Relaxant effects of the essential oil of Eucalyptus tereticornis and its main constituent 1,8-cineole on guinea-pig tracheal smooth muscle

The effects of the essential oil of Eucalyptus tereticornis Sm. (EOET) on guinea-pig tracheal smooth muscle were investigated. EOET (10 - 1000 microg/mL) relaxed the tracheal basal tonus with an EC (50) value of 125.3 [52.2 - 300.9] microg/mL. Its maximal relaxation (40 +/- 6 %) was significantly lower than that evoked by aminophylline (209 +/- 34 %). The K (+)-(60 mM)-induced contractions were significantly reduced by both EOET (200 - 1000 microg/mL) and its main constituent 1,8-cineole (600 - 1000 microg/mL). Acetylcholine (1 microgM)-induced contractions were significantly enhanced by 1,8-cineole (10 - 1000 microg/mL). However, they were significantly enhanced and reduced by lower (200 - 400 microg/mL) and higher (800 - 1000 microg/mL) concentrations of EOET, respectively. Electrical field stimulation-induced contractions were significantly increased by EOET (100 - 600 microg/mL). In conclusion, EOET produces myorelaxant effects on guinea-pig isolated trachea, an effect that seems to result from a complex interaction between its monoterpenoid constituents.     

In vitro transcutaneous delivery of ketoprofen and essential polyunsaturated fatty acids from a fish oil vehicle incorporating 1,8-cineole

Transcutaneous administration of nonsteroidal anti-inflammatory drugs and essential fatty acids from fish oil, principally eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may simultaneously lead to increased cyclooxygenase inhibition and the production of less potent inflammatory mediators within joints. The objective of our study was to determine the permeation of ketoprofen, EPA, and DHA (from fish oil) across pig ear skin in vitro in the presence of the enhancer 1,8-cineole. Formulations containing 2.5% ketoprofen in fish oil with varying concentrations of 1,8-cineole were prepared and applied to full-thickness pig ear skin mounted in all glass Franz-type diffusion cells. Simultaneous permeation of ketoprofen and EPA and DHA from these formulations was determined by reverse phase HPLC over a 48-hr period (n = 6). We found that fish oil alone enhanced the permeation of ketoprofen across pig ear by a factor of 1.72 relative to a water vehicle. There was a dose-dependent increase in the rate of permeation of ketoprofen relative to the concentration of 1,8-cineole. The highest Q24 and Q48 was obtained with a 20% 1,8-cineole formulation with values of 355.78 +/- 50.73 microg cm(-2) and 963.29 +/- 136.69 microg cm(-2), respectively. Surprisingly, no clear effect upon the permeation of EPA and DHA by 1,8-cineole was observed, with the highest Q24 and Q48 values seen in a formulation containing no 1,8-cineole. This may have been due to differential solvation effects prior to or during the permeation process or modulation of the skin during the permeation process.     

Myorelaxant effects of the essential oil of Croton nepetaefolius on the contractile activity of the guinea-pig tracheal smooth muscle

The effects of the essential oil of Croton nepetaefolius (EOCN) on isolated guinea-pig trachea were investigated. EOCN decreased the preparation's basal tone (EC (50) = 4.3 microg/mL) with a maximal effect similar to that of aminophylline. EOCN fully relaxed preparations pre-contracted with 60 mM K+ (IC (50) = 113.0 microg/mL). EOCN did not alter the E (m) of smooth muscle cells in 5 and 80 mM K+. EOCN, at 300 and 600 microg/mL, reduced the contraction induced by ovalbumin (10 microg/mL) from 227.2 to 82.5 and 35.5 % of the 60 mM K+-induced contraction, respectively. EOCN blocked the submaximal contractions induced by histamine, carbachol and 60 mM K+ with a similar potency (IC (50) values = 123.9, 102.5 and 128.8 microg/mL, respectively). In conclusion, EOCN exerts respiratory smooth muscle antispasmodic activity by a mechanism that is probably myogenic and not specific for neurotransmitters and autacoids.     

Antibacterial activity and chemical composition of essential oil of Chrysanthemum boreale

The essential oil of Chrysanthemum boreale Makino was analyzed by means of GC and GC-MS. Eighty-seven constituents were identified, representing 94.13 % of the total oil and the major components were camphor, alpha-thujone, cis-chrysanthenol, 1,8-cineole, alpha-pinene, and beta-caryophyllene. Furthermore, the essential oil exhibited antibacterial activity (MIC, more than 800 microg/mL versus 0.125 microg/mL for ampicillin) after it was tested against 6 Gram(+) bacteria and 8 Gram(-) bacteria.     

