Mean Plasma Elimination Half-life Research Articles

Evaluation of Physicochemical Properties, Pharmacokinetics, Biodistribution, Toxicity, and Contrast-Enhanced Cancer MRI of a Cancer-Targeting Contrast Agent, MT218.

ObjectivesPreclinical assessments were performed according to the US Food and Drug Administration guidelines to determine the physicochemical properties, pharmacokinetics, clearance, safety, and tumor-specific magnetic resonance (MR) imaging of MT218, a peptidic gadolinium-based MR imaging agent targeting to extradomain B fibronectin for MR molecular imaging of aggressive tumors.Materials and MethodsRelaxivity, chelation stability, binding affinity, safety-related target profiling, and effects on CYP450 enzymes and transporters were evaluated in vitro. Magnetic resonance imaging was performed with rats bearing prostate cancer xenografts, immunocompetent mice bearing murine pancreatic cancer allografts, and mice bearing lung cancer xenografts at different doses of MT218. Pharmacological effects on cardiovascular, respiratory, and central nervous systems were determined in rats and conscious beagle dogs. Pharmacokinetics were tested in rats and dogs. Biodistribution and excretion were studied in rats. Single and repeated dosing toxicity was evaluated in rats and dogs. In vitro and in vivo genotoxicity, in vitro hemolysis, and anaphylactic reactivity were also performed.ResultsAt 1.4 T, the r1 and r2 relaxivities of MT218 were 5.43 and 7.40 mM−1 s−1 in pure water, 6.58 and 8.87 mM−1 s−1 in phosphate-buffered saline, and 6.54 and 8.70 mM−1 s−1 in aqueous solution of human serum albumin, respectively. The binding affinity of MT218 to extradomain B fragment is 3.45 μM. MT218 exhibited no dissociation of the Gd(III) chelates under physiological conditions. The peptide degradation half-life (t1/2) of MT218 was 1.63, 5.85, and 2.63 hours in rat, dog, and human plasma, respectively. It had little effect on CYP450 enzymes and transporters. MT218 produced up to 7-fold increase of contrast-to-noise ratios in the extradomain B fibronectin–rich tumors with a dose of 0.04 mmol/kg for at least 30 minutes. MT218 had little pharmacological effect on central nervous, cardiovascular, or respiratory systems. MT218 had a mean plasma elimination half-life (t1/2) of 0.31 and 0.89 hours in rats and dogs at 0.1 mmol/kg, respectively. No detectable Gd deposition was observed in the brain at 6 hours postinjection of MT218 at 0.1 mmol/kg in rats. MT218 was not mutagenic and had no mortality or morbidity in the rats or dogs up to 1.39 and 0.70 mmol/kg/d, respectively. The no observed adverse effect level of MT218 in Sprague-Dawley rats was 1.39 mmol/kg for single dosing and 0.46 mmol/kg/d for repeated dosing. The no observed adverse effect level in dogs was 0.07 mmol/kg/d. MT218 exhibited no genotoxicity, hemolysis, and anaphylactic reactivity.ConclusionThe preclinical assessments showed that the targeted contrast agent MT218 has high r1 and r2 relaxivities, satisfactory physicochemical properties, pharmacokinetic, and safety profiles and produces effective tumor enhancement in multiple cancer types in rats and mice at reduced doses.

Consumption of macrolides, lincosamides and streptogramins in the community, European Union/European Economic Area, 1997-2017.

ObjectivesData on the consumption of macrolides, lincosamides and streptogramins (MLS) in the community were collected from 30 EU/European Economic Area (EEA) countries over two decades. This article reviews temporal trends, seasonal variation, presence of change-points and changes in composition of the main subgroups of MLS.MethodsFor the period 1997–2017, data on consumption of MLS, i.e. ATC group J01F, in the community and aggregated at the level of the active substance, were collected using the WHO ATC/DDD methodology (ATC/DDD index 2019). Consumption was expressed in DDD per 1000 inhabitants per day and in packages per 1000 inhabitants per day. Consumption of MLS was analysed and presented as trends, seasonal variation, presence of change-points and compositional changes, using a classification based on mean plasma elimination half-life for macrolides.ResultsIn 2017, consumption of MLS in the community expressed in DDD per 1000 inhabitants per day varied by a factor of 13 between countries with the highest (Greece) and the lowest (Sweden) consumption. Consumption of MLS did not change significantly up to 2003, after which it significantly increased up to 2007. No significant change was observed after 2007. Consumption of MLS showed high seasonal variation. The proportional consumption of long-acting macrolides significantly increased over time compared with that of intermediate-acting macrolides, and proportional consumption of the latter increased compared with that of short-acting macrolides.ConclusionsConsumption of MLS did not change significantly over time during 2007–2017, while the proportional consumption of long-acting macrolides increased. Seasonal variation remained high, which suggests that MLS are still prescribed inappropriately in many countries.

