Population pharmacokinetics and probability of target attainment of meropenem in critically ill patients.

PURPOSE: Patients admitted to intensive care unit (ICU) with Klebsiella pneumoniae infections are characterized by high mortality. The aims of the present study were to investigate the population pharmacokinetics parameters and to assess the probability of target attainment of meropenem in critically ill patients to provide information for more effective regimens. METHODS: Twenty-seven consecutive patients were included in the study. Meropenem was administered as 3-h intravenous (i.v.) infusions at doses of 1-2 g every 8 or 12 h. Meropenem plasma concentrations were measured by a high-performance liquid chromatography (HPLC) method, and a population pharmacokinetics analysis was performed using NONMEM software. Meropenem plasma disposition was simulated for extended (3 h; 5 h) or continuous i.v. infusions, and the following parameters were calculated: time during which free drug concentrations were above minimum inhibitory concentration (MIC) (fT > MIC), free minimum plasma concentrations above 4× MIC (fCmin > 4× MIC), probability of target attainment (PTA), and cumulative fraction of response (CFR). RESULTS: Gender and severity of sepsis affected meropenem clearance, whose typical population values ranged from 6.22 up to 12.04 L/h (mean ± standard deviation (SD) value, 9.38 ± 4.47 L/h). Mean C min value was 7.90 ± 7.91 mg/L, suggesting a high interindividual variability. The simulation confirmed that 88 and 97.5 % of patients achieved effective C min > 4× MIC values after 3- and 5-h i.v. infusions of meropenem 2 g × 3/day, respectively. On the contrary, the same total daily doses reached the target C min > 4× MIC values in 100 % of patients when administered as continuous i.v. infusions. CONCLUSIONS: Several factors may influence meropenem pharmacokinetics in ICU patients. Continuous i.v. infusions of meropenem seem to be more effective than standard regimens to achieve optimal therapeutic targets.

HPLC determination of malondialdehyde as biomarker for oxidative stress: application in patients with alcohol dependence.

BACKGROUND: Chronic and excess ethanol exposure causes an increase in generation of free radicals which attack the polyunsaturated fatty acids in membranes to create lipid peroxides such as malondialdehyde (MDA) which is widely used as an indirect biomarker of oxidative stress. METHODS: In this study a sensitive and reproducible high performance liquid chromatography (HPLC) method for measurement of MDA was applied in a group of alcohol dependent patients who underwent detoxification treatment. RESULTS: Compared to the control group, mean MDA concentrations at baseline were significantly higher in alcohol dependent patients (1.28 +/- 0.58 microM vs. 0.9 +/- 0.21 microM; p < 0.02). However, MDA levels remained almost unchanged after three weeks of detoxification treatment (1.28 +/- 0.58 microM vs. 1.38 +/- 0.61 microM; p > 0.05). Among alcoholic patients, the MDA plasma concentration in smokers was higher than in non smokers both at baseline and after three weeks. CONCLUSIONS: The failure to reduce the levels of MDA after 3 weeks of detoxification treatment suggests that patients with chronic alcohol dependence have difficulty in compensating for alcohol-induced excessive production of free radicals. Furthermore, the possibility of cigarette smoke affecting the MDA plasma concentration cannot be ruled out.

Activation of a lateral hypothalamic-ventral tegmental circuit gates motivation.

Across species, motivated states such as food-seeking and consumption are essential for survival. The lateral hypothalamus (LH) is known to play a fundamental role in regulating feeding and reward-related behaviors. However, the contributions of neuronal subpopulations in the LH have not been thoroughly identified. Here we examine how lateral hypothalamic leptin receptor-expressing (LHLEPR) neurons, a subset of GABAergic cells, regulate motivation in mice. We find that LHLEPR neuronal activation significantly increases progressive ratio (PR) performance, while inhibition decreases responding. Moreover, we mapped LHLEPR axonal projections and demonstrated that they target the ventral tegmental area (VTA), form functional inhibitory synapses with non-dopaminergic VTA neurons, and their activation promotes motivation for food. Finally, we find that LHLEPR neurons also regulate motivation to obtain water, suggesting that they may play a generalized role in motivation. Together, these results identify LHLEPR neurons as modulators within a hypothalamic-ventral tegmental circuit that gates motivation.

Electrophysiological properties and projections of lateral hypothalamic parvalbumin positive neurons.

Cracking the cytoarchitectural organization, activity patterns, and neurotransmitter nature of genetically-distinct cell types in the lateral hypothalamus (LH) is fundamental to develop a mechanistic understanding of how activity dynamics within this brain region are generated and operate together through synaptic connections to regulate circuit function. However, the precise mechanisms through which LH circuits orchestrate such dynamics have remained elusive due to the heterogeneity of the intermingled and functionally distinct cell types in this brain region. Here we reveal that a cell type in the mouse LH identified by the expression of the calcium-binding protein parvalbumin (PVALB; LHPV) is fast-spiking, releases the excitatory neurotransmitter glutamate, and sends long range projections throughout the brain. Thus, our findings challenge long-standing concepts that define neurons with a fast-spiking phenotype as exclusively GABAergic. Furthermore, we provide for the first time a detailed characterization of the electrophysiological properties of these neurons. Our work identifies LHPV neurons as a novel functional component within the LH glutamatergic circuitry.

The acute effect of cannabis on plasma, liver and brain ammonia dynamics, a translational study.

