Therapeutic drug monitoring of caffeine in preterm infants: Could saliva be an alternative to serum?

Objective: Evaluate whether saliva could be a useful alternative to serum for routine therapeutic drug monitoring of caffeine in preterm infants using the enzyme multiplied immunoassay technique (EMIT) assay.

Methods: We conducted a prospective study including preterm infants (less than 34 weeks' amenorrhea) admitted to the intensive care and neonatal medicine department. All infants received 5, 10, 15, 20 and 25mg/kg/day of citrate caffeine intravenously from the first to the fifth day of birth, respectively. For each patient, two concomitant blood and saliva samples corresponding to the trough concentrations were collected 24hours after each caffeine dose. The caffeine concentrations were determined using the EMIT2000 caffeine assay.

Results: Thirteen preterm infants were included. The saliva and the serum caffeine concentration increased proportionally to the administered dose. Saliva and serum kinetics were comparable and the saliva caffeine concentrations were correlated to the serum ones (r=0.76).

Conclusion: Saliva caffeine monitoring by EMIT is a valid, useful and safe alternative to serum in preterm infants.