In-vitro transcutaneous delivery of tamoxifen and gamma-linolenic acid from borage oil containing ethanol and 1,8-cineole

The objective of this study was to examine the effects of ethanol and 1,8-cineole on the transcutaneous delivery of tamoxifen and gamma-linolenic acid (GLA) as a two-pronged anti-breast cancer therapy. Formulations containing tamoxifen and varying concentrations of borage oil (approximately 25% GLA), 1,8-cineole and ethanol were prepared and the simultaneous permeation of tamoxifen and GLA determined across full-thickness pig skin using Franz-type diffusion cells over 48 h. Analysis of tamoxifen and GLA (as methyl ester) were by reverse-phase HPLC. The highest flux of tamoxifen of 488.2 +/- 191 x 10(-3) microg cm(-2) h(-1) was observed with a formulation containing 20% 1,8-cineole and 20% ethanol. The same formulation also provided the greatest flux of GLA, 830.6 x 10(-3) microg cm(-2 )h(-1). The findings from this work demonstrate the ability of 1,8-cineole and ethanol to enhance the in-vitro permeation of tamoxifen and GLA across the skin and support the plausibility of simultaneously delivering tamoxifen and GLA transcutaneously as a two-pronged anti-breast cancer system.     

Pharmacokinetics of micafungin in healthy volunteers, volunteers with moderate liver disease, and volunteers with renal dysfunction

Micafungin is an antifungal agent metabolized by arylsulfatase with secondary metabolism by catechol-O-methyltransferase. The objectives of this study were to estimate the pharmacokinetic parameters and plasma protein binding of micafungin in volunteers with moderate hepatic dysfunction (n = 8), volunteers with creatinine clearance < 30 mL/min (n = 9), and matched controls (n = 8 and n = 9, respectively). Single-dose micafungin pharmacokinetics were estimated using noncompartmental techniques. There was a statistically lower area under the observed micafungin concentration-time curve (AUC) from time 0 to infinity for subjects with moderate hepatic dysfunction as compared to control subjects (97.5 +/- 19 microg.h/mL vs 125.9 +/- 26.4 microg.h/mL, P = .03), although there was no difference in micafungin weight-adjusted clearance (10.9 +/- 1.7 mL/h/kg vs 9.8 +/- 1.8 mL/h/kg, P = .2). The difference in area under the concentration-time curve may be explained by the differences in body weight between subjects and controls. Renal dysfunction did not alter micafungin pharmacokinetics.     

Biotransformation of 1,8-cineole in the brushtail possum (Trichosurus vulpecula)

1. The metabolic fate of 1,8-cineole was investigated in the brushtail possum. Six possums were fed an artificial diet to which 0.5% 1,8-cineole (wet weight) was added for 2 days. Urine and faeces were collected after the second day. A sample of each was extracted into ethyl acetate and analysed for metabolites. Both free and total levels of metabolites were identified by GC-MS and LC-MS and quantified by GC-MS. 2. The pattern of metabolite excretion was very complex in the brushtail possum. Nineteen metabolites were found in total. Metabolites were categorized into four groups according to the oxidation they had undergone: hydroxycineoles (n = 3), cineolic acids (n = 2), dihydroxycineoles (n = 3) and hydroxycineolic acids (n = 11). No hydroxycineolic acid metabolites have been previously reported as metabolites of 1,8-cineole. 3. Fractional recovery of the ingested dose (2.4 +/- 0.5 g; mean +/- SD) was 0.44 +/- 0.14 (mean +/- SD) in 24 h. Sixty percent of excreted metabolites were hydroxycineolic acids, the most extensively oxidized metabolites. Conjugation with glucuronic acid was inversely related to metabolite polarity, being greatest for hydroxycineoles (41-82%) and minimal for hydroxycineolic acids. 4. Traces of most metabolites were also found in the faeces.     

