Stability of sildenafil in combination with heparin and dopamine

PURPOSE

The stability of sildenafil in combination with heparin and dopamine was evaluated.

METHODS

A stability-indicating high-performance liquid chromatography method with ultraviolet detection was developed for sildenafil citrate and validated. The method was applied to the investigation of sildenafil alone, sildenafil with heparin, sildenafil with dopamine, and sildenafil with heparin and with dopamine, all in 5% dextrose injection at room temperature and under refrigeration for 30 days. Samples of 100 μL were pulled from each storage bottle on each sampling day, diluted in mobile phase, and assayed in duplicate. Samples were tested on days 0, 1, 2, 3, 4, 5, 7, 9, 12, 14, 21, and 30. Each preparation was visually inspected for precipitation and color change. The percent recovery in each study sample was determined by comparing the peak area of sildenafil in the sample with the peak area of sildenafil from a freshly prepared 100-μg/mL standard in mobile phase.

RESULTS

The sildenafil alone, sildenafil with heparin, and sildenafil with dopamine remained within 90-110% of the expected sildenafil potency for at least 30 days at both temperatures. The preparation of sildenafil with both heparin and dopamine fell below 90% potency after 3 days at room temperature and 21 days in the refrigerator.

CONCLUSION

Sildenafil prepared in 5% dextrose injection alone, with heparin, and with dopamine retained over 90% potency after 30 days of storage at room temperature and under refrigeration. Sildenafil prepared with both heparin and dopamine had a potency of <90% after 3 days of storage at room temperature and 21 days of storage under refrigeration.

Stability of Commercially Available Grape and Compounded Cherry Oral Vancomycin Preparations Stored in Syringes and Cups

The purpose of this study was to evaluate the stability of two preparations of vancomycin oral solution in two different storage containers, capped amber oral-dosing syringes and heat-sealed oral-dosing cups, stored under refrigerated conditions. Commercially available grape-flavored vancomycin oral preparation and compounded vancomycin for intravenous use in cherry syrup oral preparation were divided into 5-mL aliquots into heat-sealed plastic dosing cups and capped oral-dosing syringes. All samples were stored under refrigeration (2°C to 8°C) and evaluated at days 0, 3, 7, 14, 30, 60, and 90. For each evaluation, samples were visually inspected and analyzed for potency using a stability-indicating high-performance liquid chromatographic method with ultraviolet detection. Over the study period, at least 90% of the initial concentrations for the preparation and the product in both storage containers were retained at 60 days. The commercially available oral vancomycin further demonstrated stability within 90% out to 90 days in the syringe and the unit-dose cups. Visual inspection revealed no changes in the grape-flavored vancomycin oral preparation, but a detectable red-dye precipitate could be seen in the crevices of the dosing cups from the vancomycin in cherry syrup oral preparation after 60 days. Commercially available grape-flavored vancomycin oral preparation was stable up to 90 days, and com- pounded vancomycin for intravenous use in cherry syrup oral preparation maintained stability for 60 days when dispensed in capped amber polypropylene oral-dosing syringes and heat-sealed plastic dosing cups when stored at refrigerated conditions.

Nitrilotriacetate stimulation of anaerobic Fe(III) respiration by mobilization of humic materials in soil

An enrichment culture capable of naphthalene mineralization reduced Fe(III) oxides without direct contact in anaerobic soil microcosms when the Fe(III) was placed in dialysis membranes or entrapped within alginate beads. Both techniques demonstrated that a component in soil, possibly humic materials, facilitated Fe(III) reduction when direct contact between cells and Fe(III) was not possible. The addition of the synthetic Fe(III) chelator, nitrilotriacetic acid (NTA), to soil enhanced Fe(III) reduction across the dialysis membrane and alginate beads, with the medium changing from clear to a dark brown color. An NTA-soil extract was more effective in Fe(III) reduction than the extracted soil itself. Characteristics of the NTA extract were consistent with that of humic substances. The results indicate that NTA improved Fe(III) reduction not by Fe(III) solubilization but by extraction of humic substances from soil into the aqueous medium. This is the first study in which stimulation of Fe(III) reduction through the addition of chemical chelators is shown to be due to the extraction of electron-shuttling compounds from the soil and not to solubilization of the Fe(III) and indicates that mobilization of humic materials could be an important component of anaerobic biostimulation.