Compatibility of haloperidol and hyoscine-N-butyl bromide in mixtures for subcutaneous infusion to cancer patients in palliative care

The administration of drugs by s.c. infusion is routinely practiced in palliative medicine for the management of patients who are no longer able to take oral medication. It is not uncommon for two or more drugs to be combined in s.c. infusion solutions. Unfortunately, the compatibility and stability of haloperidol and hyoscine-N-butyl bromide has not yet been determined. The objective of this study was to study the compatibility and stability of solutions containing both drugs in polypropylene syringes. Nine different solutions were assessed for up to 15 days following preparation. The solutions were prepared in polypropylene syringes with 0.9% saline as a diluent and stored at 4°C and 25°C. High-performance liquid chromatography was the analytical technique used to measure haloperidol and hyoscine-N-butyl bromide. The initial concentration ranges were 0.3125–1.25 mg/ml for haloperidol and 2.5–10.0 mg/ml for hyoscine-N-butyl bromide. Haloperidol was precipitated at a concentration of ≥1.25 mg/ml when it was combined with hyoscine-N-butyl bromide. Concentrations of hyoscine-N-butyl bromide lower than 10 mg/ml in mixtures with haloperidol or 0.625 mg/ml of haloperidol in mixtures with hyoscine-N-butyl bromide for s.c. infusion allow for the administration of both drugs without any significant loss after storage at 25°C for periods of up to 15 days, with approximately ≥90% and 88%, respectively, of haloperidol and hyoscine-N-butyl bromide remaining. However, after storage of the mixtures for equivalent periods at 4°C the losses of hyoscine-N-butyl bromide observed at the end of the study were higher than 20%, while the percentages of haloperidol remaining after 15 days at this temperature were ≥94.37%.