Stability of benzylpenicillin during continuous home intravenous therapy

The aim of this study was to investigate the temperature profile of home intravenous (iv) antibiotic reservoirs and the stability of 16 megaunits of benzylpenicillin sodium in 120 mL of sodium chloride 0.9% at constant and variable temperatures.

A Tinytag computerized thermometer recorded temperatures every minute in the home iv antibiotic reservoir pouches of nine patients over a 24 h period. Similar bags containing benzylpenicillin sodium (16 megaunits) were maintained either at a constant 36 degrees C, 26 degrees C or 21-22 degrees C or were worn in a pouch by five healthy volunteers for a 24 h period. Other bags were stored at 3-5 degrees C for 10 days. The bags were sampled at timed intervals and benzylpenicillin concentrations assayed by HPLC.

Median temperatures recorded in the infusion bags worn by the nine patients were in the range 16.7-34.1 degrees C. For infusion bags maintained at 36 degrees C, 26 degrees C and 21-22 degrees C, the concentrations of benzylpenicillin dropped below 90% of the initial concentration at a mean time of 5 h 18 min, 12 h 54 min and 13 h 20 min, respectively, whereas for bags worn by the healthy volunteers the mean time for 10% loss of benzylpenicillin was 9 h 20 min. In contrast, at 3-5 degrees C, concentrations of benzylpenicillin only dropped below 90% of the initial concentration at 8 days.

Significant temperature-dependent degradation of benzylpenicillin occurs during continuous home iv antibiotic programme infusions, which could result in loss of efficacy.