Simultaneous determination of chloramphenicol and its succinate ester by high-performance liquid chromatography

Therapy of experimental meningitis due to Salmonella enteritidis

In many areas of the developing world, Salmonella spp. account for greater than 50% of the gram-negative enteric organisms isolated from cerebrospinal fluid (CSF). The response of Salmonella meningitis to conventional therapy (chloramphenicol and/or ampicillin) is slow, complications arise frequently, and mortality rates of 60 to 80% are common. Two newer agents, ceftriaxone and imipenem, were compared with ampicillin, chloramphenicol, and trimethoprim-sulfamethoxazole (TMP-SMX) in the therapy of experimental Salmonella meningitis beginning 14 h after intracisternal inoculation and continued by constant intravenous infusion for 8 h. Drug concentrations in serum and CSF closely approximated those achieved in the sera and CSF of humans receiving standard parenteral regimens. Penetration into purulent CSF [(concentration of drug in CSF/concentration of drug in serum) x 100] ranged from 18 to 41%. The rate of bacterial killing in CSF was significantly (P less than 0.001) more rapid during therapy with ceftriaxone and imipenem than it was during therapy with chloramphenicol or TMP-SMX. Ceftriaxone and imipenem sterilized the CSF of six of seven animals at 8 h, whereas it sterilized the CSF of three of eight animals treated with ampicillin (P = 0.18), one of eight animals treated with chloramphenicol, and none of seven animals treated with TMP-SMX (P less than or equal to 0.01; ceftriaxone or imipenem versus chloramphenicol or TMP-SMX). New beta-lactams, including ceftriaxone and imipenem, appear to be effective therapy against Salmonella spp. in this animal model and deserve further evaluation in humans.

Lack of predictability of chloramphenicol toxicity in paediatric patients

We studied 45 patients (new-born to 12 year olds) who received 50-100 mg/kg/day chloramphenicol sodium succinate i.v. over 2-49 days for the treatment of central nervous system infections. Multiple blood samples were obtained to measure serum concentrations of chloramphenicol and its succinate ester by high pressure liquid chromatography (HPLC). Haematological parameters (haemoglobin, white cell, neutrophil, eosinophil and platelet counts) were also determined. Chloramphenicol therapy was effective in all patients. Anaemia was present in 10, leukopenia in four, neutropenia in four, and eosinophilia in 16 patients. These adverse effects occurred between 3 and 34 days after the initiation of therapy. Chloramphenicol therapy had to be discontinued only in three patients, who had absolute neutrophil counts less than 800/mm3. All adverse effects were reversible. Demographic factors, daily dose, duration of therapy, steady-state peak and trough serum concentrations, area under the serum concentration-time curve normalized for dose, and the elimination half-life were not correlated with the occurrence of adverse effects of chloramphenicol. The mean cumulative dose of chloramphenicol succinate was the only factor always higher but not statistically different in patients with adverse effects compared to those without. The mean cumulative dose of chloramphenicol succinate ranged from 1.2 to 1.8 g/kg in patients with adverse effects and 0.9-1.1 g/kg in those without. These data suggest that the adverse effects of chloramphenicol may not be predictable in paediatric patients. However, a high cumulative dose may possibly be an important factor in predisposing some patients to certain chloramphenicol toxicity.

Solid-phase extraction of chloramphenicol with graphitized carbon black

The sorption and desorption properties of graphitized carbon black (GCB) were evaluated for enrichment of highly polarizable chloramphenicol (CP) from biological fluids. The distribution of CP between GCB and water lay strongly toward GCB. Among the organic solvents examined, methanol gave the lowest adsorption coefficient. The optimum packing amount of GCB, and the optimum volume and flow-rate of the eluent were deduced from the breakthrough curve and methanol elution curve, respectively. The inner diameter of GCB extraction columns was chosen from the sorption efficiency curve obtained by plotting CP recovery against column inner diameter. The solid-phase extraction method using GCB was applied to the assay of CP in serum samples in the concentration range of 5 to 50 micrograms/ml.

High-performance liquid chromatographic determination of chloramphenicol and four analogues using reductive and oxidative electrochemical and ultraviolet detection

A high-performance liquid chromatographic procedure is described for the separation, quantitation and identification of chloramphenicol, dehydrochloramphenicol, nitrophenylaminopropanedione, nitrosochloramphenicol and aminochloramphenicol. An isocratic reversed-phase system with ultraviolet and electrochemical detectors in tandem was assembled and used. The system was constructed with special accommodation to enable us to use the electrochemical detector in both reductive and oxidative modes. Retention characteristics, hydrodynamic voltammograms under reductive and oxidative conditions and ultraviolet absorbance are reported. Applicability of the procedure to biological fluids was demonstrated by separation and detection of chloramphenicol after incubation with human blood.

Hospital routine analysis of penicillins, third-generation cephalosporins and aztreonam by conventional and high-speed high-performance liquid chromatography

A high-performance liquid chromatographic procedure for the measurement of fifteen beta-lactam antibiotics in body fluids is described, with special reference to high-speed techniques. The procedure involves a unique sample preparation before analysis for all the following fifteen compounds: benzylpenicillin, ampicillin, cloxacillin, ticarcillin, mezlocillin, azlocillin, piperacillin, cefotaxime and its desacetyl metabolite, cefsulodin, cefoperazone, cefmenoxime, ceftazidime, ceftriaxone and the monobactam aztreonam; thus all biological samples arriving at the laboratory can be treated in batch. Of these fifteen antibiotics, eleven can be chromatographed with the same type of mobile phase, which consists of a mixture of ammonium acetate and acetonitrile in various ratios. Three others need ionpairing chromatography because of their polarity, and ticarcillin requires citric acid. High-speed high-performance liquid chromatography seems to be particularly suitable for the routine analysis of beta-lactam antibiotics because columns equilibrate more rapidly, retention times are much shorter, detection limits are lower and the longer lifetime of columns reduces analysis costs.