Comparative Safety, Bioavailability, and Pharmacokinetics of Oral Dexamethasone, 4-mg and 20-mg Tablets, in Healthy Volunteers Under Fasting and Fed Conditions: A Randomized Open-label, 3-way Crossover Study

BackgroundGlucocorticoids, particularly dexamethasone, are often used in combination with novel agents in multiple myeloma. This study compared the safety, rate, and extent of absorption of a single dose of an orally administered 20-mg dexamethasone tablet to five 4-mg tablets (total, 20 mg). Patients and MethodsThis was a single-center, open-label, randomized, 3-way crossover comparative study. Thirty-six volunteers received at least 1 dose of either a single 20-mg dexamethasone tablet, under fasting or fed conditions, or five 4-mg dexamethasone tablets (total, 20 mg). Blood samples were collected before study drug administration and at 21 time points for up to 36 hours after drug administration. ResultsMean area under the concentration-time curve from time zero to the time of last non-zero concentration (AUC0–t), mean area under the concentration-time curve from time zero to infinity (extrapolated) (AUC0–∞), and maximum observed concentration (Cmax) were 1314.38 ng × h/mL, 1329.24 ng × h/mL, and 257.22 ng/mL, respectively for fasting test formulation (single dexamethasone 20-mg tablet), 1339.74 ng × h/mL, 1358.07 ng × h/mL, and 194.56 ng/mL, respectively, for the fed test formulation (single dexamethasone 20-mg tablet), and 1325.12 ng × h/mL, 1342.12 ng × h/mL, and 244.12 ng/mL, respectively, for the reference formulation (5 dexamethasone 4-mg tablets). The median time of observed Cmax was 0.997 hours for the fasting and 2.502 hours for the fed test formulation, compared with 1.495 hours for the reference. Mean plasma elimination half-lives (t1/2) were 4.0 hours (test fasting), 4.03 hours (test fed), and 3.96 hours (reference). The point estimates and 90% confidence intervals (CIs) for AUC0-t, AUC0-∞, and Cmax were 99.37% (90% CI, 95.65%-103.24%), 99.24% (90% CI, 95.47%-103.16%), and 106.28% (90% CI, 97.69%-115.62%), respectively, satisfying the bioequivalence criteria of the United States Food and Drug Administration guidelines. ConclusionThe 2 formulations were well-tolerated, and one 20-mg tablet or five 4-mg tablets of dexamethasone are bioequivalent under fasting conditions and thus may be prescribed interchangeably.

An up-to-date overview of sublingual sufentanil for the treatment of moderate to severe pain

ABSTRACT Introduction Sufentanil is a selective µ-opioid agonist, used intravenously and intrathecally for moderate to severe acute pain. Sublingual sufentanil nanotablets have been developed; 15 mcg tablet for a patient-controlled analgesia device and 30-mcg tablet for a single-dose device administered by a healthcare professional. Dosing interval is a minimum of 20 min for a 15 mcg tablet and a treatment duration of up to 72 hours. The single 30-mcg nanotablet dosing interval is 1 hour. Mean plasma elimination half-life is 13 hours and bioavailability 47–57% after the first sublingual sufentanil tablet. Areas covered This review focuses on the effectiveness, safety, and feasibility of sublingual sufentanil 30-mcg single dose suspended by a healthcare professional for the management of moderate to severe acute pain. A few Phase 4 studies concerning the sublingual sufentanil tablet system containing 15-mcg nanotablets are also reviewed. Expert opinion Sufentanil sublingual 30-mcg nanotablets provide effective pain relief in various acute moderate to severe pain states. The safety profile of sublingual sufentanil 30 mcg is typical to opioids nausea, vomiting, and sedation being the most common ones. Sublingual sufentanil 30-mcg nanotablet has the potential for efficient moderate to severe pain management in supervised healthcare facilities.

