Francesco Scaglione

Characterization and Mapping of Melatonin Receptors in the Brain of Three Mammalian Species: Rabbit, Horse and Sheep

Melatonin receptors were characterized in the brains of three mammals (rabbit, horse and sheep) by an in vitro binding technique, using 2-[125I]iodomelatonin as labelled ligand. Although binding sites for melatonin have been described recently in several vertebrate species (including the sheep), the rabbit and the horse have not been the subject of investigation so far. Apart from characterization, the present report describes receptor distribution in a number of brain regions, thus allowing for direct interspecies comparison under the same methodological conditions. 2-[125I]iodomelatonin labelled high-affinity binding sites in crude membrane preparations from these species. A series of kinetic and saturation experiments revealed that the binding was rapid, stable, saturable, reversible, of high affinity (Kd in the low picomolar range) and low capacity (Bmax between 1 and 20 fmol/mg protein). The competition studies showed that the relative order of potency of a variety of indoles for inhibition of 2-[125I]iodomelatonin binding was as follows: 2-iodomelatonin greater than 6-chloromelatonin greater than melatonin much much greater than 5-methoxytryptophol greater than 5-methoxytryptamine, and that it was similar in the different brain regions. Prazosin, which has been reported as an extremely potent melatonin analog in the hamster brain, possessed no potency in all preparations from different regions in the three species under investigation. The regional distribution of the receptor showed insignificant species differences. Highest density was always recorded in the median eminence/pars tuberalis (ME/PT) area. Other regions (SCN, POA and certain cortical areas), showed lower, but significant, receptor content. Saturation and competition studies revealed that these binding sites were also of high affinity, low capacity and high specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

Clarithromycin Clinical Pharmacokinetics

SummaryClarithromycin is a semisynthetic macrolide antibiotic, structurally related to erythromycin. It has a more favourable pharmacokinetic profile than erythromycin, thus allowing twice-daily administration and possibly increasing compliance among outpatients.Clarithromycin is well absorbed from the gastrointestinal tract and its systemic bioavailability (about 55%) is reduced because of first-pass metabolism. It undergoes rapid biodegradation to produce the microbiologically active 14-hydroxy-(R)-metabolite. The maximum serum concentrations of clarithromycin and its 14-hydroxy metabolite, following single oral doses, are dose proportional and appear within 3 hours.With multiple doses, steady-state concentrations are attained after 5 doses and the maximal serum concentrations of clarithromycin and of the 14-hydroxy derivative appear within 2 hours after the last dose. Clarithromycin is well distributed throughout the body and achieves higher concentrations in tissues than in the blood. Also, the 14-hydroxy metabolite exhibits high tissue concentrations, with values about one-third of the parent compound concentrations. The presence of food appears to have no clinically significant effect on clarithromycin pharmacokinetics.The main metabolic pathways are oxidative N-demethylation and hydroxylation, which are saturable and result in nonlinear pharmacokinetics. The primary metabolite (14-hydroxy derivative) is mainly excreted in the urine with the parent compound.A reduction in urinary clearance in the elderly and in patients with renal impairment is associated with an increase in area under the plasma concentration-time curve, peak plasma concentrations and elimination half-life. Mild hepatic impairment does not significantly modify clarithromycin pharmacokinetics.In conclusion, clarithromycin, because of its antibacterial activity and pharmacokinetic properties, appears to be a useful alternative to other macrolides in the treatment of community acquired infections.

Pharmacokinetics/pharmacodynamics of antibacterials in the Intensive Care Unit: setting appropriate dosing regimens.

Patients admitted to Intensive Care Units (ICUs) are at very high risk of developing severe nosocomial infections. Consequently, antimicrobials are among the most important and commonly prescribed drugs in the management of these patients. Critically ill patients in ICUs include representatives of all age groups with a range of organ dysfunction related to severe acute illness that may complicate long-term illness. The range of organ dysfunction, together with drug interactions and other therapeutic interventions (e.g. haemodynamically active drugs and continuous renal replacement therapies), may strongly impact on antimicrobial pharmacokinetics in critically ill patients. In the last decade, it has become apparent that the intrinsic pharmacokinetic (PK) and pharmacodynamic (PD) properties are the major determinants of in vivo efficacy of antimicrobial agents. PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. In this review, we analyse the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach of the antimicrobial agent classes commonly utilised in the ICU setting.

