The passage of cloxacillin into cerebrospinal fluid in the absence of meningitis

Development and validation of a dosing nomogram for continuous infusion cloxacillin in infective endocarditis

BACKGROUND

Cloxacillin is the first-line treatment for methicillin-susceptible staphylococcal infective endocarditis (IE). The recommended dose is 12 g per day regardless of the patient characteristics, despite the importance of renal function on its pharmacokinetics.

OBJECTIVES

We sought to build a population pharmacokinetics model of continuous infusion cloxacillin in IE patients to evaluate the influence of multiple covariates and then develop a nomogram based on significant covariates for individual adaptation.

PATIENTS AND METHODS

We included patients of a local IE cohort who were treated with cloxacillin administered by continuous infusion, excluding those who received intermittent or continuous dialysis, extracorporeal membrane oxygenation or extracorporeal circulation. The population pharmacokinetic analysis was performed using Pmetrics. The influence of weight, ideal weight, height, body mass index, body surface area, glomerular filtration rate (GFR) calculated with the Chronic Kidney Disease Epidemiology Collaboration formula (both expressed in mL/min/1.73 m² and in mL/min) and serum protein level on cloxacillin pharmacokinetics was assessed. Accounting for relevant covariates, a dosing nomogram was developed to determine the optimal daily dose required to achieve a steady-state plasma concentration range of 20-50 mg/L with a probability ≥0.9.

RESULTS

A total of 114 patients (331 plasma concentrations) were included. A one-compartment model including GFR expressed in mL/min as a covariate was chosen. Using the nomogram, achieving the cloxacillin concentration target requires a daily dose ranging from 3.5 to 13.1 g for a GFR ranging from 20 to 125 mL/min.

CONCLUSIONS

This work provided a practical tool for cloxacillin dose adjustment in IE according to renal function.

Pharmacokinetics of Antimicrobials in Children with Emphasis on Challenges Faced by Low and Middle Income Countries, a Clinical Review

Effective antimicrobial exposure is essential to treat infections and prevent antimicrobial resistance, both being major public health problems in low and middle income countries (LMIC). Delivery of drug concentrations to the target site is governed by dose and pharmacokinetic processes (absorption, distribution, metabolism and excretion). However, specific data on the pharmacokinetics of antimicrobials in children living in LMIC settings are scarce. Additionally, there are significant logistical constraints to therapeutic drug monitoring that further emphasize the importance of understanding pharmacokinetics and dosing in LMIC. Both malnutrition and diarrheal disease reduce the extent of enteral absorption. Multiple antiretrovirals and antimycobacterial agents, commonly used by children in low resource settings, have potential interactions with other antimicrobials. Hypoalbuminemia, which may be the result of malnutrition, nephrotic syndrome or liver failure, increases the unbound concentrations of protein bound drugs that may therefore be eliminated faster. Kidney function develops rapidly during the first years of life and different inflammatory processes commonly augment renal clearance in febrile children, potentially resulting in subtherapeutic drug concentrations if doses are not adapted. Using a narrative review approach, we outline the effects of growth, maturation and comorbidities on maturational and disease specific effects on pharmacokinetics in children in LMIC.

Pharmacokinetic Evaluation of Cefazolin in the Cerebrospinal Fluid of Critically Ill Patients

Background

The relative distribution of cefazolin into the cerebrospinal fluid (CSF) remains debated. Determining the distribution of cefazolin into the CSF in noninfected adults may allow for further treatment applications of cefazolin. This prospective pharmacokinetic study aimed to determine the pharmacokinetic parameters of cefazolin in serum and CSF from external ventricular drains (EVDs) in neurologically injured adults.

Methods

Blood and CSF were collected, using a biologic waste protocol, for cefazolin quantification and trapezoidal rule–based pharmacokinetic analysis in a total of 15 critically ill adults receiving 2000 mg intravenously every 8 hours or the renal dose equivalent for EVD prophylaxis.

Results

A median (range) of 3 (2–4) blood and 3 (2–5) CSF samples were collected for each patient. The most common admitting diagnosis was subarachnoid hemorrhage (66.7%). The median calculated cefazolin CSF C_max and C_min values (interquartile range [IQR]) were 2.97 (1.76–8.56) mg/L and 1.59 (0.77–2.17) mg/L, respectively. The median (IQR) CSF to serum area under the curve ratio was 6.7% (3.7%–10.6%), with time-matched estimates providing a similar estimate (8.4%). Of those receiving cefazolin every 8 hours, the median and minimum directly measured CSF cefazolin concentration ≥4 hours following administration were 1.87 and 0.78 mg/L, respectively.

Conclusions

Cefazolin dosed for EVD prophylaxis achieved CSF concentrations suggesting viability as a therapeutic option for patients with meningitis or ventriculitis due to susceptible bacteria such as methicillin-susceptible Staphylococcus aureus. Further clinical trials are required to confirm a role in therapy for cefazolin. Population-based pharmacokinetic–pharmacodynamic modeling may suggest an optimal cefazolin regimen for the treatment of central nervous system infections.

