Kerry Fehr-Snyder
The Arizona Republic
Jun. 21, 2003 12:00 AM

The first drug developed in Mexico for use in the United States will be tested soon in Arizona.

The drug, a new antivenin for Arizona's deadliest scorpion, is expected to be ready just as the state's supply of existing antivenin runs out.

"We're cutting it close," said Dr. Leslie Boyer, medical director for the Arizona Poison and Drug Information Center at the University of Arizona in Tucson.

Boyer will lead the testing of the new antivenin in hopes of winning FDA approval before the existing antivenin runs out at the end of next year.

The testing will take several months to organize and even longer to analyze. The drug is already used in Mexico and has proved to be safe and effective. But winning approval from the federal Food and Drug Administration is a laborious process even for drugs designed for use in relatively few people.

Each year, thousands of residents who are stung by desert-dwelling bark scorpions call the UA center. Several thousand more call the Banner Poison Control Center at Banner Good Samaritan Medical Center in Phoenix.

But only a fraction of scorpion sting victims require infusions of antivenin.

Small children are most vulnerable for severe reactions to both scorpion stings and the existing antivenin. The venom creates a burning sensation at the sting location but travels throughout the nervous system and can cause children to salivate, jerk and have trouble breathing.

The antivenin can cause its own set of problems, primarily an allergic reaction that results in hives, throat tightness and in extreme cases, changes in blood pressure. Two years ago, a small child in southern Arizona died after receiving the antivenin, Boyer said.

The new antivenin is made by Bioclon, a division of Silanes, which has factories in Mexico City, Toluca and Cuernavaca. It has teamed up with Rare Disease Therapeutics in Nashville to get FDA approval.

"This is a very safe product and very much needed," said Bo Allen, Rare Disease's vice president. "The fact that there's a limited supply is the least of why we need a new product."

The current antivenin was made by Marilyn Bloom, a retired immunology research specialist at Arizona State University. She injected goats with scorpion venom to create an immune response and then drew blood with antibodies that could be purified and given to human scorpion victims.

Allergic reactions occur in the majority of cases because patients actually receive goat protein.

The new antivenin is made in horses but has been chemically altered to remove proteins that can cause an allergic reaction.

Scorpion season runs from May to October and peaks in the summer, when the nights get warmer. The ASU antivenin has been the serum of choice, but it doesn't have FDA approval because it is not sold outside the state.

"It is my objective to have (the new antivenin) available for next season," Allen said.

The toughest part of working with a Mexican drugmaker has been translating its manufacturing practices from Spanish into English for the FDA, Allen said.

But Allen said the company's facilities are first-rate. "This company is very innovative," he said. "They have extremely good scientists."