Pharmacokinetic monitoring during aminoglycosides: optimal therapy method of individual amikacin dosing]

One of the most successful approaches to adjustment of dosage regimens on the basis of single determinations of drug contents in blood specimens provides the blood sampling at the "ideal" moment (t*), i. e. at the time equal to the inverse value of the elimination rate constant. The above version of the one-point method is applicable to drugs obeying the one-compartment model. In practice, however, it is never known a priori whether the individual pharmacokinetic profile (PKP) is monoexponential or not. An attempt was made to apply the one-point method to individual amikacin (Am) intravenous bolus dosing in 27 patients with PKPs described not only by mono- but also by biexponential equations. The individual doses (Dc) estimated on the basis of Am concentrations recorded at the "ideal", point (2.75 hours after the administration) by the equation Dc = Dp.Cp(t*)/Ci(t*) were compared to the doses (DCl) found on the basis of greater than or equal to 4 determinations of the Am concentration (within 0.5 to 6 hours after the administration), i. e. by the equation DCl = Dp.Cli/Clp, where: Dp is the population value of an Am dose (7.5 mg/kg); Cp (t*) is the population value of an Am concentration at t* (6.7 mg/l), Clp is that of the total clearance [81.2 ml/(h.kg)] and Ci (t*) and Cli are the individual values of an Am concentration and clearance, respectively. The correlation coefficient of the DCl vs. Dc estimates was equal to 0.87. In 17 patients with monoexponential PKPs it was higher (r = 0.99).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetic monitoring during aminoglycoside treatment: the optimal method for individualizing the dosage of tobramycin

The results of tobramycin concentration monitoring in 33 patients with nonspecific pulmonary infections showed a marked individual variability of the antibiotic blood levels and model-independent pharmacokinetic parameters: total clearance, steady-state volume of distribution and mean residence time whose values were distributed log-normally. Adjusting of the tobramycin dosage by the individual values of the clearance (three-point method, by concentrations 1 h (C1), 3 h (C3) and 6 h (C6), after intramuscular single administration of the antibiotic and one-point method, by C3, after repeated administrations of the antibiotic) provided by the end of a 7-day course a 1.7-fold decrease in the individual ranges of the antibiotic concentration as compared to those without the dosage adjusting. Retrospective analysis revealed that reliable individual dosing of tobramycin was provided with the simplest one-point method when the only blood specimen was collected 3 hours after the injection, i.e. the time interval inversed to the elimination rate constant. According to this method individual doses Dind were calculated by the equation Dind = DpopCpop/Cind, where pop was the population value of D and C. The values of Dind estimated in such a way did not practically differ from those estimated with the more complicated two-point (by C1 and C6) and three-point methods. Application of the equation to the tobramycin "maximum" concentration C1 or the "minimum" one (toward the end of the dosing interval, C6) resulted in less accurate and unbiased estimation of Dind.     

Efficacy of mycobacterial components in the immunotherapy of mice with pulmonary tumor deposits

Summary The effectiveness of each of two mycobacterial components and a synthetic analog of one of them in the eradication of pulmonary deposits of intravenously injected syngeneic fibrosarcoma 1023 in C3H mice was studied. BCG cell walls (BCG CW), trehalose 6,6-dimycolate (TDM) or 6,6-di-0-2-tetradecyl, 3-hydroxyoctadecanoyl-,-trehalose (C76), a synthetic analog of TDM, was administered in emulsified form by three different routes: intraperitoneal, intradermal, or intravenous, 24 h after intravenous injection of 1023 tumor cells. The most effective form of therapy was TDM given by the intraperitoneal route; about 50% of treated animals were cured. Higher doses of BCG CW or C76 also led to a significant number of cures. Each agent caused a significant prolongation of survival time of the treated mice at two or more of the dosages tested; however, their routes of optimal activity varied.     