La pharmacologie des antibiotiques dans le liquide cérébrospinal

Le liquide cérébrospinal (LCS) est produit par les plexus choroïdes des ventricules cérébraux avec pour rôle de protéger le système nerveux central des agressions mécaniques (chocs) et infectieuses (virus, bactéries, parasites) et de lui apporter des nutriments essentiels à son fonctionnement optimal. Il est anatomiquement à l'interface entre le compartiment sanguin, le liquide interstitiel cérébral et le compartiment lymphatique. Sa composition est fortement influencée par ces structures. Deux barrières permettent de réguler le passage moléculaire dans le système nerveux central et limitent fortement l'accès à ce dernier : la barrière hématoencéphalique et la barrière hématoméningée. La diffusion des antibiotiques dans le LCS, mais également dans le parenchyme cérébral dépend de plusieurs facteurs : la taille de la molécule, sa lipophilie, la liaison aux protéines plasmatiques et l'intégrité des barrières hématoencéphalique et hématoméningée. Les phénomènes d'inflammation méningée observés dans les méningites bactériennes augmentent la perméabilité des barrières et facilitent la diffusion des agents antibiotiques. Les molécules diffusant le mieux dans le LCS sont les fluoroquinolones, le linézolide, l'association triméthoprime- sulfaméthoxazole, la rifampicine et la fosfomycine. Les bêtalactamines présentent une diffusion assez faible mais qui augmente fortement en cas d'inflammation méningée. Des posologies journalières très élevées permettent de contourner l'écueil de la diffusion. De nombreux paramètres influencent la diffusion des antibiotiques dans le LCS. Le choix de l'antibiothérapie adaptée se fait en fonction de ces paramètres et du type d'infection à traiter en concertation pluridisciplinaire.

Flucloxacillin does not achieve therapeutic cerebrospinal fluid levels against meticillin-sensitive Staphylococcus aureus in adults: A case report and review of the literature

It is uncertain whether flucloxacillin achieves therapeutic concentrations against meticillin-sensitive Staphylococcus aureus (MSSA) in cerebrospinal fluid (CSF). In this study, plasma and CSF concentrations of flucloxacillin and vancomycin in an adult patient were compared. Unlike vancomycin, the flucloxacillin CSF level was not therapeutic. Flucloxacillin monotherapy should be used with caution for MSSA central nervous system infection in adults.

Cloxacillin-induced seizure in a hemodialysis patient

We are reporting a cloxacillin-induced seizure in a patient with stage 5 chronic kidney disease requiring hemodialysis. To our knowledge, there are no published case reports of seizures induced by parenteral cloxacillin in hemodialysis patients. A young hemodialysis female was admitted to the hospital with decreased level of consciousness. Blood cultures revealed methicillin-sensitive Staphylococcus aureus where cloxacillin 2 g intravenously every 4 hours was initiated. Head computed tomography (CT) was not significant. After 14 hours of cloxacillin therapy (4 doses), the patient demonstrated tonic/clonic seizure activity, where phenytoin and lorazepam were initiated. The anti-seizure medications partially reduced seizure activity. Once the cloxacillin was discontinued, the seizures stopped. Two weeks later, all anti-seizure medications were stopped with no further seizure activity. Cloxacillin elimination in hemodialysis patients is similar to patients with normal kidney function. Although cloxacillin does not significantly cross the blood-brain barrier, the correlation between the start of seizures and cloxacillin initiation was confirmed by the negative CT and blood chemistry laboratory results. Moreover, seizure activity was terminated upon discontinuation of cloxacillin. Although further investigation for the cause of such seizures is warranted, clinicians should use caution when giving high doses of cloxacillin in hemodialysis patients.

Overton's rule helps to estimate the penetration of anti-infectives into patients' cerebrospinal fluid

In 1900, Ernst Overton found that the entry of anilin dyes through the cell membranes of living cells depended on the lipophilicity of the dyes. The brain is surrounded by barriers consisting of lipid layers that possess several inward and outward active transport systems. In the absence of meningeal inflammation, the cerebrospinal fluid (CSF) penetration of anti-infectives in humans estimated by the ratio of the area under the concentration-time curve (AUC) in CSF (AUC(CSF)) to that in serum (AUC(CSF)/AUC(S)) correlated positively with the lipid-water partition coefficient at pH 7.0 (log D) (Spearman's rank correlation coefficient r(S) = 0.40; P = 0.01) and negatively with the molecular mass (MM) (r(S) = -0.33; P = 0.04). The ratio of AUC(CSF) to the AUC of the fraction in serum that was not bound (AUC(CSF)/AUC(S,free)) strongly correlated with log D (r(S) = 0.67; P < 0.0001). In the presence of meningeal inflammation, AUC(CSF)/AUC(S) also correlated positively with log D (r(S) = 0.46; P = 0.002) and negatively with the MM (r(S) = -0.37; P = 0.01). The correlation of AUC(CSF)/AUC(S,free) with log D (r(S) = 0.66; P < 0.0001) was as strong as in the absence of meningeal inflammation. Despite these clear correlations, Overton's rule was able to explain only part of the differences in CSF penetration of the individual compounds. The site of CSF withdrawal (lumbar versus ventricular CSF), age of the patients, underlying diseases, active transport, and alterations in the pharmacokinetics by comedications also appeared to strongly influence the CSF penetration of the drugs studied.

