Generic or Brand?

Today I thought I’d talk about something that has come up a lot this past week.  I have been hearing a lot of questions about brand vs. generic drugs.  With the high (and rising) cost of prescription meds it’s natural that people are interested in switching to generic medications to save money.  So is it a good idea to switch whenever you can?  Off to the Internet I go…

The FDA has some interesting information.  As the gatekeeper to the world of prescription drugs, the FDA is charged with protecting the safety and quality of the American people’s medications.  On the FDA website there is a bunch of info about generic vs. brand medications.  They maintain that generic drug manufacturers have to prove their meds have the same active ingredient, the same purity/strength/potency/quality/etc as their branded precursor.

It took a little digging but I found an FDA document that showed the standard for generic bioequivalence is that the generic must have 80-125% the activity of the branded precursor.  To put it another way, suppose you have a prescription for brand Tenormin (a blood pressure med) at 100 mg.  If you choose to buy the generic med atenolol, which is substantially cheaper, it has to be the equivalent of 80-125 mg of Tenormin.

So…  Is this good enough?  Surprisingly enough, usually it is.  Tenormin, for instance, comes in 25, 50 and 100 mg.  So the generic doesn’t overlap at all, even though the dose ranges are broad (20-31.25, 40-62.5, 80-125).

However you need to be careful with medications with small steps from one dose to the next, like levothyroxine (generic Synthroid).  Synthroid comes in 75, 88, 100, 112 and 125 mcg, among others.  So if 100 mcg levothyroxine could actually behave like 80-125 mcg, that overlaps quite a few other doses.  The broad dose ranges kind of become a smear, right?  In fact, the American Academy of Endocrinologist issued a policy statement expressing disappointment about the FDA approving generic levothyroxine and recommended more frequent blood tests in patients taking generic thyroid medication for just that reason.

Another class of medications that you need to be careful with is meds that have what is called a “narrow therapeutic window,” which means the difference of blood concentrations between the minimum effective level and the toxic level is small.  Synthroid is one of them.  So are many seizure drugs, heart drugs (like digoxin) and theophylline.  A good question to ask is, does my doctor do blood tests to check blood levels of my medicine.  (Not tests to check the EFFECTIVENESS of the medicine, like cholesterol or gout meds, but to directly test the level of the drug in your blood.)  If so, you might want to ask your doctor if a generic is ok or if you’d be safer with the brand-name drug.

One last consideration with generic meds is that the fillers and binders (stuff the manufacturer puts in to make the pill stay a pill until you swallow it) are not the same from brand to generic and even from one generic to the next.  Since pharmacy companies sometimes change generic suppliers as often as every three months, if you’re sensitive to dyes and fillers you might notice a difference in how you feel from time to time.

In spite of all this stuff I’ve written, I usually encourage patients to go ahead and get the generic.  Generally they are safe and effective, and definitely less expensive.  Sometimes they’re not, though, and you will be asked to choose whether you want to save money by getting more frequent blood tests and office visits, or just to bite the bullet, open your wallet, and pay the brand copay.  There’s no right answer, it’s an individual choice between you and your doctor.  As long as you have the facts, you’ll make the right decision for YOU.


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