Inclusion of Aceclofenac in Mesoporous Silica Nanoparticles: Drug Release Study and Statistical Optimization of Encapsulation Efficiency by Response Surface Methodology

ABSTRACTAceclofenac (ACE) is a most commonly used drug for the relief of pain and inflammation associated with rheumatoid arthritis. The mean plasma elimination half-life of ACE is around 4 hrs and, therefore, frequent dosing is required which leads to patient noncompliance. Hence, to reduce the dosing frequency and adverse side effect, sustained release formulation of aceclofenac-loaded silica nanoparticles (ASiNPs) is beneficial to improve the patient noncompliance. Mesoporous silica nanoparticles (SiNPs) were prepared by precipitation method using tetra ethyl ortho silicate (TEOS) as a precursor. Response surface methodology (RSM) was used to optimise the independent variables such as SiNPs and 3-amino-propyl trimethoxysilane (APTMS) concentration, respectively, for dependent variables such as encapsulation efficiency (%EE) by using Design Expert software. The developed ASiNPs were characterized for their physiochemical properties. Results obtained from physiochemical characterisation confirmed the successful incorporation of drug in the SiNPs. The %EE was found to be in the range of 14.64–76.42%. In vitro drug release of ASiNPs in intestinal pH 6.8 shows sustained release up to 15 hrs compared to the pure ACE. From this study, we can conclude that ASiNPs would be able to sustain the drug release, reduced side effects and better patient compliance in combination with tablets and capsule.

Pharmacokinetics of oxycodone/naloxone and its metabolites in patients with end-stage renal disease during and between haemodialysis sessions

The pharmacokinetics of oxycodone in patients with end-stage renal disease (ESRD) requiring haemodialysis are largely unknown. Therefore, we investigated the pharmacokinetics of oxycodone/naloxone prolonged release and their metabolites in patients with ESRD during and between haemodialysis sessions. Single doses of oxycodone/naloxone (5/2.5 or 10/5 mg) were administered in nine patients with ESRD using a cross-over design on the day of dialysis and on a day between dialysis sessions. Plasma, dialysate and urine concentrations of oxycodone, naloxone and their metabolites were determined up to 48 h post-dosing using a liquid chromatography-tandem mass spectrometry system. Haemodialysis performed 6-10 h after dosing removed ∼10% of the administered dose of oxycodone predominantly as unconjugated oxycodone and noroxycodone or conjugated oxymorphone and noroxymorphone. The haemodialysis clearance of oxycodone based on its recovery in dialysate was (mean ± SD) 8.4 ± 2.1 L/h. The geometric mean (coefficient of variation) plasma elimination half-life of oxycodone during the 4-h haemodialysis period was 3.9 h (39%) which was significantly shorter than the 5.7 h (22%) without haemodialysis. Plasma levels of the active metabolite oxymorphone in its unconjugated form were very low. Oxycodone is removed during haemodialysis. The pharmacokinetics including the relatively short half-life of oxycodone in patients with ESRD with or without haemodialysis and the absence of unconjugated active metabolites indicate that oxycodone can be used at usual doses in patients requiring dialysis.

Pharmacokinetic and metabolic studies of ginsenoside Rb3 in rats using RRLC-Q-TOF-MS.

Ginsenoside Rb3 is one of major ginsenosides in Panax ginseng with effect on cardio-vascular and central nervous system. The aim of this study is to develop a rapid resolution liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (RRLC-Q-TOF-MS) method for pharmacokinetic study of ginsenoside Rb3 and simultaneous determination of metabolites in rats. The results showed that the concentration-time profile of ginsenoside Rb3 conformed to a two-compartment pharmacokinetic model after intravenous administration at the dosage of 2.0 mg/kg for rats. The mean plasma elimination half-lives were 13.77 ± 1.23 min and 2045.70 ± 156.20 min for the distribution and exterminate phases t1/2α and t1/2β. In the metabolic study, prototype ginsenoside Rb3 and deglycosylation metabolites were characterized by comparison with the retention time of the standard compounds, accurate mass measurement and the characteristic fragment ions obtained from MS/MS. Two major metabolites Mb1 and M2' were tentatively identified in rat urine samples after intravenous administration, and four possible metabolites Mb1, F2, M2' and CK were detected in rat feces samples after oral administration. The deglycosylation was found to be the major metabolic pathways of ginsenoside Rb3 in rat. The in vivo metabolic pathway of ginsenoside Rb3 was summarized.

