Some medicines may degrade quickly when they're shipped through the mail and exposed to extreme temperatures, a new study suggests.

Researchers specifically found that a common inhaled asthma medication delivered less than half its expected punch and showed significant physical change after being in 150-degree Fahrenheit temperatures for four hours _ the equivalent of being inside a mailbox or car in Arizona during a summer day.

"Inhaled medications are calculated to deliver a specific dosage for each use. Extreme temperatures can affect medications in just a few hours, causing them to deliver inaccurate doses," said Dr. Gregory Chu, a chest specialist at the Carl T. Hayden Veterans Affairs Medical Center and Banner Good Samaritan Medical Center, both in Phoenix. He presented the findings Wednesday during a meeting of the American College of Chest Physicians, in Seattle.

"For patients who rely on their medications to relieve acute breathing difficulties, inaccurate medication dosage can lead to serious medical consequences," he added.

Chu and colleagues tested the effect of heat on formoterol capsules, heating them to 150 degrees in the original packaging. The drug comes as powder in a capsule; the powder is inhaled through the mouth using a special inhaler.

The capsules were then removed from packages and put into the inhaler and dispensed into a filter tube. The filters were weighed before and after each test.

The researchers found that filter weights were less than half those that used capsules that hadn't been exposed to heat. And the capsules that had been heated also were distorted and showed visible clumping.

"Although mail-order prescriptions have become increasingly popular, many patients do not realize that most medications have storage requirements regarding exposure to excessive temperature," said Dr. Richard Robbins, study co-author, also at the VA Medical Center.

In 2003, mail orders totaled more than $35 billion in sales in the United States, accounting for about 17 percent of retail prescription drug sales. Employers and insurers encourage people with chronic conditions to use mail-order systems because they are less expensive to administer, and patients save by paying co-payments less often for a typical 90-day supply.

Conventional pharmacists and some consumer advocates have been warning for some time, however, that shipping methods used by the companies may not respect drugmakers' warnings about temperature or humidity for storing certain drugs.

"We strongly advise that patients avoid exposing medications to the extreme heat found in mailboxes and car interiors and inspect all mail-order medications prior to consumption," Robbins said.

The researchers note that asthma medications and other drugs delivered in the extreme heat of the Southwest are not the only drugs at risk. Any situation that exposes a drug, particularly those with gelatin capsules or containing a powder, to extreme temperatures can cause alterations.

Dr. Paul Kvale, president of the American College of Chest Physicians, noted that companies that fill prescriptions by mail need to pay more attention to how they package and ship at-risk medications.

"It is also important for patients to review manufacturer storage directions to ensure that medications are not exposed to extreme temperatures either inside or outside the home," Kvale said.

On the Net: http://www.chestnet.org

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