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Why demerol cause dilated pupils?

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Practicing since : 2005
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why demerol cause dilated pupils
Posted Wed, 14 Aug 2013 in Medicines and Side Effects
Answered by Dr. Shanthi.E 35 minutes later
Hi Hiba,

Demerol causes dilated pupils because it constricts or causes spasm of the smooth muscle (sphincter) around the pupil. When this smooth muscle contracts, the pupils become wider.

See the image (sphincter) at this link.

I hope this is clear to you. Let me know if you have more queries.


Above answer was peer-reviewed by
Follow-up: Why demerol cause dilated pupils? 6 hours later
What the mechanism of action when you take demerol to dilate the pupil
Answered by Dr. Shanthi.E 15 hours later

The mechanism of action of Demerol is smooth muscle contraction. It causes contraction of all the visceral smooth muscles like intestinal smooth muscle contraction leading to constipation.

In the eye, it causes contraction of the sphincter pupillae. When the muscle contracts due to Demerol, it shortens in length. Thus causing pupillary dilatation.

Hope this is clear to you now.
Above answer was peer-reviewed by
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