Prolonged infusion of linezolid is associated with improved pharmacokinetic/pharmacodynamic (PK/PD) profiles in patients with external ventricular drains.

OBJECTIVE: We previously investigated the pharmacokinetic and pharmacodynamic (PK/PD) parameters of routine linezolid infusions (1 h) in patients with external ventricular drains (EVD). The aim of the study was to determine whether extended linezolid infusions (200 mg/h for 3 h) were more efficacious than short linezolid infusions (600 mg/h for 1 h). METHODS: We collected cerebrospinal fluid (CSF) and plasma samples from 10 patients who received linezolid infusions after cerebral hemorrhage surgery with EVDs. Linezolid concentrations were measured by high-performance liquid chromatography (HPLC). A Monte Carlo simulation was used to measure the probability of target attainments (PTA) and the PK/PD indexes at four minimum inhibitory concentrations (MIC). RESULTS: When the same dose (600 mg) was given as an extended infusion (3 h), linezolid reached its maximum concentrations in the plasma and CSF at 3.00 h and 4.40 h, respectively. The mean penetration of linezolid in CSF was 41.31%. Using the parameter of AUC0-24 h/MIC ≥ 100, the plasma PTA provided good coverage at > 90% when MIC was ≤ 1 µg/mL, while the values were 0 in CSF. Using the parameter %T (time) > MIC ≥ 85%, the PTA in both the plasma and CSF provided good coverage when MIC ≤ 2 µg/mL. Compared with routine infusions, prolonged infusion times (3 h) showed increased PTA of linezolid. CONCLUSIONS: Prolonged infusion times increased the concentration of linezolid in the plasma, leading to improved therapeutic outcomes. However, this improvement did not exist in CSF. Lastly, the PK/PD indicator AUC/MIC ≥ 100 may be used to achieve improved outcomes in patients with critical infections.

Comparative pharmacokinetics of tedizolid in rat plasma and cerebrospinal fluid.

To investigate the possibility of tedizolid phosphate's application in the treatment of intracranial infection, a preclinical comparative pharmacokinetic study was designed. Based on the assumption that the classic efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) may participate in the transportation of TDZ, two groups of rats were intravenously administered 6 mg/kg tedizolid phosphate alone or 6 mg/kg tedizolid phosphate combined with 1 mg/kg elacridar which was an inhibitor of P-gp and BCRP. Plasma and cerebrospinal fluid samples were collected according to a pharmacokinetic schedule. All the plasma and cerebrospinal fluid samples were assessed with a validated LC-MS/MS method. The penetration ratio of tedizolid from the blood to cerebrospinal fluid was calculated, and a comparison of the penetration ratios between the two groups was made. The mean Cmax of tedizolid in the CSF in the tedizolid phosphate group and the tedizolid phosphate combined with elacridar group was 154 ng/mL and 300 ng/mL, respectively, and the mean penetration ratio of tedizolid in the tedizolid phosphate group and the tedizolid phosphate combined with elacridar group was 2.16% and 3.53%, respectively. The relatively high Cmax in the CSF proved the possibility of tedizolid phosphate's application in the treatment of intracranial infection, and the higher penetration ratios, Cmax, csf and AUCcsf of the rats in co-administered elacridar group than those in the single-administration group indicated that the transporters P-gp and BCRP might be involved in the transportation of tedizolid.

Effect of ABCC2 and ABCG2 Gene Polymorphisms and CSF-to-Serum Albumin Ratio on Ceftriaxone Plasma and Cerebrospinal Fluid Concentrations.

