In daily paediatrics, drugs are commonly used off-label, as they are not approved for children. Approval is lacking because the required clinical studies were limited to adults in the past. Without clinical studies, evidence-based recommendations for drug use in children are limited. Information on off-label drug dosing in children can be found in different handbooks, databases, and scientific publications but the dosing recommendations can differ considerably. To improve safety and efficacy of drugs prescribed to children and to assist the prescribers, stakeholders in Swiss paediatrics started a pilot project, supported by the Federal Office of Public Health, with the aim to create a database, providing healthcare professionals with so called “harmonised” dosage recommendations based on the latest available scientific evidence and best clinical practice. A standardised process for dosage harmonisation between paediatric experts was defined, guided, and documented in an electronic tool, developed for this purpose. As proof of principle, a total of 102 dosage recommendations for 30 different drugs have been nationally harmonised in the pilot phase considering the current scientific literature and the approval of the most experienced national experts in the field. This approach paved the way for unified national dosage recommendations for children. The project was successful and regular operation of SwissPedDose started in 2018. The database is extended since with recommendations for at least 100 additional drugs by the end of 2021.

Aim: Metamizole (dipyrone) is a prodrug not detectable in serum or urine after oral ingestion. The primary metabolite is 4-methylaminoantipyrine (4-MAA), which can be N-demethylated to 4-aminoantipyrine (4-AA) or oxidized to 4-formylaminoantipyrine (4-FAA) by cytochrome P450 (CYP)-dependent reactions. Our aim was to identify the CYPs involved. Methods: We investigated the metabolism of 4-MAA in vitro using CYP expressing supersomes and the pharmacokinetics of metamizole in the presence of CYP inhibitors in healthy volunteers. Results: The experiments in supersomes revealed CYP1A2 as the major CYP for 4-MAA N-demethylation and 4-FAA formation. CYP2C19 and CYP2D6 contributed to N-demethylation but not to FAA formation. In the subsequent clinical study, we investigated the influence of ciprofloxacin (strong CYP1A2 inhibitor), fluconazole (strong CYP2C19 inhibitor) and the combination ciprofloxacin/fluconazole on the pharmacokinetics of a single dose of metamizole in n=12 healthy volunteers in a randomized, placebo-controlled, double-blind study. Both ciprofloxacin and fluconazole inhibited the metabolism of 4-MAA, confirming the in vitro results. Ciprofloxacin, fluconazole and ciprofloxacin/fluconazole increased the AUC0-12h of 4-MAA by 51%, 17% and 92%, respectively. Ciprofloxacin, fluconazole and ciprofloxacin/fluconazole decreased the AUC0-12h of 4-AA by 27%, 12% and 24%, respectively, and of 4-FAA by 33%, 9% and 51%, respectively. Ciprofloxacin, fluconazole and ciprofloxacin/fluconazole increased the half-life of 4-MAA from 3.22 h (placebo) to 3.91, 3.69 and 6.07 h, respectively. Conclusion: CYP1A2 is the major CYP for the conversion of 4-MAA to 4-AA and 4-FAA. CYP1A2 inhibition increases the 4-MAA exposure by a factor of approximately 1.5, which could be relevant for dose-dependent adverse reactions.