RESIN

It has no definite melting point and no tendency to crystallize.

resin is used to give gloss, flow, adhesion, and water resistance to cosmetics. This is a brittle substance, usually translucent or transparent, that can be found in nature or synthetically manufactured. Among the natural resins are dammar, elemi, and sandarac, which are formed from the hardened secretions of these plants. Toxicity and allergenicity depend on the source used.

A yellowish insoluble organic compound exuded by trees as a viscous liquid that gradually hardens on exposure to air to form a brittle amorphous solid. Synthetic resins are artificial polymers used in making adhesives, insulators and paints. See also rosin.

Originally a category of vegetable substancessoluble in ethanol but insoluble in water, resinin modern technology is generally an organicpolymer of indeterminate molecular weight.The class of flammable, amorphous secretionsof conifers or legumes are considered true resins,and include kauri, copal, dammar, mastic,guaiacum, jalap, colophony, shellac, andnumerous less well-known substances. Waterswellablesecretions of various plants, especiallythe Burseraceae, are called gum resinsand include myrrh and olibanum The officialresins are benzoin, guaiac, mastic, and resin.Other natural resins are copal, dammar,dragon’s blood, elaterium, lac, and sandarac.The natural vegetable resins are largely polyterpenesand their acid derivatives, which find application in the manufacture of lacquers,adhesives, varnishes, and inks.

Prior to the introduction of the statins in the mid to late 1980s, the bile acid–sequestering drugs cholestyramine (Questran) and colestipol (Colestid) were primary drugs for lowering plasma cholesterol. Today they are second-line drugs that can safely be given with a statin to enhance cholesterol lowering or as an alternative for patients intolerant to a statin or concerned with statin’s potential for toxicity.Alone, the resins can achieve 20 to 25% reductions in LDL cholesterol, but when used with a statin, such as lovastatin, reductions of 50% and more can be seen.
These drugs are basically anion exchange resins that remain in the gut, bind intestinal bile acids, and greatly increase their fecal excretion.
The lowered concentration of bile acids returning to the liver by the enterohepatic circulation results in derepression of 7-α-hydroxylase, the rate-limiting enzyme for conversion of cholesterol to bile acids.This results in increased use of cholesterol to replace the excreted bile acids and lowering of hepatic cholesterol. Thus, similar to the statins, the ultimate actions of the bile acid–sequestering resins are upregulation of transcription of the LDL receptor gene, increased hepatic receptor activity, and lowering of plasma LDL cholesterol.

The bile acid sequestering resins lower elevated LDL cholesterol and therefore are useful in the treatment of type IIa hyperlipoproteinemia. However, because the resins can raise plasma VLDL in some patients, they are not recommended for treatment of combined hyperlipidemias when both LDL cholesterol and VLDL triglycerides are high or in other conditions of elevated triglycerides.

The resins are interesting drugs because they have profound metabolic effects without truly entering the body. Perhaps for this reason they are relatively safe, with constipation being the chief complaint. Because the resins are given as the chloride salt and the chloride is exchanged for the negatively charged bile salt, bile acid resins can lead to hyperchloremic acidosis in vulnerable patients (children and patients with kidney failure).