Oral pivampicillin and amoxycillin in newborn infants.

Ampicillin was administered intramuscularly and amoxycillin or pivampicillin orally to 14 fasting newborn infants, 6-13 days old, in a cross-over trial. The dose was 50 mg/kg twice daily. The mean peak plasma level of amoxycillin and pivampicillin was 58% (range 35-96%) and 48% (33-82%) of that noted after i.m. ampicillin, which gave a value of about 44 +/- 5 micrograms/ml (mean +/- SEM) in both groups. The area under the time-concentration curve was 75% (range 60-101%) of that of i.m. ampicillin for amoxycillin and 51% (20-76%) for pivampicillin (p less than 0.05). Both drugs, especially amoxycillin, should be useful for oral treatment of neonatal infections caused by susceptible microorganisms in infants who are not critically ill.