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Antibiotics in Neonates

By

Brenda L. Tesini

, MD, University of Rochester School of Medicine and Dentistry

Last full review/revision Jul 2020| Content last modified Jul 2020
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In neonates, the extracellular fluid (ECF) constitutes up to 45% of total body weight, requiring relatively larger doses of certain antibiotics (eg, aminoglycosides) compared with adults. Lower serum albumin concentrations in premature infants may reduce antibiotic protein binding. Drugs that displace bilirubin from albumin (eg, sulfonamides, ceftriaxone) increase the risk of kernicterus.

Absence or deficiency of certain enzymes in neonates may prolong the half-life of certain antibiotics (eg, chloramphenicol) and increase the risk of toxicity. Changes in glomerular filtration rate and renal tubular secretion during the first month of life necessitate dosing changes for renally excreted drugs (eg, penicillins, aminoglycosides, vancomycin).

Table
icon

Recommended Dosages of Selected Parenteral Antibiotics for Neonates

Intervals of Administration

Antibiotic

Route of Administration

Individual Dose

Body Weight ≤ 2000 g

Body Weight > 2000 g

Comments

Age

Age

≤ 7 days

8–28 days

≤ 7 days

8–28 days

Amphotericin B deoxycholate

IV

1 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

After dilution in 5% or 10% D/W (saline solution should not be used), infusion of a test dose of 0.1 mg/kg (maximum 1 mg) over 1 hour to assess patient’s febrile and hemodynamic response;* if no serious adverse effects are observed, infusion of a therapeutic dose (usually 0.25–1.5 mg/kg over 2–6 hours), which may be given the same day as the test dose

After the patient improves, may give the dose every other day until therapy is complete

Monitoring of potassium levels and hematologic and renal functions required

Amphotericin B lipid complex

IV

5 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Amphotericin B liposomal

IV

5 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Ampicillin

IV, IM

50–75 mg/kg

50 mg/kg every 12 hours

75 mg/kg every 12 hours

50 mg/kg every 8 hours

50 mg/kg every 8 hours

IV as 15- to 30-minute infusion ( 10 mg/kg/minute)

For GBS meningitis

IV

75–100 mg/kg

100 mg/kg every 8 hours

75 mg/kg every 6 hours

100 mg/kg every 8 hours

75 mg/kg every 6 hours

Azithromycin

IV

10 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

For chlamydial pneumonia, 20 mg/kg every 24 hours

Aztreonam

IV, IM

30 mg/kg

Every 12 hours

Every 8 hours†

Every 8 hours

Every 6 hours

Limited data

For gram-negative bacilli only

Cefazolin

IV, IM

25 mg/kg

Every 12 hours

Every 8 hours†

Every 12 hours

Every 8 hours

Limited data

No primary indication; not used as initial therapy for sepsis or meningitis

Cefepime

IV, IM

30–50 mg/kg

30 mg/kg every 12 hours

30 mg/kg every 12 hours

50 mg/kg every 12 hours

50 mg/kg every 12 hours

May be used for Pseudomonas aeruginosa infections (consider using 50 mg/kg every 8 hours for P. aeruginosa and other serious gram-negative pathogens)

Sometimes used for meningitis, although usually as a 2nd-line drug and not always recommended

Cefotaxime

IV, IM

50 mg/kg

Every 12 hours

Every 8 hours†

Every 12 hours

Every 8 hours

Often a first-line therapy for neonatal meningitis

Cefoxitin

IV, IM

33–35 mg/kg

35 mg/kg every 12 hours

33 mg/kg every 8 hours†

33 mg/kg every 8 hours

33 mg/kg every 8 hours

Ceftazidime

IV, IM

50 mg/kg

Every 12 hours

Every 8 hours†

Every 12 hours

Every 8 hours

Penetrates well into inflamed meninges

70–90% of drug excreted unchanged in urine

Ceftriaxone

IV, IM

50 mg/kg

Every 24 hours

Every 24 hours

Limited data

May cause biliary pseudolithiasis and, in jaundiced premature infants, may increase risk of bilirubin encephalopathy via displacement of bilirubin from albumin

Contraindicated in neonates receiving or expected to receive infusions of calcium-containing solutions

2nd-line drug for meningitis, after the first week of life (40–50 mg/kg every 12 hours or 80–100 mg/kg every 24 hours)

Cefuroxime

IV, IM

50 mg/kg

Every 12 hours

Every 8 hours†

Every 12 hours

Every 8 hours

Chloramphenicol

IV, IM

25 mg/kg

Every 24 hours

Every 12 hours†

Every 24 hours

Every 12 hours

Doses adjusted by monitoring serum drug levels and hematologic parameters

For meningitis, desired peak serum levels = 15–25 mcg/mL (46.4–77.4 micromol/L) and trough levels = 5–15 mcg/mL (15.5–46.4 micromol/L)