1,8-cineole protects against liver failure in an in-vivo murine model of endotoxemic shock

The effects of 1,8-cineole on D-galactosamine/lipopolysaccharide (GalN/LPS)-induced shock model of liver injury was investigated in mice. The co-administration of GalN (700 mg kg(-1), i.p.) and LPS (5 microg kg(-1), i.p.) greatly elevated serum concentrations of tumour necrosis factor-alpha (TNF-alpha), alanine aminotransferase and aspartate aminotransferase, and induced massive hepatic necrosis and lethality in 100% of control mice. Pretreatment with 1,8-cineole (400 mg kg(-1), p.o.) and dexamethasone (1 mg kg(-1), s.c.), 60 min before GalN/LPS, offered complete protection (100%) against the lethal shock and acute elevation in serum TNF-alpha and serum transaminases. Hepatic necrosis induced by GalN/LPS was also greatly reduced by both 1,8-cineole and dexamethasone treatment. The results indicate that 1,8-cineole protects mice against GalN/LPS-induced liver injury through the inhibition of TNF-alpha production, and suggest that 1,8-cineole may be a promising agent to combat septic-shock-associated pathologies.     

Delayed preconditioning via Angiotensin-converting enzyme inhibition: pros and cons from an experimental study

1. Bradykinin B(2) receptor activation confers preconditioning from ischaemic injury. In the present study, we tested whether an angiotensin-converting enzyme (ACE) inhibitor (captopril) could mediate delayed preconditioning and, thus, cardioprotection. 2. New Zealand white rabbits received 15 mL infusion of either saline (control group; n = 7) or drugs (0.3 mg/kg captopril (CAP group; n = 7) or 0.3 mg/kg captopril + 0.1 mg/kg HOE 140 (CAPHOE group; n = 7)) via a marginal ear vein over 30 min. After 24 h, hearts were connected to a Langendorff apparatus and buffer perfused. The experimental protocol consisted of 20 min global normothermic hypoxia, followed by 120 min reperfusion. 3. Compared with baseline, the mean (SEM) contractile state (= dP/dt(max)) at 120 min reperfusion was decreased to 42 +/- ;23, 72 +/- ;16 (*P < 0.05 vs control) and 49 +/- ;22% in the control, CAP and CAPHOE groups, respectively. Early relaxation (= dP/dt(min)) was reduced to 55 +/- ;28, 73 +/- ;15 (*P < 0.05 vs control) and 52 +/- ;19% in the control, CAP and CAPHOE groups, respectively. The estimate for myocardial oxygen consumption (MVO(2)= rate-pressure product) was decreased to 52 +/- ;15, 69 +/- ;24 (*P < 0.05 vs control) and 56 +/- ;15% in the control, CAP and CAPHOE groups, respectively. Similarly, coronary flow was decreased in the control, CAP and CAPHOE groups to 49 +/- ;20, 67 +/- ;18 and 46 +/- ;19%, respectively. In contrast, ventricular extrasystoles during reperfusion were significantly elevated in both the CAP and CAPHOE groups (1.3 +/- ;0.2 and 1.1 +/- ;0.3 /min, respectively) compared with control (0.4 +/- ;0.2 /min). 4. Captopril confers delayed preconditioning against stunning via a B(2) receptor-mediated pathway. This pharmacological preconditioning protects against systolic and diastolic stunning, against vascular stunning and preserves cardiac metabolism. In addition to its accepted cardioprotective effects in early preconditioning, captopril should induce delayed preconditioning (e.g. for routine interventional cardiology or in elective cardiac surgery).     

Cytotoxic constituents from Cratoxylum arborescens

A new natural xanthone, 1,3-dihydroxy-6,7-dimethoxy-2,8-diprenylxanthone, together with four known compounds, fuscaxanthone C, 1,7-dihydroxyxanthone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone and 2-geranylemodin were isolated from the stem bark of Cratoxylum arborescens (Vahl) Blume. The structure elucidations were achieved through spectroscopic analyses. Compounds 1 and 5 showed moderate activity against the human small cell lung cancer NCI-H187 cell line with the IC50 values of 3.69 +/- 1.27 microg/mL and 3.08 +/- 0.73 microg/mL, respectively.     