Mouse cachexia induced by trehalose dimycolate from Nocardia asteroides

Trehalose dimycolate (TDM) isolated from Nocardia asteroides induced in mice a severely wasted condition known as cachexia. Intraperitoneal injection of mice with five 10 micrograms doses of TDM in mineral oil at intervals of 2 d killed 90% of the animals within 26 d. Death followed a precipitous weight loss and an inflammatory process in the peritoneal cavity. When mice were injected intraperitoneally with a single 10 micrograms dose of TDM, 48 h later, they had begun to lose weight and exhibited extreme hypertriglyceridaemia and hypoglycaemia. Tumour necrosis factor (or cachectin) was detected in the plasma from animals injected with TDM. This cytokine released by mononuclear phagocytes may be involved in the induction of cachexia by TDM.     

Trehalose dimycolate enhances survival of fission neutron-irradiated mice and Klebsiella pneumoniae-challenged irradiated mice

The survival of B6D2F1 female mice exposed to lethal doses of fission neutron radiation is increased when trehalose dimycolate (TDM) preparations are given either 1 h after exposure or 1 day before exposure to radiation. TDM in an emulsion of squalene, Tween 80, and saline was the most effective formulation for increasing the 30-day survival of mice when given 1 day before (90%) or 1 h after (88%) exposure to radiation. An aqueous suspension of a synthetic analog of TDM was less effective at increasing 30-day survival (60%) when given 1 day prior to radiation exposure and not effective when given 1 h after radiation. Mice receiving a sublethal dose (3.5 Gy) of fission neutron radiation and either the TDM emulsion or synthetic TDM 1 h after irradiation were substantially more resistant to challenge with 10, 100, 1000, or 5000 times the LD50/30 dose of Klebsiella pneumoniae than untreated mice.     

Vth Latin American Symposium of Chronobiology Guest Editorial

Abstract

Use of intermittent white noise (60 and 70 dB) as an additional synchronizer in the light period (12 h) gave a rise in the level of mitotic index and moved the maximal values 1 to 3 h forward in time. The effects increased with the sound level. Unskilled handling of the animals in itself could produce a significant decrease in mitotic index. Independent of the various external conditions injection of ‘HTdR (1 /μCi/g body weight; 6 Ci/m mol) increased the mitotic index during the first hours after injection.     

Time course and cellular site of mitotic activity in the exocrine pancreas of the rat during sustained hormone stimulation

Summary Previous studies from our laboratory indicate that the adaptive response of the exocrine pancreas of the rat to prolonged stimulation with optimal doses of caerulein (0.25 g × kg^-1 × h^-1) follows a characteristic time course in which each step in the secretory pathway is activated. The immediate response is the depletion of zymogen-granule stores followed by coordinate and anticoordinate changes in individual rates of (pro-)enzyme synthesis after a lag period of 2 h. The sum of such changes leads to an increase in total rate of protein synthesis by 3 h which is combined with acceleration of intracellular transport packaging and granule discharge. In the present study the time course of DNA synthesis and the labeling index of five populations of pancreatic cells have been analyzed after caerulein stimulation for periods ranging from 6 to 72 h, using in vivo labeling with 1 Ci/g ³H-thymidine 1 h prior to sacrifice of the animals. DNA synthesis did not change during the initial 18 h in spite of persistent stimulation indicated by a 80% reduction of enzyme content. Following this lag period a sharp rise in DNA synthesis 20- to 25-fold above control levels was observed, which decreased by 48 h to reach control levels by 72 h. Increase in DNA synthesis was most pronounced in animals with lowest enzyme content in the pancreas. From the five cell populations studied by autoradiography interlobular duct cells and islet cells had no significant increase in labeling index at any time of stimulation. Acinar cells, intralobular duct cells and interstitial cells showed a marked increase in labeling index after a latent period of 18 h with peak values at 36 h 30 to 50 times higher in intralobular duct and acinar cells, respectively, and 4 times higher in interstitial cells. The increased labeling indices in all three cell populations reverted to lower values at 48 h and reached control values by 72 h. The data indicate a phasic and limited growth response of the rat exocrine pancreas to persistent stimulation with acinar cells as the major contributing cell population.Supported by a grant from Deutsche Forschungsgemeinschaft (SFB215-C 3)     

