a reduction in anxiety pupil constriction

It has been shown that diphenhydramine also possesses anticholinergic effects due to its affinity for muscarinic cholinoceptors. ĭiphenhydramine is a first-generation antihistamine, which has high affinity for H1 histamine receptors, without any affinity for H2 histamine receptors. These drugs, although highly sedative, have been reported not to influence pupillary diameter. Another class of drug not conforming to the general rule of an association between sedation and miosis are the benzodiazepines. Thus the sedation caused by these drugs is expected to induce miosis, whereas their atropine-like effect on the iris is predicted to lead to mydriasis. Many of these drugs, apart from causing sedation, presumably due to the blockade of central H1 histamine receptors, also have anticholinergic effects, due to their affinity for muscarinic cholinoceptors. An example of such a class of drug may be the first-generation antihistamines. This relationship may not hold in the case of drugs which, apart from causing sedation, may directly influence, by a separate pharmacological action, the pupil control mechanism. In fact, it has been stated that sedative drugs ‘all decrease pupillary diameter in proportion to their sedative-hypnotic effects: the closer the recipient drifts toward somnolence, the smaller the pupils’.

It is generally accepted that there is a close relationship between the level of arousal of the central nervous system and pupil diameter: any decrease in arousal is accompanied by a decrease in pupil diameter.

A reduction in anxiety pupil constriction