Role of hypothalamic alpha-adrenoceptor activity in fructose-induced hypertension

The aim of the present study was to investigate the effects of the alpha2-adrenoceptor antagonist yohimbine on blood pressure and heart rate (HR) regulation, as well as on adrenergic and serotoninergic neurotransmission, in fructose hypertensive (F) rats. The anterior hypothalamic area of control (C) and F rats was perfused with Ringer's solution containing 10 and 100 microg/mL yohimbine through a microdialysis concentric probe. The effects of yohimbine on mean arterial pressure (MAP) and HR, as well as on hypothalamic dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5-HIAA) levels, were measured according to perfusion time. Although intrahypothalamic perfusion of yohimbine increased blood pressure in C rats (DeltaMAP 9 +/- 1 and 11 +/- 2 mmHg for 10 and 100 microg/mL yohimbine, respectively; P < 0.05 vs Ringer's perfusion), the alpha-adrenoceptor antagonist did not modify MAP in F. Intrahypothalamic yohimbine had no effect on HR at either concentration tested. Intrahypothalamic perfusion of 10 and 100 microg/mL yohimbine increased DOPAC levels in C rats (135 +/- 6 and 130 +/- 5% of basal levels, respectively; both n = 6; P < 0.05 vs Ringer's perfusion), but not in F animals (115 +/- 6 and 102 +/- 6% of basal levels, respectively; both n = 6). In both C and F rats, yohimbine administration induced an increase in 5-HIAA dialysate levels. The results of the present study support the notion that alpha2-adrenoceptor tone of the anterior hypothalamus of normotensive rats, which contributes to normal blood pressure regulation, is not involved in the control of HR in either normotensive C or hypertensive F rats. The absence of changes in MAP after yohimbine perfusion in F rats suggests that the alpha2-adrenoceptor tone could be decreased in this group of rats and that this may be responsible for the maintenance of hypertension in this model. Intrahypothalamic perfusion of yohimbine increased DOPAC in the dialysate only in C rats, suggesting changes in presynaptic alpha2-adrenoceptor activity in fructose-overloaded rats. Conversely, increased 5-HIAA levels did not differ between C and F groups.     

Phenacetin O-deethylation in extrahepatic tissues of rats.

Phenacetin O-deethylation is a marker reaction of CYP450 1A2 activity. The drug-metabolizing enzyme is constitutively expressed in liver. In this study, an in vivo rat model for assessment of extrahepatic metabolism was used to investigate phenacetin O-deethylation and the alterations in the disposition of phenacetin due to the loss of liver function. Rats were divided into the model and normal control groups. The model was established according to our previously described method. The concentrations of phenacetin and its major metabolites acetaminophen, glucuronate-acetaminophen and sulfate-acetaminophen in plasma and urine were determined by HPLC. 30 min after intravenous administration of 0.16% phenacetin 10 mg x kg(-1), plasma acetaminophen in the model group was only 3.6% of that in the control group (0.09+/-0.04 microg x mL(-1) vs 2.49+/-0.85 microg x mL(-1), n = 8). 30 min after intragastric injection of 0.4% phenacetin 30 mg x kg(-1), plasma acetaminophen formation was very slight, about 8.6% of plasma phenacetin in the model group (0.74+/-0.43 microg x mL(-1) acetaminophen vs 8.57+/-8.42 microg x mL(-1) phenacetin) and 6.8% in the control group (1.06+/-0.59 microg x mL(-1) acetaminophen vs 15.47+/-7.21 microg x mL(-1) phenacetin, n = 8); no significant differences were observed in plasma phenacetin, total acetaminophen and the ratio of acetaminophen to phenacetin between control and model groups. In the urine collected for 3 h after intravenous administration of 0.16% phenacetin 10 mg x kg(-1), the total recovery of acetaminophen (as free, glucuronate- and sulfate-acetaminophen ) in the model group was 4.6% of that in the control group (4.47+/-4.27 microg vs 96.63+/-8.50 microg, n = 6), but phenacetin recovery in the model group was 9 times higher than that in the control group (15.03+/-17.72 microg vs 1.66+/-0.50 microg). The results indicate that phenacetin O-deethylation in the extrahepatic tissues and the first-pass metabolism of the probe compound seem to be negligible in rats, but the renal excretion of phenacetin, as a compensation, dramatically increases in model rats.     

