joesgirl asked
Does a manufacturer (Greenstone) use the same inactive ingredients each time they make a new lot of the drug Xanax XR 0.5 mgs? If I asked my CVS pharmacist to only order my next prescription from Greenstone, will it have the same active and inactive ingredients as my last script? Also, how different are the inactive ingredients are in the brand name of .5mg Xanax XR and the generic from Greenstone? I'm asking because after many years of using the only brand name, I had to switch for two months to the Greenstone generic brand. First month was pretty bad mentally and physically for me but by the middle of the second month I started feeling better than I did when using brand name. The Greeenstone generic didn't seem as strong as the brand name but that seem to be better suited for me. I have been back on the brand name for almost nine days and feel bad again...sedated in the morning and restless sleep and disturbing dreams at night. I'm sort of sorry I went back to the brand name instead of staying on the generic from Greenstone but I didn't know then what I just learning now about inactive ingredients. I might add that I've always been super sensitive to almost all meds. I'm very interested in seeing what your answer will be. Thanks....
Answer
Brand name and generic medications share the same active ingredient, but more often than not have different inactive ingredients. Approved (i.e. substitutable) generic products are considered "bioequivalent" to their brand name counterpart, meaning that the rate and extent of absorption of the generic products needs to match the brand (within an acceptable range).
However, many individuals do in fact experience differences between brand and generic products (and between different generic manufacturers too). This is sometimes attributed to the inactive ingredients of a medication, which could cause slight changes in areas such as dissolution, absorption and tolerability.
Xanax XR Ingredients
The ingredients of Xanax XR 0.5 mg (manufactured by Pfizer) are as follows:
- Alprazolam 0.5 mg
- Hypromellose Phthalate
- Lactose
- Magnesium Stearate
- Silicon Dioxide (Colloidal)
The package insert describing the ingredients for the Pfizer product can be found here.
Alprazolam XR Ingredients
The ingredients of Alprazolam XR 0.5 mg (manufactured by Greenstone) are as follows:
- Alprazolam 0.5 mg
- Hypromellose
- Lactose
- Magnesium Stearate
- Silicon Dioxide (Colloidal)
The package insert describing the ingredients for the Greenstone products can be found here.
The ingredients in Xanax XR and alprazolam XR are identical (or neatly identical depending on the amounts used). This is relatively uncommon to see, but is the case in this situation and isn't surprising as Greenstone LLC is a wholly owned subsidiary of Pfizer.
Drug manufactures do not change their inactive ingredients from lot to lot, as this could lead to variability in the product. If changes were made, they would have to notify the FDA and in some cases, need to have their products evaluated further to ensure they continue to meet the standards of bioequivalence with the brand name.
