Physical Inspection and pH Measurements

Each individual solution of IR (nominal concentra­tions of 0.61 mg/mL and 0.65 mg/mL) and LV (7.20, 2.72, and 1.36 mg/mL) was initially clear and colourless. Mixing these individual solutions did not result in generation of gas, change in colour, or development of a precipitate in any of the 54 experimental solutions created for the 18 individual experiments.

The pH of each IR and LV solution used in the study (various concentrations) before mixing and the pH of each mixture (in glass) is reported in Table 2. These data show that before mixing, the pH of the LV solution was always greater than that of the IR solution. The pH of each mixture fell between the observed pH for the separate solutions, but was often driven by the component with the highest concentration. As a result, the solution containing 0.32 mg/mL IR and 3.60 mg/mL LV (treatment scenario 3a in Table 1) had the highest pH (6.50) of all mixtures.
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Table 2. Observed Mean Concentration (± Standard Deviation) of Irinotecan and Leucovorin in 5% Dextrose in Water Solutions Stored in Glass


Scenario 1a


Scenario 1b


Scenario 2a


Scenario 2b


Scenario 3a


Scenario 3b


Characteristic


(IR 0.56,


(IR 0.53,


(IR 0.59,


(IR 0.56,


(IR 0.32,


(IR 0.30,


LV 0.94)


LV 0.74)


LV 0.66)


LV 0.27)


LV 3.60)


LV 0.68)


Irinotecan


Initial concentration (mg/mL)


0.56±0.01


0.56±0.01


0.59±0.02


0.59±0.02


0.35±0.01


0.30±0.01


pH before mixing


3.12


3.12


3.06


3.06


4.02


4.02


%
remaining


At 0.5
h


99.40±2.50


98.67±0.84


99.68±0.04


99.89±0.97


95.09±3.14


98.54±1.95


At 1
h


98.12±1.56


97.84±1.64


99.69±0.20


100.10±0.76


89.08±4.83


98.00±1.36


At 24 h


92.48±0.99


92.78±0.66


96.47±1.10


97.56±2.04


77.23±4.59


95.52±1.03


Leucovorin


Initial concentration (mg/mL)


0.91±0.02


0.73±0.00


0.68±0.01

0.26±0.00


3.65±0.11


0.62±0.05


pH before mixing

6.08


5.88


5.55


5.41


7.01


5.65


%
remaining


At 0.5
h


100.33±2.51


100.79±0.68


99.19±1.27


100.05±2.96


101.30±1.87


99.44±0.48


At 1 h


100.50±1.34


100.43±0.58


98.99±0.52


98.95±2.45


101.55±1.80


100.27±0.73


At 24 h


101.26±0.89


99.78±0.97


98.84±0.19


96.31±0.83


100.81±0.84


99.57±1.75


Mixture


pH after mixing


5.56


5.42


5.33


4.76


6.50


5.52