Bioavailability and tissular distribution of docetaxel, a P-glycoprotein substrate, are modified by interferon-alpha in rats

Interferon-alpha (IFN-alpha) inhibits intestinal P-glycoprotein (P-gp) expression in rats. In the present study, the effects of repeated pre-treatment with recombinant human INF-alpha (rhIFN-alpha) on oral and intravenous pharmacokinetics of a P-gp substrate, docetaxel (DTX; Taxotere) were investigated in a rat model. The bioavailability and distribution in different organs were also studied. Sprague-Dawley rats were subcutaneously pre-treated with either rhIFN-alpha for 8 days (4MIU kg(-1), once daily) or with pegylated-IFN-alpha (ViraferonPeg; 60 microg kg(-1), Days 1, 4 and 7). The rats were then distributed into sub-groups (n = 5-6) according to the pre-treatment type, and received one dose of [(14)C]DTX (20 mgkg(-1)) either orally or intravenously. Pharmacokinetics studies were then performed over 240 min, at the end of which tissues (intestine, liver, kidneys, lung, heart and brain) were immediately removed for radioactivity quantitation. Non-pegylated and pegylated IFN-alpha both increased DTX oral bioavailability parameters: C(max) (17.0+/-4.0 microg L(-1) (P < 0.02) and 18+/-5.5 microg L(-1) (P < 0.05), respectively, vs 7.4+/-2.5 microg L(-1) for the control) and AUC (0.036+/-0.010 microg h mL(-1) (P < 0.01) and 0.033+/-0.009 microg h mL(-1) (P < 0.01), respectively, versus 0.012+/-0.004 microg h mL(-1) for the control). IFN-alpha also delayed DTX absorption from 60 min in controls to about 95 min and 80 min in non-pegylated and pegylated treated animals, respectively. However, IFN-alpha did not affect intravenous DTX pharmacokinetics and it had a limited effect on tissue distribution at 240 min. [(14)C]DTX was decreased in intestine and enhanced in brain in both pre-treated groups. rhIFN-alpha modified the P-gp-dependent pharmacokinetics of DTX, limited its intestinal efflux and markedly enhanced its oral bioavailability.     

Synergistic and antagonistic interactions of anticholinesterase terpenoids in Salvia lavandulaefolia essential oil

In vitro anticholinesterase activities of eight commercially available terpenoid constituents of Salvia lavandulaefolia have been investigated. These included 1,8-cineole, camphor, alpha-pinene, beta-pinene, borneol, caryophyllene oxide, linalool and bornyl acetate. Dose-dependent inhibition of acetylcholinesterase (AChE) by these chemical constituents was determined using the method of Ellman [Biochem. Pharmacol. 7 (1961) 88]. The IC50 value of 1,8-cineole was 0.06+/-0.01 mg/ml similar to that of the essential oil (0.05+/-0.01 mg/ml). Analyses of the expected inhibitions based on the prediction of a zero interactive response of a combination at its naturally occurring ratios were carried out in comparison with observed inhibition. Minor synergy was apparent in 1,8-cineole/alpha-pinene and 1,8-cineole/caryophyllene oxide combinations, with interaction indexes not exceeding 0.5. In contrast, a combination of camphor and 1,8-cineole was antagonistic with an interaction index of 2. A combination of all eight compounds was zero interactive. A combination of six constituents, excluding 1,8-cineole and camphor, was used to compare the method of expected response of a combination with a method of summation. These findings reveal that the inhibitory activity of the oil results from a complex interaction between its constituents, which produce both synergistic and antagonistic responses between the component terpenes. Understanding such interactions is important in comparing species on the basis of chemical composition.     

In Vitro Transcutaneous Delivery of Ketoprofen and Essential Polyunsaturated Fatty Acids from a Fish Oil Vehicle Incorporating 1,8-Cineole

Transcutaneous administration of nonsteroidal anti-inflamma- tory drugs and essential fatty acids from fish oil, principally eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), may simultaneously lead to increased cyclooxygenase inhibition and the production of less potent inflammatory mediators within joints. The objective of our study was to determine the permeation of ketoprofen, EPA, and DHA (from fish oil) across pig ear skin in vitro in the presence of the enhancer 1,8-cineole. Formulations containing 2.5% ketoprofen in fish oil with varying concentrations of 1,8-cineole were prepared and applied to full-thickness pig ear skin mounted in all glass Franz-type diffusion cells. Simultaneous permeation of ketoprofen and EPA and DHA from these formulations was determined by reverse phase HPLC over a 48-hr period (n = 6). We found that fish oil alone enhanced the permeation of ketoprofen across pig ear by a factor of 1.72 relative to a water vehicle. There was a dose-dependent increase in the rate of permeation of ketoprofen relative to the concentration of 1,8-cineole. The highest Q₂₄ and Q₄₈ was obtained with a 20% 1,8-cineole formulation with values of 355.78 ± 50.73 μg cm^-2 and 963.29 ± 136.69 μg cm^-2, respectively. Surprisingly, no clear effect upon the permeation of EPA and DHA by 1,8-cineole was observed, with the highest Q₂₄ and Q₄₈ values seen in a formulation containing no 1,8-cineole. This may have been due to differential solvation effects prior to or during the permeation process or modulation of the skin during the permeation process.     

