Effect of ampicillin on bleeding time in very low birth-weight neonates during the first week after birth

J Perinatol. 2011 Jul;31(7):477-80. doi: 10.1038/jp.2010.154. Epub 2011 Mar 3.


Objective: On the day of birth, the bleeding time of very low birth-weight (VLBW, <1500 g) neonates is generally prolonged, compared with term neonates. However, their bleeding time generally improves (shortens) over the next 7 to 10 days. Ampicillin can prolong the bleeding times of term and late preterm neonates, but its effect on VLBW neonates, who already have a somewhat prolonged bleeding time initially, is not known.

Study design: This was a prospective, single-centered, paired, before vs after test of the effect of ampicillin on template bleeding time and PFA-100 time (platelet function analyzer). Ampicillin was dosed at every 12 h intravenously, but decisions about discontinuation were made by the responsible clinician, independent of this study.

Result: A total of 20 VLBW neonates were studied. They ranged from 23- to 30-weeks gestation at birth and weighed 500 t 1410 g. Initial bleeding times averaged 166 s (95% CI, 138 to 194) and initial PFA-100 times averaged 119 s (95% CI, 90 to 148). In all, 10 had ampicillin dosing stopped after a shorter course (4 to 7 doses) and 10 had it continued for a longer course (10 to 15 doses). Blood cultures were sterile in all 20, and no differences in laboratory or clinical features were found between those treated with a shorter vs longer course. After stopping the ampicillin following a short course the bleeding times and PFA-100 times were similar to the initial values. However, after a longer course the bleeding times were prolonged by an average of 2 min, to 284 s (95% CI, 242 to 326; P=0.001 vs initial). The PFA-100 times also trended longer by an average of 44 s (P=0.07). The number of doses of ampicillin received in the first week correlated with the degree of prolongation in bleeding time (r=0.68).

Conclusion: Over the first week of life, a period when the bleeding time of VLBW neonates normally shortens, the opposite occurred (the bleeding time lengthened) if ≥ 10 doses of ampicillin were administered.

Publication types

  • Comparative Study

MeSH terms

  • Ampicillin / administration & dosage*
  • Ampicillin / adverse effects
  • Anti-Bacterial Agents / administration & dosage
  • Anti-Bacterial Agents / adverse effects
  • Bleeding Time*
  • Blood Platelets / drug effects*
  • Cohort Studies
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Female
  • Follow-Up Studies
  • Humans
  • Infant, Newborn
  • Infant, Premature
  • Infant, Very Low Birth Weight*
  • Intensive Care Units, Neonatal
  • Male
  • Prospective Studies
  • Reference Values
  • Risk Assessment
  • Term Birth*
  • Time Factors
  • Treatment Outcome


  • Anti-Bacterial Agents
  • Ampicillin