Compatibility and stability of linezolid injection admixed with three quinolone antibiotics

Compatibility of linezolid with commercial peritoneal dialysis solutions

PURPOSE

Results of a compatibility and stability study of linezolid admixed in commercial peritoneal dialysis (PD) solutions stored at various temperatures are reported.

METHODS

Test samples were prepared by adding linezolid i.v. injection (2 mg/mL) to infusion bags of 4 PD solutions (Extraneal, Nutrineal, Physioneal 40 Glucose 1.36%, and Physioneal 40 Glucose 2.27%, all from Baxter Healthcare Corporation). Assessments were conducted at various time points during storage of test samples at refrigeration temperature (6 °C) or room temperature (25 °C) for 14 days and at body temperature (37 °C) for 24 hours. Linezolid concentrations over time were determined by high-performance liquid chromatography, physical compatibility was determined by pH measurement and visual inspection, and antimicrobial activity was monitored by a disk diffusion method. The influence of solution warming by heating plate on drug stability was investigated.

RESULTS

Linezolid was stable in all tested solutions for 14 days at refrigeration and room temperatures and for 24 hours at body temperature. No linezolid adsorption to container material was detected. There were only minor variations in pH values, and visual inspection revealed no diluent abnormalities. With 1 exception, antimicrobial activity of >90% was retained in all PD solution samples for the duration of the study under all temperature conditions.

CONCLUSION

Linezolid injection 2 mg/mL remained stable and was compatible with the PD solutions studied for up to 2 weeks at refrigeration or room temperature and up to 24 hours at body temperature.

Stability of Ciprofloxacin and Vancomycin Hydrochloride in AutoDose Infusion System Bags

The objective of this study was to evaluate the physical and chemical stability of ciprofloxacin 400 mg/100 mL and vancomycin as the hydrochloride 1 g/100 mL each admixed in 0.9% sodium chloride injection packaged in AutoDose Infusion System bags.

Triplicate test samples were prepared by admixing the necessary amount of each antibiotic with a portion of 0.9% sodium chloride injection and bringing the admixture of each drug to a final volume of 100 mL with additional 0.9% sodium chloride injection. The test solutions were packaged in ethylene vinyl acetate (EVA) plastic containers (AutoDose dags) designed for use in the AutoDose Infusion System. Samples were protected from light and evaluated at appropriate intervals for up to 7 days at 23°C and up to 30 days at 4°C.

Physical stability was assessed using a multistep evaluation procedure that included turbidimetric and particulate measurement as well as visual inspection. Chemical stability was assessed using stability-indicating HPLC analytical techniques based on the determination of drug concentrations initially and at appropriate intervals over the study periods. The admixtures were clear and colorless when viewed in normal fluorescent room light and with a Tyndall beam. Measured turbidity and particulate content were low and exhibited little change. HPLC analysis found that both ciprofloxacin and vancomycin hydrochloride remained stable for 30 days at 4°C and 7 days at 23°C.

Both ciprofloxacin and vancomycin hydrochloride exhibited physical and chemical stability consistent with previous studies on these drugs. The AutoDose Infusion System bags were not found to affect adversely the physical and chemical stability of these antibiotics.

Incompatibility of Erythromycin Lactobionate and Sulfamethoxazole/Trimethoprim with Linezolid Injection

The objective of this study was to evaluate the physical compatibility and chemical stability of linezolid 200 mg/100 mL admixed with erythromycin lactobionate 500 mg and separately with sulfamethoxazole 400 mg/trimethoprim 80 mg for up to 7 days at 4° C and 23° C. The test samples were prepared by adding the required amount of erythromycin lactobionate and sulfamethoxazole/trimethoprim to separate bags of linezolid injection. Evaluations were made at the initial time point and at 1, 3, 5, and 7 days of storage at temperatures of 4° C and 23° C for physical and chemical stability. Physical stability was assessed using visual observation in normal light and a high-intensity monodirectional light beam (Tyndall beam). In addition, turbidity and particle content were measured electronically. Chemical stability was evaluated by using stability-indicating high-performance liquid chromatographic (HPLC) analytical techniques. The linezolid admixtures with erythromycin lactobionate were clear and colorless when viewed in normal fluorescent room light and using a Tyndall beam. Measured turbidity and particulate content were low and exhibited little change. HPLC analysis found no loss of linezolid in any sample stored at either temperature throughout the study. However, erythromycin lactobionate underwent rapid and extensive losses. Under refrigeration, erythromycin losses were about 45% in 24 hours; at room temperature, losses of over 80% occurred during the first day. The linezolid admixtures with sulfamethoxazole/trimethoprim resulted in gross precipitation nearly immediately upon preparation of all samples. The precipitate consisted of white needle-like crystals. HPLC analysis found that both sulfamethoxazole and trimethoprim had precipitated. Consequently, no further analysis was performed on these samples.

