Journal
HUMAN PSYCHOPHARMACOLOGY-CLINICAL AND EXPERIMENTAL
Volume 26, Issue 2, Pages 133-139Publisher
WILEY-BLACKWELL
DOI: 10.1002/hup.1184
Keywords
H1-antihistamine; histamine H1 receptor occupancy; loratadine; positron emission tomography (PET); proportional impairment ratio; non-sedating
Funding
- Ministry of Education, Science, Sports, and Culture of Japan
- Shionogi
- Schering-Plough
- Grants-in-Aid for Scientific Research [21590754] Funding Source: KAKEN
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Aims We have evaluated the sedative properties of H1-antihistamines by using positron emission tomography (PET) and (11)C-doxepin. The purpose of the present study was to measure histamine H1 receptor occupancy (H1RO) of loratadine 10 mg in patients with allergic rhinitis and to compare this occupancy with that of d-chlorpheniramine 2 mg, a first-generation antihistamine. We also compared our PET findings with the proportional impairment ratio reported by McDonald et al. Methods The H1RO of loratadine 10 mg and d-chlorpheniramine 2mg were evaluated in human brains in a double-blind and crossover design using (11)C-doxepin PET. Eleven young male patients with allergic rhinitis were examined by PET following oral single administration of loratadine 10 mg and d-chlorpheniramine 2 mg. Results Loratadine 10 mg occupied 11.7 +/- 19.5% of histamine H1 receptors in the cortex, whereas d-chlorpheniramine 2mg occupied 53.0 +/- 33.2% in the same area, suggesting a non-sedating property of loratadine at a dose of 10mg. The H1RO values of loratadine and d-chlorpheniramine as well as those of previous studies were found to be significantly proportional to the proportional impairment ratio (r = 0.899). Conclusion Measurement of H1RO is a sensitive and absolute method to characterize the non-sedating property of drugs with H1 antagonistic activity. Copyright (C) 2011 John Wiley & Sons, Ltd.
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