Environmental heat exposure may degrade mail-order prescriptions of the asthma drug formoterol, researchers at Carl Hayden Veterans Affairs Medical Center in Phoenix report.

Dr. Gregory T. Chu found that heating capsules of the asthma medication formoterol to 70 degrees Celsius causes the gel capsules to melt and the powdered drug to clump, which impairs deliver when it’s inhaled. He said metal mailboxes in Phoenix and other sunbelt areas regularly reach the 70-degree mark.

Speaking here at the annual meeting of the American College of Chest Physicians, Chu said that patients at the VA center alerted him to the problem when they asked if they should use capsules that appeared to be “bent and burned.” The patients received their medication from a mail-order pharmacy, Chu said.

In their experiment, Chu and his colleagues heated formoterol capsules in original blister packaging to 70 degrees C (158 degrees F) for four hours. Capsules were then removed from the packaging and inserted into vacuum setup to dispense the formoterol into a filter tube.

Weights of the filter tube before and after dispensing the drug were obtained to calculate simulated drug delivery. These measurements were compared with those obtained from capsules that had not been heated.

The changes in filter weights from capsules that underwent heating was 5.5 milligrams, significantly less than the 12.7 milligrams obtained from capsules that had not been heated.

In addition, visual inspection revealed gross distortion of heated capsules as well as visible clumping of formoterol.

Based on these findings, Chu recommends that patients be cautioned about the effects of heat exposure on mail-ordered drugs.