Stability of reconstituted solutions of ceftazidime for injections: an HPLC and CE approach

Amino Acids Improve Aerosolization and Chemical Stability of Potential Inhalable Amorphous Spray-dried Ceftazidime for Pseudomonas aeruginosa Lung Infection

Pseudomonas aeruginosa infection is common in cystic fibrosis as well non-cystic fibrosis bronchiectasis. The pathogen presents challenges for treatment due to its adaptive antibiotic-resistance, mainly pertaining to its biofilm-forming ability, as well as limitations associated with conventional drug delivery in achieving desired therapeutic concentration in the infection site. Hence, therapeutic approach has shifted towards the inhalation of antibiotics. Ceftazidime is a potent antibiotic against the pathogen; however, it is currently only available as a parenteral formulation. Here, spray-dryer was employed to generate inhalable high dose ceftazidime microparticles. In addition, the use of amino acids (valine, leucine, methionine, phenylalanine, and tryptophan) to improve aerosolization as well as chemical stability of amorphous ceftazidime was explored. The particles were characterized using X ray diffraction, infrared (IR) spectroscopy, calorimetry, electron microscopy, particle size analyzer, and next generation impactor. The chemical stability at 25 °C/<15% was assessed using chromatography. All co-spray dried formulations were confirmed as monophasic amorphous systems using calorimetry. In addition, principal component analysis of the IR spectra suggested potential interaction between tryptophan and ceftazidime in the co-amorphous matrix. Inclusion of amino acids improved aerosolization and chemical stability in all cases. Increase in surface asperity was clear with the use of amino acids which likely contributed to the improved aerosol performance, and potential interaction between amino acids and ceftazidime was plausibly the reason for improved chemical stability. Leucine offered the best aerosolization enhancement with a fine particle fraction of 78% and tryptophan showed stabilizing superiority by reducing chemical degradation by 51% over 10 weeks in 1:1 molar ratio. The protection against ceftazidime degradation varied with the nature of amino acids. Additionally, there was a linear relationship between degradation protection and molar mass of amino acids or percentage weight of amino acids in the formulations. None of the amino acids were successful in completely inhibiting degradation of ceftazidime in amorphous spray-dried powder to prepare a commercially viable product with desired shelf-life. All the amino acids and ceftazidime were non-toxic to A549 alveolar cell line.

Stability of Ceftazidime Pentahydrate Investigated by Thermal Analysis Techniques

Cephalosporins are among the most frequently used broad-spectrum antimicrobial agents. Ceftazidime is a semisynthetic β-lactam antibiotic for parenteral administration widely used in the clinical practice, which has been categorized as a third-generation cephalosporin antibiotic. This drug crystallizes as a pentahydrate and, as all cephalosporins, it is unstable and subject to hydrolytic degradation. Taking this into account, this study investigates the stability under 2 different conditions (high temperature and exposition to vacuum) by using various techniques, as thermal analysis, Raman spectroscopy, and X-ray powder diffraction supported by multivariate curve resolution. It was proved that ceftazidime pentahydrate is unstable under the studied variables, exhibiting several transformation processes, which were discussed in terms of the crystalline structure.

Ceftazidime stability and pyridine toxicity during continuous i.v. infusion

Purpose

This article reviews the literature concerning ceftazidime stability and potential for toxicity from pyridine (a degradation product) in the light of decades of apparent safe use of this antibiotic when given by continuous i.v. infusion but recent changes in regulatory body/manufacturer advise a need to change infusion devices more frequently.

Summary

In the outpatient setting, ceftazidime is ideally administered by continuous i.v. infusion because of its short half-life and lack of post-antibiotic effect. While continuous i.v. infusion provides the optimal pharmacokinetic/pharmacodynamic profile, the frequency with which infusion devices need to be changed is critical to the practicality in the outpatient setting, especially where trained staff are required to visit the patient in their home to change the device. The rate of ceftazidime degradation (and pyridine formation) is temperature, concentration, and solvent dependent. By using the lowest effective dose (guided by pathogen minimum inhibitory concentration [MIC] so as to achieve a blood concentration ≥ 4 × MIC over the whole dosage interval), keeping ceftazidime concentration ≤ 3%, using 0.9% sodium chloride injection as diluent and maintaining temperature between 15-25°C when connected to the patient, the amount of pyridine formed over a 24-hour period can be minimized and toxicity prevented. When pathogen MIC dictates that > 6 g ceftazidime/day is required, alternative antibiotics should be considered and/or greater attention paid to temperature and concentration of the infusion solution.