Penetration of drugs through the blood-cerebrospinal fluid/blood-brain barrier for treatment of central nervous system infections

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.

[GEIPC-SEIMC (Study Group for Infections in the Critically Ill Patient of the Spanish Society for Infectious Diseases and Clinical Microbiology) and GTEI-SEMICYUC ( Working Group on Infectious Diseases of the Spanish Society of Intensive Medicine, Critical Care, and Coronary Units) recommendations for antibiotic treatment of gram-positive cocci infections in the critical patient]

In recent years, an increment of infections caused by gram-positive cocci has been documented in nosocomial and hospital-acquired-infections. In diverse countries, a rapid development of resistance to common antibiotics against gram-positive cocci has been observed. This situation is exceptional in Spain but our country might be affected in the near future. New antimicrobials active against these multi-drug resistant pathogens are nowadays available. It is essential to improve our current knowledge about pharmacokinetic properties of traditional and new antimicrobials to maximize its effectiveness and to minimize toxicity. These issues are even more important in critically ill patients because inadequate empirical therapy is associated with therapeutic failure and a poor outcome. Experts representing two scientific societies (Grupo de estudio de Infecciones en el Paciente Crítico de la SEIMC and Grupo de trabajo de Enfermedades Infecciosas de la SEMICYUC) have elaborated a consensus document based on the current scientific evidence to summarize recommendations for the treatment of serious infections caused by gram-positive cocci in critically ill patients.

Recomendaciones GEIPC-SEIMC y GTEI-SEMICYUC para el tratamiento antibiótico de infecciones por cocos grampositivos en el paciente crítico

In recent years, an increment of infections caused by gram-positive cocci has been documented in nosocomial and hospital-acquired infections. In diverse countries, a rapid development of resistance to common antibiotics against gram-positive cocci has been observed. This situation is exceptional in Spain but our country might be affected in the near future. New antimicrobials active against these multi-drug resistant pathogens are nowadays available. It is essential to improve our current knowledge about pharmacokinetic properties of traditional and new antimicrobials to maximize its effectiveness and to minimize toxicity. These issues are even more important in critically ill patients because inadequate empirical therapy is associated with therapeutic failure and a poor outcome. Experts representing two scientific societies (Grupo de estudio de Infecciones en el Paciente Critico de la SEIMC and Grupo de trabajo de Enfermedades Infecciosas de la SEMICYUC) have elaborated a consensus document based on the current scientific evidence to summarize recommendations for the treatment of serious infections caused by gram-positive cocci in critically ill patients.

Risk Factors for Adult Nosocomial Meningitis After Craniotomy Roleof Antibiotic Prophylaxis

OBJECTIVE

To evaluate incidence and risk factors of postoperative meningitis, with special emphasis on antibiotic prophylaxis, in a series of 6243 consecutive craniotomies.

METHODS

Meningitis was individualized from a prospective surveillance database of surgical site infections after craniotomy. Ventriculitis related to external ventricular drainage or cerebrospinal fluid shunt were excluded. From May 1997 until March 1999, no antibiotic prophylaxis was prescribed for scheduled, clean, lasting less than 4 hours craniotomies, whereas emergency, clean-contaminated, or long-lasting craniotomies received cloxacillin or amoxicillin-clavulanate. From April 1999 until December 2003, prophylaxis was given to every craniotomy. Independent risk factors for meningitis were studied by a multivariate analysis. Efficacy of antibiotic prophylaxis in preventing meningitis was studied as well as consequences on bacterial flora.

RESULTS

The overall meningitis rate was 1.52%. Independent risk factors were cerebrospinal fluid leakage, concomitant incision infection, male sex, and surgical duration. Antibiotic prophylaxis reduced incision infections from 8.8% down to 4.6% (P < 0.0001) but did not prevent meningitis: 1.63% in patients without antibiotic prophylaxis and 1.50% in those who received prophylaxis. Bacteria responsible for meningitis were mainly noncutaneous in patients receiving antibiotics and cutaneous in patients without prophylaxis. In the former, microorganisms tended to be less susceptible to the prophylactic antibiotics administered. Mortality rate was higher in meningitis caused by noncutaneous bacteria as compared with those caused by cutaneous microorganisms.

CONCLUSION

Perioperative antibiotic prophylaxis, although clearly effective for the prevention of incision infections, does not prevent meningitis and tends to select prophylaxis resistant microorganisms.