Differential inhibition of hepatic and duodenal sulfation of (−)-salbutamol and minoxidil by mefenamic acid

Objective: The aim of this investigation was to determine whether mefenamic acid and salicylic acid inhibit the sulfation of (−)-salbutamol and minoxidil in the human liver and duodenum, and if so, to ascertain whether the 50% inhibitory concentration (IC₅₀) estimates are different in the two tissues. Methods: Sulfotransferase activities were measured for 10 mM (−)-salbutamol and 5 mM minoxidil, and the concentration of 3′-phosphoadenosine-5′-phosphosulphate-[³⁵S] was 0.4 μM. Results: The IC₅₀ estimates for (−)-salbutamol and minoxidil sulfation of mefenamic acid were 72 ± 5.4 nM and 1.5 ± 0.6 μM (liver), respectively, and 161 ± 23 μM and 420 ± 18 μM (duodenum), respectively. The figures for the liver were significantly lower (P < 0.0001) than those for the duodenum. The IC₅₀ estimates for (−)-salbutamol sulfation of salicylic acid were 93 ± 11 μM (liver) and 705 ± 19 μM (duodenum, P < 0.0001). Salicylic acid was a poor inhibitor of minoxidil sulfation. Conclusion: The IC₅₀ estimates for (−)-salbutamol sulfation of mefenamic acid and salicylic acid are lower than their unbound plasma concentrations after standard dosing, suggesting that mefenamic acid and salicylic acid should inhibit the hepatic sulfation of (−)-salbutamol in vivo. Received: 11 November 1999 / Accepted in revised form: 28 April 2000     

<Emphasis Type="Italic">In vitro</Emphasis> anti-inflammatory activity of carvacrol: Inhibitory effect on COX-2 catalyzed prostaglandin E<Subscript>2</Subscript> biosynthesisb

Possible anti-inflammatory effect of carvacrol was evaluated by in vitro cyclooxygenase-2 (COX-2) assay. Carvacrol inhibited production of prostaglandin E₂ catalysed by COX-2 with an IC₅₀ value of 0.8 μM what is practically the same concentration as the IC₅₀ obtained for the standard inhibitors indomethacin and NS-398 with values of 0.7 μM and 0.8 μM, respectively. The COX-1 was inhibited approximately at the same rate (IC₅₀ of 0.7 μM for carvacrol), which suggests non-selective inhibition of both enzyme isoforms. The results of the study demonstrate possible anti-inflammatory potential of this compound due to the inhibition of inducible COX-2 isoform.     

Inhibitory activity of nitric oxide production in RAW 264.7 cells of daldinals A–C from the fungus Daldinia childiae and other metabolites isolated from inedible mushrooms

Three benzophenone derivatives, daldinals A–C, from the Japanese fungus Daldinia childiae were evaluated for their inhibitory activity of nitric oxide (NO) production stimulated by lipopolysaccharide (LPS) in RAW 264.7 cells. They strongly suppressed the LPS-induced production of NO with IC₅₀ values of 15.2, 4.6 and 6.4 μM, respectively. To clarify the mechanism involved, total RNA extraction, followed by reverse-transcribed, polymerase chain reaction (PCR) for inducible nitric oxide synthase (iNOS) mRNA and finally electrophoresis on agarose gel were performed. These experimental results suggest that the inhibition of the LPS-induced NO production of daldinal B is due to the inhibition of iNOS mRNA synthesis. Further, their biological activities were compared with those of other metabolites obtained during our studies on biologically active substances from inedible fungi in recent years.     

Dilatory effects of phosphodiesterase inhibitors on human hand veins in vivo

Objective: To compare the venodilator potencies of the phosphodiesterase (PDE) III inhibitors amrinone and enoximone with the unspecific PDE inhibitors theophylline and pentoxifylline in human hand veins in vivo. Methods: Eighteen healthy nonsmokers (16 men and two women) were studied using the dorsal hand vein technique. After preconstriction with the selective α₁-adrenergic-receptor agonist phenylephrine dose–response curves were constructed for amrinone (1–270 μg · min⁻¹), enoximone (1–270 μg · min⁻¹), theophylline (5–1500 μg · min⁻¹) and pentoxifylline (2–877 μg · min⁻¹) in a random order on separate occasions. Due to limitation in the maximum dose infused in order to avoid systemic effects, full dose–response curves could not be constructed for pentoxifylline. In this case, the individual dose of pentoxifylline and theophylline producing 50% venodilation were compared. Results: All PDE inhibitors induced dose-dependent venodilation. The value of maximum venodilation was the same for amrinone, enoximone and theophylline. The infusion rate needed to induce 50% of maximum venodilation (ED₅₀) was not significantly different for amrinone (geometric mean, 8.8 μg · min⁻¹) and enoximone (14.2 μg · min⁻¹), whereas the ED₅₀ of theophylline (84.0 μg · min⁻¹) was significantly higher than either amrinone or enoximone. The dose necessary to dilate the vein to 50% the maximum dilation (as determined during sodium chloride infusion) was significantly higher for pentoxifylline than for theophylline (409 vs 71 μg · min⁻¹). Conclusions: These findings demonstrate that enoximone and amrinone have similar venodilatory potency which is six times higher than that of theophylline. The least potent vasodilator in this study was pentoxifylline. Received: 16 September 1997 / Accepted in revised form: 4 December 1997     