Voriconazole and posaconazole therapeutic drug monitoring: a retrospective study

Background

Therapeutic drug monitoring (TDM) aims to minimize the clinical impact of posaconazole and voriconazole pharmacokinetic variability. However, its benefits on clinical outcomes are still being defined. Additionally, TDM data are limited for posaconazole IV and delayed-release tablet formulations among specific patient populations, including critically ill. The aim of this study was to determine the percentage of therapeutic posaconazole and voriconazole drug levels across all formulations in a real-world clinical setting and elucidate factors affecting attainment of target concentrations.

Methods

This study was a retrospective cohort study conducted at the University of Colorado Hospital between September 2006 and June 2015 that evaluated patients who received posaconazole or voriconazole TDM as part of routine care.

Results

Voriconazole (n = 250) and posaconazole (n = 100) levels were analyzed from 151 patients. Of these, 54% of voriconazole and 69% of posaconazole levels were therapeutic. For posaconazole, 14/38 (37%), 28/29 (97%) and 27/33 (82%) levels were therapeutic for the oral suspension, IV, and delayed-release tablet, respectively. Intravenous and delayed-release tablet posaconazole were 20 fold (p < 0.01) and sevenfold (p = 0.002) more likely than the oral suspension to achieve a therapeutic level. Subsequent levels were more likely to be therapeutic after dose adjustments (OR 3.31; 95% CI 1.3–8.6; p = 0.02), regardless of timing of initial non-therapeutic level. In a multivariable logistic regression analysis, no characteristics were independently predictive of therapeutic voriconazole levels and only absence of H2RA/PPI use was independently predictive of therapeutic posaconazole levels. There was no correlation between survival and therapeutic drug levels for either voriconazole (p = 0.67) or posaconazole (p = 0.50).

Conclusions

A high percentage of drug levels did not achieve TDM targets for voriconazole and posaconazole oral suspension, supporting the need for routine TDM for those formulations. The utility of TDM for the IV and delayed-release tablet formulations of posaconazole is less apparent.

     

Benefits of Therapeutic Drug Monitoring of Vancomycin: A Systematic Review and Meta-Analysis

Background and Objective

The necessity of therapeutic drug monitoring (TDM) for vancomycin is controversial. The objective of the current review was to evaluate the available evidence for the necessity of TDM in patients given vancomycin to treat Gram-positive infections.

Methods

Medline, Embase, Web of Sciences, the Cochrane Library and two Chinese literature databases (CNKI, CBM) were searched. Randomized controlled studies and observational studies that compared the clinical outcomes of TDM groups vs. non-TDM groups were included. Two reviewers independently extracted the data. The primary outcome was clinical efficacy of therapy. Secondary outcomes included vancomycin associated nephrotoxicity, duration of vancomycin therapy, length of hospital stay, and mortality. Meta-analysis was performed using the Mantel-Haenszel fixed effect method (FEM). Odds ratios (ORs) or weighted mean differences (WMD) with 95% confidence intervals (95%CIs) were calculated for categorical and continuous outcomes, respectively.

Results

One randomized controlled trial (RCT) and five cohort studies were included in the meta-analysis. Compared with non-TDM groups, TDM groups had significantly higher rates of clinical efficacy (OR = 2.62, 95%CI 1.34–5.11 P = 0.005) and decreased rates of nephrotoxicity (OR = 0.25, 95%CI 0.13–0.48 P<0.0001). Subgroup analyses showed that TDM group had significantly higher rates of clinical efficacy in both cohort studies subgroup (OR = 3.04, 95%CI 1.34–6.90) and in Asian population subgroup (OR = 3.04, 95%CI 1.34–6.90). TDM group had significantly decreased rates of nephrotoxicity in all subgroup. There was no significant difference in duration of vancomycin therapy (WMD = −0.40, 95%CI −2.83–2.02 P = 0.74) or length of stay (WMD = −1.01, 95%CI −7.51-5.49 P = 0.76) between TDM and non-TDM groups. Subgroup analyses showed there were no differences in duration of vancomycin therapy. Only one study reported mortality rates.

