Meperidine-General Anaesthetics and its pharmacology

Description:-

A meperidine congener used as an antidiarrheal, usually in combination with atropine. At high doses, it acts like morphine. Its unesterified metabolite difenoxin has similar properties and is used similarly. It has little or no analgesic activity. This medication is classified as a Schedule V under the Controlled Substances Act by the Food and Drug Administration (FDA) and the DEA in the United States when used in preparations. When diphenoxylate is used alone, it is classified as a Schedule II.

This compound belongs to the class of organic compounds known as diphenylacetonitriles. These are cyclic aromatic compounds containing a diphenylacetonitrile moiety, which consists of a diphenylmethane linked to and acetonitrile to form 2,2-diphenylacetonitrile.

Pharmacodynamics:- 

Diphenoxylate, an antidiarrheal, is effective as adjunctive therapy in the management of diarrhea. Diphenoxylate is rapidly and extensively metabolized in man by ester hydrolysis to diphenoxylic acid (difenoxine), which is biologically active and the major metabolite in the blood.

Pharmacokinetics:-

Absorption:- 90%

Protein binding:- 74-95%

Metabolism:- Hepatic

Half life:- 12-14 hours

Drug Interactions:-

1. 3,4-Methylenedioxyamphetamine + diphenoxylate = 3,4-Methylenedioxyamphetamine may increase the analgesic activities of Diphenoxylate.

2. 3,4-Methylenedioxymethamphetamine  + diphenoxylate = 3,4-Methylenedioxymethamphetamine may increase the analgesic activities of Diphenoxylate.

3. 7-Nitroindazole  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with 7-Nitroindazole.

4. Acepromazine  + diphenoxylate = Acepromazine may increase the hypotensive activities of Diphenoxylate.

5. Acepromazine  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Acepromazine.

6. Aceprometazine  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Aceprometazine.

7. Acetazolamide  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Acetazolamide.

8. Aclidinium  + diphenoxylate = The risk or severity of adverse effects can be increased when Aclidinium is combined with Diphenoxylate.

9. Adipiplon  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with adipiplon.

10. Agomelatine  + diphenoxylate = The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Agomelatine

Side effects:-

Major side effects:-

•     Bloating
•     Constipation
•     Loss of appetite
•     Stomach pain (severe) with nausea and vomiting
•     Blurred vision (continuing) or changes in near vision
•     Drowsiness (severe)
•     Dryness of mouth, nose, and throat (severe)
•     Fast heartbeat
•     Shortness of breath or troubled breathing (severe)
•     Unusual excitement, nervousness, restlessness, or irritability
•     Unusual warmth, dryness, and flushing of the skin

Rare:-

•     Increased sweating
•     Muscle cramps
•     Nausea or vomiting
•     Shivering or trembling
•     Stomach cramps

Therapeutic Uses:-

Used to treat diarrhea. it helps to decrease the no. $ frequency of bowel movement. it works by slowing the movement of  the intestines.

Diphenoxylate is similar to narcotic pain relievers but it acts mainly to slow the gut.

REFERENCE:-Tripathi K D"Essential of medical pharmacology",7th edition ,page no-386,474,475-76,478.