Antibiotic monitoring in body fluids

Analytical procedures recently described for the quantitative determination of antibiotics in body fluids are reviewed. High-performance liquid chromatography (HPLC) and immunoassays appear as an alternative to current microbiological assays. HPLC has been applied to most antibiotics in clinical use and a major part of the review deals with this technique. Attention is given to sample pretreatment, characteristics of chromatography and detection, and limit of sensitivity. Non-isotopic immunoassays have been essentially applied to aminoglycosides and vancomycin and are also reviewed. Advantages and drawbacks of HPLC and immunoassays are presented.

Clinical pharmacokinetics of chloramphenicol and chloramphenicol succinate

In recent years there has been a renewal of interest in chloramphenicol, predominantly because of the emergence of ampicillin-resistant Haemophilus influenzae, the leading cause of bacterial meningitis in infants and children. Three preparations of chloramphenicol are most commonly used in clinical practice: a crystalline powder for oral administration, a palmitate ester for oral administration as a suspension, and a succinate ester for parenteral administration. Both esters are inactive, requiring hydrolysis to chloramphenicol for anti-bacterial activity. The palmitate ester is hydrolysed in the small intestine to active chloramphenicol prior to absorption. Chloramphenicol succinate acts as a prodrug, being converted to active chloramphenicol while it is circulating in the body. Various assays have been developed to determine the concentration of chloramphenicol in biological fluids. Of these, high-performance liquid chromatographic and radioenzymatic assays are accurate, precise, specific, and have excellent sensitivities for chloramphenicol. They are rapid and have made therapeutic drug monitoring practical for chloramphenicol. The bioavailability of oral crystalline chloramphenicol and chloramphenicol palmitate is approximately 80%. The time for peak plasma concentrations is dependent on particle size and correlates with in vitro dissolution and deaggregation rates. The bioavailability of chloramphenicol after intravenous administration of the succinate ester averages approximately 70%, but the range is quite variable. Incomplete bioavailability is the result of renal excretion of unchanged chloramphenicol succinate prior to it being hydrolysed to active chloramphenicol. Plasma protein binding of chloramphenicol is approximately 60% in healthy adults. The drug is extensively distributed to many tissues and body fluids, including cerebrospinal fluid and breast milk, and it crosses the placenta. Reported mean values for the apparent volume of distribution range from 0.6 to 1.0 L/kg. Most of a chloramphenicol dose is metabolised by the liver to inactive products, the chief metabolite being a glucuronide conjugate; only 5 to 15% of chloramphenicol is excreted unchanged in the urine. The elimination half-life is approximately 4 hours. Inaccurate determinations of the pharmacokinetic parameters may result by incorrectly assuming rapid and complete hydrolysis of chloramphenicol succinate. The pharmacokinetics of chloramphenicol succinate have been described by a 2-compartment model. The reported values for the apparent volume of distribution range from 0.2 to 3.1 L/kg.(ABSTRACT TRUNCATED AT 400 WORDS)

Chloramphenicol: new perspectives on an old drug

Chloramphenicol is an old antibiotic being used with increasing frequency in serious childhood infections largely due to the emergence of ampicillin-resistant Hemophilus influenzae type b. Because of this renewed popularity and the recent availability of accurate analytical techniques for measurement of chloramphenicol, there have been many recent articles examining the pharmacokinetics of chloramphenicol and its two major prodrug esters, chloramphenicol succinate and chloramphenicol palmitate. New data from these studies include the incomplete bioavailability of chloramphenicol succinate, the possible superior bioavailability of chloramphenicol palmitate vs. chloramphenicol succinate, and the wide interpatient variability in chloramphenicol clearance. These observations, coupled with the known serious hematologic toxicity (reversible bone marrow suppression or irreversible aplastic anemia) and metabolic toxicity (gray baby syndrome) associated with chloramphenicol use, require that initial antibiotic doses be selected by age and be carefully individualized by measurement of peak serum chloramphenicol concentrations.

Effect of intravenous flow rate and injection site on in vitro delivery of chloramphenicol succinate and in vivo kinetics

The delivery rates of chloramphenicol succinate from a standard pediatric intravenous infusion set were studied in vitro at varying flow rates and injection sites of the infusion set. The pharmacokinetic properties of CAPS and chloramphenicol were then studied in 15 children given intravenous injections of CAPS via the infusion set at the flashball and Buretrol sites in a crossover fashion on successive days. In vitro, the actual times required for 95% delivery of CAPS from the infusion set were two- to fourfold longer than the predicted infusion times at flow rates of 5, 15, and 29 ml/min and at all three available injection sites. In vivo, flashball injections vs Buretrol injections resulted in significantly higher mean peak serum concentrations of CAPS and CAP, with peaks occurring significantly sooner after the beginning of the intravenous infusion. These results suggest a need for considering characteristics of CAPS infusion when monitoring and interpreting serum concentration values.