Occurrence of 11-oxotetrodotoxin in the red-spotted newt, Notophthalmus viridescens, and further studies on the levels of tetrodotoxin and its analogues in the newt's efts.

An analogue of tetrodotoxin (TTX), 11-oxoTTX, was semi-purified from the red-spotted newt, Notophthalmus viridescens, and identified by ESI-MS and 1H NMR spectra. The levels of TTX, 11-oxoTTX and 6-epiTTX in early stage of development (efts) of this newt were investigated by a post-column fluorescent-HPLC system, and compared with those of adult newts. The level of 11-oxoTTX in both of adults and efts were remarkably high, almost close to those of TTX, while 6-epiTTX was a minor component in both stages. The level of 6-epiTTX in efts (1.8+/-1.3 microg/g, SD, n=10) was significantly larger than that in adults (0.51+/-0.26 microg/g, SD, n=12) (p<0.05), while no significant difference was observed in the levels of TTX and 11-oxoTTX between efts (13+/-7.4 and 9.1+/-5.6 microg/g) and adult newts (16+/-6.3 and 13+/-6.2 microg/g, respectively) (p>0.05).     

The effect of enzyme inhibitor and absorption site following [D-ala2, D-leu5]enkephalin oral administration in rats

The effects of enzyme inhibitor, amastatin, and absorption site following intravenous (i.v.) oral (p.o.), jejunal and ileal administration of [D-ala(2), D-leu(5)]enkephalin (YdAGFdL) were investigated in rats. Model dependent and independent pharmacokinetic parameters were obtained and compared. Linear pharmacokinetics of YdAGFdL were evaluated at 0.28 and 500 microg doses for i.v. and at 1, 500, and 1000 microg for p.o. and ileal routes. Plasma samples were collected and assayed for intact YdAGFdL using a radiometric thin layer chromatography. The clearance (CL) and half lives of the distribution and elimination phases following the 0.28 microg (n=6) i.v. dose were 42.7+/-26.2 (S.D.) ml/min, 0.48+/-0.17 min, and 3.98+/-0.92 min, while those of the 500 microg dose (n=6) were 48.0+/-23.3 ml/min, 0.59+/-0.25, and 6.81+/-3.12 min, respectively, suggesting apparent linear kinetics. The CL values were close to the cardiac output of rats (50 ml/min) indicating very rapid elimination from the body. Mean bioavailability (F) values following p.o. (n=15), jejunal (n=4), and ileal (n=16) administration were 0.40+/-0.24% (S.E.), 1.25+/-0.39, and 1.78+/-0.40, respectively, and were not significantly different (p<0.05) among three doses (1, 1000, 5000 microg). The F value of YdAGFdL following ileal administration in the presence of amastatin was 8.76+/-4.47% (n=6), a 22 fold increase over po administration and a five fold increase over ileal administration without an inhibitor. These results indicate that 'effective' oral delivery of small peptides may be achievable.     

A novel inexpensive murine model of oral chronic digitalization

A novel inexpensive murine model of oral administration of digitoxin (100 micro g/kg per day) added to routine chow is described. Serum digitoxin levels achieved after oral (n = 5; 116 +/- 14 ng/mL) and subcutaneous (n = 5; 124 +/- 11 ng/mL) administration were similar. A significant increase in the maximal left ventricular pressure rise of treated (n = 9) compared with control (n = 6) rats (dP/dt: 8956 +/- 233 vs 7980 +/- 234 mmHg/s, respectively; P = 0.01) characterized the positive inotropic action of digitoxin. In addition, no differences were observed in treated compared with control rats with regard to the electrocardiogram and systolic and diastolic left ventricular pressures.     