Conclusion

Ceftazidime can be used safely and effectively via continuous i.v. infusion in the outpatient setting with once-daily changes of infusion device provided the concentration and temperature of the infusion solution is controlled. In this way, more frequent changes of infusion device (that increase the risk of blood-borne infection and reduce the practicality of continuous i.v. infusion in the home) can be avoided.

Systematic review of stability data pertaining to selected antibiotics used for extended infusions in outpatient parenteral antimicrobial therapy (OPAT) at standard room temperature and in warmer climates

Aim

To determine if there are sufficient stability data to confirm appropriate prescribing of antibiotics commonly used in outpatient parenteral antimicrobial therapy (OPAT) in warmer climates.

Data sources

Four databases were systematically searched using the terms 'beta-lactams', or 'antibiotics', or 'anti-bacterial agents' and 'drug stability' or drug storage' for studies specific to drug stability published between 1966 and February 2018.

Study selection

The search strategy initially identified 2879 potential articles. After title and abstract review, the full-texts of 137 potential articles were assessed, with 46 articles matching the inclusion and exclusion criteria included in this review.

Results

A large volume of stability data is available for the selected drugs. Stability data at temperatures higher than 25°C were available for several of the medications, however few drugs demonstrated stability in warmer climates of 34°C or higher. Only buffered benzylpenicillin, cefoxitin and buffered flucloxacillin were found to have stability data supporting OPAT in warmer climates. Sequential data, profiling the drug for an extended period in solution under refrigeration prior to the run-out period at the higher temperatures, are also lacking.

Limitations

This study was limited by including only peer reviewed articles. There may be further grey literature supporting the stability of some of the drugs mentioned.

Conclusion

There are insufficient stability data of antibiotic use in warmer climates. Studies to verify the stability and appropriate use of many antibiotics used in OPAT at standard room temperature and in warmer climates are urgently required. Several drugs in current use in the OPAT settings are lacking stability data.

Implications

Further research in this field is needed to develop structured evidence-based guidelines. Results of this review should be further compared with observed patient outcomes in current clinical practice.

Stability of a 50 mg/mL Ceftazidime Eye-Drops Formulation

Background

Microbial keratitis are severe infectionsgenerally linked to risk factors. High-doses antibiotic eye-drops could be required to avoid severe complications. In such cases, hospital pharmacists are in charge of their production given the lack of such formulations on the market. The stability of these antibiotic eye-drops is generally limited to a couple of days and publications generally do not describe addition of microbial preservatives even though it is a European Pharmacopeia requirement. The aim of this study was to describe a new ceftazidime eye-drops formulation at 50 mg/mL with a antimicrobial additive, benzalkonium chloride at 0.04 mg/mL.

Methods

Physico-chemical studies of this new formulation were performed by a stability indicating HPLC-UV method validated according to ICH standards, osmolality measurements, pH monitoring and visual examinations. Antimicrobial preservative efficacy was evaluated according to the method from the European Pharmacopeia.

Results

After 75 days at −20 °C followed by 7 days at 4 °C, or after 7 days at 4 °C, the eye-drops were stable. A degradation trend was finally observed at day 14 at 4 °C.

Conclusions

A new ceftazidime eye-drops formulation is proposed with a stability of 7 days. Outpatients do not need to return to the hospital pharmacy for repeat dispensing, thus possibly improving treatment compliance.

Stability and Compatibility of Antibiotics in Peritoneal Dialysis Solutions Applied to Automated Peritoneal Dialysis in The Pediatric Population

