Atropine + Morphine

[aspiringmd1015]

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Giving morphine to a patient causes spasm of the sphincters in the body, professor just said that giving an antimuscuranic(atropine) will counteract the spasms(but muscuranics promote relaxation of the sphincters...and an antimuscuranic would then cause contraction)...so how would antimuscuranics prevent spasm of the sphincters?

 

[pathologyDO]

Was your professor by chance talking about the pupillary sphincter? Morphine causes the pupillary sphincter to contract which produces miosis or pinpoint pupils, while an anticholinergic/antimuscaranic (e.g. atropine) will cause the sphincter to relax which results in mydriasis or pupil dilation.

 

[aspiringmd1015]

nope, specificallyt alking about the constipation morphine patients experience.

 

[pathologyDO]

nope, specificallyt alking about the constipation morphine patients experience.

Opioids = activate both contraction (ACh-mediated) and relaxation (vasoactive peptides) during peristalsis. Administering an anticholinergic like atropine, you decrease the contraction phase which I assume is what your professor is calling "spasticity." Hopefully this helps...

"Peristalsis consists of two phases, contraction and relaxation. Acetylcholine mediates contraction, and vasoactive peptide mediates relaxation.[12,13] Whereas anticholinergic drugs constipate by inhibiting this first process, opioids may modulate both components. Opioid receptor involvement in mediation of acetylcholine and vasoactive peptide is not strictly a local action on the gastrointestinal tract, as parenteral opioids also reduce gut transit time.[53,61] Parenteral and transdermal opioids may decrease the frequency of constipation minimally, but this is a source of controversy. Opioid-induced constipation should be monitored continually despite route of administration.[7,21]"

Source: http://www.medscape.com/viewarticle/427442_4