Intranasal loteprednol etabonate in healthy male subjects: pharmacokinetics and effects on endogenous cortisol

Loteprednol etabonate (LE) is a glucocorticoid soft drug that is currently in development for intranasal use. The main objectives of this study were to examine the pharmacokinetics and potential effects on systemic cortisol of two intranasal suspension formulations of LE and to compare these findings with placebo and fluticasone propionate (FP, Flonase) control treatments. In this randomized, double-blind (except for FP), parallel-group study (n = 8/group), all subjects received for 14 days once daily in the morning two puffs of the following nasal spray formulations into each nostril: LE 0.1% (400 microg/day), LE 0.2% (800 microg/day), FP 0.05% (200 microg/day), and placebo. Drug trough levels were determined on days 1, 5, 12, 13, and 14, and a full pharmacokinetic profile was established on day 14, and 24-hour serum cortisol profiles were assessed prior to treatment (i.e., at baseline) and after the last dose. All subjects completed the protocol without treatment-emergent adverse findings. All formulations were rapidly absorbed (t(max) less than 1 h). The rather short mean terminal half-lives of 2.2 +/- 1.5 hours and 1.8 +/- 1.0 hours for LE 400 microg and LE 800 microg, respectively, and 4.2 +/- 1.8 hours for the 200-microg FP treatment explained the lack of any accumulation. Mean peak concentrations (C(max)) were 139 +/- 57 pg/mL with LE 400 microg and 164 +/- 54 pg/mL with LE 800 microg and thus fairly independent from dose. The 200-microg FP treatment resulted in a C(max) of only 15.5 +/- 5.9 pg/mL. Mean measured AUC(0-t) values (193 +/- 87 pg/h/mL(-1), 300 +/- 183 pg/h/mL(-1), and 40 +/- 34 pg/h/mL(-1) for LE 400 microg, LE 800 microg, and FP 200 microg, respectively) showed high variability and suggested nonlinear pharmacokinetics for the LE formulations, indicative of a less complete systemic uptake of LE from the 0.2% concentration. None of the treatments (LE 400 microg, LE 800 microg, and FP 200 microg) showed evidence for serum cortisol suppression when compared with placebo, respectively. The uptake and systemic exposure appears less complete from the 0.2% LE concentration, which principally favors this formulation for further clinical development.     

Suramin inhibits the toxic effects of presynaptic neurotoxins at the mouse motor nerve terminals.

Clinically available chemical antagonists of snake neurotoxins still await to be identified. In this study, we demonstrate that an anti-trypanosomiasis agent, suramin, is an effective inhibitor of beta-bungarotoxin isolated from the venom of Formosan Krait snake. Following intraperitoneal injection (12 ng/g) of beta-bungarotoxin in mice, the time to paralysis (loss a limb withdrawal reflex, 21. 8+/-3.4 h, n=4) was significantly prolonged after intravenous injection (16 microg/g) of suramin (35.9+/-4.0 h, n=4, P<0.05). The mechanism of this inhibitory effect of suramin was analyzed at the mouse nerve terminals. beta-Bungarotoxin (1 microg/ml) produces an irreversible blocking effect of nerve-evoked muscle contractions of mouse phrenic nerve-diaphragm (blocking time 135+/-6 min, n=6). Pretreatment with suramin (0.3 mM) significantly prolonged the blocking time by three-fold. This selective inhibitory effect of suramin was further confirmed when suramin was shown to delay the neuromuscular blocking effect of another presynaptic neurotoxin, crotoxin (from American rattlesnake venom), but not that of the postsynaptic neurotoxin, alpha-bungarotoxin. Furthermore, suramin inhibited beta-bungarotoxin in blocking transmitter release as revealed by prolonging the time to abolish the end-plate potential amplitude (with suramin, 391+/-8 min; without treatment, 141+/-5 min). K(+) current was measured in the mouse triangularis sterni preparation; suramin (0.3 mM) had no significant effect on beta-bungarotoxin in inhibiting K(+) current (77+/-3% of control; with suramin 75+/-3% of control, respectively). These findings clearly show that suramin is an inhibitor of presynaptic neurotoxins, mediated by interrupting the toxins in blocking the releasing mechanism of transmitter at the motor nerve terminals. The implication of these findings is that suramin and related compounds can become useful agents in management of snakebites.