?????????????????????? C??? ??, ??, ??
??? ??
White or almost white, fine powder, hygroscopic.
??
Antihyperlipidemic;
ion-exchange resin (bile salts).
??
A synthetic, strongly basic anion exchange resin that
contains functional quaternary ammonium groups
linked to a styrene-divinylbenzene copolymer.
Indications
Cholestyramine
is a powder that is mixed with water or another fluid before ingesting.
Colestipol (Colestid) is another ion exchange resin that may be substituted
in patients who find cholestyramine too constipating. Like charcoal, ion
exchange resins may bind other orally administered drugs.
?? ??
Cholestyramine (Cuemid,Questran) is the chloride form of a strongly basic anionexchangeresin. It is a styrene copolymer with divinylbenzenewith quaternary ammonium functional groups. After oral ingestion,cholestyramine resin remains in the gastrointestinaltract, where it readily exchanges chloride ions for bile acids inthe small intestine, to be excreted as bile salts in the feces.Cholestyramine resin is also useful in lowering plasma lipids.The reduction in the amounts of reabsorbed bile acids resultsin increased catabolism of cholesterol in bile acids in the liver.The decreased concentration of bile acids returning to theliver lowers the feedback inhibition by bile acids of 7- -hydroxylase, the rate-limiting enzyme in the conversion ofcholesterol to bile acids, increasing the breakdown of hepaticcholesterol. Although biosynthesis of cholesterol is increased,it appears that the rate of catabolism is greater, resulting in anet decrease in plasma cholesterol levels by affecting LDLclearance. The increase of LDL receptors in the liver that occurswhen its content of cholesterol is lowered augments thisbiochemical event.
??? ?? ??
Hygroscopic [Merck.] Insoluble in water.
?? ???
An amine. Amines are chemical bases. They neutralize acids to form salts plus water. These acid-base reactions are exothermic. The amount of heat that is evolved per mole of amine in a neutralization is largely independent of the strength of the amine as a base. Amines may be incompatible with isocyanates, halogenated organics, peroxides, phenols (acidic), epoxides, anhydrides, and acid halides. Flammable gaseous hydrogen is generated by amines in combination with strong reducing agents, such as hydrides.
???
Low toxicity; tumorigen; questionable carcinogen; teratogen.
????
SYMPTOMS: Symptoms of exposure to CHOLESTYRAMINE RESIN may include nausea, abdominal discomfort indigestion and constipation. It also causes vitamin K deficiency, rash, mucous membrane irritation, osteoporosis and eosinophilia. Other symptoms include flatulence, vomiting, diarrhea, heartburn, anorexia, steatorrhea, vitamin A and D deficiencies and hyperchloremic acidosis in children.
????
Flash point data for CHOLESTYRAMINE RESIN are not available. CHOLESTYRAMINE RESIN is probably combustible.
Pharmacology
Cholestyramine, an anion exchange resin,
is frequently effective, although, as mentioned earlier, its antipruritic effect
seems separate from its ability to normalize bile salt levels.
Clinical Use
Cholestyramine resin is the drug of choice for type IIa hyperlipoproteinemia.When used in conjunction with a controlleddiet, it reduces -lipoproteins. The drug is an insolublepolymer and, thus, probably one of the safest because itis not absorbed from the gastrointestinal tract to cause systemictoxic effects.
Safety Profile
Low toxicity by
ingestion. Questionable human carcinogenproducing colon tumors. An experimental
teratogen. Other experimental reproductive
effects. Toxic effects by ingestion: acidosis
and nosebleeds. When heated to
decomposition it emits acrid smoke and
irritating fumes.
?????????????????????? ?? ?? ? ???
???
?? ??
