>A week after discontinuing the synthetic opiate (sub: Vicodin) I was
>given for a back injurt, elimination is still not back to normal.
>I am now acutely curious as to the exact mechanism by which opiates,
>whether synthetic or natural, cause constipation, and why it take so
>long to get back to normal  (A member of my family had morphine for a
>transplant, with same results).
>Detailed explanation much appreciated.
>Polar

> >A week after discontinuing the synthetic opiate (sub: Vicodin) I was
> >given for a back injurt, elimination is still not back to normal.

> >I am now acutely curious as to the exact mechanism by which opiates,
> >whether synthetic or natural, cause constipation, and why it take so
> >long to get back to normal  (A member of my family had morphine for a
> >transplant, with same results).

> >Detailed explanation much appreciated.

> >Polar

> As far as I understand, and according to a Pharmacology textbook,
> opiates cause constipation in the following manner:

> Opiates act on the nerve plexuses of the bowel, blocking acetycholine
> release (ie. decreases the nerve impulses reaching the bowel).  This
> results in decreased motility (movement) and increased tone in the
> bowel walls.  The net result is that bowel contents take longer
> (sometimes MUCH longer) to pass through the bowel.

> The longer material (feces) sits in the large bowel, the more water
> and electrolytes (sodium, etc.) are absorbed back into the body and
> the drier and harder the stool gets.  The harder stool gets, the more
> difficult it is to pass.

> Most opiates are cleared from the body quite quickly (almost all are
> cleared in under 24 hours).  However, the hard stool can remain
> "backed up" in the large bowel for prolonged periods, slowing things
> down behind the blocked up area and continuing the constipation.
> Until this is cleared, the constipation could continue.

> Most (I hope) physicians use stool softeners and/or stimulants to help
> offset this constipating effect if a patient is to be on opiates for
> more than a day or two.  Something like Milk of Magnesia works to
> accomplish both actions (softening and stimulating).

> Hope this helps.

> Brian

> > >A week after discontinuing the synthetic opiate (sub: Vicodin) I was
> > >given for a back injurt, elimination is still not back to normal.

> > >I am now acutely curious as to the exact mechanism by which opiates,
> > >whether synthetic or natural, cause constipation, and why it take so
> > >long to get back to normal  (A member of my family had morphine for a
> > >transplant, with same results).

> > >Detailed explanation much appreciated.

> > >Polar

> > As far as I understand, and according to a Pharmacology textbook,
> > opiates cause constipation in the following manner:

> > Opiates act on the nerve plexuses of the bowel, blocking acetycholine
> > release (ie. decreases the nerve impulses reaching the bowel).  This
> > results in decreased motility (movement) and increased tone in the
> > bowel walls.  The net result is that bowel contents take longer
> > (sometimes MUCH longer) to pass through the bowel.

> > The longer material (feces) sits in the large bowel, the more water
> > and electrolytes (sodium, etc.) are absorbed back into the body and
> > the drier and harder the stool gets.  The harder stool gets, the more
> > difficult it is to pass.

> > Most opiates are cleared from the body quite quickly (almost all are
> > cleared in under 24 hours).  However, the hard stool can remain
> > "backed up" in the large bowel for prolonged periods, slowing things
> > down behind the blocked up area and continuing the constipation.
> > Until this is cleared, the constipation could continue.

> > Most (I hope) physicians use stool softeners and/or stimulants to help
> > offset this constipating effect if a patient is to be on opiates for
> > more than a day or two.  Something like Milk of Magnesia works to
> > accomplish both actions (softening and stimulating).

> > Hope this helps.

> > Brian

> My wife took large doses of {*filter*} for {*filter*} cancer which had spread to the
> spine. She always had a constipation problem.  The doctor prescribed
> Senokot-S
> in large doses.  Two or three tablets a day.  It helped but did not cure the
> problem.  She never quit the {*filter*}, but died of the cancer.