sodium bicarbonate

Physical Compatibility

All admixture samples remained clear and colourless over the 28-day study period. There were no significant changes in pH in any of the admixture samples under the stated storage conditions (changes of less that 0.4 for samples containing epinephrine and less than 0.12 for plain lidocaine samples).

Chemical Stability

The epinephrine degradation peaks did not interfere with either the parent compound or the internal standard peaks over the study period. The purity of all parent peaks from the degradation samples was confirmed by UV spectral overlay and multiwavelength analysis. viagra 50 mg

Table 1. Stability of Buffered Lidocaine Solutions, With and Without Epinephrine, Packaged in Polypropylene Syringes and Stored at 5°C with Protection from Light

Drug or Drug Combination; % of Initial Concentration Remaining

Study day

Epinephrine

Lidocaine 1%

Epinephrine

Lidocaine 2%

Lidocaine 1%

Lidocaine 2%

Mean initial concentrationt

0.009 ± 0.0001

9.5 ± 0.07

0.009 ± 0.0001

18.8 ± 0.12

8.9 ± 0.06

18.1 ± 0.21

Day 3

97.3 ± 1.1

NC

98.1 ± 1.1

NC

NC

NC

Day 7

95.9 ± 1.7

97.5 ± 1.8

93.3 ± 0.7

98.5 ± 2.1

101.1 ± 0.7

98.0 ± 1.6

Day 10

91.8 ± 1.6

NC

9.8 ± 0.9

NC

NC

NC

Day 14

84.6 ± 1.2

98.3 ± 0.6

84.3 ± 0.7

96.9 ± 2.3

101.1 ± 0.8

95.3 ± 1.0

Day 17

81.9 ± 2.8

NC

77.8 ± 1.6

NC

NC

NC

Day 21

75.3 ± 1.7

96.9 ± 1.5

74.4 ± 1.6

95.9 ± 1.2

100.6 ± 0.6

97.1 ± 0.6

Day 24

69.9 ± 2.6

NC

68.4 ± 1.0

NC

NC

NC

Day 28

61.8 ± 1.8

95.2 ± 1.9

63.9 ± 2.5

95.1 ± 1.6

98.9 ± 1.1

94.7 ± 0.4

After 9 days of monitoring the lidocaine degradation samples, the concentration of the acidic sample had not changed much (Figure 1A) whereas the concentration of drug in the alkaline and oxidized samples had declined to 81% (Figure 1B) and 79% (Figure 1C), respectively. There were no interfering peaks under any of the degradation conditions. The known degradation peak did not interfere with the parent peak (Figure 1D). Epinephrine peaks were not visible in chromatograms generated by the lidocaine assay, as they were outside the limit of detection for this method. Given the substantial difference in mobile phases between the epinephrine and lidocaine, it was expected that if the epinephrine were to be seen it would have co-eluted with the solvent front, along with the faster- eluting degradation products, and would not have interfered with the lidocaine peak or internal standard. canadian antibiotics

Figure 1. Sample chromatograms

Figure 1. Sample chromatograms of lidocaine hydrochloride and its degradation products. A: Acid-degraded lidocaine after 9 days. B: Alkali-degraded lidocaine after 9 days. C: Oxidized sample after 9 days. D: A known degradation product, 2,6-dimethylaniline. Au = absorbance units full scale.

The intraday coefficient of variance for the lidocaine method was 3.1% over a 25-h period. The average linear coefficient for 5 separate days was 0.9996, and the accuracy of the method, as determined by analysis of recovery samples, was 100.8% ± 1.3%. The interday coefficient of variance from analysis of testing on 5 separate days was 4.94%, based on the daily average area ratios of the recovery samples. The sensitivity for detection of lidocaine was 2.5 ^g.

All lidocaine peaks in the degradation samples were con­firmed to be pure by multiwavelength and UV spectral analysis. generic cialis 20mg

Stability Study

The results of the chemical stability study are summarized in Table 1. Both the 1% and 2% buffered lidocaine samples were stable for up for 28 days when mixed with sodium bicarbonate (8.4%), packaged in polypropylene syringes, and stored at 5°C with protection from light. In contrast, the solutions containing the lidocaine and epinephrine mixture were stable for only 7 days (based on the results for epinephrine).