Cheaper prescription drugs required by HMOs actually may increase the cost of medical care in the long run, a study published last week suggests.
The study in the American Journal of Managed Care says the practice, a longtime cornerstone of medical cost control, may mean access to some drugs is restricted and sometimes the most effective medicines aren't used.
The results may be longer illnesses, more trips to hospitals and emergency rooms, and increased use of prescriptions, the study said.
The study, which covered 13,000 patients in six HMOs, was funded by the unidentified HMOs and by the National Pharmaceutical Council, which represents drug companies.
More than 100 million Americans belong to managed-care plans that require or encourage their physicians to prescribe drugs from formularies, or lists of preferred drugs. The programs also encourage pharmacists to recommend the less-expensive generic medications.
Researchers said patients covered by plans with the most restrictive prescription rules used other medical services twice as often as patients with no such restrictions.
Generic drugs can vary in strength and effectiveness or may work differently than other prescriptions. Strict HMO formularies might therefore exclude the most effective, though more costly, medicines.
"We didn't believe the results when we first got them" in 1993, said University of Utah researcher Susan Horn, the study's main author.
"This simplistic approach, of restricting what drugs are available and automatically prescribing generic substitutes, may work fine for some patients, but for most patients it doesn't," Horn said.
Some health researchers said the methodology used in the study raised questions about its conclusions.
Richard L. Kravitz of the University of California at Davis, author of an editorial accompanying the report, noted that only six HMOs were involved. He also pointed out that patients weren't drawn randomly.