Silvia Garazzino

The Relationship between Nevirapine Plasma Concentrations and Abnormal Liver Function Tests

Abnormal liver function tests are frequently observed in HIV-infected individuals receiving nevirapine (NVP). Here we investigate the relationship between total and unbound plasma concentrations of NVP and the liver enzymes alanine aminotransferase (ALT) and gamma-glutamyl transferase (gammaGT). HIV-infected individuals [n = 85, 22 female, 34 hepatitis C or B virus (HCV or HBV(+))] receiving NVP (200 mg bd; median duration 66 weeks, range 3-189) and two nucleoside reverse transcriptase inhibitors (NRTIs) were enrolled into this study. Blood samples were taken at C(trough) (12 hr postdose) for measurement of NVP and liver function tests (ALT and gammaGT). Plasma protein bound and unbound drug was separated using ultrafiltration and NVP concentrations quantified using HPLC-MS/MS. A linear relationship was observed between total and unbound NVP C(trough) (r(2) = 0.77, p < 0.0001). Patients with elevated ALT (>37 IU/liter; n = 31) had higher NVP unbound C(trough) than those with ALT within the normal range (median 2268 vs. 1694 ng/ml, p = 0.04) but there was no difference in total C(trough). Logistic regression revealed no association between higher NVP C(trough) and ALT elevations. Significantly higher NVP total and unbound C(trough) were observed in patients with increased gammaGT (>40 IU/liter; n = 63; total 6747 vs. 4530 ng/ml, p = 0.001; unbound 2113 vs. 1557 ng/ml, p = 0.03). Significantly higher unbound NVP C(trough) was observed in HCV/HBV(+) (median 2275 vs. 1726 ng/ml, p = 0.02) and on bivariate analysis, higher NVP C(trough) was associated with HCV/HBV coinfection (chi(2) = 4.228; p = 0.04). Overall we found no strong association between NVP concentrations and hepatotoxicity. Although in this study NVP was well tolerated in HCV/HBV coinfected patients, higher plasma concentrations were observed.

Nevirapine Plasma Exposure Affects both Durability of Viral Suppression and Selection of Nevirapine Primary Resistance Mutations in a Clinical Setting

ABSTRACT The relationship between nevirapine plasma concentrations and the durability of both viral suppression (VS) and selection of nevirapine primary resistance mutations (PRMs) was evaluated. A nevirapine trough concentration (Ctrough) of >4,300 ng/ml was found to predict longer VS. Patients with nevirapine Ctroughs ranging from 3,100 to 4,300 ng/ml had higher probabilities of developing PRMs than those with nevirapine Ctroughs below and above this concentration interval.

Twelve-Week Treatment of Acute Hepatitis C Virus with Pegylated Interferon-α-2b in Injection Drug Users

Injection drug use is the leading risk factor for infection with hepatitis C virus, and interferon (IFN) treatment in this context is associated with a poor rate of adherence. In this article, we review our experience with injection drug users with acute hepatitis C who are treated with pegylated IFN- alpha -2b for 12 weeks. Acute hepatitis C was diagnosed according to standardized criteria, and patients were treated with a median dosage of IFN- alpha -2b of 1.33 microg/kg per week. A sustained virological response was achieved in 17 (74%) of 23 patients. A sustained virological response was achieved in 14 (87%) of 16 patients treated with a dosage of >or=1.33 microg/kg per week and in 3 (43%) of 7 patients treated with a lower dosage. Sustained virological response was significantly associated only with a pegylated IFN- alpha -2b dosage >or=1.33 microg/kg per week (P=.022). A 12-week regimen of pegylated IFN to treat injection drug users with hepatitis C has a compliance that is much higher than that reported with a 24-week regimen. Adverse effects are minimal if patients are carefully selected.

Simultaneous quantification of linezolid, rifampicin, levofloxacin, and moxifloxacin in human plasma using high-performance liquid chromatography with UV.

A high-performance liquid chromatography method with UV detection was developed and validated for the simultaneous quantification of linezolid (LZD), rifampicin (RFP), levofloxacin (LEVO), and moxifloxacin (MOXI) in human plasma. The method is based on a simple organic protein precipitation that guarantees rapid sample preparation and a direct injection into the high-performance liquid chromatography system. The use of quinoxaline as internal standard improved accuracy (relative standard deviation, RSD% <14.9%) and precision (RSD% <14.3%). The recovery was 75.9% (RSD% = 5.8). The limits of quantification were 0.234 μg/mL for LEVO, 0.312 μg/mL for LZD, 0.156 μg/mL for MOXI, and 0.622 μg/mL for RFP. This method allows the simultaneous measurement of LEVO, LZD, MOXI, and RFP in human plasma and may be used for both routine clinical applications and pharmacokinetic studies.

