TABLE 3.

Probability of target attainment for predefined peak and trough concentration targets following an optimal dosing regimen (i.e., the administration of 7.5 mg/kg over different dosing intervals according to patient characteristics)^a

Dosing regimen (mg/kg; h)b	Demographic characteristics	First dose			After 1 wk of treatment
		% neonates with ratio peak/MIC of >10	% neonates with trough of:		% neonates with ratio peak/MIC of >10	% neonates with trough of:
			<1 mg/liter	<2 mg/liter		<1 mg/liter	<2 mg/liter
MIC = 0.5 mg/liter
4; 36	PNA < 7, GA ≤ 28	98	62	100	98	43	94
4; 36	PNA < 7, GA > 28	97	91	100	97	86	99
4; 36	PNA ≥ 7, GA ≤ 28	96	88	100	97	70	96
4; 24	PNA ≥ 7, GA > 28	94	80	99	95	65	93
MIC = 1.0 mg/liter
7.5; 48	PNA < 7, GA ≤ 28	98	40	98	98	38	87
7.5; 48	PNA < 7, GA > 28	91	85	99	92	84	97
7.5; 48	PNA ≥ 7, GA ≤ 28	95	81	99	95	67	92
7.5; 36	PNA ≥ 7, GA > 28	90	83	99	91	74	95

^aAbbreviations: PNA, postnatal age (days); GA, gestational age (weeks). To achieve a probability of target attainment (PTA) of 90% would require a dosing interval of 60 h (PTA = 97%). After a second dose with a dosing interval of 48 h (96 h after the start of treatment), the PTA would still be 93%.

^bDosing regimens are expressed as follows: amount (mg/kg); interval (h). Hence, “4; 36” indicates “4 mg/kg administered every 36 h.”