We measured ceftriaxone pharmacokinetics in patients' plasma and cerebrospinal fluid (CSF) and assessed the influence of biometric, demographic, genetic (ABCB1, ABCC2, ABCB11, ABCG2, and SLCO1A2 polymorphisms) and pathological features. Adult patients with signs and symptoms of central nervous system infections, receiving intravenous ceftriaxone, were enrolled. Ceftriaxone plasma and CSF concentrations were measured by high-precision liquid chromatographic methods; allelic discrimination was performed by real-time polymerase chain reaction. Forty-three patients were included: median ceftriaxone maximal concentration was 15,713 ng/mL in plasma and 3512 ng/mL in CSF with a CSF-to-plasma ratio of 0.3. ABCC2 1249 rs2273697 (P = .027) and ABCG2 1194+928 rs13120400 (P = .015) variants were significantly associated with CSF concentrations and CSF-to-plasma ratios. At linear regression analysis, CSF-to-serum albumin ratio was an independent predictor of ceftriaxone CSF concentrations (P = .001; also in those with intact blood-brain barrier: P = .031) and CSF-to-plasma ratio (P = .001; also in those with blood-brain barrier impairment: P = .040). We here report the role of transporters' genetic variants as well as of blood-brain barrier permeability in predicting ceftriaxone exposure in the central nervous system.

Pharmacokinetics of Cefuroxime in Synovial Fluid.

Cefuroxime is frequently used as preoperative antibiotic prophylaxis and may be used for the treatment of septic arthritis. A prerequisite for successful treatment of septic arthritis is the ability of an antibiotic agent to penetrate into the target site. Therefore, the concentration of cefuroxime in synovial fluid was evaluated. Ten patients who underwent elective knee arthroscopy were included in this study. Patients were treated with a single dose of 1,500 mg cefuroxime intravenously, and subsequently, the concentrations in plasma, the interstitial fluid of muscle tissue, and synovial fluid were measured by using microdialysis. Pharmacokinetic/pharmacodynamic calculations to predict bacterial killing were performed using the epidemiologically defined MIC90 for clinical isolates and CLSI breakpoints. Cefuroxime penetrated excellently into muscle tissue (ratio of the area under the concentration-time curve [AUC] for muscle tissue/AUC for free plasma, 1.79) and synovial fluid (ratio of the AUC for synovial fluid/AUC for free plasma, 1.94). The cefuroxime concentration was greater than the MIC90 for Staphylococcus aureus and S. epidermidis strains (≤2 mg/liter) over the complete dosing interval (the percentage of the dosing interval during which the free cefuroxime concentration exceeded the MIC for the pathogen [fTMIC]). CLSI defines staphylococci with MICs of ≤8 mg/liter to be susceptible to cefuroxime. For staphylococci with MICs of ≤8 mg/liter, the fTMIC in plasma was 52.5%, while the fTMIC in muscle tissue and synovial fluid was 93.6% and 96.3%, respectively. Cefuroxime may be used to treat septic arthritis caused by susceptible bacterial strains (MIC ≤ 8 mg/liter). The activity of cefuroxime in septic arthritis might be underestimated when relying exclusively on plasma concentrations.

Cerebrospinal fluid penetration of meropenem in neurocritical care patients with proven or suspected ventriculitis: a prospective observational study.

BACKGROUND: Ventriculitis is a complication of temporary intraventricular drains. The limited penetration of meropenem into the cerebrospinal fluid (CSF) is well known. However, ventricular CSF pharmacokinetic data in patients with ventriculitis are lacking. The aim of this study was to evaluate meropenem pharmacokinetics in the serum and CSF of neurocritical care patients with proven or suspected ventriculitis. METHODS: We conducted an observational pharmacokinetic study of neurocritical care patients with proven or suspected ventriculitis receiving meropenem. Multiple blood and CSF samples were taken and were described using nonparametric pharmacokinetic modelling with Pmetrics. RESULTS: In total, 21 patients (median age 52 years, median weight 76 kg) were included. The median (range) of peak and trough concentrations in serum were 20.16 (4.40-69.00) mg/L and 2.54 (0.00-31.40) mg/L, respectively. The corresponding peak and trough concentrations in CSF were 1.20 (0.00-6.20) mg/L and 1.28 (0.00-4.10) mg/L, respectively, with a median CSF/serum ratio (range) of 0.09 (0.03-0.16). Median creatinine clearance ranged from 60.7 to 217.6 ml/minute (median 122.5 ml/minute). A three-compartment linear population pharmacokinetic model was most appropriate. No covariate relationships could be supported for any of the model parameters. Meropenem demonstrated poor penetration into CSF, with a median CSF/serum ratio of 9 % and high interindividual pharmacokinetic variability. CONCLUSIONS: Administration of higher-than-standard doses of meropenem and therapeutic drug monitoring in both serum and CSF should be considered to individualise meropenem dosing in neurocritical care patients with ventriculitis.

