Functional neuroimaging of cognition impaired by a classical antihistamine, d-chlorpheniramine
Version of Record online: 30 JAN 2009
2000 British Pharmacological Society
British Journal of Pharmacology
Volume 129, Issue 1, pages 115–123, January 2000
How to Cite
Okamura, N., Yanai, K., Higuchi, M., Sakai, J., Iwata, R., Ido, T., Sasaki, H., Watanabe, T. and Itoh, M. (2000), Functional neuroimaging of cognition impaired by a classical antihistamine, d-chlorpheniramine. British Journal of Pharmacology, 129: 115–123. doi: 10.1038/sj.bjp.0702994
- Issue online: 30 JAN 2009
- Version of Record online: 30 JAN 2009
- (Received March 15, 1999, Revised July 19, 1999, Accepted October 6, 1999)
- H1 receptor antagonists;
- sedation in man;
- positron emission tomography;
- receptor occupancy;
- cerebral blood flow
Antihistamine induced cognitive decline was evaluated using positron emission tomography (PET) measurement of histamine H1 receptor (H1R) occupancy and regional cerebral blood flow (rCBF).
Cognitive performance in attention-demanding task deteriorated dose-dependently and the effects were statistically significant after the treatment of 2 mg of d-chlorpheniramine. There was no significant change in subjective sleepiness in the same dose.
The regional blockade of H1R was observed mainly in the frontal, temporal and anterior cingulate cortices, and the intravenous administration of d-chlorpheniramine as a therapeutic dose (2 mg) blocked over 60% of H1R in the frontal cortices.
The results from activation study using visual discrimination tasks demonstrated that enhanced activity in the right prefrontal and anterior cingulate cortices as well as a decreased activity in the left temporal and frontal cortices and midbrain after the treatment of d-chlorpheniramine.
There were no changes in global CBF for the subjects treated with 2 mg d-chlorpheniramine (pre; 44.8±3.3 ml dl−1 min−1vs post; 44.4±4.7 ml dl−1 min−1).
The results indicated that the attention system of human brain could be altered by therapeutic doses of H1R antagonists. These findings provide the information as to the potential risk of antihistamines in our daily activities.
British Journal of Pharmacology (2000) 129, 115–123; doi:10.1038/sj.bjp.0702994