Population Pharmacokinetics of Liposomal Amphotericin B in Immunocompromised Children

BACKGROUND Liposomal amphotericin B (LAmB) is widely used in the treatment of invasive fungal disease (IFD) in adults and children. There are relatively limited PK data to inform optimal dosing in children that achieves systemic drug exposures comparable to those of adults. OBJECTIVES To describe the pharmacokinetics of LAmB in children aged 1-17 years with suspected or documented IFD. METHODS Thirty-five children were treated with LAmB at dosages of 2.5-10 mg kg(-1) daily. Samples were taken at baseline and at 0.5-2.0 hourly intervals for twenty-four hours after receipt of the first dose (n=35 patients) and on the final day of therapy (n=25 patients). LAmB was measured using high performance liquid chromatography (HPLC). The relationship between drug exposure and development of toxicity was explored. RESULTS An evolution in PK was observed during the course of therapy resulting in a proportion of patients (n=13) having significantly higher maximum serum concentration (Cmax) and area under the concentration time curve (AUC0-24) later in the course of therapy, without evidence of drug accumulation (Cmin accumulation ratio, AR < 1.2). The fit of a 2-compartment model incorporating weight and an exponential decay function describing volume of distribution best described the data. There was a statistically significant relationship between mean AUC0-24 and probability of nephrotoxicity (OR 2.37; 95% CI 1.84-3.22, p=0.004). CONCLUSIONS LAmB exhibits nonlinear pharmacokinetics. A third of children appear to experience a time-dependent change in PK, which is not explained by weight, maturation or observed clinical factors

Pharmacokinetics of zidovudine administered intravenously and orally in children with human immunodeficiency virus infection

Zidovudine pharmacokinetics were determined in 16 children with human immunodeficiency virus infection who were being treated intravenously and orally on an intermittent schedule (every 6 hours). The intravenous doses studied were 80 (n=3), 120 (n=4), and 160 (n=5) mg/m 2/dose, infused over 1 hour. Fourteen patients were monifored after an oral dose of zidovudine at 120 (n=2), 180 (n=7), or 240 (n=5) mg/m 2/dose. Zidovudine was assayed with a reverse-phase high-pressure liquid chromatography method. Zidovudine disapperance after intravenous administration was rapid and blexponential, with half-lives of 14 and 90 minutes and a total clearance of 641±161 ml/min/m 2. The volume of distribution at steady state was 45±28 L/m 2. These pharmacokinetics parameters are very similar to those reported in adults. When administered orally, zidovudine was rapidly absorbed. The fraction of the oral dose that was bioavailable was 0.68±0.25, so that a 50% increment in the dose, in the conversion from intravenous to oral administration, resulted in plasma zidovudine concentrations after oral dosing that were nearly identical to those achieved with the 1-hour intravenous infusion. However, a dose of 180 mg/m 2 given orally every 6 hours maintained plasma zidovudine concentrations in the target range of 1 μmol/L for less than half of the dosing interval. Other schedules, routes of administration, or oral drug formulations may have to be considered if sustained continuous exposure to micromolar zidovudine concentrations is desired

Effect of Continuous Intravenous Infusion of Zidovudine (AZT) in Children with Symptomatic HIV Infection

To produce concentrations of zidovudine (AZT) in plasma and cerebrospinal fluid that would provide constant inhibition of the replication of human immunodeficiency virus (HIV), we gave AZT by continuous intravenous infusion to 21 children ranging in age from 14 months to 12 years who had acquired HIV infection through transfusions or perinatally. All patients were symptomatic before AZT treatment (Class P2 of the Centers for Disease Control); 13 (62 percent) had evidence of neurodevelopmental abnormalities. The mean CD4/CD8 ratio was 0.18; 11 patients had CD4 counts below 0.2 x 10(9) per liter. We administered AZT at four dose levels: 0.5, 0.9, 1.4, and 1.8 mg per kilogram of body weight per hour. The plasma drug concentrations achieved at the respective dose levels were 1.9 +/- 0.3, 2.8 +/- 1.4, 3.1 +/- 1.1, and 4.5 +/- 1.0 microM. The steady-state cerebrospinal fluid:plasma ratio was 0.24 +/- 0.07. The only evidence of toxicity was bone marrow suppression. Transfusion was required in 14 patients because of low levels of hemoglobin (5 mmol per liter [less than 8 g per deciliter]). Dose-limiting neutropenia (less than 0.5 x 10(9) polymorphonuclear leukocytes per cubic millimeter) occurred in most patients who received doses of 1.4 mg per kilogram per hour or more. Improvement in neurodevelopmental abnormalities occurred in all 13 children who had presented with encephalopathy before treatment. Serial measurements of IQ before therapy and after three and six months of continuous therapy with AZT showed that IQ scores, including those for verbal and performance IQ, rose in these 13 patients and in 5 other children who had no detectable evidence of encephalopathy before treatment. Most patients also had increased appetite and weight, decreased lymphadenopathy and hepatosplenomegaly, decreased immunoglobulin levels, and increased numbers of CD4 cells. In some patients the improvement in the features of encephalopathy occurred despite the absence of immunologic improvement. We conclude that AZT is beneficial in children with symptomatic HIV infection, especially those with encephalopathy (which may be subclinical), and that the optimal continuous intravenous dose of AZT in children is between 0.9 and 1.4 mg per kilogram per hour

Potential mediators of in ovo delivered double stranded (ds) RNA-induced innate response against low pathogenic avian influenza virus infection

Abstract Background Toll like receptor (TLR) 3 is a critically important innate pattern recognizing receptor that senses many viral infections. Although, it has been shown that double stranded (ds) RNA can be used for the stimulation of TLR3 signaling pathway in a number of host-viral infection models, it’s effectiveness as an antiviral agent against low pathogenic avian influenza virus (LPAIV) needs further investigation. Methods In this study, first, we delivered TLR3 ligand, dsRNA, in ovo at embryo day (ED)18 since in ovo route is routinely used for vaccination against poultry viral and parasitic infections and infected with H4N6 LPAIV 24-h post-treatment. A subset of in ovo dsRNA treated and control groups were observed for the expressions of TLR3 and type I interferon (IFN)s, mRNA expression of interleukin (IL)-1β and macrophage recruitment coinciding with the time of H4N6 LPAIV infection (24 h post-treatment). Additionally, Day 1 chickens were given dsRNA intra-tracheally along with a control group and a subset of chickens were infected with H4N6 LPAIV 24-h post-treatment whereas the rest of the animals were observed for macrophage and type 1 IFN responses coinciding with the time of viral infection. Results Our results demonstrate that the pre-hatch treatment of eggs with dsRNA reduces H4N6 replication in lungs. Further studies revealed that in ovo delivery of dsRNA increases TLR3 expression, type I IFN production and number of macrophages in addition to mRNA expression of IL-1β in lung 24-h post-treatment. The same level of induction of innate response was not evident in the spleen. Moreover, we discovered that dsRNA elicits antiviral response against LPAIV correlating with type I IFN activity in macrophages in vitro. Post-hatch, we found no difference in H4N6 LPAIV genome loads between dsRNA treated and control chickens although we observed higher macrophage recruitment and IFN-β response coinciding with the time of viral infection. Conclusions Our findings imply that the TLR3 ligand, dsRNA has antiviral activity in ovo and in vitro but not in chickens post-hatch and dsRNA-mediated innate host response is characterized by macrophage recruitment and expressions of TLR3 and type 1 IFNs