Recent reports of ammonia released during cannabis smoking raise concerns about putative neurotoxic effects. Cannabis (54mg) was administered in a double-blind, placebo-controlled design to healthy cannabis users (n=15) either orally, or through smoking (6.9%THC cigarette) or inhalation of vaporized cannabis (Volcano®). Serial assay of plasma ammonia concentrations at 0, 2, 4, 6, 8, 10, 15, 30, and 90min from onset of cannabis administration showed significant time (P=0.016), and treatment (P=0.0004) effects with robust differences between placebo and edible at 30 (P=0.002), and 90min (P=0.007) and between placebo and vaporized (P=0.02) and smoking routes (P=0.01) at 90min. Furthermore, plasma ammonia positively correlated with blood THC concentrations (P=0.03). To test the hypothesis that this delayed increase in plasma ammonia originates from the brain we administered THC (3 and 10mg/kg) to mice and measured plasma, liver, and brain ammonia concentrations at 1, 3, 5 and 30min post-injection. Administration of THC to mice did not cause significant change in plasma ammonia concentrations within the first 5min, but significantly reduced striatal glutamine-synthetase (GS) activity (P=0.046) and increased striatal ammonia concentration (P=0.016). Furthermore, plasma THC correlated positively with striatal ammonia concentration (P<0.001) and negatively with striatal GS activity (P=0.030). At 30min, we found marked increase in striatal ammonia (P<0.0001) associated with significant increase in plasma ammonia (P=0.042) concentration. In conclusion, the results of these studies demonstrate that cannabis intake caused time and route-dependent increases in plasma ammonia concentrations in human cannabis users and reduced brain GS activity and increased brain and plasma ammonia concentrations in mice.

Measurement of sorafenib plasma concentration by high-performance liquid chromatography in patients with advanced hepatocellular carcinoma: is it useful the application in clinical practice? A pilot study.

Pharmacokinetics and dose-finding studies on sorafenib were conducted on heterogeneous groups of patients with solid tumors. Portal hypertension, gut motility impairment and altered bile enterohepatic circulation may explain different sorafenib toxicological profile in cirrhotic patients. This study evaluated sorafenib plasma concentration in a homogeneous group of cirrhotic patients with hepatocellular carcinoma (HCC). Sorafenib concentrations were determined by liquid chromatography in 12 consecutive patients. Data have been evaluated by the generalized estimating equations method (p value statistical level was set at α = 0.05). (1) There were not significant differences between sorafenib concentrations in patients who tolerate the full dose versus patients with reduced dose due to toxicity; (2) the average sorafenib concentrations measured 3 h after the morning dosing were lower than those measured 12 h after the evening dosing (p = 0.005); (3) sorafenib concentrations decrease overtime (p < 10(-4)); (4) it has been found an association between the development of severe adverse reactions and sorafenib concentrations (p < 10(-5)). The relationship between dose and concentration of sorafenib in HCC patients is poor and not clinically predictable, confirming the variability both in the maximum tolerated dose and in plasma concentrations. Several factors may influence the pharmacokinetics in patients with liver disease. This may explain the inter-patient variability of concentrations and the lack of differences in concentration at different dosages. It could be interesting to extend the series of HCC patients to enhance information on the kinetics of the drug; furthermore, to establish a threshold of plasma sorafenib concentrations to predict severe adverse reactions would be clinically useful.

Uncommon serum creatine phosphokinase and lactic dehydrogenase increase during diosmin therapy: two case reports.

INTRODUCTION: Short-term administration of diosmin is usually considered safe, with only minor side effects (stomach and abdominal pain, diarrhea, dermatological disorders, and headache) occasionally observed. Within a 4-year period, a general practitioner noticed 17 cases of mild, diosmin-induced side effects, two of which showed particular interest. CASES PRESENTATION: Case 1: A 55-year-old Caucasian woman presented with chronic leg venous insufficiency. She was prescribed diosmin 450 mg twice a day. After 5 days of therapy, she developed pain in the legs (myalgia), and diosmin therapy was suspended. She made a spontaneous attempt of drug rechallenge and her leg pain reappeared. Thus, she underwent blood analysis, which showed elevation of creatine phosphokinase levels. Creatine phosphokinase values normalized only after prolonged discontinuation of the therapy. Case 2: A 79-year-old Caucasian man, who was diagnosed with acute hemorrhoidal syndrome. After 21 days of continuous diosmin treatment, increased levels of serum lactic dehydrogenase were detected. In both cases a comprehensive analysis of all possible causes for enzyme elevation was made. CONCLUSIONS: A feasible hypothesis to explain these rare effects could be that exaggerated adrenergic activity occurred on microcirculation, leading to an excessive peripheral vasoconstriction and subsequent ischemic damage. An individual predisposition is strongly suggested. A concurrence of events was probably responsible for the elevation of nonspecific tissue necrosis markers. Physicians and patients must be aware of these rare, but possible, adverse drug reactions.

Involvement of the mu-opioid receptor gene polymorphism A118G in the efficacy of detoxification of alcohol dependent patients.

INTRODUCTION: The A118G (rs 1799971) polymorphism in the mu-opioid receptor gene (OPRM1) has been reported to be associated with alcohol addiction. METHODS: In this study 109 patients diagnosed with alcohol dependence in accordance with DMS-IV criteria and 95 healthy subjects were enrolled and everyone has been genotyped. RESULTS: The percentage of alcoholic patients with higher than normal gamma-glutamyl transferase (GGT) levels significantly decreased after six months of standard detoxification treatment, both in patients with A/A genotype and in the other ones with A/G genotype. However, the percentage of alcohol dependent patients with the A/A genotype recorded a slight decrease of the GGT and the mean corpuscolar volume of erythrocytes (MCV) combination marker after six months of therapy (30% vs 12%), while subjects with the A/G genotype showed no variation. CONCLUSION: This finding suggests that alcohol dependent patients with the A/A genotype could have a faster restoration of their liver function than those ones with the A/G genotype: it might be possible that the presence of G allele confers on these patients a reduced ability in abstaining from drinking alcohol.