Population Pharmacokinetics and Dosing Regimen Optimization of Meropenem in Cerebrospinal Fluid and Plasma in Patients with Meningitis after Neurosurgery.

Meropenem is used to manage postneurosurgical meningitis, but its population pharmacokinetics (PPK) in plasma and cerebrospinal fluid (CSF) in this patient group are not well-known. Our aims were to (i) characterize meropenem PPK in plasma and CSF and (ii) recommend favorable dosing regimens in postneurosurgical meningitis patients. Eighty-two patients were enrolled to receive meropenem infusions of 2 g every 8 h (q8h), 1 g q8h, or 1 g q6h for at least 3 days. Serial blood and CSF samples were collected, and concentrations were determined and analyzed via population modeling. Probabilities of target attainment (PTA) were predicted via Monte Carlo simulations, using the target of unbound meropenem concentrations above the MICs for at least 40% of dosing intervals in plasma and at least of 50% or 100% of dosing intervals in CSF. A two-compartment model plus another CSF compartment best described the data. The central, intercentral/peripheral, and intercentral/CSF compartment clearances were 22.2 liters/h, 1.79 liters/h, and 0.01 liter/h, respectively. Distribution volumes of the central and peripheral compartments were 17.9 liters and 3.84 liters, respectively. The CSF compartment volume was fixed at 0.13 liter, with its clearance calculated by the observed drainage amount. The multiplier for the transfer from the central to the CSF compartment was 0.172. Simulation results show that the PTAs increase as infusion is prolonged and as the daily CSF drainage volume decreases. A 4-hour infusion of 2 g q8h with CSF drainage of less than 150 ml/day, which provides a PTA of >90% for MICs of ≤8 mg/liter in blood and of ≤0.5 mg/liter or 0.25 mg/liter in CSF, is recommended. (This study has been registered at ClinicalTrials.gov under identifier NCT02506686.).

Amoxicillin and amoxicillin/clavulanate reduce ethanol intake and increase GLT-1 expression as well as AKT phosphorylation in mesocorticolimbic regions.

Studies have shown that administration of the ß-lactam antibiotic ceftriaxone (CEF) attenuates ethanol consumption and cocaine seeking behavior as well as prevents ethanol-induced downregulation of glutamate transporter 1 (GLT-1) expression in central reward brain regions. However, it is not known if these effects are compound-specific. Therefore, the present study examined the effects of two other ß-lactam antibiotics, amoxicillin (AMOX) and amoxicillin/clavulanate (Augmentin, AUG), on ethanol drinking, as well as GLT-1 and phosphorylated-AKT (pAKT) levels in the nucleus accumbens (Acb) and medial prefrontal cortex (mPFC) of alcohol-preferring (P) rats. P rats were exposed to free-choice of ethanol (15% and 30%) for five weeks and were given five consecutive daily i.p. injections of saline vehicle, 100 mg/kg AMOX or 100mg/kg AUG. Both compounds significantly decreased ethanol intake and significantly increased GLT-1 expression in the Acb. AUG also increased GLT-1 expression in the mPFC. Results for changes in pAKT levels matched those for GLT-1, indicating that ß-lactam antibiotic-induced reductions in ethanol intake are negatively associated with increases in GLT-1 and pAKT levels within two critical brains regions mediating drug reward and reinforcement. These findings add to a growing literature that pharmacological increases in GLT-1 expression are associated with decreases in ethanol intake and suggest that one mechanism mediating this effect may be increased phosphorylation of AKT. Thus, GLT-1 and pAKT may serve as molecular targets for the treatment of alcohol and drug abuse/dependence.