For other infections, dose adjusted to attain a peak level of 10–20 mcg/mL (31–62 micromol/L) and a trough level of 5–10 mcg/mL (15.5–31 micromol/L)

Large variability in serum levels and serum half life, especially in preterm neonates

Clindamycin

IV, IM

5–9 mg/kg

5 mg/kg every 8 hours

5 mg/kg every 8 hours

7 mg/kg every 8 hours

9 mg/kg every 8 hours

For anaerobes and gram-positive cocci (not enterococci)

Daptomycin

IV

6 mg/kg

Every 12 hours

Every 12 hours

Every 12 hours

Every 12 hours

Neurotoxicity potential; use with caution if no other options

Fluconazole

For treatment

IV

12 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Loading dose of 25 mg/kg followed 24 hours later by maintenance dose listed

For prophylaxis

IV

6 mg/kg

Twice weekly

Twice weekly

Twice weekly

Twice weekly

Linezolid

IV

10 mg/kg

Every 12 hours

Every 8 hours

Every 8 hours

Every 8 hours

Meropenem

For meningitis

IV

40 mg/kg

Every 12 hours

Every 8 hours§

Every 8 hours

Every 8 hours

For sepsis, intra-abdominal infection§

IV

20–30 mg/kg

20 mg/kg every 12 hours

20 mg/kg every 8 hours§

20 mg/kg every 8 hours

30 mg/kg every 8 hours

Metronidazole

IV

7.5–10 mg/kg

7.5 mg/kg every 12 hours

7.5 mg/kg every 12 hours

7.5 mg/kg every 8 hours

10 mg/kg every 8 hours

Limited data

Loading dose of 15 mg/kg

Nafcillin, oxacillin

For meningitis

IV, IM

50 mg/kg

Every 12 hours

Every 8 hours†

Every 8 hours

Every 6 hours

Monitoring of CBC and liver tests required

Excretion may be decreased due to renal and hepatic immaturity, leading to possible accumulation in serum, which may have adverse effects

For other diseases

IV, IM

25 mg/kg

Every 12 hours

Every 8 hours†

Every 8 hours

Every 6 hours

Oxacillin (see Nafcillin, oxacillin)

Penicillin G, benzathine

IM

50,000 units/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Penicillin G, crystalline (aqueous)

For congenital syphilis, other indications

IV

50,000 units/kg

Every 12 hours

Every 8 hours

Every 12 hours

Every 8 hours

For GBS meningitis

IV

100,000 units/kg

Every 6 hours

Every 6 hours

Every 6 hours

Every 6 hours

Penicillin G, procaine

IM

50,000 units/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

CAUTION: Sterile abscess and procaine toxicity

Piperacillin/tazobactam

IV (dose based on piperacillin component)

80–100 mg/kg

100 mg/kg every 8 hours

80 mg/kg every 6 hours║

80 mg/kg every 6 hours

80 mg/kg every 6 hours

Rifampin

IV

10 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Vancomycin (see Table: Vancomycin Dosage for Neonates)

Dosing based on gestational age and serum creatinine (see Table: Vancomycin Dosage for Neonates)

* The need to administer a test dose of amphotericin B is controversial.

† Use the dose for age ≤ 7 days until 14 days of age if the birth weight is < 1000 g.

Cefazolin does not cross the blood-brain barrier.

§ Adjust dosage after 14 days of age instead of after 7 days of age.

║ When postmenstrual age reaches > 30 weeks.

CBC = complete blood count; GBS = group B streptococcus.

Adapted from Bradley JS, Nelson JD: Nelson's Pediatric Antimicrobial Therapy, ed. 24. Itasca, American Academy of Pediatrics, 2018.

Table
icon

Recommended Dosages of Select Aminoglycosides for Neonates

Interval of Administration

Aminoglycoside

Route of Administration

Individual Dose

< 30 Week Gestation

30–34 Week Gestation

≥ 35 Week Gestation

Comments

Postnatal Age

Postnatal Age

Postnatal Age

0–14 days

> 14 days

0–10 days

> 10 days

0–7 days

> 7 days

Amikacin*

IV, IM

15–17 mg/kg

15 mg/kg every 48 hours

15 mg/kg every 24 hours

15 mg/kg every 24 hours

15 mg/kg every 24 hours

15 mg/kg every 24 hours

17.5 mg/kg every 24 hours

Monitoring of serum drug levels required

Peak level target 20–35 mg/L (34.2–59.8 micromol/L) or 10 × MIC; trough < 7 mg/L (12 micromol/L)

Dose reduction required for impaired renal function

Gentamicin*, tobramycin

IV, IM

4–5 mg/kg

5 mg/kg every 48 hours

5 mg/kg every 36 hours

5 mg/kg every 36 hours

5 mg/kg every 36 hours

4 mg/kg every 24 hours

5 mg/kg every 24 hours

Monitoring of serum drug levels required

Peak level target 6–12 mg/L (12.5–25.1 micromol/L) or 10 × MIC; trough < 2 mg/L (4.2 micromol/L)

Dose reduction required for impaired renal function

* Sample should be obtained 30 minutes after a 30-minute IV infusion.

