(MONEY Magazine) – When Merck yanked the arthritis wonder drug Vioxx off shelves this fall, it not only devastated the company's stock and reputation, it raised fears about the safety of every big new drug. After all, Vioxx grew into a $2.5-billion-a-year pharma phenom (20 million people have used it since its 1999 launch) by appealing to worries that ibuprofen and similar over-the-counter remedies cause internal bleeding. Vioxx was supposed to be safer—that is, until studies showed that it raised the risk of heart attacks in some users. And Vioxx isn't the nth of it. Concerns have also surfaced about other COX-2 inhibitors like Celebrex, widely prescribed statins like Crestor, and antidepressants taken by kids.

Perhaps it was inevitable that among the 1,000 or so new drugs to hit the market since 1995, some potentially dangerous side effects would escape discovery. One problem is that the clinical trials that lead to government approval of drugs are "conducted in relatively idealized populations and only for a limited time," says Dr. Eric Larson, chairman of the board of regents of the American College of Physicians. So when a drug hits the general population, the variations among us—age, race, gender, weight, health conditions—can bring to light previously undetected side effects.

On top of that are all the other drug interactions you need to be aware of in an increasingly medicated age. Now more than ever, it's important to take an active role in understanding the risks of your meds—with the not unpleasant side effect of saving some cash. While you can't turn yourself into a physician or pharmacologist, you can follow a few prudent practices and use a growing number of online resources to find the right questions to ask before popping those pills.

Patient, heal thyself. Quick: Can you name all the drugs you take—with dosages and frequency? Most of us can't. To prevent interactions, fill out a drug worksheet, including over-the-counter medicines, and show it to every doctor you consult. (You can find a sample at citizen.org/eletter/drugworksheet.htm.) Don't know where to start? Put all your pills in a bag and bring them to your doctor.

It's easy to be impressed by (or sold on) a new remedy. But older, more established medicines will often do just fine with less risk. A study of 548 new drugs approved by the FDA between 1975 and 1999 (published in the Journal of the American Medical Association in 2002) showed that the worst adverse side effects weren't known for about seven years. That's because drug research continues long after approval. "I tend to be a late adopter as a prescriber," says Larson, "because I've seen so many drugs come on the market and be withdrawn when the true side-effect profile becomes visible."

An added benefit of older drugs: You may save money too. Employer-sponsored health plans typically offer tiered pricing, meaning you'll pay more for a new drug than for a plan-favored one or a generic. The average co-pay for a preferred drug (including generics) is $21 vs. $33 for a nonpreferred one, according to the Kaiser Family Foundation.

Get drug-smart. Wading through medical data can make corporate annual reports read like Green Eggs and Ham. Rather than relying on one source of info, gather as much as you can from as many places as possible. Here are a few websites, including their pluses and minuses:

• Physicians' Desk Reference (pdrhealth.com) is the most popular resource by far, but it's limited to industry information. Check here for the basics, like dosages, interactions and side effects.

• PhRMA Clinical Study Results (clinicalstudyresults.org), sponsored by the pharma industry, went live Oct. 1. Here's where to find clinical study data. The problem: It's voluntary.

• The FDA's MedWatch (fda.gov/medwatch) gives the heads-up on recalls and changes to risks and usage information. Don't count on it to tell you anything beyond the official line.

• The National Institutes of Health's MedlinePlus (medlineplus.gov) is a consumer-friendly government site with an impressive breadth of information on prescription and over-the-counter drugs.

• Public Citizen's Worst Pills (worstpills.org) offers details on risks and adverse reactions. It's easy to use, if a bit alarmist. The group tallies 160 drugs (including Crestor and the Alzheimer's med Aricept) that it says you should avoid or use only as a last resort.

• Drug blogs Sure, you'll need to take their advice with a boulder of salt, but these sites can be helpful in getting details your doctor might not offer regarding specific therapies—and in finding out the experiences of others who took them. Two especially informative postings: Depression Blog (depressionblog.com), which runs discussion boards on seven prescription antidepressants, and About.com's thyroid forum (thyroid.about.com), a moderated space for thyroid problems and medications.