Generic Drugs Are Much Cheaper, but Use Caution for Those That Have 'Narrow Therapeutic Windows'

Oct. 27, 2009— -- Generic drugs can be as much as 90 percent cheaper than name-brand prescriptions. And more than 70 percent of prescription medications taken today are generics. They are a tremendous bargain, and the vast majority are absolutely safe and effective. But they're not necessarily identical to name-brand drugs, and that's what causes confusion and concern.

When Sassee Ann Arnold had a bad reaction to a generic medication; the physical pain was terrible but not being able to do things she loved hurt more.

"I was devastated," she told "Good Morning America."

Sassee has an underactive thyroid, but she's managed it easily for 35 years with a prescription medicine called Synthroid. Then, a few months ago, she received the generic version, levothyroxine, instead.

"It actually hurt to pick my grandchildren, my youngest up. It actually hurt," she said. "I hated climbing the stairs to go to bed at night. The pain would shoot down to my left leg to my feet. I would get charley horses in my toes and feet. My hair started falling out."

When Sassee switched back to the familiar name-brand drug, her painful symptoms vanished.

"I'm ambitious. I've got back in the woodshop, sewing, taking care of the grandchildren," she said.

There are hundreds of anecdotes like Sassee's posted on peoplespharmacy.com.

"GMA" asked the Food and Drug Administration if generic drugs are as safe and effective as their name-brand counterparts.

"Generic drugs are 70 percent of all prescriptions filled, So a huge number of Americans -- the majority of Americans taking medicine -- are well maintained on their generic drugs, and they're satisfied with those drugs," said Dr. Janet Woodcock of the Food and Drug Administration.

But the FDA acknowledged that a handful of prescription medications, including the one Sassee takes, have what's called a "narrow therapeutic window," meaning that too little isn't effective and too much is toxic, and switching can be difficult.

"For the very sensitive drugs, we do look more carefully at the generic applications. We look at the chemistry and the manufacturing and the bioequivalance studies very carefully to make sure they're going to meet our standards," Woodcock said.