MIC = minimum inhibitory concentration.

Adapted from Bradley JS, Nelson JD: Nelson's Pediatric Antimicrobial Therapy, ed. 24. Itasca, American Academy of Pediatrics, 2018.

Table
icon

Vancomycin Dosage for Neonates

Serum Creatinine (mg/dL)

Dose* (IV)

Interval of Administration

≤ 28 Week Gestation

> 28 Week Gestation

< 0.5

< 0.7

15 mg/kg

Every 12 hours

0.5–0.7

0.7–0.9

20 mg/kg

Every 24 hours

0.8–1

1–1.2

15 mg/kg

Every 24 hours

1.1–1.4

1.3–1.6

10 mg/kg

Every 24 hours

> 1.4

> 1.6

15 mg/kg

Every 48 hours

* Dose is given by slow IV infusion, over at least 60 minutes. Begin with a 20 mg/kg loading dose. Ideally, adjust dosage to achieve 24 hours AUC:MIC of 400 mg • hours/L. If this calculation cannot be done, monitor serum trough level (target typically = 10–12 mcg/mL [6.9–8.3 micromol/L]).

AUC = area under the plasma concentration–time curve; MIC = minimum inhibitory concentration.

Adapted from Bradley JS, Nelson JD: Nelson's Pediatric Antimicrobial Therapy, ed. 24. Itasca, American Academy of Pediatrics, 2018.

Table
icon

Recommended Dosages of Selected Oral Antibiotics for Neonates*

Interval of Administration

Antibiotic

Dose

Body Weight ≤ 2000 g†

Body Weight > 2000 g

Comments

Postnatal Age

Postnatal Age

≤ 7 days

8–28 days

≤ 7 days

8–28 days

Amoxicillin (may be combined with clavulanate)

15 mg/kg

Every 12 hours

Every 12 hours

Limited data for use in neonates < 2000 g

Higher doses may be used for severe infections or anthrax

Use only the 125 mg/5 mL suspension if combined with clavulanate

Azithromycin

10 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

Preferred drug for treatment or prevention of pertussis in neonates < 1 month;

10 mg/kg given once/day for 5 days

May be used for treatment of chlamydial ophthalmia, most commonly 20 mg/kg every 24 hours for 3 days

Associated with idiopathic hypertrophic pyloric stenosis, but less commonly than with erythromycin

Clindamycin

5–9 mg/kg

5 mg/kg every 8 hours

5 mg/kg every 8 hours

7 mg/kg every 8 hours

9 mg/kg every 8 hours

Limited data

Erythromycin

10 mg/kg

Every 6 hours

Every 6 hours

Every 6 hours

Every 6 hours

For chlamydial infections or pertussis in neonates > 1 month

Associated with idiopathic hypertrophic pyloric stenosis

Fluconazole

Loading dose of 25 mg/kg followed 24 hours later by maintenance dose listed

During the 1st 2 weeks of life, adjustment of dosing interval to every 48 hours may be necessary

For treatment

12 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

For minor candidal infections (eg, thrush), 6 mg/kg on day 1, then 3 mg/kg/dose every 24–72 hours

For prophylaxis

6 mg/kg

Twice/week

Twice/week

Twice/week

Twice/week

Flucytosine

25 mg/kg

Every 8 hours

Every 6 hours

Every 6 hours

Every 6 hours

Limited data

Used only with amphotericin B to slow emergence of resistance

Dosing interval may need to be increased with abnormal renal function

Monitoring of levels recommended

Desired serum concentrations: Peak 50–100 mg/L, trough 25–50 mg/L

Linezolid

10 mg/kg

Every 12 hours

Every 8 hours

Every 8 hours

Every 8 hours

Used for resistant gram-positive infections

Metronidazole

7.5–10 mg/kg

7.5 mg/kg every 12 hours

7.5 mg/kg every 12 hours

7.5 mg/kg every 8 hours

10 mg/kg every 8 hours

Loading dose 15 mg/kg

Limited data

Rifampin

10 mg/kg

Every 24 hours

Every 24 hours

Every 24 hours

Every 24 hours

For treatment

Additional dosing regimens may be used for Haemophilus influenzae type b and meningococcal disease prophylaxis

* Unless otherwise stated, doses are for neonates (≤ 28 days postnatal age).

† Use ≤ 7 days dosing until 14 days old if the birth weight is < 1000 g.

Adapted from Bradley JS, Nelson JD: Nelson's Pediatric Antimicrobial Therapy, ed. 24. Itasca, American Academy of Pediatrics, 2018.

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