Call it the luck of the draw. When a series of viral infections destroyed my wife's thyroid gland she needed to take a hormone replacement drug. Her health insurer mailed a 90-day supply of Levothyroxine, the generic version of Synthroid, which had no effect.

When she refilled the prescription the insurer mailed another 90-day supply, but this time the pill was etched with the brand name Synthroid. Within days she felt better.

This seemed strange, since the Food and Drug Administration (FDA) says that brand name and generic drugs, which can be produced when the brand name comes off patent, are "bioequivalent." But what does bioequivalent really mean?

Indifferent insurers

I switched jobs and, in turn, health insurers, and soon discovered that our new insurance company wasn't interested in the difference in efficacy between Synthroid and its generic Levothyroxine. Our insurer told her it would only pay most of the cost of the generic and that she would have to pay out of pocket for the brand name - even though the generic didn't provide any results.

Talking with drug company representatives, pharmacists and doctors, it became clear that this is a common problem, especially since 80 percent of all prescriptions filled nationwide are now generic, according to The New York Times. It also became clear that -- despite the FDA's assertions to the contrary -- brand name and generic are not the same.

Shards of glass

Generic drugs are, first of all, cheaper. Only the pharmaceutical company with the patent can manufacture the brand name, but the generic can be made by any pharmaceutical firm worldwide. And while the FDA may say the active ingredient is the same, it's not just the active ingredient that can cause problems with a generic drug. Some generics incorporate lactose, a sugar found in milk products, as a "binder" to hold the drug in place within the pill. But those who are lactose intolerant could have a severe reaction to the generic, say pharmacists.

In one instance, the FDA got Ranbaxy Pharmaceuticals Inc. to stop manufacturing a generic version of the "bad" cholesterol-lowering drug Lipitor after the FDA discovered that these pills contained tiny shards of glass. Generic Lipitor or Atorvastatin is the fifth most consumed drug in this country.

And this wasn't the first time Ranbaxy was in trouble with the FDA, which had already banned shipments from this India-based company in 2009. Despite its setbacks, Ranbaxy, now back in business, has been producing one of every three of the generic version of Lipitor, according to ABC News.

Cheaper by the million

So why do insurers insist on patients taking generic drugs?

"You can pay 10 times the price for a brand name as for a generic," says Dr. Stephen Klein, an internist in Suffern, N.Y.

Even among the generic drug makers there is intense competition as the large mail-order on-line pharmacies such as Medco and Express Scripts (now merged) shop around for the best price. "If they can save a penny a pill, and they sell millions of pills, it adds up to real money," says Dr. Klein.

'It ain't necessarily so'

So is it really the same drug? Not necessarily, according to pharmacists. The generic drug must only be equivalent within a range of 80 to 125 percent of the brand name, according to Dr. Glenn Sudnick, a Mercerville, N.J., pharmacist.

"The reason that Synthroid and Coumadin [a blood thinner] come up in conversations with patients is because they treat problems where this minus 20 percent to plus 25 percent differential is actually very significant," says Dr. Sudnick.

On the FDA's website, Robert West, the deputy director of the Office of Generic Drugs, disputes this, saying that "those numbers relate to the complex statistical calculation used to analyze bioequivalence studies," and that the same amount of actual drug gets in the blood stream. But some medical professionals aren't convinced.

"I tell people, 'If you can stay with the same brand, that's good,'" says Dr. Sudnick. But if you have to switch from brand name to generic or from one generic to another, he recommends having a blood test to see if you're tolerating the difference.

'DAW'

Drug company representatives say there's a box on each prescription form that could give you ammunition to fight back -- if your doctor is willing to help. The doctor has to check the "DAW" box, which stands for "Dispense as Written." But even if your doctor insists on the brand name, your health insurer isn't obligated to pay most of the cost. In this instance, you'll need additional help from your doctor to convince your insurer.

'Suicidal'

"I tell my patients that if you want to fight your insurance company on this, send me a note explaining why you want brand name only," says Dr. Klein. "I had a patient who was taking Prozac. She switched to the generic and became suicidal. She sent me 30 pages. It was the first time that I ever saw an insurer take this seriously. Most of the time it just doesn't happen."

Here's some ammunition for those who want to undertake the fight, which shows that brand name and generic are not necessarily created equal:

  • The well-known painkiller OxyContin will have to be prescribed in a different form when it comes off patent because the FDA fears that the original pill is too easy for addicts to abuse.
  • Several brand name pharmaceutical companies are paying their generic counterparts to keep the generic version off the market, thus creating a restraint of trade, according to a case before the Supreme Court.
  • In another Supreme Court case, the justices are deciding whether to clarify the recourse that consumers have if injured by a generic drug. The high court previously limited consumers' ability to sue generic manufacturers because they have no control over the warning labels.
'Stretching' the prescription

A final, and sad, footnote. Both brand name and generic drug expenditures are likely to increase 6.6 percent a year between 2015 and 2021 despite President Obama's Affordable Care Act, according to the Kaiser Family Foundation.

The end result: at least 13 percent of those taking prescription medication under the age of 65 are "stretching" them, according to the Centers for Disease Control, further reducing whatever benefit they have.