Bretylium tosylate intravenous admixture compatibility. I: Stability in common large-volume parenteral solutions.

The stability of bretylium tosylate in 11 common large-volume parenteral solutions was studied. Two containers of each solution, one glass and one plastic (except for mannitol and sodium bicarbonate solutions, which were available in glass only), were stored at each of the following conditions: intense light (1400-2000 foot candles), ambient room temperature with normal light, 40 degrees C, and 4 degrees C. All samples were tested at 0 and 24 hours; some samples were also tested at 48 hours and 7 days. Testing included measurement for optical density at 4000 and 600 nm, pH level, and bretylium content as determined by HPLC. The admixtures remained clear and colorless, except that mannitol precipitated out of mannitol solutions stored at 4 degrees C. No appreciable changes in pH were observed. HPLC assays showed no significant changes in bretylium tosylate concentrations. Bretylium tosylate is compatible with each of the 11 common intravenous solutions chosen for investigation under the storage conditions studied. Admixtures with mannitol should not be refrigerated, because mannitol crystallizes from solution at refrigerator temperatures.

Nitroglycerin compatibility with intravenous fluid filters, containers, and administration sets.

The effect of intravenous filters, containers and administration sets on nitroglycerin potency was studied. Solutions of nitroglycerin (50 and 100 microgram/ml) in water for injection, in 5% dextrose injection and in 0.9% sodium chloride injection were prepared. The concentration of these solutions was measured after (1) filtration through a 0.2-micron filter, (2) storage in glass and plastic containers and (3) administration through eight i.v. administration sets. Filters decreased nitroglycerin concentration by 2--55%. Nitroglycerin concentration was not changed after storage for 48 hours in glass bottles. In plastic i.v. bags, concentration decreases were substantial and related to surface contact area and storage temperature. The i.v. administration sets caused immediate, substantial decreases in nitroglycerin concentration that were a function of drip rate, surface area, length of exposure to tubing, and tubing materials. The study suggests that concentrations of nitroglycerin solutions could be reduced by as much as 80% when filtered, placed in a plastic i.v. bag and given through an i.v. administration set.