Objectives The product information and literature does not provide confirmation of compatibility for co-administration of all commonly used drug pairs in obstetrics. However, there is a need for co-administration of these drugs over one lumen for this group of patients. Therefore, this study focuses on Y-site compatibility. Since different conditions between clinical and laboratory settings can lead to discrepancies in results, a novel approach for drug intravenous compatibility testing was designed to reflect clinical conditions. The aim was to study the compatibility of nine commonly used drug pairs in obstetrics and to evaluate the clinical value of the designed method.

Methods The clinical situation was reflected by using different temperature ranges (20°C and 37°C), actual Y-site flow ratios, clinically relevant drug pairs and an observation time of 120 min. The clinically relevant drugs pairs include atosiban, nicardipine, amoxicillin/clavulanic acid, oxytocin, remifentanil, labetalol and magnesium sulpfate. Drug pairs were visually assessed according to the European Pharmacopoeia (Ph. Eur.) and pH was measured. When incompatibility of a drug pair seemed likely based on literature review or observed abnormalities during visual assessment, subvisual analysis was performed using a particle counter. Y-site compatibility applied for drug pairs when no visual changes occurred or when no additional particles were formed during the observation time.

Results Eight of the nine combinations showed no visual changes or noticeable changes in pH during the observation time. The amoxicillin/clavulanic-acid-oxytocin combination showed a colour change at 37°C at the actual Y-site flow ratio. However, subvisual particle counting showed no formation of additional particles.

Conclusions Y-site compatibility was established for all tested drug pairs. The new clinical approach for analysing Y-site compatibility provides a high certainty of outcomes for clinical practice. In this way, clinical complications and use of several additional intravenous catheters can be avoided.