drowsiness. Non-sedating antihistamine have no antimuscarinic effect.
Digestive system: rarely – dry mouth, nausea, vomiting, abdominal pain, gastritis, and in some cases – liver function abnormalities.
Allergic reactions: very rarely – Antihistamines may sometimes cause rashes and hypersensitivity reactions (including bronchospasm, angioedema, and anaphylaxis) urticaria, pruritus, fever, chills and cross-sensitivity to related drugs may occur.
Hematopoietic system: very rarely – agranulocytosis, leukopenia, hemolytic anemia, and thrombocytopenia.
CNS: rarely – undue fatiguability, headache, convulsions, paraesthesia, tremor, insomnia, and depression.
Cardiovascular system: rarely – heart rate, arrhythmias, lowering blood pressure. Other adverse effects that have been reported in some cases with the antihistamines include convulsions, sweating, alopecia, myalgia, tinnitus, loss of hair, paraesthesias, extrapyramidal effects, tremor, sleep disturbances, depression, confusion, hypotension. Despite reports suggesting a possibility of human fetal abnormalities resulting from the use of some antihistamines, especially the piperazine derivatives, a causal relationship has largely been rejected. Some antihistamines have been abused for their mental effects.