Cerebrospinal fluid-compensated medication reservoir for an implantable infusion device: concept and preliminary evaluation.

Conventional gas-compensated medication reservoirs used for implantable infusion devices require perfect sealing of the gas chamber, because the gases used are generally toxic. In addition, the physical properties of selected gas critically affect the performance of infusion devices and hydraulic performance of the infusion device can be affected by the amount of medication discharged.
In this study, we suggest a new medication reservoir that adopts a cerebrospinal fluid (CSF)-compensating mechanism, such that when a medication is released from the reservoir by a mechanical actuator, native CSF enters into the reservoir to minimize the build-up of pressure drop. We evaluated in vitro performance and conducted in vivo feasibility tests by using an intrathecal infusion device developed at the Korean National Cancer Center. Experimental results showed that the proposed CSF-compensated infusion pump was essentially less affected by ambient temperature or pressure conditions compared to the gas-compensated infusion pump. Moreover, it showed moderate implant feasibility and operating stability during an animal experiment performed for 12 days. We believe that the proposed volume-compensating mechanism could be applied in various medical fields that use implantable devices.

Cerebral microdialysis in clinical studies of drugs: pharmacokinetic applications.

The ability to deliver drug molecules effectively across the blood-brain barrier into the brain is important in the development of central nervous system (CNS) therapies. Cerebral microdialysis is the only existing technique for sampling molecules from the brain extracellular fluid (ECF; also termed interstitial fluid), the compartment to which the astrocytes and neurones are directly exposed. Plasma levels of drugs are often poor predictors of CNS activity. While cerebrospinal fluid (CSF) levels of drugs are often used as evidence of delivery of drug to brain, the CSF is a different compartment to the ECF. The continuous nature of microdialysis sampling of the ECF is ideal for pharmacokinetic (PK) studies, and can give valuable PK information of variations with time in drug concentrations of brain ECF versus plasma. The microdialysis technique needs careful calibration for relative recovery (extraction efficiency) of the drug if absolute quantification is required. Besides the drug, other molecules can be analysed in the microdialysates for information on downstream targets and/or energy metabolism in the brain. Cerebral microdialysis is an invasive technique, so is only useable in patients requiring neurocritical care, neurosurgery or brain biopsy. Application of results to wider patient populations, and to those with different pathologies or degrees of pathology, obviously demands caution. Nevertheless, microdialysis data can provide valuable guidelines for designing CNS therapies, and play an important role in small phase II clinical trials. In this review, we focus on the role of cerebral microdialysis in recent clinical studies of antimicrobial agents, drugs for tumour therapy, neuroprotective agents and anticonvulsants.

[Penetration of ceftriaxone into the cerebrospinal fluid and its relationship to inflammatory markers during bacterial meningitis]. / Prunik ceftriaxonu do likvoru a jeho v vztah k markerum zánetu v prubehu invazivní bakteriální infekce.

AIM: To evaluate the penetration of ceftriaxone into the cerebrospinal fluid (CSF) in patients with invasive bacterial infection and to define correlation between the penetration and laboratory markers of inflammation. MATERIAL AND METHODS: Levels of ceftriaxone in the serum and CSF of 17 patients with purulent meningitis were examined. Serum concentrations of ceftriaxone before and after its administration were measured in 9 patients (18 samples, 52.9 %) by microbiological assay based on the agar diffusion test. In all patients, the CSF/serum quotient for ceftriaxone was calculated and correlated with laboratory markers of inflammation (C-reactive protein, fibrinogen and neutrophils). The CSF from nine patients with positive culture for bacteria was used for a modified bactericidal test. RESULTS: Ceftriaxone levels in the serum before and after administration (31.2 mg/l -/+ SD 12.29 and 300.0 mg/l -/+ SD 125.9, respectively) were different (p = 0.000156). The decrease of ceftriaxone levels in the CSF was gradual. There was also a significant difference between the levels of inflammatory markers and CSF/serum quotient of ceftriaxone. Patients with the values higher than 0.1 had higher CRP serum levels (p = 0.00192), fibrinogen serum levels (p = 0.0178) as well as neutrophil count in the CSF (p = 0.0112). However, no inflammatory markers (or their combinations) predicted the extent of penetration of ceftriaxone into the CSF. CONCLUSION: High serum concentration of ceftriaxone causes higher penetration through the inflamed blood-brain barrier. Higher antibiotic penetration correlated with the extent of systemic inflammatory response. However, no inflammatory marker predicted the rate of ceftriaxone crossing the blood-brain barrier. Ceftriaxone penetration, with a 24-hour regimen of administration, remains reliable and efficient therapy of purulent meningitis.

