Tb Drug Dose May Need Boost in Children

NEW YORK (Reuters Health) - Children eliminate the anti-tuberculosis drug isoniazid faster and need higher dosages than adults, South African researchers report.

"Isoniazid is the most important drug in current anti-tuberculosis treatment regimens," Dr. H. Simon Schaaf told Reuters Health. "According to WHO guidelines, children and adults should receive the same dosage of isoniazid per kilogram body weight, but from our study it is clear that young children eliminate isoniazid much faster than adults."

Schaaf of Stellenbosch University, Tygerberg, and colleagues evaluated the absorption and elimination of isoniazid in 64 children with TB who were younger than 13 years old.

The average rate of elimination differed significantly among the children depending on their genetic make-up, the team reports in the Archives of Disease in Childhood.

However, within groups of the same genetic type, the researchers found that the elimination rate decreased with age. Comparison with ethnically similar adults showed that average blood concentrations of isoniazid for each genetic type were significantly higher than in children.

"Children develop less side effects from isoniazid compared with adults," Schaaf commented. "A dose of 10 milligrams per kilogram, as we now recommend, should be safe in by far the majority of cases, and is currently already the recommended dose in children in developed countries."

In an accompanying editorial, Dr. N. Cranswick of the University of Melbourne, Australia and Dr. K. Mulholland of the School of Medical and Tropical Hygiene, London, note that the study "highlights the fact that not only are higher doses required in childhood...but also that children are as metabolically (variable) as adults."

SOURCE: Archives of Disease in Childhood, June 2005.