Conclusions

Studies to date show that TDM significantly increases the rate of clinical efficacy and decreases the rate of nephrotoxicity in patients treated with vancomycin.     

Control of the carcinogenic potential of 99mTechnetium by the immunologic hormone lymphotoxin

Summary Immunologic prevention of the carcinogenicity of the diagnostic gamma-emitting radionuclide ^99mTechnetium (^99mTc) by lymphotoxin was evaluated using an in vivo-in vitro assay of carcinogenesis. Pregnant Syrian golden hamsters received 125–2,300 Ci ^99mTc/kg body weight by injection, and 7 days later colonies of morphologically transformed cells were quantitated in vitro. The transformation frequency increased directly with the radionuclide concentration, and cells derived from transformed colonies produced tumors in athymic nude mice. The total absorbed ^99mTc dose was 0.20 rad following injection of 250 Ci ^99mTc/kg hamster body weight; this compares with an exposure of 0.13 rad following injection of 143 Ci ^99mTc/kg body weight in humans. Intravenous injection of purified hamster lymphotoxin immediately after ^99mTc caused a dose-dependent reduction in the transformation frequency. Transformation was essentially completely prevented (97%) by injection of 8,000 U of lymphotoxin. Thus, the immune system, through the action of lymphotoxin, has the potential to prevent carcinogenesis induced by gamma-radiation from ^99mTc. This emphasizes the importance of considering the recipient's immune and other homeostatic mechanisms as part of a complete diagnostic or therapeutic gamma-radiation regimen.     

Prediction of the pharmacokinetic parameters of triptolide in rats based on endogenous molecules in pre-dose baseline serum

Background

Individual variances usually affect drug metabolism and disposition, and hence result in either ineffectiveness or toxicity of a drug. In addition to genetic polymorphism, the multiple confounding factors of lifestyles, such as dietary preferences, contribute partially to individual variances. However, the difficulty of quantifying individual diversity greatly challenges the realization of individualized drug therapy. This study aims at quantitative evaluating the association between individual variances and the pharmacokinetics.

Methodology/Principal Findings

Molecules in pre-dose baseline serum were profiled using gas chromatography mass spectrometry to represent the individual variances of the model rats provided with high fat diets (HFD), routine chows and calorie restricted (CR) chows. Triptolide and its metabolites were determined using high performance liquid chromatography mass spectrometry. Metabonomic and pharmacokinetic data revealed that rats treated with the varied diets had distinctly different metabolic patterns and showed differential C_max values, AUC and drug metabolism after oral administration of triptolide. Rats with fatty chows had the lowest C_max and AUC values and the highest percentage of triptolide metabolic transformation, while rats with CR chows had the highest C_max and AUC values and the least percentage of triptolide transformation. Multivariate linear regression revealed that in baseline serum, the concentrations of creatinine and glutamic acid, which is the precursor of GSH, were linearly negatively correlated to C_max and AUC values. The glutamic acid and creatinine in baseline serum were suggested as the potential markers to represent individual diversity and as predictors of the disposal and pharmacokinetics of triptolide.

Conclusions/Significance

These results highlight the robust potential of metabonomics in characterizing individual variances and identifying relevant markers that have the potential to facilitate individualized drug therapy.     

Individualization of the amikacin administration regimen on the basis of the relationship between its pharmacokinetics and the patient's status