Bioavailability and pharmacokinetic comparison of tanshinones between two formulations of Salvia miltiorrhiza in healthy volunteers

Salvia miltiorrhiza (SM) is widely used to treat microcirculatory disturbance-related diseases; its lipophilic components play important roles in this application. Cryptotanshinone (CTS), tanshinone I (TSI) and tanshinone IIA (TSA) are the most widely-studied lipophilic ingredients, but low oral bioavailability limits their clinical application. It has been proven that micronization could improve the bioavailability of some drugs, so we’ve conducted this randomized study to investigate whether micronized granular powder (GP) of SM could improve the bioavailability of tanshinones compared with traditional decoction (TD). An oral dose of TD or GP of SM was administrated to subjects and blood samples were collected at predetermined time points. The plasma concentrations of tanshinones were detected by a validated method and pharmacokinetic parameters were calculated using a non-compartmental model. GP of SM resulted in a significant increase in mean maximum plasma concentration (Cmax), elimination half-life and area under concentration-time curve (AUC) of tanshinones, with the plasma AUC of CTS, TSI and TSA in GP 5–184, 4–619 and 5–130 times higher than TD. In addition, the individual variances of Cmax and AUC were much lower after GP administration. Summarily, tanshinones in micronized GP of SM had higher oral bioavailability and lower individual variances, thus we speculate that it may indicate a better clinical efficacy and be a better choice than current treatments.

Pharmacokinetics of a new ivermectin/praziquantel suspension after intramuscular administration in sheep

A new oil suspension containing 0.10% ivermectin (IVM) and 15% praziquantel (PZQ) (Tivm+pzq) for intramuscular injection was developed for sheep, and its pharmacokinetics was investigated in sheep. The quality of the new product met the technical standards set by the Ministry of Agriculture of the People’s Republic of China. In pharmacokinetics, the commercially available single-component products approved by the Chinese Ministry of Agriculture and widely used in the livestock industry in China were selected as reference products (Rivm and Rpzq). The results showed that all of the IVM pharmacokinetic parameters of Tivm+pzq were similar to those of the reference. However, after adminstraion of Tivm+pzq, mean residence time (MRT) and plasma elimination half-life (t1/2z) were 20.36h and 11.65h, which were 2.61 and 3.22 times longer than those of Rpzq (7.81h and 3.62h). In summary, the MRT and t1/2z of PZQ in Tivm+pzq were prolonged and IVM pharmacokinetic parameters were similar to commerical product, therefore the new injection may be an alternative choice for sheep to control parasites sensitive to IVM and PZQ.

A single-dose mass balance and metabolite-profiling study of vemurafenib in patients with metastatic melanoma.

Vemurafenib, a selective inhibitor of oncogenic BRAF kinase carrying the V600 mutation, is approved for treatment of advanced BRAF mutation–positive melanoma. This study characterized mass balance, metabolism, rates/routes of elimination, and disposition of 14C-labeled vemurafenib in patients with metastatic melanoma. Seven patients with metastatic BRAF-mutated melanoma received unlabeled vemurafenib 960 mg twice daily for 14 days. On the morning of day 15, patients received 14C-labeled vemurafenib 960 mg (maximum 2.56 MBq [69.2 μCi]). Thereafter, patients resumed unlabeled vemurafenib (960 mg twice daily). Blood, urine, and feces were collected for metabolism, pharmacokinetic, and dose recovery analysis. Within 18 days after dose, ∼95% of 14C-vemurafenib–related material was recovered from feces (94.1%) and urine (<1%). The parent compound was the predominant component (95%) in plasma. The mean plasma elimination half-life of 14C-vemurafenib–related material was 71.1 h. Each metabolite accounted for <0.5% and ≤6% of the total administered dose in urine and feces, respectively (0–96 h postdose). No new metabolites were detected. Vemurafenib was well-tolerated. Excretion of vemurafenib via bile into feces is considered the predominant elimination route from plasma with minor renal elimination (<1%).