♦ OBJECTIVES: Assess the stability of several antibiotics in peritoneal dialysis (PD) solutions under common conditions of use in pediatrics, particularly in automated PD. ♦ METHODS: Amoxicillin, cefazolin, cefepime, ceftazidime, imipenem, cotrimoxazole, tobramycin, vancomycin, and the association of ceftazidime + vancomycin and ceftazidime + tobramycin, were tested in 3 different PD solutions: bicarbonate/lactate solution with 2 glucose concentrations (Physioneal 1.36 and 3.86%; Baxter Healthcare Corporation, Deerfield, IL, USA) and an icodextrin-containing solution (Extraneal; Baxter Healthcare Corporation, Deerfield, IL, USA). Concentrations were those recommended in guidelines for the treatment of peritonitis in pediatrics. Physioneal bags were incubated at 37°C for 24 hours, whereas Extraneal bags were stored 12 hours at room temperature (22 ± 2°C) and then 12 hours at 37°C. Drug concentrations were determined using high performance liquid chromatography (HPLC). Each measure was taken in triplicate. Stability of antibiotics was defined as less than 10% degradation of the drug over time. ♦ RESULTS: Cefazolin, cotrimoxazole, tobramycin, and vancomycin were stable under studied conditions. Ceftazidime was stable 24 hours in icodextrin, 12 hours in Physioneal 1.36% and 6 hours in Physioneal 3.86%. The association of tobramycin or vancomycin did not influence the stability of ceftazidime. Cefepime and amoxicillin were stable 6 h, 4 h, and 8 h in Physioneal 1.36%, 3.86% and Extraneal, respectively. The stability of imipenem was very low: 2 h in Physioneal and 6 h in Extraneal. Moreover, an increasingly yellow coloration was observed with the use of imipenem, whereas no color change or precipitation occurred in other bags. ♦ CONCLUSION: Cefazolin, tobramycin, cotrimoxazole, and vancomycin are stable in PD solutions up to 24 hours and can be administered in the PD bag for the treatment of peritonitis, even in automated PD under studied conditions. However, amoxicillin, cefepime, ceftazidime, and imipenem must be used with caution due to their lack of stability.

How to minimize toxic exposure to pyridine during continuous infusion of ceftazidime in patients with cystic fibrosis?

Ceftazidime is particularly efficient against Pseudomonas aeruginosa in cystic fibrosis patients. Thus, the spontaneous production of pyridine, which is a toxic product, raises some concern. Our aim was to examine the kinetics of degradation of ceftazidime in portable infusion pumps either at 4°C, 22°C, or 33°C and to propose some recommendations in order to reduce the pyridine exposure. Two administration models were studied in vitro. In model 1, we administered 12 g of ceftazidime infused over 23 h (once-daily infusion) compared to 6 g infused over 11.5 h in model 2 (twice-daily regimen). Samples were collected at 0 h and then every 4 and 2 h after the shaping of portable infusion pumps in models 1 and 2, respectively. Both ceftazidime and pyridine were analyzed using an ultraviolet high-performance liquid chromatograph. Production of pyridine is highly depending on the temperature. The in situ production of pyridine per day of treatment decreases at a ratio close to 1/6 and 1/3 between 33°C and 4°C in models 1 and 2, respectively. Regardless of the conditions, the production of pyridine is significantly lower in model 2, whereas the total delivery amount of ceftazidime is significantly higher at 4°C and 33°C compared to that in model 1. According to a the precautionary principle, these findings lead to three major recommendations: (i) exposing a solution of ceftazidime to over 22°C should be strictly avoided, (ii) a divided dose of 6 g over 11.5 h instead of a once-daily administration is preferred, and (iii) infusion should be administered immediately after reconstitution.

Biological and physicochemical stability of ceftazidime and aminophylline on glucose parenteral solution

Ceftazidime is a broad spectrum antibiotic administered mainly by the parenteral route, and it is especially effective against Pseudomonas aeruginosa. The period of time in which serum levels exceed the Minimum Inhibitory Concentration (MIC) is an important pharmacodynamic parameter for its efficacy. One of the forms to extend this period is to administer the antibiotic by continuous infusion, after prior dilution in a Parenteral Solution (PS). The present work assessed the stability of ceftazidime in 5% glucose PS for 24 hours, combined or not with aminophylline, through High Performance Liquid Chromatography (HPLC). The physicochemical evaluation was accompanied by in vitro antimicrobial activity compared MIC test in the 24-hour period. Escherichia coli and Pseudomonas aeruginosa were the microorganisms chosen for the MIC comparison. The HPLC analysis confirmed ceftazidime and aminophylline individual stability on PS, while the MIC values were slightly higher than the mean described in the literature. When both drugs were associated in the same PS, the ceftazidime concentration by HPLC decreased 25% after 24 hours. Not only did the MIC values show high loss of antibiotic activity within the same period, but also altered MIC values immediately after the preparation, which was not detected by HPLC. Our results indicate that this drug combination is not compatible, even if used right away, and that PS might not be the best vehicle for ceftazidime, emphasizing the importance of the MIC evaluation for drug interactions.