Vertically acquired hepatitis C virus infection: Correlates of transmission and disease progression

The worldwide prevalence of hepatitis C virus (HCV) infection in children is 0.05%-0.4% in developed countries and 2%-5% in resource-limited settings, where inadequately tested blood products or un-sterile medical injections still remain important routes of infection. After the screening of blood donors, mother-to-child transmission (MTCT) of HCV has become the leading cause of pediatric infection, at a rate of 5%. Maternal HIV co-infection is a significant risk factor for MTCT and anti-HIV therapy during pregnancy seemingly can reduce the transmission rate of both viruses. Conversely, a high maternal viral load is an important, but not preventable risk factor, because at present no anti-HCV treatment can be administered to pregnant women to block viral replication. Caution is needed in adopting obstetric procedures, such as amniocentesis or internal fetal monitoring, that can favor fetal exposure to HCV contaminated maternal blood, though evidence is lacking on the real risk of single obstetric practices. Mode of delivery and type of feeding do not represent significant risk factors for MTCT. Therefore, there is no reason to offer elective caesarean section or discourage breast-feeding to HCV infected parturients. Information on the natural history of vertical HCV infection is limited. The primary infection is asymptomatic in infants. At least one quarter of infected children shows a spontaneous viral clearance (SVC) that usually occurs within 6 years of life. IL-28B polymorphims and genotype 3 infection have been associated with greater chances of SVC. In general, HCV progression is mild or moderate in children with chronic infection who grow regularly, though cases with marked liver fibrosis or hepatic failure have been described. Non-organ specific autoantibodies and cryoglobulins are frequently found in children with chronic infection, but autoimmune diseases or HCV associated extrahepatic manifestations are rare.

Glycopeptide Bone Penetration in Patients with Septic Pseudoarthrosis of the Tibia

Background and objective: In the treatment of bone infections, a major determinant of the clinical response is the active drug concentration at the infected site. Because of the high prevalence of meticillin (methicillin)-resistant staphylococci and enterococci, glycopeptides are widely used for the treatment of bone and joint infections, but data on their penetration into human bone are lacking. The aim of our study was to measure vancomycin and teicoplanin concentrations in infected human bone under steady-state conditions and verify their relationship with inflammatory markers, patient demographic characteristics and pharmacodynamic microbiological markers.Methods and patients: Twenty-seven adult orthopaedic patients undergoing surgical debridement for septic pseudoarthrosis of the tibia and receiving either intravenous vancomycin (Vancocina® 1 g twice daily) or teicoplanin (Targosid® 10 mg/kg/day) were studied from January 2004 to January 2008. Plasma and bone specimens were simultaneously collected during surgery for pharmacokinetic and microbiological assays at a variable interval after antimicrobial administration. Bone samples were dissected into cortical and cancellous bone, cleaned of soft tissues, crushed and eluted into phosphate buffer. Necrotic samples and sequestra were not analysed.Plasma and bone antimicrobial concentrations were measured by a validated method of high-performance liquid chromatography with UV detection, and bone/plasma concentration ratios were calculated. Cortical and cancellous bone area under the concentration-time curve (AUC) over 24 hours (AUC24) values were measured by the linear-log trapezoidal rule, using WinNonlin® software, and were compared with the minimum inhibitory concentrations (MICs) of the infecting agents.Results: For vancomycin, the mean ± SD concentrations were 2.66 ± 1.2 mg/L in cortical bone and 11.53 ± 7.8 mg/L in cancellous bone (corresponding to 20.67% and 89.39% of intraoperative plasma concentrations), and the mean ± SD tissue AUC24 values were 55.15 ± 25.26 h · mg/L for cortical bone and 299.16 ± 299.54 h · mg/L for cancellous bone. For teicoplanin, the mean ± SD concentrations were 2.01 ± 1.7 and 7.51 ± 7.0 mg/L in cortical and cancellous bone, respectively (12.35% and 48.6% of intraoperative plasma concentrations), and the mean ± SD teicoplanin tissue AUC24 values were 34.08 ± 23.6 h · mg/L and 155.17 ± 132.8 h · mg/L for cortical bone and cancellous bone, respectively. The mean vancomycin AUC24/MIC ratios were 215.02 for plasma, 47.14 for cortical bone and 268.95 for cancellous bone. The mean teicoplanin AUC24/MIC ratios were 336.48, 36.27 and 197.21 for plasma, cortical bone and cancellous bone, respectively.Conclusions: Bone penetration of both glycopeptides ranged from poor (<15%) to satisfactory (15–30%) in the cortical compartment, while it was far higher into the highly vascularized cancellous tissue. Vancomycin bone penetration was slightly higher than with teicoplanin, but the difference was not statistically significant. Higher bone concentrations were observed with higher inflammatory markers, possibly as a result of increased vascularization and vascular permeability under inflammatory conditions. Bone concentrations over the MIC and AUC/MIC ratios suggested that both glycopeptides achieve a satisfactory pharmacokinetic exposure in the cancellous bone, as far as Gram-positive pathogens are concerned. On the other hand, cortical bone exposure was suboptimal in most patients. Furthermore, as antimicrobial penetration may be affected by impaired blood supply, the role of radical surgical removal of purulent and necrotic tissues appears to be essential in order to shorten treatment duration and to reduce the risk of treatment failure.

