Early and late neutropenia in children treated with cotrimoxazole (trimethoprim-sulfamethoxazole).

The incidence of hematologic abnormalities was evaluated in 120 children with otitis media treated respectively with cotrimoxazole (trimethoprim-sulfamethoxazole) (group 1), cotrimoxazole plus folinic acid (group 2) and amoxicillin (group 3) in therapeutic doses for ten days. Only eosinophilia (an absolute count greater than or equal to 0.5 X 10(9)/l) (group 1 = 10%, 2 = 5%, 3 = 7.5%) and neutropenia (polymorphonuclear neutrophilic leucocyte count less than or equal to 1.5 X 10(9)/l) (group 1 = 35%, 2 = 17.5%, 3 = 13.3%) were noted. Early neutropenia (evident on the 5th day of therapy) occurred in all the treatment groups, thus it is not related to cotrimoxazole administration and in most cases neutrophil count reversed to normal in few days without drug discontinuation. Late neutropenia (evident after 10 days of treatment) appeared only in cotrimoxazole treated children (p less than 0.05). No superimposed bacterial infection was demonstrated in any case. Late neutropenia seems to be strictly related to the sequential blockage of folinic acid metabolism and can be prevented by the concomitant administration of folinic acid.