[Concentration of benzylpenicillin sodium salt in the cerebrospinal fluid of patients with late neurosyphilis as an indicator of efficacy of specific therapy].

A permeability of crystallized benzylpenicillin sodium salt (CBSS) through a blood-brain barrier (BBB) in patients with late neurosyphilis and experimental animals has been studied. Forty-six patients with vascular and late meningovascular neurosyphilis have been examined. A group of experimental animals included 50 rabbits. The injection of CBSS to patients and animals was followed by the measurement of antibiotic's concentration in the cerebrospinal fluid (CSF) using high performance liquid chromatography. The level of CSF penicillin concentration was estimated as an indicator of efficacy of the treatment. The treponemocide concentration of antibiotics in the CSF was reached only in patients with meningovascular neurosyphilis (0.029+/-0.003 mcg/ml; p<0.05). There was an increase of BBB permeability for CBSS and concentration of the latter in CSF from 0.0012+/-0.001 mcg/ml to 0.02+/-0.0012 mcg/ml (p<0.05) after the injection of mannitol in rabbits.

Role of glial cells in the functional expression of LL-37/rat cathelin-related antimicrobial peptide in meningitis.

Antimicrobial peptides are intrinsic to the innate immune system in many organ systems, but little is known about their expression in the central nervous system. We examined cerebrospinal fluid (CSF) and serum from patients with active bacterial meningitis to assess antimicrobial peptides and possible bactericidal properties of the CSF. We found antimicrobial peptides (human cathelicidin LL-37) in the CSF of patients with bacterial meningitis but not in control CSF. We next characterized the expression, secretion, and bactericidal properties of rat cathelin-related antimicrobial peptide, the homologue of the human LL-37, in rat astrocytes and microglia after incubation with different bacterial components. Using real-time polymerase chain reaction and Western blotting, we determined that supernatants from both astrocytes and microglia incubated with bacterial component supernatants had antimicrobial activity. The expression of rat cathelin-related antimicrobial peptide in rat glial cells involved different signal transduction pathways and was induced by the inflammatory cytokines interleukin 1beta and tumor necrosis factor. In an experimental model of meningitis, infant rats were intracisternally infected with Streptococcus pneumoniae, and rat cathelin-related antimicrobial peptide was localized in glia, choroid plexus, and ependymal cells by immunohistochemistry. Together, these results suggest that cathelicidins produced by glia and other cells play an important part in the innate immune response against pathogens in central nervous system bacterial infections.

Management of complicated shunt infections: a clinical report.

OBJECTIVES: The authors present their experience with a protocol for the treatment of patients with complicated shunt infections. METHODS: Complicated shunt infections are defined for the purpose of this protocol as multiple compartment hydrocephalus, multiple organism shunt infection, severe peritonitis, or infections in other sites of the body. The initial treatment protocol for these patients was 3 weeks of intravenous antibiotic therapy and 2 weeks of twice daily intraventricular/intrashunt antibiotic therapy. Cerebrospinal fluid (CSF) cultures were monitored during therapy and obtained again 48 hours after completion. The shunt was completely replaced. Additionally, follow-up cultures were obtained in all patients 3-6 months after therapy was completed. RESULTS: A cure of the infection was achieved in all patients as defined by negative cultures obtained at completion of antibiotic therapy and in follow-up studies. The follow-up period was 2-11 years (mean 4.4 +/- 2.5 years). The treatment protocol was modified in the patients treated after 1991, and 18 patients were treated with this modified treatment regime. In these patients, intraventricular antibiotics were administered only once daily for 14 days, and the CSF was cultured 24 hours after antibiotic therapy had been stopped instead of after 48 hours. The results were similar to those obtained with the initial protocol. CONCLUSIONS: Based on their prospective nonrandomized series, the authors believe that patients with complicated shunt infections can be successfully treated with 2 weeks of intraventricular antibiotic therapy administered once daily, concurrent with 3 weeks of intravenous antibiotic therapy. This protocol reduces length of treatment and hospital stay, and avoids recurrence of infection.

