 Pharmacodynamics of paracetamol, fentanyl, midazolam, phenobarbital, doxapram, levetiracetam and sildenafil will be explored in all included preterm neonates. Fluconazole will only be studied for the pharmacokinetics. Drug specific effects of drugs e.g. pain scores for morphine, blood pressure for dopamine as well as side effects and short term effects on morbidity and outcome will be analyzed. Additional pharmacodynamic endpoints for the 7 PKPD study drugs is the drug target concentration for each drug that is related to the desired effect. 