Dosage individualization based on quantitative relationships between pharmacokinetic parameters and anatomophysiological and/or pathological factors, patient's factors (PFs) is of importance in designing optimal regimens. Unfortunately, the attempts to correlate aminoglycoside pharmacokinetic parameters and PFs often failed perhaps due to insufficient numbers of PFs under investigation. That is why we sought to involve more PFs, especially nontraditional ones, for explaining intersubject variability of the amikacin model-independent parameter in 20 patients with purulent inflammatory processes. Amikacin plasma concentrations in specimens collected 0.5, 1, 2, 4, 5 and 6 hours after the drug administration (500 mg, i.v.) were determined with the FRIA-technique (TDx, Abbott). The mean values of the total clearance (Cl), steady-state volume of distribution (Vss) and the mean residence time (MRT) were 87.5 +/- 18.4 ml/(h.kg), 0.33 +/- 0.07 l/kg and 4.0 +/- 0.6 h, respectively. Stepwise multivariate regression analysis made it possible to establish statistically significant correlations between the Cl and 8 PFs, including age, sodium plasma concentrations, plasma osmolarity, partial pressure of oxygen and carbon dioxide, volumes of transfused plasma and blood and artificial pulmonary ventilation (r = 0.99), as well as between the MRT and 6 PFs, including sex, plasma osmolarity, plasma creatinine concentrations, volumes of transfused plasma and artificial pulmonary ventilation (r = 0.94). Multiple correlations were also found between the area under the drug concentration/time curve and 11 PFs (r = 0.99). The coefficient of the multiple correlation between the Vss and volume of the transfused plasma proved to be much lower (r = 0.67). The multiple regression equation for the Cl prediction provided a reliable indirect estimation of the parameter individual values without the amikacin concentration data. Thus, it appeared possible to adjust the aminoglycoside dosage by taking into account 8 PFs before the TDM data were available.     

Glyphosate affects chlorophyll,photosynthesis and water use of four Intacta RR2 soybean cultivars

The planting of RR2 Intacta soybeans by farmers has been expanding strongly. However, some visual injuries have been noted after glyphosate application. The aim of this study was to evaluate the influence of glyphosate application on chlorophyll, photosynthesis and water use of four Intacta RR2 soybean cultivars. The experiment was conducted in a greenhouse, in a randomized block design with a 3 × 4 factorial scheme, consisting of three glyphosate rates and four soybean cultivars. The glyphosate formula used was isopropylamine salt + potassium salt. The parameters analyzed were phytotoxicity at 7, 14, 21 and 28 days after application, and total chlorophyll index at 0, 3, 7, 14, 21, 28, 35, 42 and 49 days after application. Furthermore, 40 days after application, the net CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (G), and internal CO₂ concentration (Ci) were evaluated as well. The water-use efficiency (WUE) and carboxylation efficiency were calculated. The data were submitted to analysis of variance and compared by the Tukey’s test (p ≤ 0.05), followed by regression analysis. The phytotoxicity influence could be seen until 21 days after application, in which Monsoy 6210 IPRO cultivar was the most injured. The increasing doses promoted a reduction of the chlorophyll level up to 35 days after application in Monsoy 6410 IPRO. The cultivars tested here showed similar chlorophyll index values. On the 3rd, 7th and 14th DAA (Fig. 5a–c), there was a significant linear decline in the chlorophyll index with rising glyphosate dose for all four cultivars. The chlorophyll index cultivars were not influenced by the doses on the 42nd and 49th DAA. There was no difference in water use and carboxylation efficiency. The parameters A, E and A/Ci showed a positive correlation as the doses increased, while Ci declined, in both cultivars. The application of glyphosate on these soybean cultivars causes different injuries according to the sensitivity. In general, RR2 soybeans have the ability to recover from visual intoxication injuries and reestablish the normal chlorophyll production and photosynthetic parameters after glyphosate application.     

Autoradiograhic localization of the opiate receptor in rat brain.

One hour after injection of the potent opiate antagonist ³H-diprenorphine (125 μCi, 13 Ci/mmole) 75–85% of the drug is associated with opiate receptor sites. Autoradiography of fresh frozen unfixed brain has been carried out to visualize receptor distribution. Dense clusters of autoradiographic grains are highly localized in the caudate-putamen, locus coeruleus, zona compacta of the substantia nigra and the substantia gelatinosa.     