The pharmacokinetics of dexmedetomidine administered as a constant rate infusion in horses

Dexmedetomidine, the most selective α2-adrenoceptor agonist in clinical use, is increasingly being used in both conscious and anaesthetized horses; however, the pharmacokinetics and sedative effects of this drug administered alone as an infusion are not previously described in horses. Seven horses received an infusion of 8 μg dexmedetomidine/kg/h for 150 min, venous blood samples were collected, and dexmedetomidine concentrations were assayed using liquid chromatography-mass spectrometry (LC/MS) and analyzed using noncompartmental pharmacokinetic analysis. Sedation was scored as the distance from the lower lip of the horse to the ground measured in centimetre. The harmonic mean (SD) plasma elimination half-life (Lambda z half-life) for dexmedetomidine was 20.9 (5.1) min, clearance (Cl) was 0.3 (0.20) L/min/kg, and volume of distribution at steady-state (Vdss ) was 13.7 (7.9) L/kg. There was a considerable individual variation in the concentration of dexmedetomidine vs. time profile. The level of sedation covaried with the plasma concentration of dexmedetomidine. This implies that for clinical use of dexmedetomidine constant rate infusion in conscious horses, infusion rates can be easily adjusted to effect, and this is preferable to an infusion at a predetermined value.

Design, development and evaluation of diacerein sustained release matrix tablets

This work aims at investigating the use of hydroxy propyl methyl cellulose (HPMC) polymer to formulate sustained release matrix tablets containing diacerein. The sustained release tablets of diacerein were prepared by wet granulation method using HPMC as a release retarding polymer. Various kinetic models were applied to interpret the release of drug from the matrix system. A complete cross over bioavailability study of the developed sustained and immediate release tablets was carried out in rabbits to prove the safety and efficacy of the formulation. The release of the drug from tablets showed non-fickian diffusion obeying first order kinetics. The pharmacokinetic parameters such as AUCo-∞ value were 20.449±8.83 and 13.479 6.31 µg/h/ml, Cmax values were 2.22±1.15 and 3.30±0.02 µg/ml, tmax values were 4±0.69 and 2±0.24 h and mean plasma elimination half life (t½) were 0.145±0.03 and 0.294±0.07 h, respectively, for the developed sustained and immediate release tablets of diacerein. The extent of absorption of drug from the developed diacerein sustained release tablets was significantly higher than that for developed diacerein tablets due to lower elimination rate and longer half-life. Key words: Diacerein, hydroxy propyl methyl cellulose (HPMC), hydrophilic matrix, bioavailability.

Plasma Pharmacokinetics and Routes of Excretion of [14C]-Labeled Arruva, a High-Potency Sweetener, Following Oral Administration to Beagle Dogs

[14C]-Labeled arruva [sodium/potassium (2R,4R)-2-amino-4-carboxy-4-hydroxy-5-(3-indolyl) pentanoate] was administered as a single gavage dose (10 mg/kg bw) to male and female Beagle dogs and 1 bile duct-cannulated male. The mean peak arruva plasma concentration equivalent of 1.2 µg/g occurred at first sampling time point of 1 hour postdosing. The mean area under the concentration versus time curve from 0 hour postdosing to the last time point was approximately 20 µg·h/g and the mean terminal plasma elimination half-life ranged from 15 hours in females to 21 hours in males. Over 168 hours postdosing, 35% to 50% of the administered arruva was eliminated in the urine with 44% to 53% eliminated in feces; 1.3% of the administered dose was recovered in bile. Arruva and its derivatives were identified using tandem mass spectrometry, and the relative percentage of each substance was quantified via radio high-performance liquid chromatography. Over a 168-hour collection period, combined urine and feces extract data from the 6 noncannulated dogs showed that approximately 91% of the dose was excreted as unchanged parent arruva (41% in urine and 50% in feces). In the cannulated male, 95.3% was excreted as unchanged parent arruva; 50.2% in urine, 43.9% in feces, and 1.3% in bile. Lactone and lactam derivatives of arruva and 1 unidentified substance were detected in urine only during the first 24 hours postdosing with the greatest amounts detected during the first 6 hours of collection; up to 1% of lactone or lactam derivatives were detected in bile samples. Plasma pharmacokinetics data indicated rapid absorption of arruva with the majority of radioactivity located in the feces collected in the first 48 hours.

