Diphenoxylate/atropine (Lomotil)

Schedule II agent oral agent.

Trade name Lomotil.

Has a protein binding of 74-95% and a half-life of 12–14 hours.

An opioid agonist used for the treatment of diarrhea.

Acts by slowing intestinal contractions and peristalsis.

Prolongs transit time, allowing the intestines to draw moisture out of them and therefore stop the formation of loose and liquid stools.

It is the main active ingredient in the anti-peristaltic medication Lomotil, which also contains atropine.

Diphenoxylate is the prototype of a small subfamily of opioids including diphenoxylic acid an active metabolite and loperamide, and works exclusively in the intestines because it only crosses the blood–brain barrier in very small amounts.

Diphenoxylate works by decreasing the speed and amplitude of wave-like movements of the intestinal peristalsis.

By decreasing peristalsis it allows the body time to remove moisture from the intestinal contents and consolidate waste product into a dense solid form rather than loose and watery as is diarrhea.

Usually administered as a loading dose of two tablets or the quantity of liquid containing 5 mg of diphenoxylate, and then the standard dose of one tablet every 3 to 4 hours as needed over a time period not to exceed 48 hours.

Long-term intermittent use can result in tolerance.

Metabolized in the body to yield difenoxin.

Difenoxin is a centrally acting antidiarrhoeal that is 250 to 400 per cent strength of diphenoxylate via the oral route and is distributed as Motofen.

The Diphenoxylate-Loperamide subfamily of gastrointestinal drugs works directly on opioid receptors.

Such opioid receptors.which can be found in the intestine, brain, and spinal cord.

Crosses the blood–brain barrier, and therefore is potentially habit-forming.

Physical dependence may occur with high doses and/or long-term use.

The CNS activity can cause euphoria and other psychoactive effects, which could over time lead to habituation and dependency.

To prevent abuse is has been combined with atropine.

Lomotil contains diphenoxylate hydrochloride 2.5 mg, and atropine sulfate 0.025 mg to discourage overdosage and injection.

The atropine additive anticholinergic effect of atropine will produce severe weakness and nausea if standard dosage is exceeded.

The only other narcotic to use this strategy is Motofen (difenoxin 1 mg with 25 µg atropine sulfate).

The 25 µg of atropine present in each 2½ mg Lomotil tablet is 1/40 of the standard therapeutic dose of atropine.

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