Pharmacokinetics of aztreonam in healthy subjects and patients with cystic fibrosis and evaluation of dose-exposure relationships using monte carlo simulation.

Aztreonam (AZM) is a monobactam antibiotic with a high level of activity against gram-negative micro-organisms, including Pseudomonas aeruginosa. We evaluated AZM pharmacokinetics and pharmacokinetic-pharmacodynamic relationships in patients with cystic fibrosis (CF) and healthy subjects. Pharmacokinetic data in eight CF patients and healthy subjects that were matched for age, gender, weight, and height were obtained and analyzed by using the nonparametric adaptive grid algorithm. Probabilities of target attainment using percentages of time of unbound concentration above the MIC (fT>MIC) were obtained by using a Monte Carlo simulation. AZM total body clearance was significantly higher in CF patients (100.1 +/- 17.1 versus 76.2 +/- 7.4 ml/min in healthy subjects; P < 0.01). The pharmacokinetic parameter estimates for terminal half-life (1.54 +/- 0.17 h [mean +/- the standard deviation]) and volume of distribution (0.20 +/- 0.02 liters/kg in patients with CF patients were not different from those in healthy subjects. Monte Carlo simulations with a target of a fT>MIC of 50 to 60% at a dose of 1,000 mg every 8 h indicated a clinical breakpoint of 4 mg/liter and 1 to 2 mg/liter for healthy subjects and CF patients, respectively. This study using matched controls showed that AZM total body clearance and not the volume of distribution is higher in CF patients as a result of increased renal clearance. Pharmacokinetic parameter estimates in healthy subjects resulted in a clinical susceptibility breakpoint of < or =4 mg/liter for a dose of 1,000 mg every 8 h. Patients suspected of having high clearance rates, such as CF patients, should be monitored closely, with dosing regimens adjusted accordingly.

Antibiotic prophylaxis in cerebrospinal fluid shunting: reassessment of Cefotiam penetration into human CSF.

OBJECTS: Shunt infection is a major complication of shunt implantation. Numerous clinical studies give evidence that antibiotic prophylaxis is efficacious in preventing infections after cerebrospinal fluid shunting. In CSF shunting, antibiotics need to reach sufficient concentrations not only in the blood shielding the operative field but also in tissues and the CSF compartment. Cefotiam is widely used for prophylaxis in neurosurgery. Some clinical trials report that this beta-lactam is able to penetrate considerably into the CSF. However, these studies include disease patterns which are most likely to be associated with a pathological permeability of the blood-brain barrier. Therefore, this study was designed to investigate the extent of penetration of Cefotiam into human CSF in patients without morphological disruption of the blood-brain barrier. METHODS: The penetration of Cefotiam into human CSF was investigated in 23 patients without morphological disruption of the blood-brain barrier undergoing CSF shunt surgery. 2 g Cefotiam was administered prior to surgery as a short-term infusion for a period of 15 min. Samples of blood and CSF were collected intraoperatively. The concentrations of Cefotiam were determined by bioassay. RESULTS: All patients (n=23) showed moderate to high plasma levels of Cefotiam (range: 19.8-146.2 mg/L); the pharmacokinetic profiles in blood accorded well with published data. In contrast to earlier studies, no Cefotiam was detected in CSF. CONCLUSION: This study clearly demonstrates that Cefotiam does not penetrate through an intact blood-brain barrier into human CSF. Although Cefotiam has been shown to be valuable for the perioperative prophylaxis of shunt infection, other antibiotics might be superior if they are capable of entering the CSF. Further studies are required to address this assumption.

