I decided to look up Welchol, and sure enough, it is much more effective at binding bile salts (it would have to be in order to be more effective at lowering LDL cholesterol):
Non-Systemic Drugs: A Critical Review6.2.4. Bile Acid Binders
The first generation of bile acid binders is embodied by cholestyramine, a crosslinked polystyrene resin functionalized with quaternary ammonium groups. It sequesters bile acids in the GI tract and up-regulates bile acid biosynthesis from circulating cholesterol, lowering plasma LDL-cholesterol. To achieve significant LDL-cholesterol reduction, 5 to 25 g of resin per day is needed, clearly limiting patient compliance. In the distal segment of the ileum, bile acids are avidly re-absorbed by the IBAT, thus limiting the efficacy of bile acid resins, a situation analogous to that of phosphate binders competing with the NaP2b phosphate transporter. Researchers at GelTex / Genzyme rationally designed terpolymers with a careful balance of cationic and hydrophobic groups to increase affinity to bile acids [60]; as important as binding capacity is that the polymer retain bile acids past the ileal segment, where free bile acids drop drastically as a result of IBAT-mediated bile acid re-uptake. The resulting drug, colesevelam (Welchol®), is significantly more potent than cholestyramine in lowering LDL-cholesterol. Anecdotally, sevelamer, a phosphate binder composed of a hydrophilic crosslinked polyaliphatic amine, has an LDL lowering capacity close to colesevelam’s, which could be easily explained by the co-binding of fatty acids and bile acids forming a tight complex [61]. In clinical studies, bile acids binders such colesevelam and colestilan showed a modest but significant diminution of HbA1c, stimulating a debate on the origin of the effect [62]. A plausible mechanism is that bile acids leak from the complex polymer / bile acid and induce GLP-1 secretion via stimulation of TGR5 receptors in colonic L cells.
Dosage can be very important when using a bile acid sequestrant, but if Welchol caused you to have blurry vision, you are probably allergic to one of the ingredients in it. Hopefully that won't be the case with cholestyramine.
Tex