Can PK/PD be used in everyday clinical practice

Over the last decade much insight has been gained in the relationships between dosing regimens of antimicrobials and bacterial eradication and clinical efficacy. These pharmacokinetic-pharmacodynamic (PK/PD) relationships have become available as tools in individualising antimicrobial therapy. To be able to do this, the PK parameters of the antimicrobial in the individual patient have to be known or estimated, and the MIC of the micro-organism causing the infection, known. In our hospital, we have started a programme using this approach. Preliminary results suggest that dose optimisation leads to increased efficacy and lower costs.

Panax ginseng C.A. Mayer G115 modulates pro-inflammatory cytokine production in mice throughout the increase of macrophage toll-like receptor 4 expression during physical stress

The effect of Panax ginseng C.A. Meyer G115 on inflammatory cytokine production and toll-like receptor 4 (TLR4) RNA expression was examined in mice during 4 weeks of swimming stress. Mice were assigned to four groups: (1) control (no exercise); (2) control-G115 (25 mg/kg/day p.o.); (3) stress (kept swimming for 60 min daily); and (4) stress-G115 (25 mg/kg/day p.o. and kept swimming for 60 min daily). Peritoneal macrophages were collected at rest each week. RNA was extracted and processed for real-time PCR. An aliquot of macrophages was lipopolysaccharide (LPS)-stimulated for TNF-alpha and IL-1beta production. Different expression patterns between untreated and treated groups, and between TLR2 and TLR4 were found. High levels of TLR4 expression in the control-G115 group were detectable significantly at the first, and at the second week (P<.01 and P<.001, respectively). In the stress group, TLR4 showed a peak at the first week (P<.001 vs. controls) and then decreased gradually. In the stress-G115 group, the levels of TLR4 expression increased gradually at the second week (P<.001 vs. controls) with a peak at the third week (P<.001). Levels of TLR4 expression at the fourth week had returned to the basal level. Levels of TLR2 expression were not affected by treatment in all groups. A significant increase of LPS-stimulated IL-1beta and TNF-alpha concentrations was present in trained animals with similar patterns of TLR4 expression. These results support the hypothesis that enhancement of the production of pro-inflammatory cytokine can be linked to an increased expression of TLR4 on macrophages. Moreover, G115 increases the expression of TLR4 and the release of cytokines with a different pattern compared to the stressed alone group.

Influence of pharmacokinetics/pharmacodynamics of antibacterials in their dosing regimen selection

The choice of antimicrobial dosing in clinical practice in the past was based upon a ‘penicillin mentality’, that is, on the assumption that the in vivo antimicrobial efficacy is dependent on the duration of drug levels above the minimum inhibitory concentration of target microorganisms. Really, a rational antimicrobial therapy is strongly related to a basic understanding of the influence the patient has on the antibiotic (pharmacokinetics [PKs]) and the patient’s response to the specific drug effects (pharmacodynamics [PDs]). PK/PD parameters are essential in facilitating the translation of microbiological activity into clinical situations, ensuring a successful outcome. This review will analyze the typical patterns of antimicrobial activity and the corresponding PK/PD parameters, with a special focus on a PK/PD dosing approach with the most commonly utilized antimicrobial agent classes.

Class-dependent relevance of tissue distribution in the interpretation of anti-infective pharmacokinetic/pharmacodynamic indices