Safety, Tolerability, Pharmacokinetics and Pharmacodynamics of Single and Repeat Inhaled Doses of Umeclidinium in Healthy Subjects: Two Randomized Studies

Chronic obstructive pulmonary disease (COPD) has a significant negative impact on quality of life and increases the risk of premature death. Umeclidinium is a long-acting muscarinic receptor antagonist in development for the treatment of COPD with the aim to broaden treatment options for clinicians and patients by providing improved symptom control. To characterize the safety, tolerability, pharmacokinetics and pharmacodynamics of single and repeat inhaled doses of umeclidinium in healthy subjects. Two randomized, placebo-controlled, ascending-dose studies were conducted in healthy ipratropium bromide-responsive subjects. In the single-dose study, subjects (n=20) received umeclidinium (10-350μg), tiotropium bromide 18μg and placebo in a crossover dosing schedule. In this study, lung function was assessed for 24h by measuring specific airways conductance (sGaw) and forced expiratory volume in 1s (FEV1). In the repeat-dose study, subjects (n=36) received umeclidinium (250-1,000μg) and placebo for 14days in a parallel-group schedule. Adverse events (AEs) were reported in five subjects (single-dose study) and 23subjects (repeat-dose study); none were serious. In both studies, no abnormalities in 12-lead electrocardiogram parameters, 24-h Holter monitoring or lead II monitoring were reported as AEs. Umeclidinium was rapidly absorbed following single-dose administration [time to reach the maximum plasma concentration (tmax) 5-15min] and repeat-dose administration (tmax 5-7min). Following repeat dosing, the geometric mean plasma elimination half-life was approximately 27h and statistically significant accumulation was observed for the area under the plasma concentration-time curve, maximum plasma concentration and cumulative amount of unchanged drug excreted into the urine at 24h (range 1.5- to 4.5-fold). Umeclidinium at doses of 100μg and above, and tiotropium bromide demonstrated statistically significant bronchodilatory effects relative to placebo at 12h post-dosing, which lasted up to 24h for umeclidinium 350μg and for tiotropium bromide. Relative to placebo, these increases in sGaw were 24-34% at 12h post-dose and 13% at 24h post-dose. Increases in FEV1 achieved statistical significance at 12 and 24h for umeclidinium 100μg and 350μg compared with placebo. Umeclidinium was well tolerated and demonstrated bronchodilatory effects in healthy subjects for up to 24h. These bronchodilatory effects can be potentially clinically important in patients with airway obstruction such as COPD. The data obtained have informed dose selection for subsequent trials in subjects with COPD.

The exogenous fluorophore, fluorescein, enables in vivo assessment of the gastrointestinal mucosa via confocal endomicroscopy: optimization of intravenous dosing in the dog model

This study described the pharmacokinetics of the intravenous fluorophore, fluorescein, and aimed to evaluate its utility for use in upper gastrointestinal confocal endomicroscopy (CEM). Six healthy, mature, mixed-breed dogs were anesthetized and then dosed intravenously with fluorescein at 15 mg/kg. Blood samples were collected at predetermined time-points. Dogs were examined by upper gastrointestinal confocal endomicroscopy and monitored for adverse effects. Plasma fluorescein concentrations were measured using high-performance liquid chromatography (HPLC) with UV/Vis detection. Mean plasma concentration at 5 min was 57.6 ± 18.2 mg/L, and plasma concentrations decreased bi-exponentially thereafter with a mean concentration of 2.5 mg/L ± 1.26 at 120 min. Mean terminal plasma elimination half-life (t½β ) was 34.8 ± 8.94 min, and clearance was 9.1 ± 3.0 mL/kg/min. Apparent volume of distribution at steady-state was 0.3 ± 0.06 L/kg. Fluorescein provided optimal fluorescent contrast to enable in vivo histologically equivalent evaluation of topologic mucosal morphology within the first 30 min following intravenous administration. Adverse effects were not observed. Based upon the calculated clearance, a constant rate infusion at a rate of 0.18 mg/kg/min is predicted to be adequate, following an initial loading dose (2 mg/kg), to maintain plasma concentration at 20 mg/L for optimal CEM imaging during the study period.

