BACKGROUND
The skin of preterm infants is defective as a barrier and does not function like that of mature until about 2 weeks of age.
METHODS
Percutaneous drug absorption was studied by observing the blanching response to aqueous solutions of 10% Neosynephrin applied to a small area of skin on the internal surface of the thigh. The subjects, 10 preterm infants born at gestational ages 29 to 32 weeks (mean: 31 weeks 2 days), were tested when they were aged from day 0 to 7. The controls were 8 normal newborns aged 2 days. All preterm infants were tested a second time at the age 7 to 17 days (mean: 10 days). The blanching response was measured after 5 minutes, and graded on a scale of 0 to 4.
RESULTS
The first test was positive grade 2 to 4 in all the preterm babies, while it was negative in the normal newborns. The second test was negative in 7 of the 10 preterm infants; in other 3, the grade was at least 50% lower. Infants nursed under radiant heaters were not different from the other infants.
CONCLUSION
Skin permeability is increased in immature infants, but falls steadily until about the age of 10 days. The results of the Neosynephrin test could be useful in predicting the response to topically administered drug.