Stability and antibacterial potency of ceftazidime and vancomycin eyedrops reconstituted in BSS against Pseudomonas aeruginosa and Staphylococcus aureus

PURPOSE

We aimed to study the stability and the in vitro antibacterial potency of ceftazidime and vancomycin eyedrops against Pseudomonas aeruginosa and Staphylococcus aureus, respectively, under different storage temperatures and light conditions.

METHODS

Solutions of ceftazidime 50 mg/ml and vancomycin 50 mg/ml were prepared by reconstituting with balanced salt solution (BSS) and stored at 4 degrees C and at 24 degrees C with and without exposure to light. The minimum bactericidal concentrations against P. aeruginosa and S. aureus were measured to evaluate the antimicrobial potency over a 4-week period. Changes in the pH values and physical characteristics of the solutions were recorded over the same period of time.

RESULTS

The antibacterial potency of ceftazidime decreased significantly from days 3 and 7 onwards at storage temperatures of 24 degrees C and 4 degrees C, respectively, but was not affected by light exposure. The pH value progressed from acidic to alkaline, peaking at day 3, in all solutions. The antibacterial potency of vancomycin remained stable during the 4-week period, but its pH showed a slight progression from acidic to less acidic, in all solutions.

CONCLUSIONS

Ceftazidime eyedrops in BSS appear to remain effective against P. aeruginosa for > or = 7 days when stored at 4 degrees C, but were less effective when stored at 24 degrees C. Loss of antibacterial potency coincides with the appearance of visual and olfactory signs of degradation. The transient rise in pH at day 3 is a matter of possible concern, however, as it may affect patient tolerance. By contrast, vancomycin eyedrops in BSS can be safely used for > or = 4 weeks, stored at either 4 degrees C or 24 degrees C.

Analysis of cephalosporin antibiotics

A comprehensive review with 276 references for the analysis of members of an important class of drugs, cephalosporin antibiotics, is presented. The review covers most of the methods described for the analysis of these drugs in pure forms, in different pharmaceutical dosage forms and in biological fluids.

Continuous infusion of ceftazidime in critically ill patients undergoing continuous venovenous haemodiafiltration: pharmacokinetic evaluation and dose recommendation

Introduction

In seriously infected patients with acute renal failure and who require continuous renal replacement therapy, data on continuous infusion of ceftazidime are lacking. Here we analyzed the pharmacokinetics of ceftazidime administered by continuous infusion in critically ill patients during continuous venovenous haemodiafiltration (CVVHDF) in order to identify the optimal dosage in this setting.

Method

Seven critically ill patients were prospectively enrolled in the study. CVVHDF was performed using a 0.6 m² AN69 high-flux membrane and with blood, dialysate and ultrafiltration flow rates of 150 ml/min, 1 l/hour and 1.5 l/hour, respectively. Based on a predicted haemodiafiltration clearance of 32.5 ml/min, all patients received a 2 g loading dose of ceftazidime, followed by a 3 g/day continuous infusion for 72 hours. Serum samples were collected at 0, 3, 15 and 30 minutes and at 1, 2, 4, 6, 8, 12, 24, 36, 48 and 72 hours; dialysate/ultrafiltrate samples were taken at 2, 8, 12, 24, 36 and 48 hours. Ceftazidime concentrations in serum and dialysate/ultrafiltrate were measured using high-performance liquid chromatography.

Results

The mean (± standard deviation) elimination half-life, volume of distribution, area under the concentration-time curve from time 0 to 72 hours, and total clearance of ceftazidime were 4 ± 1 hours, 19 ± 6 l, 2514 ± 212 mg/h per l, and 62 ± 5 ml/min, respectively. The mean serum ceftazidime steady-state concentration was 33.5 mg/l (range 28.8–36.3 mg/l). CVVHDF effectively removed continuously infused ceftazidime, with a sieving coefficient and haemodiafiltration clearance of 0.81 ± 0.11 and 33.6 ± 4 mg/l, respectively.

Conclusion

We conclude that a dosing regimen of 3 g/day ceftazidime, by continuous infusion, following a 2 g loading dose, results in serum concentrations more than four times the minimum inhibitory concentration for all susceptible pathogens, and we recommend this regimen in critically ill patients undergoing CVVHDF.

