Stability of midazolam hydrochloride in a flavored, dye-free oral solution.

The stability of injectable midazolam hydrochloride in a solution for oral use was studied at three temperatures over 56 days. A 2.5-mg/mL oral solution was prepared from injectable midazolam hydrochloride and a flavored, dye-free syrup. Samples of solution were stored in amber glass bottles at 7, 20, or 40 degrees C. Duplicate samples were analyzed by high-performance liquid chromatography on days 0, 1, 3, 5, 14, 21, 35, and 56. Samples were also visually inspected on each sampling day. The concentrations of all samples remained greater than 90% of the original concentration and there were no visual signs of microbial growth or changes in color, turbidity, or odor throughout the 56-day period. A 2.5-mg/mL solution of injectable midazolam in syrup was stable for 56 days at 7, 20, or 40 degrees C.

Pseudoresistance of Pseudomonas aeruginosa resulting from degradation of imipenem in an automated susceptibility testing system with predried panels.

During the use of a single lot of custom breakpoint panels (Sensititre; Radiometer America Inc., Westlake, Ohio), imipenem susceptibility declined from 70 to 44% for clinical isolates of Pseudomonas aeruginosa. With a new lot, susceptibility increased to 73%. Subsequent evaluations with P. aeruginosa ATCC 27853 revealed a similar susceptibility pattern and an increase in the MIC of imipenem when determined in panels with increasing ages. Imipenem concentrations were determined by high-performance liquid chromatography by using 11 different lots of MIC and breakpoint panels (139 to 893 days of age). The amount of imipenem remaining declined from 94.4 to 13.8% (r = 0.9225) over the age range of the panels. These data suggest that imipenem in Sensititre MIC and breakpoint panels degrades over time and that the decrease in imipenem may be largely responsible for the decline in P. aeruginosa susceptibility.

In vitro evaluation of nasogastric administration methods for phenytoin.

The effect on phenytoin recovery of various methods of nasogastric administration of phenytoin suspension was studied. Phenytoin acid suspension 4 mL (100 mg) was administered through a nasogastric (NG) tube using 10 methods designed to simulate clinical situations. The suspension was given either undiluted or diluted, with or without irrigation of the NG tube. Solutions of 5% dextrose injection, 0.9% sodium chloride injection, sterile water for irrigation, and lactated Ringer's injection were used as diluents or irrigants. After each administration, 40 mL of air was forced through the NG tube to expel any remaining suspension. Phenytoin concentration was assayed by high-performance liquid chromatography before and after administration through the NG tube. In the method that used no diluent or irrigation, 75.5 +/- 5.3% of the initial dose volume was lost, significantly more loss than with any of the other methods. The mean dose volume lost for all of the other nine methods was 6.4 +/- 3.4%. The type of fluid used for dilution or irrigation had little influence on phenytoin recovery. Until other methods can be evaluated, phenytoin suspension should be diluted and irrigated with at least 20 mL of fluid when given by nasogastric tube. Evacuation of the tube with 40 mL of air after phenytoin administration is also recommended.