Superior preclinical efficacy of gemcitabine developed as chitosan nanoparticulate system

Gemcitabine, an anticancer nucleoside analogue, undergoes rapid enzymatic degradation following intravenous injection. This necessitates the administration of a high order of doses to observe a required therapeutic response, while such high doses result in significant side effects. To improve the intravenous delivery of gemcitabine and simultaneously enhance its antitumor activity, we have investigated its incorporation into a drug nanoplatform based on the biodegradable polymer chitosan. Two gemcitabine loading methods have been investigated: (i) entrapment into the polymeric network (entrapment procedure): drug incorporation prior to the coacervation process that leads to the formation of gemcitabine-loaded chitosan (GemChit) nanoparticles; and (ii) surface deposition onto already formed chitosan nanoparticles after incubation in gemcitabine solution (adsorption procedure). The former method produced much higher gemcitabine loading values and a sustained release profile. The main factors determining the gemcitabine loading and release kinetic have also been analyzed. Following intravenous injection, the GemChit formulation displayed a significantly improved antitumor activity comparatively to free gemcitabine, which was further confirmed by histology and immunohistochemistry studies, suggesting the potential of this chitosan-based gemcitabine nanomedicine for the effective treatment of tumors.     

Turnover rate of molecular species of sphingomyelin in rat brain

Turnover rate of individual molecular species of sphingomyelin of adult rat brain myelin and microsomal membranes was determined after an intracerebral injection of 100 Ci of [C³H₃]choline. Myelin and microsomal membrane sphingomyelins were isolated from the rest of the lipids. The individual molecular species of benzoylated sphingomyelin were separated and quantitated by reversed-phase high performance liquid chromatography. All individual major molecular species of microsomal and myelin sphingomyelin had maximum incorporation at 6 and 15 days, respectively, after the injection. The specific radioactivity of all the various molecular species of both myelin and microsomal sphingomyelin declined at a similar rate after reaching a maximum. There was no significant difference in the turnover rate of short chain (16:0, 18:0) and long chain (>22:0) fatty acid containing sphingomyelin. The average apparent turnover rate of myelin and microsomal sphingomyelin molecular species was about 14–16 days for the fast pool and about 45 days for the slow pool. It is concluded that individual molecular species of sphingomyelin of myelin and microsomal membranes turned over at a similar rate. Thus, turnover rate of sphingomyelin in myelin and microsomal membranes is not affected by the fatty acyl composition of the lipid.     

Role of Mental Retardation-Associated Dystrophin-Gene Product Dp71 in Excitatory Synapse Organization,Synaptic Plasticity and Behavioral Functions

Background

Duchenne muscular dystrophy (DMD) is caused by deficient expression of the cytoskeletal protein, dystrophin. One third of DMD patients also have mental retardation (MR), likely due to mutations preventing expression of dystrophin and other brain products of the DMD gene expressed from distinct internal promoters. Loss of Dp71, the major DMD-gene product in brain, is thought to contribute to the severity of MR; however, the specific function of Dp71 is poorly understood.

Methodology/Principal Findings

Complementary approaches were used to explore the role of Dp71 in neuronal function and identify mechanisms by which Dp71 loss may impair neuronal and cognitive functions. Besides the normal expression of Dp71 in a subpopulation of astrocytes, we found that a pool of Dp71 colocalizes with synaptic proteins in cultured neurons and is expressed in synaptic subcellular fractions in adult brains. We report that Dp71-associated protein complexes interact with specialized modular scaffolds of proteins that cluster glutamate receptors and organize signaling in postsynaptic densities. We then undertook the first functional examination of the brain and cognitive alterations in the Dp71-null mice. We found that these mice display abnormal synapse organization and maturation in vitro, altered synapse density in the adult brain, enhanced glutamatergic transmission and reduced synaptic plasticity in CA1 hippocampus. Dp71-null mice show selective behavioral disturbances characterized by reduced exploratory and novelty-seeking behavior, mild retention deficits in inhibitory avoidance, and impairments in spatial learning and memory.

Conclusions/Significance

Results suggest that Dp71 expression in neurons play a regulatory role in glutamatergic synapse organization and function, which provides a new mechanism by which inactivation of Dp71 in association with that of other DMD-gene products may lead to increased severity of MR.