European Surveillance of Antimicrobial Consumption (ESAC): outpatient macrolide, lincosamide and streptogramin (MLS) use in Europe (1997–2009)

Data on more than a decade of outpatient macrolide, lincosamide and streptogramin (MLS) use in Europe were collected from 33 countries within the European Surveillance of Antimicrobial Consumption (ESAC) project, funded by the European Centre for Disease Prevention and Control (ECDC), using the WHO Anatomical Therapeutic Chemical (ATC)/defined daily dose (DDD) methodology. For the period 1997-2009, data on outpatient use of systemic MLS aggregated at the level of the active substance were collected and expressed in DDD (WHO, version 2011) per 1000 inhabitants per day (DID). Using a classification based on mean plasma elimination half-life, macrolide use was analysed for trends over time, seasonal variation and composition. Total outpatient MLS use in 2009 varied by a factor of 18 between the countries with highest (11.5 DID in Greece) and lowest (0.6 DID in Sweden) use. MLS use showed high seasonal variation. Short-, intermediate- and long-acting macrolides were the most commonly used agents in 2, 25 and 5 countries, respectively (mainly erythromycin, clarithromycin and azithromycin, respectively). In Sweden, mainly lincosamides (clindamycin) were used. Lincosamide use was observed in all countries, while substantial use of a streptogramin was only seen in France (pristinamycin). For Europe, a significant increase in outpatient MLS use was found, as well as a significant seasonal variation, which increased over time from 1997 to 2009. Relative use of long-acting macrolides and lincosamides significantly increased over time with respect to intermediate-acting macrolides, and relative use of the latter increased with respect to short-acting macrolides. The observed differences between European countries in the levels of MLS use and the extreme seasonal variations in their use suggest that this subgroup of antibiotics is still prescribed inappropriately in many countries.

6β-Naltrexol, a Peripherally Selective Opioid Antagonist that Inhibits Morphine-Induced Slowing of Gastrointestinal Transit: An Exploratory Study

Opioid-induced constipation is a frequent side effect of opioid pain therapy due to opioid effects on the enteric nervous system, including gastric emptying and fluid absorption. The current exploratory studies were conducted to determine whether the neutral opioid antagonist 6β-naltrexol, the primary metabolite of naltrexone, could selectively inhibit gastrointestinal opioid effects in human subjects. Volunteers participated in a randomized, double-blind, placebo-controlled, five-way crossover study under an Exploratory Investigational New Drug application. 6β-Naltrexol has been reported to act as a neutral antagonist with peripheral selectivity in opioid-naïve and opioid-dependent systems in vitro and in vivo. Ten healthy, opioid-naïve male volunteers were enrolled in the study. Oral-cecal transit time was measured using the lactulose-hydrogen breath test. For central nervous system effects, analgesia was evaluated using a cold pressor test, and pupil size was measured. Blood samples were collected over 36 hours for pharmacokinetic analyses. The mean terminal plasma elimination half-life of 6β-naltrexol was 11.1±2.4 hours. 6β-Naltrexol potently blocked morphine-induced slowing of gastrointestinal transit, with a median effective dose (ED(50) ) of ~3 mg. In contrast, no effect was observed with 6β-naltrexol doses up to 20 mg on morphine-induced analgesia or pupil constriction. Intravenous 6β-naltrexol infusion over 30 minutes was well-tolerated up to the highest dose tested. 6β-Naltrexol acts as a potent, peripherally selective opioid antagonist. The compound was well-tolerated in this study and may have clinical potential in the therapy of peripheral opioid effects such as opioid-induced constipation.

Pharmacokinetic differences between the epimers of cefotetan disodium after single intravenous injection in healthy Chinese volunteers