Determination of ceftazidime and cefepime in plasma and dialysate-ultrafiltrate from patients undergoing continuous veno-venous hemodiafiltration by HPLC

We have developed and validated a new, rapid and reproducible HPLC method for the determination of cefepime and ceftazidime in plasma and dialysate-ultrafiltrate samples obtained from intensive care unit (ICU) patients undergoing continuous veno-venous hemodiafiltration (CVVHDF). The method for plasma samples involved protein precipitation with acetonitrile, followed by washing with dichloromethane to remove apolar lipophilic compounds. Dialysate-ultrafiltrate samples did not require any preparation. Separation was performed on a muBondapak C18 (30 cm x 3.9 mm x 10 microm) with UV detection. The mobile phase contained acetate buffer: ACN and was delivered at 2 ml/min. The coefficients of determination of the calibration curves were always > or = 0.998 and R.S.D.% of the response factors <10%. The intra and inter-assay precision and accuracy of the quality controls (QC) and limit of quantification (LOQ) were satisfactory in all cases. Plasma and dialysate-ultrafiltrate samples were stable at -20 and -80 degrees C for 2 months and also after three freeze/thaw cycles. Dialysate-ultrafiltrate samples were stable in the chromatographic rack for 24h at room temperature, but we recommend storing processed plasma samples at 4 degrees C until the analysis. The described method has proved to be useful to give accurate measurements of ceftazidime and cefepime in samples obtained from patients undergoing CVVHDF.

Determination of ceftazidime in plasma and cerebrospinal fluid by micellar electrokinetic chromatography with direct sample injection

A simple micellar electrokinetic chromatography (MEKC) with UV detection at 254 nm for analysis of ceftazidime in plasma and in cerebrospinal fluid (CSF) by direct injection without any sample pretreatment is described. The separation of ceftazidime from biological matrix was performed at 25 degrees C using a background electrolyte consisting of Tris buffer with sodium dodecyl sulfate (SDS) as the electrolyte solution. Under optimal MEKC condition, good separation with high efficiency and short analyses time is achieved. Several parameters affecting the separation of the drug from biological matrix were studied, including pH and concentration of the Tris buffer and SDS. Using cefazolin as an internal standard (IS), the linear ranges of the method for the determination of ceftazidime in plasma and in CSF were all over the range of 3-90 microg/mL; the detection limit of the drug in plasma and in CSF (signal-to-noise ratio = 3; injection 0.5 psi, 5 s) was 2.0 microg/mL. The applicability of the proposed method for determination of ceftazidime in plasma and CSF collected after intravenous administration of 2 g ceftazidime in patients with meningitis was demonstrated.

Comparative stability studies of antipseudomonal beta-lactams for potential administration through portable elastomeric pumps (home therapy for cystic fibrosis patients) and motor-operated syringes (intensive care units)

The stability of antipseudomonal beta-lactams in concentrated solutions was examined in view of their potential administration by continuous infusion with external pumps (for intensive care patients) or with portable pumps carried under clothing (for cystic fibrosis patients). Aztreonam (100 g/liter), piperacillin (128 g/liter, with tazobactam), and azlocillin (128 g/liter) remained 90% stable for up to more than 24 h at 37 degrees C (mezlocillin [128 g/liter] was stable at 25 degrees C but not at 37 degrees C). Ceftazidime (120 g/liter), cefpirome (32 g/liter), and cefepime (50 g/liter) remained 90% stable for up to 24, 23.7, and 20.5 h at 25 degrees C but only for 8, 7.25, and 13 h at 37 degrees C, respectively. The control of temperature therefore appears to be critical for all three cephalosporins that cannot be recommended for use in portable pumps carried under clothes for prolonged periods for reasons of stability. Cefpirome and cefepime solutions developed an important color change (from light yellow to dark red) upon exposure when stored at 30 degrees C or higher. Degradation of ceftazidime was accompanied by the liberation of pyridine which, at 37 degrees C, was in excess of what is allowed by the U.S. Pharmacopeia, i.e., 1.1 mg/liter, after 8 and 12 h for drug concentrations of 12 and 8.3%, respectively. Imipenem and meropenem are too unstable (10% degradation at 25 degrees C after 3.5 and 5.15 h, respectively) to be recommended for use by continuous infusion. Faropenem, examined in comparison with imipenem and meropenem, proved as stable as aztreonam or piperacillin.

