Stability of penicillins in total parenteral nutrient solution

The stability of ticarcillin, mezlocillin, and piperacillin in total parenteral nutrient (TPN) solutions at concentrations commonly used in adults was determined. Each antibiotic was added separately to three different amino acids-dextrose TPN solutions in two concentrations: 10 and 20 mg/mL. Amino acids concentration ranged from 25 g/L to 50 g/L. Dextrose concentration ranged from 100 g/L to 350 g/L. Solutions were assayed for antibiotic concentration immediately after mixing (time 0) and at 4, 8, 24, and 48 hours by high-performance liquid chromatography. The effect of the added penicillins on the stability of amino acids and other TPN additives was not investigated. Mezlocillin and piperacillin 10 and 20 mg/mL exhibited stability in TPN solution at 24 hours. Ticarcillin was stable for 24 hours at a concentration of 10 mg/mL, but at 20 mg/mL it was unstable at all times tested. The three antibiotics demonstrated the same characteristic stability in all three TPN solutions, suggesting that the concentrations of dextrose and amino acids did not affect stability. Ticarcillin, mezlocillin, and piperacillin are stable for 24 hours in the TPN solutions studied.