MJ du Preez(1) , JH Botha(1) , ML McFadyen(2) and M. Adhikari(3)
Departments of Pharmacology(1) , University of Natal,
University of Durban-Westville(2)
Department of Paediatrics(3) , University of Natal, Durban, South Africa
The study aims to investigate the relationship between plasma concentrations of theophylline and its effect on the incidence and duration of apnoea in premature neonates.
Premature apnoeic neonates are closely monitored during the first few days of life, before and at varying times after theophylline dosing. Apnoea incidence and duration, oxygen saturation, nasal airflow, respiratory rate and pulse rate, are recorded using a neonatal capnograph. All other clinical and demographic details are recorded. Blood samples for measurement of theophylline and caffeine are obtained during the monitoring periods. Apnoeas are classified as significant, non-significant and periodic breathing. Each of these is assigned a value leading to an overall scoring system which is used to compare apnoeic responses before and after drug therapy.
Preliminary results will be presented. Twenty patients have been monitored and 50 serum concentrations have been obtained to date. Mean(SD) weights and gestational ages of the babies were 1.23(0.3)kg and 30(0.7) weeks respectively. The concentration-effect relationship is complicated by the finding that approximately 40% of the patients were non-responders. Possible reasons for their lack of response will be presented. Among the responders, there appears to be some relationship between effect and theophylline concentration, up to a maximum of 20mg/l.