The pharmacokinetic/pharmacodynamic (PK/PD) indices useful for predicting antimicrobial clinical efficacy are well established. The most common indices include the time free drug concentration in plasma is above the minimum inhibitory concentration (MIC) (fT(>MIC)) expressed as a percent of the dosing interval, the ratio of maximum concentration to MIC (C(max)/MIC), and the ratio of the area under the 24-h concentration-time curve to MIC (AUC(0-24)/MIC). A single PK/PD index may correlate well with an entire antimicrobial class. For example, the beta-lactams correlate well with the fT(>MIC). However, other classes may be more complex and a single index cannot be generalised to the class, e.g. the macrolides. The rationale behind which PK/PD index best correlates with efficacy depends on several factors, including the mechanism of action, the microbial kill kinetics, the degree of protein binding and the degree of tissue distribution. Studies have traditionally emphasised the first two factors, whilst the significance of protein binding and tissue distribution is increasingly appreciated. In fact, the latter two factors may partially elucidate why the magnitude of reported target indices are not always as expected. For example, tigecycline and telithromycin are clinically efficacious with average serum concentrations below their MICs over a 24-h period. Therefore, to understand more fully the PK/PD relationship of antibiotics and to better predict the clinical efficacy of antibiotic dosing regimens, assessment of free drug concentrations at the site of action is warranted.

Comparison of the Potency of Different Brands of Serenoa Repens Extract on 5α-Reductase Types I and II in Prostatic Co-Cultured Epithelial and Fibroblast Cells

Background:Serenoa repens extract is the phytotherapeutic agent most frequently used for the treatment of the urological symptoms caused by benign prostatic hyperplasia. There are many extracts in the market and each manufacturer uses different extraction processes; for this reason, it’s possible that one product is not equivalent to another. The aim of this study was to compare the activity of different extracts of Serenoa repens marketed in Italy. Methods: The following extracts were tested on 10 day co-cultured epithelial and fibroblast cells by a 5α-reductase activity assay: Permixon®, Saba®, Serpens®, Idiprost®, Prostamev®, Profluss® and Prostil®. In order to assess the variability in Serenoa repens products, 2 different batches for each brand were evaluated. Results and Conclusions: All extracts tested, albeit variably, are able to inhibit both isoforms of 5α-reductase. However, the potency of the extracts appears to be very different, as well as the potencies of 2 different batches of the same extract. This is probably due to qualitative and quantitative differences in the active ingredients. So, the product of each company must be tested to evaluate the clinical efficacy and bioactivity.

Pharmacokinetics and Tissue Distribution of Amoxicillin plus Clavulanic Acid after Oral Administration in Man

Augmentin (875 amoxicillin and 125 mg potassium clavulanate) was administered orally to patients with chronic bronchitis. Concentrations of amoxicillin and clavulanic acid were measured in serum, sputum and urine. Peak serum levels for amoxicillin of 11.23 +/- 2.61 micrograms/ml were observed at 2 hours and for clavulanic acid of 2.55 +/- 0.54 micrograms/ml at 1 hour. After 9 hours, 50% of the amoxicillin and 39% of the clavulanic acid had been renally excreted. The peak sputum concentration of amoxicillin was 1.31 +/- 0.42 micrograms/ml at 4 hours and of clavulanate was 0.79 +/- 0.23 micrograms/ml at 2 hours. Patients awaiting surgery received an oral dose of augmentin as above. Samples of lung, tonsil, middle ear mucosa and prostate were obtained and tissue concentrations of both compounds measured. Peak levels of amoxicillin ranged from 0.87 micrograms/g (tonsil) to 2.56 micrograms/g (lung) and of clavulanic acid from 0.20 micrograms/g (prostate) to 0.56 micrograms/g (lung) between 3 and 4 hours after dosing.

Transdermal apomorphine permeation from microemulsions: a new treatment in Parkinson's disease

We studied absorption, efficacy, and tolerability in Parkinsons disease (PD) of a new preparation of apomorphine included in a microemulsion and administered by transdermal route (Apo‐MTD). Twenty‐one PD patients were treated with levodopa plus oral dopamine‐agonists (T0), with levodopa alone (T1), finally with levodopa plus Apo‐MTD (T2). Apo‐MTD provided therapeutic plasma levels for many hours, improved Unified Parkinsons Disease Rating Scale III scores, and reduced total duration of off periods compared to T0 and T1. We concluded that Apo‐MTD is absorbed and demonstrates clinical efficacy and long action. Therefore, it seems a promising add‐on treatment for uncontrolled prolonged off phases in PD patients, but chronic tolerability needs further study.