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Some pharmacists legally switch a drug prescribed by a doctor in a common practice called therapeutic substitution. The new drug is in the same class as the old and treats the same condition, but it's not precisely the same medication.
updated 6/2/2009 8:13:47 AM ET 2009-06-02T12:13:47

When you hand a pharmacist a prescription, you expect to get the medication your doctor ordered. But because of a perfectly legal loophole in rules that govern how drugs are dispensed, you may not — and the consequences can be dire.

Just ask Amy Detrick of Grove City, Ohio.

For months after the former social worker, 40, was diagnosed with epilepsy, her doctor fine-tuned the precise cocktail of meds that would keep her from having seizures — adding and subtracting drugs, calibrating doses, and carefully tracking how she responded. When her condition was finally under control, she filled a prescription for one of two drugs she took — Tegretol — and shortly afterward had a seizure while riding a bicycle. She fell off the bike, broke her leg, and had a hairline fracture in her left eye socket. While the doctors were treating her, they noticed the blood level of her medication had declined. Her pharmacist, she learned, had exchanged her Tegretol for a generic that worked a little differently. "Just imagine what could have happened had I been behind the wheel of a car," she says.

Detrick's story sounds like a medical mistake, but it wasn't. Instead, she experienced a potentially deadly consequence of a common practice called "therapeutic substitution," wherein her pharmacist legally switched a drug prescribed by her doc — but without telling her or her physician. Usually, pharmacists replace a brand-name drug with a generic formulation of the exact same medication. Therapeutic substitution is similar but with one crucial distinction: The new drug is in the same class as the old and treats the same condition, but it's not precisely the same medication.

To understand the nuance, think of statins. They constitute a single class of medication because they all lower cholesterol by reducing its production in the liver. But not every statin lowers cholesterol by the same amount or with the same balance of LDL to HDL. So if your doctor orders a brand-name drug but your pharmacist switches it for the cheaper version of a different medication (but still a statin), you may not get the precise benefit your doctor had in mind — and may, in fact, suffer unexpected side effects.

In one way, at least, patients can benefit from substitution — smaller co-pays. But two-thirds of people who reported having meds switched in a National Consumers League survey said they weren't consulted. Of those, 40 percent said the new drug was not as effective, and a third said it had more side effects. "It's not okay for your insurance company or pharmacist to change your drugs without your knowledge," says NCL Executive Director Sally Greenberg.

Unfortunately, therapeutic substitution is likely here to stay — meaning you need to be on the lookout to make sure you're not harmed by the practice. Here are three common reasons you could end up with a less effective drug and steps you can take to ensure you get the medication to treat your condition properly.

1. Your pharmacy misreads the law
After Tony Catizone of Chicago had a stroke while using a widely prescribed blood pressure medication, his doctor wrote a prescription for a new one, but a mail-order pharmacy changed the prescription back to the old drug. His son, Carmen, caught the substitution and called the pharmacy. "They told me that legally, they had to make the switch," says Carmen. Yet no state mandates therapeutic substitution, and even out-of-state mail-order houses must comply with the laws in your state. In Illinois, therapeutic substitution is allowed only in hospitals, where doctors control the process.

"The pharmacy was misinformed, evidently taking the insurer's list of covered drugs as the law," Carmen says. He knew this because he is executive director of the National Association of Boards of Pharmacy. "I told them I had a copy of the Illinois Practice Regulations and knew the law entitled my father to the right drug," he says. After transferring him from a customer service rep to a real pharmacist, the pharmacy corrected the switch.

Video: How safe are generic drugs? Get the right drug: If your doctor believes her drug of choice should not be switched for another, ask her to write "medically necessary," "may not substitute," or "DAW" — for "dispense as written" — on the prescription. That obligates the pharmacist to check with you and your doctor before making any switches.

If a pharmacy tells you the law requires a substitution, find out which ones your state allows, and challenge the switch if the pharmacy has overstepped its authority. To get the information you need, contact your state's board of pharmacy; go to and click on the Boards of Pharmacy button to bring up a contacts list for every state office.

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Pick a pharmacy you like and stick with it. "That way, your pharmacy will have a long record of your prescription history and know if a drug didn't work for you," says Carmen Catizone, whose father had stopped going to a neighborhood drugstore when his insurance company changed to mail-order prescriptions only.

Ask your pharmacist to put a blanket statement in your records that you don't want any medications switched unless you and your doctor approve. "It's a way of getting your pharmacist's attention," says Catizone. "When pharmacists know more, they can do a better job of advocating for patients."

2. Your insurance company won't pay
Insurance plan formularies — the lists of drugs that insurers cover — are at the heart of most substitution battles. "The insurance company will tell me that the drug I prescribed for a patient is not approved or is at the higher co-pay, so I need to submit documentation justifying why insurance should cover it instead of making a substitution," says Lori Heim, MD, president-elect of the American Academy of Family Physicians.

If a doctor persuades the insurance company that a particular drug is medically necessary, the insurer may cover it after all. But the haggling, follow-ups, and appeals can be time-consuming — and infuriating. One frustrated Ohio doctor sued Medco, a large pharmacy benefits management company, asking to be compensated for time wasted on prescription hassles — and won a small award. Court testimony in the case revealed that the company sent 57 times more prescription-related inquiries to physicians in 2007 than it did 10 years earlier.

Meanwhile, as doctors deal with an ocean of paperwork and bicker with insurers, patients suffer. "I've had patients who did not have control of their allergy symptoms — sneezing and feeling miserable — while I jumped through hoops showing that these other drugs didn't work for them," says Heim.

Ask your doctor up front — before you fill your prescription — which generics, if any, are acceptable subs for the drug that she wants you to take: A switch at the pharmacy may be perfectly fine (and often cheaper for you). Write down the name of the prescribed medication and the approved subs on a piece of paper separate from the prescription slip, and then check the filled order against your list. If your pharmacist makes an unapproved switch, call your doctor right away so she can begin documenting why insurance should cover the original drug or an appropriate alternative.

Video: Are we popping too many pills? If your doctor doesn't fight a substitution, make sure he isn't just taking the path of least resistance or losing your prescription in the shuffle. "Busy doctors sign papers quickly, so it's easy for a substitution to sneak through," says Robert Reneker, MD, urgent care physician at Spectrum Health, a hospital system in Grand Rapids, MI. Ask: Will the new drug work better? How will I know if it does or doesn't? Are side effects different from those associated with the original prescription? How will it interact with other medications or supplements I might be taking?

3. Your pharmacy cheats
You'd hope pharmacies are paragons of ethical behavior. "But they're not always aboveboard," says Reneker. Sometimes, he says, pharmacies make drug switches because profit margins are higher on cheaper substitutes. "Pharmacies are directly reimbursed by insurance companies and make more money from generics even though the sticker price for brand-name drugs is higher," says Reneker. "I've had pharmacies tell me a drug isn't on the formulary when I've already checked with the insurance company and know that it is. The switch to a cheaper substitute is motivated purely by profit."

Get the right drug: Shop for prescriptions at stores that have slashed prices on generics — a move that lowers profit margins and reduces the temptation for pharmacists to make sneak switches. Giant retailers like Wal-Mart and Target have led the way on price cuts, pressuring smaller pharmacies to match their discounts. "Drugs have become a way to attract people to stores so they'll spend money on other items," says Reneker.

Call your insurance provider to confirm whether a drug is really covered if your pharmacist says it isn't.

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