HPLC separation of antibiotics present in formulated and unformulated samples

Analysis of antibiotics in formulated and unformulated samples demand a highly specific and rapid method as many antibiotics (e.g. beta-lactams) have serious stability problems. HPLC techniques can provide a valuable tool for generating highly pure preparations for characterizing the antimicrobial activities. In the present review article, column and mobile phase conditions for the various classes of antibiotics viz. penicillins, cephalosporins, macrolides, tetracyclines, aminoglycosides, quinolones, rifamycins etc. have been presented from April 1998 to November 2000. A brief discussion on chemical structure, spectrum of activity and action mechanism of each class has also been given.

Comparison of ceftazidime degradation in glass bottles and plastic bags under various conditions

OBJECTIVE

To study the effect of type of container on ceftazidime stability in intravenous solutions.

METHODS

One hundred millilitre polypropylene (PP) and polyvinyl chloride (PVC) bags and 100-mL glass bottles were filled with 5% dextrose or 0.9% sodium chloride solutions containing ceftazidime (Fortumset) at 40 mg/mL. Three containers of each solution were stored at 20 and 35 degrees C. One millilitre samples were drawn from each container at 0 and 20 h and assayed. Pyridine concentrations, the main degradation product of ceftazidime, were determined by high-pressure liquid chromatography.

RESULTS

Pyridine levels increased during storage and were higher in PVC and PP bags than in glass bottles in both diluents. Solutions stored in PP bags showed better stability than in PVC bags.

CONCLUSION

This study shows that ceftazidime undergoes slower degradation in PP than PVC containers although the difference is small. Glass bottles seems to be the better container for storing ceftazidime solutions, whatever storage temperature and diluent used.

Fortum stability in different disposable infusion devices by pyridine assay

The stability of ceftazidime in 5% dextrose injection and 0.9% sodium chloride injection when stored in a different disposable infusion device was determined. Solutions of ceftazidime 40 mg/ml were used to fill the drug administration devices. Stability was determined for both 5% dextrose injection and 0.9% sodium chloride injection solutions at 37 degrees C in four disposable infusion devices. Ceftazidime and its mean degradation product, pyridine, were simultaneously assayed in triplicate by a stability-indicating high-performance liquid chromatographic (HPLC) method. This method was simple, sensitive (limit of quantitation (LOQ), 2 ng injected for both compounds), rapid (run time was 7 min) and precise (mean recovery was 100.5+/-2.9 and 103.6+/-1.9% for pyridine and ceftazidime, respectively). The ceftazidime stability in the 5% dextrose solution was lower than in the 0.9% sodium chloride solution. When stored at 37 degrees C in a disposable infusion device, the stability of the ceftazidime is included in large hourly range, depending strongly on the manufacturer. The stability of ceftazidime exceed 19 h in none studied cases. The pyridine formed in 24 h was in the range of 100-400 mg depending on devices and infusions.

Analysis of antibiotics by capillary electrophoresis

This article reviews recent developments in the characterization of antibiotics. Many capillary electrophoretic techniques have been utilized in their analyses, addressing various aspects of quantifying, profiling and monitoring. Sensitive electrochemical and laser-induced fluorescence detection systems have been utilized, demonstrating trace level determinations in clinical settings and in environmental samples. Different sample introduction methods have been explored, enhancing detection sensitivity, or reducing or eliminating sample manipulation prior to injection.

Stability and compatibility of ceftazidime administered by continuous infusion to intensive care patients

The stability and compatibility of ceftazidime have been examined in the context of its potential use in concentrated solutions for continuous infusion in patients suffering from severe nosocomial pneumonia and receiving other intravenous medications by the same route. Ceftazidime stability in 4 to 12% solutions was found satisfactory (<10% degradation) for 24 h if kept at a temperature of 25 degrees C (77 degrees F) maximum. Studies mimicking the simultaneous administration of ceftazidime and other drugs as done in clinics showed physical incompatibilities with vancomycin, nicardipine, midazolam, and propofol and a chemical incompatibility with N-acetylcystein. Concentrated solutions (50 mg/ml) of erythromycin or clarithromycin caused the appearance of a precipitate, whereas gentamicin, tobramycin, amikacin, isepamicin, fluconazole, ketamine, sufentanil, valproic acid, furosemide, uradipil, and a standard amino acid solution were physically and chemically compatible.