Investigation of Drug-Polymer Compatibility Using Chemometric-Assisted UV-Spectrophotometry

A simple chemometric-assisted UV-spectrophotometric method was used to study the compatibility of clindamycin hydrochloride (HC1) with two commonly used natural controlled-release polymers, alginate (Ag) and chitosan (Ch). Standard mixtures containing 1:1, 1:2, and 1:0.5 w/w drug-polymer ratios were prepared and UV scanned. A calibration model was developed with partial least square (PLS) regression analysis for each polymer separately. Then, test mixtures containing 1:1 w/w drug-polymer ratios with different sets of drug concentrations were prepared. These were UV scanned initially and after three and seven days of storage at 25 °C. Using the calibration model, the drug recovery percent was estimated and a decrease in concentration of 10% or more from initial concentration was considered to indicate instability. PLS models with PC3 (for Ag) and PC2 (for Ch) showed a good correlation between actual and found values with root mean square error of cross validation (RMSECV) of 0.00284 and 0.01228, and calibration coefficient (R²) values of 0.996 and 0.942, respectively. The average drug recovery percent after three and seven days was 98.1 ± 2.9 and 95.4 ± 4.0 (for Ag), and 97.3 ± 2.1 and 91.4 ± 3.8 (for Ch), which suggests more drug compatibility with an Ag than a Ch polymer. Conventional techniques including DSC, XRD, FTIR, and in vitro minimum inhibitory concentration (MIC) for (1:1) drug-polymer mixtures were also performed to confirm clindamycin compatibility with Ag and Ch polymers.

The determination of levofloxacin by flow injection analysis using UV detection, potentiometry, and conductometry in pharmaceutical preparations

A flow injection analysis (FIA) using UV detection, potentiometry and conductometry for levofloxacin (LVF) are described in this study. The best solvent system was found to consist of 0.2 M acetate buffer at pH 3 having 10% MeOH. A flow rate of 1 ml min(-1) was pumped and active material was detected at 288 nm. The detection limit (LOD) and limit of quantification (LOQ) for FIA were calculated to be 3 x 10(-7) M (S/N = 3) and 1 x 10(-7) M (S/N = 10), respectively. In the analysis of tablets, the RSD values were found to be 0.83, 0.98 and 0.99 for FIA, potentiometric and conductometric methods, respectively.

Linezolid: pharmacokinetic characteristics and clinical studies

Linezolid is an oxazolidinone indicated in the treatment of nosocomial and community-acquired pneumonia, complicated and uncomplicated skin and skin structure infections and vancomycin-resistant Enterococcus infections. The drug is also approved for use in complicated skin infections and nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus, concurrent bacteremia associated with vancomycin-resistant Enterococcus faecium and concurrent bacteremia associated with community-acquired pneumonia caused by penicillin-susceptible Streptococcus pneumoniae.

Linezolid: an oxazolidinone antimicrobial agent

BACKGROUND

Linezolid is the first oxazolidinone anti-infective agent marketed in the United States. It is indicated for the treatment of nosocomial pneumonia, complicated skin and skin-structure infections caused by methicillin-sensitive or methicillin-resistant Staphylococcus aureus and other susceptible organisms, and vancomycin-resistant Enterococcus faecium infections. It also is indicated for the treatment of uncomplicated skin and skin-structure infections caused by methicillin-sensitive S. aureus or Streptococcus pyogenes, and community-acquired pneumonia caused by penicillin-sensitive Streptococcus pneumoniae.

OBJECTIVE

This article reviews the pharmacologic properties and clinical usefulness of linezolid.

METHODS

Using the terms linezolid, PNU-100766, and oxazolidinone, we performed a literature search of the following databases: MEDLINE (1966 to September 2000), HealthSTAR (1993 to September 2000), Iowa Drug Information Service (1966 to September 2000), International Pharmaceutical Abstracts (1970 to September 2000), PharmaProjects (January 2000 version), and meeting abstracts of the Infectious Diseases Society of America and the Interscience Conference on Antimicrobial Agents and Chemotherapy (1996 to 2000).

RESULTS

Linezolid has a unique structure and mechanism of action, which targets protein synthesis at an exceedingly early stage. Consequently, cross-resistance with other commercially available antimicrobial agents is unlikely. It is primarily effective against gram-positive bacteria. To date, resistance to linezolid has been reported in patients infected with enterococci. The pharmacokinetic parameters of linezolid in adults are not altered by hepatic or renal function, age, or sex to an extent requiring dose adjustment. Linezolid is metabolized via morpholine ring oxidation, which is independent of the cytochrome P450 (CYP450) enzyme system; as a result, linezolid is unlikely to interact with medications that stimulate or inhibit CYP450 enzymes. Compassionate-use trials and other clinical studies involving mainly adult hospitalized patients with gram-positive infections have shown that linezolid administered intravenously or orally is effective in a variety of nosocomial and community-acquired infections, including those caused by resistant gram-positive organisms. Reported adverse effects include thrombocytopenia. diarrhea, headache, nausea, vomiting, insomnia, constipation, rash, and dizziness. Preliminary pharmacoeconomic data indicate that a significantly higher percentage of patients receiving linezolid therapy versus comparator could be discharged from the hospital by day 7 (P = 0.005).

CONCLUSIONS

Linezolid appears to be effective while maintaining an acceptable tolerability profile. Due to the risk of bacterial resistance, linezolid should be reserved for the treatment of documented serious vancomycin-resistant enterococcal infections.