| Abstract [eng] |
Aim of the study: To determine the dependence of beta-lactam antibiotics (amoxicillin, ceftriaxone, and imipenem) stability from various factors (solvent, storage conditions, time interval and concentration) using UV-VIS spectrophotometry. Objectives: 1. To evaluate the dependence of the stability of beta-lactam antibiotics (amoxicillin, ceftriaxone, and imipenem) from a chosen solvent using UV-VIS spectrophotometry. 2. To determine the influence of storage conditions (room and fridge temperatures) to the stability of these antibiotics. 3. To determine how the stability of beta-lactam antibiotics changes at different time points (30 min., 1, 2, 4, 6, 8, 24 hours). 4. To determine how the stability of beta-lactam antibiotics depends on their concentration. Methods: Different concentration solutions were prepared: amoxicillin – 250 mg/ml, 125 mg/ml, 50 mg/ml, ceftriaxone – 200 mg/ml, 100 mg/ml, 50 mg/ml, imipenem – 10 mg/ml, 5 mg/ml, 2,5 mg/ml. Two solvents were used – 0,9% NaCl and 5% glucose solutions. The solutions were stored in two temperatures – room (20 ± 2 °C) and fridge (3 °C). UV-VIS spectrophotometry measurements were performed at 30 min, 1, 2, 4, 6, 8, 24 hours. There were photos taken of the samples, from which the color difference was calculated using colorimetry. Results: In UV-VIS spectrophotometry spectra of amoxicillin 250 mg/ml and 125 mg/ml solutions, there was and additional peak visible, which formed after 30 minutes and kept increasing, it reflects the opening of the beta-lactam ring. This process occurred faster in higher concentration solutions. Products formed during antibiotic degradation reactions fluoresce and interfere with UV-VIS spectrophotometer readings. For this reason, the colorimetry method was used to calculate the color difference and further evaluate the stability of antibiotic solutions. The most notable color difference was calculated from amoxicillin solutions, in which after 2 hours the color difference in room temperature is 3 times higher in the highest concentration solution, compared to the lowest. The 250 mg/ml solution changed color from light yellow to brown and the 50 mg/ml solution changed color from light yellow to yellow. Conclusions: It was determined that amoxicillin, ceftriaxone and imipenem solutions remain stable in the fridge about 2,5 times longer than in room temperature. During the first 8 hours there was no difference observed in ceftriaxone and imipenem solutions, except the last 24-hour point in which a color difference from clear to yellowish is seen in 200 mg/ml and 100 mg/ml ceftriaxone and 10 mg/ml imipenem solutions. These antibiotics demonstrate good stability, compared to amoxicillin, whose highest concentration (250 mg/ml) solution changed color from light yellow to dark yellow after only 1 hour, 125 mg/ml – after 2 hours, 50 mg/ml – after 4 hours. Depending on the concentration, the color change can vary from 1,3 to 2,5 times and the decomposition processes are visible in UV-VIS spectra. The lowest, 50 mg/ml, amoxicillin concentration remained the most stable (up to 2 hours), which matches the highest concentration listed in the summary of product characteristics provided for this drug. Ceftriaxone remains stable up to 8 hours in the highest concentration solution (200 mg/ml), which matches the information in the summary as well. Imipenem at highest concentration of 10 mg/ml remains stable for 8 hours, which is more than recommended in the summary (5 mg/ml). The data on the solvents influence on stability was contradictive – UV-VIS spectrophotometry results showed better amoxicillin stability in 0,9% NaCl, but colorimetry calculations showed better stability in 5% glucose. The solvent has no influence on the stability of ceftriaxone and imipenem. Due to fluorescence of the products formed during antibiotic decomposition reactions, UV-VIS spectrophotometry is not recommended as a method to investigate the stability of beta-lactam antibiotics. |
