Measuring serum and urine concentrations of ciprofloxacin after IV and oral administration in children aged 3 months - 17 years who are treated for urinary tract infections.

Inclusion Criteria:

• age between 3 months and 17 years of age
• confirmed diagnosis of febrile urinary tract infection (a rectal body temperature of 38.5 °C.in combination with either significant leukocyturia or a positive urine nitrite test in a reliable urine sample.
• indication for treatment or uroprophylaxis with ciprofloxacin at discretion of the treating physician.

Exclusion Criteria:

• pregnancy
• impaired renal function as defined by 2x serum creatinine level for age and sex
• epilepsy
• myasthenia gravis
• long QT-syndrome
• glucose 6 phosphatase deficiency (G6PD)
• allergy to one of the substances of cipro
• concomitant use of corticosteroids
• for the oral group: co medication of antacidic drugs, ferrofumarate, calcium, magnesium or Zinc supplements.