Caution Urged in Using Bone Drug for Children
High dose of bisphosphonate tied to disorder in boy
(HealthDay is the new name for HealthScoutNews.)
WEDNESDAY, July 30, 2003 (HealthDayNews) -- A new report warns that a class of osteoporosis drugs, normally given to adults, can cause problems when administered to children.
Too-large doses of the drug, which in this case was used to treat a child's bone pain, caused him to develop the kind of abnormally dense and misshapen bones usually caused by a genetic condition, researchers report.
"This is the first report of a non-genetic case of this type of metabolic bone disease," says Dr. Michael P. Whyte, lead author of a report in the July 31 issue of the New England Journal of Medicine. "It should clarify for the medical community that these drugs are not without risk for children."
The boy had been treated with excessively large doses of a bisphosphonate called pamidronate (Aredia), a member of a family widely used to prevent bone loss conditions such as osteoporosis in adults, for about two years because of unexplained bone pain, the journal report says.
At the age of 12, he was referred to the Center for Metabolic Bone Disease and Molecular Research at the Shriners Hospitals for Children in St. Louis, because the bone pain persisted even 18 months after the drug treatment was continued. Whyte heads the center.
Using a sophisticated test, Whyte and his colleagues found the boy had osteopetrosis, where bone is made faster than it is broken down, even though he lacked the genetic abnormalities that would normally lead to this disorder. While the bones grow denser, they also grow weaker and more susceptible to fractures.
"I do not have specific information, but I think it would be correct to say several thousand children are receiving bisphosphonate treatment in the United States for a variety of disorders," Whyte says.
The case report "suggests additional ways to monitor for toxicity, and ways that should be investigated to help detect excessive dosing," he says.
Bisphosphonates are not officially approved for use in children, but they are being used to treat a variety of childhood bone diseases, such as osteogenesis imperfecta and juvenile osteoporosis, says an editorial by Dr. Joan C. Marini of the National Institute of Child Health and Human Development.
"However, bisphosphonates have a prolonged half-life in bone, and their safety and efficacy have not be established in controlled trials in children," she writes.
"These drugs are not benign in normal children," says Marini, who is chief of the institute's heritable disorders branch. "In adults they are quite different. In children they change the quality of the bone. So I think it would be better for treatment of children in the various disorders for which the drug is appropriate be done in controlled trials."
Marini is on the medical board of the Osteogenesis Imperfecta Foundation, and she says several controlled trials of bisphosphonates for that condition are under way.
Whyte has suggestions for doctors using these drugs in children, some based on research done in his facility.
"Some additional skeletal X-rays [to look for bone-shaping abnormalities] may help detect excessive dose, and monitoring the enzymes CK-BB and acid phosphatase in blood may prove to be a means for early detection of toxicity," he says.
And, he says, "physicians who have encountered any similar patient should report their findings in the medical literature, because it will improve our understanding of the effects and tolerability of bisphosphonate therapy."