Pharmacokinetics and dose proportionality of loratadine

J Clin Pharmacol. 1987 Sep;27(9):694-8. doi: 10.1002/j.1552-4604.1987.tb03090.x.


The dose proportionality and pharmacokinetics of loratadine, a new nonsedating antihistamine, were studied in 12 normal volunteers. In a three-way cross-over, each volunteer received a single 10-, 20-, or 40-mg loratadine capsule. Blood was collected up to 96 hours after dosing. Plasma loratadine concentrations were determined by radioimmunoassay (RIA), and those of a minor, but active metabolite, descarboethoxyloratadine, by high performance liquid chromatography (HPLC). Concentrations in the disposition phase were fitted to a biexponential equation for pharmacokinetic analysis. For dose proportionality, AUC- and Cmax-dose relationships were evaluated by linear regression. Also, pharmacokinetic parameters and dose-adjusted AUCs were compared by analysis of variance. Loratadine was rapidly absorbed, reaching Cmax values (4.7, 10.8, and 26.1 ng/mL) at 1.5, 1.0 and 1.2 hours for the 10-, 20-, and 40-mg doses, respectively. The loratadine t1/2 beta ranged from 7.8 to 11.0 hours. Descarboethoxyloratadine reached Cmax values (4.0, 9.9, and 16.0 ng/mL) at 3.7, 1.5, and 2.0 hours for the 10-, 20-, and 40-mg doses, respectively. Its t1/2 beta ranged from 17 to 24 hours. For both compounds, AUC- and Cmax-dose relationships were linear and there were no differences in the t1/2 beta, CL/F, or dose-adjusted AUC values among the treatments. Loratadine and descarboethoxyloratadine plasma concentrations and pharmacokinetics were not dose dependent.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Cyproheptadine / administration & dosage
  • Cyproheptadine / analogs & derivatives*
  • Cyproheptadine / pharmacokinetics
  • Dose-Response Relationship, Drug
  • Histamine Antagonists / administration & dosage
  • Histamine Antagonists / pharmacokinetics*
  • Humans
  • Loratadine
  • Male
  • Radioimmunoassay
  • Random Allocation


  • Histamine Antagonists
  • Cyproheptadine
  • Loratadine