The pharmacokinetic behaviors of the epimers of cefotetan disodium (R-CTT, S-CTT) after a single intravenous injection dose in healthy Chinese volunteers were explored in this study. In an open-label, randomized, three-way, cross-over study, 12 volunteers (6 females and 6 males) received a cross-over fashion doses of 0.5, 1.0, and 2.0 g of cefotetan disodium, separated by washout periods of 7 days. The plasma concentrations of both epimers were measured by validated high-performance liquid chromatography assays. Pharmacokinetic parameters of R-CTT, S-CTT, and total-CTT (R + S mixture) were calculated using a noncompartmental analysis. Generally, the R and S epimers showed different pharmacokinetic behaviors. Following 0.5, 1.0, and 2.0 g doses of cefotetan disodium, values of the total area under the plasma concentration-time curve (AUC(0-∞)) were 124.23 ± 19.54, 231.34 ± 39.34, and 459.09 ± 80.65 for R-CTT; 100.95 ± 14.19, 193.80 ± 30.42, and 372.66 ± 67.32 for S-CTT, respectively. Total body clearance values were 4.13, 4.43, and 4.46 L/h for R-CTT and 5.05, 5.28, and 5.50 L/h for S-CTT, respectively. Mean plasma elimination half-life (t (1/2)) values of R-CTT were 4.16, 4.13, and 4.01 h for 0.5, 1.0, and 2.0 g doses, respectively, and those of S-CTT were 3.15, 3.25, and 3.21 h. There were significant differences in t (1/2) between the two epimers (P < 0.05). The t (1/2) of R-CTT was 28% longer than that of S-CTT, which indicated that the elimination of the S-CTT was greater than that of the R-CTT. All treatments were well tolerated.

Development and Validation of a Test Dose Strategy for Once-Daily i.v. Busulfan: Importance of Fixed Infusion Rate Dosing

Intravenous (i.v.) busulfan (Bu) administered once daily in myeloablative transplant regimens is convenient, effective, and relatively well tolerated. Therapeutic drug monitoring is recommended as nonrelapse mortality increases when daily exposure, as determined by the area under the plasma concentration versus time curve (AUC), exceeds 6000 μM·min. We describe sequential studies to achieve accurate prediction of treatment doses of Bu based on the kinetics of a smaller test dose. A total of 335 patients with hematologic malignancies were given daily i.v. Bu 3.2 mg/kg × 4 and fludarabine 50 mg/m(2) × 5. Pharmacokinetic monitoring was conducted for both the test dose and first treatment dose of Bu (day -5). Three different test dose schedules were evaluated: 12 mg Bu administered over 20 minutes, 0.8 mg/kg over 3 hours, and 0.8 mg/kg infused at 80 mg/h. The 3.2 mg/kg treatment doses were infused over a fixed time of 3 hours for the first 2 test dose trials and at a fixed rate of 80 mg/h for the final protocol. All test dose infusions were on day -7. In the first 2schedules, Bu administered over a fixed time had significantly higher clearance for the test dose compared with the treatment dose. However, when both the test and the treatment doses were administered at the same infusion rate, clearance of the drug between the 2 dosing days was equivalent. Predicted day -5 AUC (AUC(-5)) showed a high linear correlation (r(2) = 0.74) to the actual AUC(-5). The error of these predictions was <20% in 98% of patients and <10% in 80%. In 24 individuals, the test dose predicted an AUC >5500μM·min; therefore, the first Bu treatment dose was reduced to a desired target AUC. All adjusted doses fell within 20% of the targeted exposure. We conclude that a test dose strategy for therapeutic drug monitoring of daily i.v. Bu is accurate if the test and treatment doses are infused at the same rate. This approach allows targeting of therapeutic doses of Bu to desired levels and the potential for improved safety and efficacy.

Antiarrhythmic and electrophysiological effects in-vivo of the major metabolite of Org 7797 found in canine and rodent liver homogenate preparations.

Org 20781, the major metabolite of Org 7797 found in in-vitro experiments was examined for antiarrhythmic and electrophysiological effects in-vivo. Org 20781 (0.5-2.0mg kg-1, i.v.) inhibited the development of early ischaemia-induced arrhythmias in rats, suppressed spontaneous ventricular tachycardia (VT) in conscious dogs with 24-h old infarcts, and prevented electrical induction of VT in dogs with 5-6 day old infarcts, actions associated with slowing of conduction at all levels of the myocardium. Cardiac refractory periods were only modestly prolonged whilst repolarization was unchanged. Peak plasma levels of the parent compound (infused to total doses of 2-4 mg kg-1) associated with suppression of late arrhythmias were 6-18 microM, whilst the mean plasma elimination half-life (in normal dogs) was 107 min. It was concluded that the major metabolite has a similar antiarrhythmic and electrophysiological profile to the parent compound, is at least half as potent and may contribute to the therapeutic effects of Org 7797 administration.