In the last few years, many blockbuster prescription medications—including some leading statins, antidepressants and drugs for hypertension, reflux disease and osteoporosis—have become available as generics, and more brands will soon join the list. About three-quarters of prescriptions in the U.S. are now for generic drugs. This has trimmed hundreds of billions of dollars from the nation’s rising health-care costs and, by allowing more people to afford the medication they need, has undoubtedly saved countless lives.

The government (notably the Food and Drug Administration, or FDA, which regulates drugs), insurers and virtually all medical groups insist that generics are as effective and safe as the original products. Still, some people believe that cheaper drugs can’t be as good as the brand names and fear that switching to a generic is risky.

How equivalent are generics?

The FDA (as well as Health Canada) requires generics to measure up to the originals in terms of strength, quality, purity and safety. Generics must deliver to the body the same amount of active ingredient, at very close to the same rate, as their brand-name counterparts—this is called bioequivalence. (Some generics are made by the same manufacturers that make the branded drugs and are then sold to the generics companies, in which case the drugs are truly identical.) The FDA requires manufacturers to do bioequivalence testing of generics, though not necessarily of all formulations; it rarely does the testing itself. Complicating matters is the fact that generics for a specific drug are typically made by several companies.

Even though brand name and generic drugs have the same active ingredient, the drugs can differ in shape, color and inactive ingredients, such as preservatives and fillers. A generic tablet may be harder or softer than the original, which could affect how quickly it dissolves and is absorbed. And a generic of a time-release drug may employ a different mechanism to gradually release the active ingredient.

For these and other reasons, generics may not be the exact bioequivalent of the originals. The FDA does allow some leeway for generics (as well as for differences among brand-name drugs). Its reviews of thousands of studies have found that the absorption of generics differs from the brand names by only 3 to 4 percent, on average, comparable to differences among batches of many brand-name drugs. Such a small difference won’t matter for most drugs, but for some it may reduce effectiveness and/or safety. Moreover, that “average” difference disguises a wider range of variability in bioequivalence.

Red flags for generics

The clearest example of a faulty generic has been the antidepressant bupropion XL, which is a stand-in for Wellbutrin XL (XL indicates extended-release). Since generic bupropion XL came on the market in 2006, many people reported problems when they switched to the generic version of the once-a-day 300-milligram tablet. Some started feeling suicidal or had panic attacks, bouts of crying and other signs that the drug wasn’t working well. There were reports of new side effects, too, including insomnia, headaches and nausea.

The FDA initially downplayed these complaints, even after a 2007 analysis by ConsumerLab.com found that one company’s bupropion XL 300 released high doses of its active ingredient in just a few hours (the original drug was designed to slowly release smaller doses over the course of the day). Recently, after conducting its own study, the FDA acknowledged this problem and told the company (Teva Pharmaceuticals) to stopped selling the drug. The FDA has asked other makers of bupropion XL 300 to do bioequivalence testing and is now looking more carefully at other extended-release generics as well.

Another potential red flag: During the last decade, patients, hospitals and researchers have reported reduced efficacy and increased side effects with certain generic anti-seizure medications for epilepsy, notably levetiracetam (brand name Keppra).

Generic safety tips

These reported problems should not make you doubt generics. The vast majority are safe and effective. Some small variations among drugs, generic or brand name, are inevitable. Insurers and government health plans very strongly encourage or require the use of generics, and for good reason. Even if your prescription form indicates a brand name, your pharmacist is likely to give you the generic version if one is available—some states even mandate this—unless your doctor specifies “brand only,“ “do not substitute” or “dispense as written.” Some states also allow you to request that the pharmacist not substitute the generic. The brand-name drug will cost you more, however.

To be on the safe side, keep the following in mind:

• If you switch from a medication (brand-name or generic) to a version by another manufacturer, be aware of any changes in your condition or side effects you may experience.
• Watch out, in particular, if you’re taking an extended-release drug for a condition that requires a constant blood level of the active ingredient and you switch to a version from another company. Extended release drugs are tricky to make. The delivery system can vary from product to product, and some may release the ingredient too quickly or too slowly.
• In addition, watch out for changes if you switch to a generic of a drug that has a narrow therapeutic window (meaning you can get in trouble if your blood level is a little too low or high). That includes thyroid medications, anti-seizure drugs and the blood thinner warfarin (brand name Coumadin). Ask your health care provider or pharmacist if your medication falls into this category.
• Pharmacies often get the same generic drug from different manufacturers, depending on price and availability. So if you’re taking one that’s working well, you may want to check the bottle for the name of the maker and tell your pharmacist you want to stick with that one, advises Tod Cooperman, M.D., president of ConsumerLab.com. If it is no longer available there, you may have to go to a different pharmacy.
• If you have problems or side effects with any drug—generic or brand-name— talk to your health care provider about possible alternatives. If it’s a generic, you should also alert your pharmacist, since he/she may want to get the drug from a different maker. Your health care provider and/or pharmacist should, if appropriate, file a MedWatch report to the FDA. You can also file a report yourself by mail or fax; call MedWatch at 800-FDA-1088 for the form. Or download it atwww.fda.gov/medwatch/how.htm.