Infección relacionada con el drenaje ventricular externo: tratamiento intravenoso versus intratecal, revisión de la literatura / External ventricular drainage infection: intravenous vs intrathecal treatment, Review

Ante la emergencia de infecciones relacionadas al drenaje ventricular externo por gérmenes multirresistentes y la necesidad de utilizar antibióticos cuya acción en el sistema nervioso central es controvertida, surge la necesidad de emplear terapéuticas para la administración de fármacos cuyos beneficios merecen ser evaluados. Se realizó una búsqueda de la literatura en PUBMED y los datos fueron extraídos de estudios publicados entre 1987-2005. En esta revisión de la literatura se analizaron los resultados obtenidos, comparando: el tratamiento endovenoso con el tratamiento intratecal en pacientes con infección asociada a la ventriculostomía, los antibióticos utilizados y su penetración al líquido cefalorraquídeo (LCR) con cada vía. Finalmente, se propuso qué pacientes podrían beneficiarse con cada terapéutica, a pesar de la falta de evidencias claras, sugiriendo la necesidad de realizar un trabajo randomizado prospectivo comparando sus beneficios. Palabras clave: infección, tratamiento, ventriculitis.

Due to the emergency of external ventricular drainage infections, cause by multiresistant bacterial strains, and the need to treat them with antibiotics, whose action in the central nervous system is controversial, arises the terapeutic necessity to administer antibiotics whose benefits should be evaluated. We search the Pubmed library. The data were extracted from published studies between 1987-2005. In this reivision the results were analyzed, comparing envovenous versus intrathecal treatment in patients with a ventriculostomy associated infection, the antibiotics that were used and their cerebrospinal fluid (CSF) levels according to each route. Finally, even though there is a lack of clear evidence, we proposed which patients could benefit with each treatment. We conclude that a randomized prospective study, comparing the benefits of each treatment is needed.

Study of intragastric administration of doxycycline: pharmacokinetics including body fluid, endometrial and minimum inhibitory concentrations.

The objectives of this study were to determine the pharmacokinetics and tissue concentrations of doxycycline after repeated intragastric administration, and to determine the minimum inhibitory concentrations (MIC) for equine pathogenic bacteria. In experiment 1, 2 mares received a single intragastric dose of doxycycline hyclate (3 mg/kg bwt). Mean peak serum concentration was 0.22 microg/ml 1 h postadministration. In experiment 2, 5 doses of doxycycline hyclate (10 mg/kg bwt), dissolved in water, were administered to each of 6 mares via nasogastric tube at 12 h intervals. The mean +/- s.e. peak serum doxycycline concentration was 0.32+/-0.16 microg/ml 1 h after the first dose and 0.42+/-0.05 microg/ml 2 h after the fifth dose. The mean trough serum concentrations were > 0.16 microg/ml. Highest mean synovial concentration was 0.46+/-0.13 microg/ml and highest mean peritoneal concentration was 0.43+/-0.07 microg/ml, both 2 h after the fifth dose. Highest urine concentration was mean +/- s.e. 145+/-25.4 microg/ml 2 h after the last dose. Highest endometrial concentration was mean +/- s.e. 1.30+/-0.36 microg/ml 3 h after the fifth dose. Doxycycline was not detected in any of the CSF samples. Mean +/- s.e. Vd(area) was 25.3+/-5.0 l/kg and mean t1/2 was 8.7+/-1.6 h. In experiment 3, minimum inhibitory concentrations of doxycycline were determined for 168 equine bacterial culture specimens. The MIC90 was < or = 1.0 microg/ml for Streptococcus zooepidemicus and 0.25 microg/ml for Staphylococcus aureus. Based on drug concentrations achieved in the serum, synovial and peritoneal fluids and endometrial tissues and MIC values determined in the present study, doxycycline at a dose of 10 mg/kg bwt per os every 12 h may be appropriate for the treatment of infections caused by susceptible (MIC < 0.25 microg/ml) gram-positive organisms in horses.