Saturday, February 2, 2013

Generic drug substitutes have wide variances

BEWARE: Not all generic substitutes are alike. The FDA allows a generic to be approved if it is 80% to 125% as effective as the brand it is copying. My own blood pressure went out of sight when MEDCO (now ExpressScripts) changed its approved generic. Since I monitor my BP, I caught the change within a few days and worked with my physician to find an appropriate other generic substitute. 
ExpressScripts requires that a physician write an explanation as to why its "lowest price to them generic" is not suitable (you pay the same co-pay no matter which generic is used). You can't tell them anything. However, you can use the local pharmacy.

The problem is called "bioavailability." The FDA permits generics to be approved if they provide the same benefit as the brand within a confidence interval of 90%-hence within 80% and 125% of the effectiveness of the brand. In terms of the active ingredient, both generics and brands can vary within a narrow band (95%-105%) so if you get a generic that has bioavailability of 80% and it happens to have a batch that contains only 95% of the active ingredient, the pill you are taking is only 76% as effective as the brand.
I'll also caution you on the one a day pill pop. The manufacturers want you to be consistent, so they bundle their formula and convince physicians to prescribe daily dosing. This is especially true of statins for high LDL cholesterol and can lead to side effects, especially muscle pain and worse. I have cut my dosage to twice a week, keeping my LDLs controlled and saving a bundle on the 50c a day CRESTOR pill I had been taking.

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