LAUSR

WHAT IS KNOWN AND OBJECTIVE Linezolid, as a substitute for vancomycin, has been used in treating methicillin-resistant Gram-positive bacterial infections in very low birth weight (VLBW) infants. However, when linezolid induces thrombocytopenia in adults, its side effects in VLBW infants are concerning. This study aimed to investigate the effect of linezolid on haematologic profiles in this specific vulnerable population. METHODS VLBW infants treated with linezolid from January, 2017, to July, 2021, were retrospectively analysed compared with vancomycin as controls. The effects of medications on haematologic parameters were compared on Days 1, 3, 5, 7, 10, 14 and 21 after medication initiation. RESULT AND DISCUSSION Totally 40 VLBW infants treated with linezolid were recruited in the study, using 45 VLBW treated with vancomycin as controls. Baseline clinical characteristics, such as gestational age and birth weight, were not significantly different between the two groups. After medication initiation, the white blood cell counts on the Days 5 and 7 in the linezolid group were significantly lower than that in the vancomycin group (D5: 11.6 ± 6.2*10⁹/L vs. 14.5 ± 6.4*10⁹/L, p = 0.013; D7: 10.8 ± 5.9*10⁹/L vs. 14.1 ± 8.0*10⁹/L, p = 0.01), while the platelet counts were significantly lower in the linezolid group on Days 10 and 14 (D10: 219.2 ± 90.5*10⁹/L vs. 287.5 ± 100.4*10⁹/L, p = 0.049; D14: 263.0 ± 110.9*10⁹/L vs. 325.0 ± 155.1*10⁹/L, p = 0.036). For substantial haematologic abnormalities, there were no significant differences in leukopenia, neutropenia, agranulocytosis and thrombocytopenia between the two groups. WHAT IS NEW AND CONCLUSIONS In VLBW infants, compared with vancomycin, linezolid tends to induce lower white blood cell and platelet counts transiently, but does not increase the severe forms of haematologic side effects.