When it comes to medication, would you consider driving a Ford instead of a Mercedes, if the more economical choice got you where you needed to go? Millions of people on cholesterol-lowering drugs face that decision now.

For about six weeks pharmacies have been selling generic, lower-cost versions of Mevacor (lovastatin). Mevacor was the first statin drug, marketed to lower high blood cholesterol levels and thereby reduce the risk of heart disease. At about $1 per pill, generic lovastatin costs just under half the price of its brand-name version. And as additional generic competitors enter the market over the next few months, that fraction could drop to one-third, if it follows industry trends noted by the Generic Pharmaceutical Association, a trade group.

That development represents enormous potential savings for the estimated 12 million people in the United States who now take statin drugs. (Treatment guidelines released last year by the federal government suggest 36 million could benefit from taking them.) But switching from Mevacor to another version of lovastatin isn't the no-brainer that changing over to a generic drug typically is. When Prozac lost its patent protection last summer, for example, millions of patients made an easy switch to fluoxetine, Prozac's generic form, saving bundles in the process.

The problem lies in the fact that Mevacor, unlike Prozac, is not a top performer in its category, medically speaking. Several more powerful drugs have been introduced since Mevacor's debut in 1987. And its once-dominant market share had fallen to under 5 percent by last year, according to Katy Wynn, a health care analyst with the research firm Datamonitor.

Even at its highest dose, 40 mg twice a day, Mevacor reduces low-density lipoprotein (LDL), the so-called bad cholesterol, by about 35 percent. Lipitor, the most potent new statin, can reduce LDL by 60 percent (at its highest dose, 80 mg taken once a day), according to the drug's label. Other new-generation statins, like Zocor and Pravachol, also outperform Mevacor. And AstraZeneca is soon to introduce a new statin, Crestor, which the company claims could be the most potent yet.

But at about $3 per day for the highest doses, Lipitor is costly, particularly for its primary users -- older patients who often don't have prescription drug coverage. While doctors say the first consideration should be which drug works best, if there is a tossup on effectiveness, it's their responsibility to consider cost as well in recommending one medication over another.

"There's no question that the newer drugs have outpaced lovastatin in terms of their LDL-lowering potential," says James Howard, a cardiologist and the medical director of the Washington Hospital Center. "But for many people, lovastatin still gives you all the LDL-lowering horsepower you need."

Even if lovastatin alone doesn't sufficiently reduce a patient's LDL, Howard said he would consider prescribing it if a patient agreed to add exercise, reduce saturated fat and use of one of the new cholesterol-lowering margarines such as Benecol or Take Control. Such lifestyle changes could reduce cholesterol levels by another 20 to 30 percent.

Cardiologists might have to rethink such flexibility if data emerge showing the newer drugs vastly superior to lovastatin in terms of heart attack and heart disease prevention. But David Pearle, head of the coronary care unit at Georgetown University Hospital, regards that as unlikely. It's doubtful that makers of generic lovastatin will fund studies on their products, and most current studies on statins involve only the newer generation of drugs.

A new product combining lovastatin and niacin -- a B vitamin that boosts the drug's effectiveness -- offers another choice for those seeking treatment of dangerous cholesterol levels, especially patients who need to raise high-density lipoprotein (HDL), or good cholesterol.

In addition to generic lovastatin, Advicor by KOS Pharmaceuticals contains a delayed-release form of niacin called Niaspan, which reduces the rate of niacin's most common side effect, facial flushing. Thirty Advicor pills, which combine 500 mg of niacin with 20 mg of lovastatin, cost $58 at a local CVS -- about $5 more than you'd pay for separate 30-pill vials of Niaspan and lovastatin.

Francesa Lunzer Kritz is a frequent contributor to the Health section.