Millions of premature babies suffer from breathing stops lasting more than twenty seconds, called apneas. These arise because the babies’ bodies are not developed enough. Sometimes their brain does not notice oxygen shortages and does not send impulses to stimulate breathing again, which could get lethal. The medicine caffeine is given to stimulate their brain, although caffeine does not always lead to the desired effect. This might still be reached, however, when the doctors would increase the doses. Nonetheless, the doctors do not know where the limits of these higher doses lay, and when so much caffeine is given toxic effects might occur. Therapeutic Drug Monitoring (TDM), which is the individualizing of a medicine’s dose based on blood concentration measurements, could be of help.