Usefulness of theophylline saliva levels in neonates

In order to establish an alternative means for monitoring serum theophylline concentrations in neonates, the reliability of salivary theophylline concentrations was investigated. Eight premature neonates with apnea of prematurity were studied. Neonates received between 1.25 and 2.5 mg/kg of intravenous aminophylline every 12 h. Simultaneous samples of blood (0.25 ml) and unstimulated saliva (0.25-0.50 ml) were obtained 4 and 8 h after drug administration. Serum and salivary theophylline concentrations statistically correlated (r = 0.98, p less than 0.01). The mean serum/saliva ratio was 1.02 +/- 0.09, with an 8.9% interpatient variation. Serum theophylline concentrations can be predicted from the equation: serum concentration = 1.069 x saliva concentration - 0.193. The data suggest that theophylline serum and saliva concentrations in the apneic neonate are approximately equal. Salivary theophylline concentrations may be clinically useful when serum is not readily available.