Clinical experience with linezolid in infants and children

The worldwide spread of multidrug-resistant organisms has required the development of new antimicrobials. Linezolid, the first oxazolidinone, has a broad spectrum of activity against Gram-positive bacteria, including resistant strains. Although approved by the Food and Drug Administration in 2002, the clinical experience with linezolid in the paediatric population is still limited, also given the fact that in most European countries the paediatric use of linezolid is off-label. In this paper we summarize the actual evidence on both licensed and off-label clinical uses of linezolid in children, including efficacy, safety and tolerability issues. Taking into account the potential bias in comparing heterogeneous clinical trials and reports, the available literature data suggest that linezolid is a safe and effective agent for the treatment of serious Gram-positive bacterial infections in neonates and children. At present, linezolid is reserved for those children who are intolerant to or fail conventional agents. A linezolid-containing regimen can be a valuable option for treating multidrug-resistant and extensively drug-resistant tuberculosis in children as well as disseminated non-tuberculous mycobacterial infections. Given the rare occurrence of serious side effects, careful monitoring of haematological parameters, possible drug interactions and neurological manifestations is recommended in linezolid-treated children, especially in case of prolonged treatments. Appropriate linezolid dosage and hospital infection control measures are essential to avoid the spread of linezolid resistance. Further studies are needed to establish novel paediatric indications for linezolid use and to assess the tolerability of long-term treatments.

Use of linezolid in infants and children: a retrospective multicentre study of the Italian Society for Paediatric Infectious Diseases

OBJECTIVES Because of the spread of drug-resistant Gram-positive bacteria, the use of linezolid for treating severe infections is increasing. However, clinical experience in the paediatric population is still limited. We undertook a multicentre study to analyse the use of linezolid in children. METHODS Hospitalized children treated with linezolid for a suspected or proven Gram-positive or mycobacterial infection were analysed retrospectively. Side effects were investigated, focusing on younger children and long-term treatments. RESULTS Seventy-five patients (mean age 6.8 years, range 7 days to 17 years) were studied. Mean ± SD linezolid treatment duration was 26.13 ± 17 days. Clinical cure was achieved in 74.7% of patients. The most frequent adverse events were diarrhoea and vomiting. Two patients had severe anaemia, two neutropenia and one thrombocytopenia. Two cases of grade 3 liver function test elevation and one case of pancreatitis were reported. The overall frequency of adverse events was similar between patients treated for >28 days and those receiving shorter treatments (30.8% versus 28.6%, P = 0.84). Children aged <2 years received linezolid for a shorter duration than older children (21.2 days versus 28.4 days, P = 0.05), whereas the frequency of adverse events was similar in the two age groups. CONCLUSIONS In our paediatric population, linezolid appeared safe and effective for the treatment of selected Gram-positive and mycobacterial infections. The adverse reactions encountered were reversible and appeared comparable to those reported in paediatric clinical trials. Nevertheless, the potential for haematological toxicity of linezolid in children means that careful monitoring is required during treatment.

Osteomyelitis Caused by Enterobacter cancerogenus Infection following a Traumatic Injury: Case Report and Review of the Literature

ABSTRACT We report a case of osteomyelitis caused by Enterobacter cancerogenus resistant to aminopenicillins in a 56-year-old male who had a motorcycle accident and suffered from multiple bone fractures with abundant environmental exposure. E. cancerogenus has rarely been associated with human infections, and its clinical significance remains unclear.

Performance of interferon-γ release assay for the diagnosis of active or latent tuberculosis in children in the first 2 years of age: a multicenter study of the Italian Society of Pediatric Infectious Diseases.

Background: The diagnosis of latent or active tuberculosis in children is often challenging. Recently, interferon-&ggr; release assays have been licensed, but their diagnostic accuracy in young children remains questionable as frequent false-negative or indeterminate results have been reported. Methods: We performed a multicenter, retrospective study in children 0–24 months of age who were tested at least once with QuantiFERON-TB Gold-in-tube (QTF-IT) ± tuberculin skin test (TST), to analyze its use and performance in clinical practice. Results: Eight-hundred and twenty-three children (449 males, median age 13.5 months) were enrolled. QTF-IT sensitivity and specificity for active tuberculosis were 92.4% and 98.6%, respectively. Indeterminate tests (4.2 %) were not related to age (P = 0.838) or gender (P = 0.223); 32 children (91.4 %) with an indeterminate QTF-IT ultimately resulted uninfected. In the 616 subjects with valid paired results of QTF-IT and TST, sensitivity and specificity were comparable (91.1% vs. 85.1% and 98.1% vs. 97.9%, respectively). Diagnostic concordance between tests was higher in Bacillus Calmétte-Guerin nonvaccinated children (&kgr; = 0.802). A high rate of discordant tests was observed in latent infections. Conclusions: QTF-IT showed good sensitivity and specificity, and a low rate of indeterminate results in the first 2 years of life, supporting its use at this age. However, considering costs and the similar performance between QTF-IT and TST, it is reasonable to suggest the latter as first-line testing in young children. The complementary use of TST and interferon-&ggr; release assays may be considered in selected cases to improve the accuracy of testing.