Simplified method for the determination of zidovudine and didanosine in children
American scientists have developed a simplified dosing regimen for the antiretroviral drugs zidovudine and didanosine for patients of different weight groups.
The dosage of antiretroviral drugs zidovudine and didanosine is based on body surface area, which can be difficult to determine in non-specialist clinics. P.J. Weidle et al. (United States), a simplified dosing regimen for these drugs has been developed for patients of different weight groups (5-6.9; 7-9.9; 10-11.9; 12-14.9; 15 -16.9; 17-19, 9; 20-24.9; 25-29.9; 30-34.9 and 35-40 kg).
During the development of the methodology, the researchers determined the differences between the doses calculated on the basis of body weight and the doses calculated on the basis of the surface area of a zidovudine solution for oral administration (10 mg / ml) , zidovudine capsules (100 mg) and didanosine chewable tablets (25, 50 and 100 mg) using standardized growth charts and actual height and weight values for children infected with HIV.
1752 clinical cases of 826 HIV-infected children (52% of boys, 48% of girls) from 9 countries of the world have been studied. The body weight of 454 children did not exceed 20 kg, in 1298 it exceeded 20 kg.
In children with body weight less than 20 kg, the mean difference between the dose calculated on the basis of body weight and on the basis of body surface area was -6.4% for the zidovudine solution (-22, 6, +13.7 variations), for zidovudine capsules + 3.1% (variations -38.8, +44.7) and for didanosine chewable tablets + 0.7% (variations -24.4, 22.5); in children weighing more than 20 kg, this indicator was 0.0% (-16.4, +11.8 variations), + 7.6% (-16.4, +36.9 variations) and +1 , 2% (variations -16.4, +14.1), respectively.
Thus, the dose received was different for children weighing less than 20 kg and more than 20 kg for the solution (P less than 0.001) and zidovudine capsules (P less than 0.001), but did not differ for the didanosine tablets.. The frequency of cases in which the dose calculated on the basis of body weight was more than 20% lower than the dose calculated on the basis of body surface for children whose body weight was less than 20 kg was 1.3 % for zidovudine solution, 27.2% for zidovudine capsules and 4.9% for didanosine chewable tablets. For children weighing more than 20 kg, the dose calculated on the basis of body weight has never been more than 20% lower than the dose calculated on the basis of body surface area.
Thus, the scheme proposed by the researchers provides a fairly precise dosing technique compared to that based on the determination of the body surface area. However, the use of zidovudine capsules in children with a body weight less than 20 kg can lead to the appointment of an underestimated dose of 20% or more. The dosage of didanosine chewable tablets is not accompanied by such errors.