All preterm infants that are admitted to the study neonatal intensive care units (NICUs) for neonatal intensive care are potential study patients, and their parents will be asked for consent.~The patient will be treated according to clinical guidelines and will be included in the study if in need for clonidine according to clinical judgment (pain scores) and as decided by the responsible clinical doctor. The dosing and administration of the drug will be implemented according to an algorithm based on pain scoring results.~Apart from extra blood sampling, the bedside monitoring, investigations (electroencephalography, EEG, echocardiography, ECG, ultrasound of the brain) and follow-up (neurologic examination and magnetic resonance imaging, MRI) are the same as for all preterm infants according to local and national guidelines.~In total 100 infants will be included.
A prospective pharmacokinetic (PK), pharmacodynamic (PD) and pharmacogenetic (PG) observation study, including the PK/PD/PG relationship, in clonidine administered for analgesia and sedation to preterm newborn infants receiving neonatal intensive care. Phase 3 - therapeutic confirmatory study