(-)-Nyasol (cis-hinokiresinol), a norneolignan from the rhizomes of <Emphasis Type="Italic">Anemarrhena asphodeloides</Emphasis>, is a broad spectrum inhibitor of eicosanoid and nitric oxide production

To assess the anti-inflammatory activity of constituents from the rhizomes of Anemarrhena asphodeloides, (-)-nyasol {cis-hinokiresinol, 4,4-[1Z,3R]-3-ethenyl-1-propene-1,3-diyl]bisphenol} was isolated and its anti-inflammatory activity was examined in lipopolysaccharide (LPS)-treated RAW 264.7 cells and A23187-treated RBL-1 cells. In vivo activity was measured using carrageenan-induced paw edema assay. At > 1 μM, (-)-nyasol significantly inhibited cyclooxygenase-2 (COX-2)-mediated PGE₂ production and inducible nitric oxide synthase (iNOS)-mediated NO production in LPS-treated RAW 264.7 cells, a mouse macrophage-like cell line, but did not affect the expression levels of COX-2 and iNOS. (-)-Nyasol also inhibited 5-lipoxygenase (5-LOX)-mediated leukotriene production in A23187-treated RBL-1 cells. Furthermore, (-)-nyasol potently inhibited carrageenan-induced paw edema in mice (28.6–77.1% inhibition at 24–120 mg/kg). Therefore, (-)-nyasol is a potential new lead compound and may contribute to the anti-inflammatory action of A. asphodeloides, possibly by inhibiting COX-2, iNOS and 5-LOX.     

Improved penetration of aminoglycosides and fluoroquinolones into the aqueous humour of patients by means of Acuvue contact lenses

Objectives: In order to improve the penetration of topically applied drugs in ophthalmology, the suitability of hydrophilic contact lenses (Acuvue, Vistacon, power −1.0 D) as a drug delivery system for antibiotics was tested. A prospective study was undertaken to determine the transcorneal penetration of five topically applied aminoglycosides and fluoroquinolones into the aqueous humour of patients. Methods: Two hundred and sixty-five patients undergoing cataract extraction received 0.3% gentamicin, kanamycin, tobramycin, ciprofloxacin or ofloxacin solution by two different modes of administration: either as eye drops (nine drops every 15 min, starting 2 h prior to surgery) or by means of a drug delivery system (Acuvue contact lenses soaked for 1 h in eye drop solution without preservatives, 1–5 h prior to surgery). At the beginning of cataract extraction, 50–100 μl aqueous fluid was aspirated from the anterior chamber and immediately stored at −80 °C. Antibiotic concentrations were measured using fluorescence polarisation immuno-assays (aminoglycosides) or high-performance liquid chromatography (fluoroquinolones). Results: After soaking for 1 h in 0.3% eye drop solutions, Acuvue contact lenses released about 190–250 μg aminoglycoside and ofloxacin and 1000 μg ciprofloxacin. These amounts are considerably lower or in the same order of magnitude than obtained with application of eye drops (1350 μg). From the aminoglycosides tested, only gentamicin and tobramycin, but not kanamycin, were able to penetrate into the aqueous humour of patients. After the wearing of antibiotic-soaked lenses, mean aqueous humour concentrations were higher than after the use of eye drops. This difference reached significance in tobramycin (1.09 (1.30) μg · ml⁻¹ vs 0.49 (0.79) μg · ml⁻¹), ciprofloxacin (1.23 (0.60) μg · ml⁻¹ vs 0.38 (0.33) μg · ml⁻¹) and ofloxacin (5.55 (2.53) μg · ml⁻¹ vs 0.56 (0.37) μg · ml⁻¹). The percentage of patients with aqueous humour concentration above the MIC₉₀ of Staphylococcus epidermidis, the most common cause of postoperative endophthalmitis, was 92% and 100% after wearing ciprofloxacin- or ofloxacin-soaked lenses, respectively. Conclusion: Gentamicin and tobramycin penetrated into the aqueous humour of patients, whereas kanamycin was not able to overcome the corneal barrier. Acuvue contact lenses soaked in 0.3% eye drop solutions can release sufficient amounts of gentamicin, ciprofloxacin and ofloxacin to produce bacteriostatic concentrations in the humor aquosus. Acuvue contact lenses can be recommended as a drug delivery system for fluoroquinolones. Received: 15 October 1998 / Accepted in revised form: 16 December 1998     

Penetration of ciprofloxacin, norfloxacin and ofloxacin into the aqueous humour of patients by different topical application modes

Objectives: A prospective study was undertaken to determine the transcorneal penetration of three topically applied fluoroquinolones into aqueous humour. Methods: Two hundred and twenty-four patients undergoing cataract extraction received 0.3% ciprofloxacin, norfloxacin or ofloxacin eye drops by two different administration modes with different frequencies and intervals of application. At the beginning of cataract extraction (0.5–3 h after the last drop), 50–100 μl aqueous fluid was aspirated from the anterior chamber and immediately stored at −80 °C. Antibiotic concentrations were measured using high-performance liquid chromatography. Results: Generally, topical ofloxacin and ciprofloxacin yielded aqueous humour levels higher than topical norfloxacin. The highest concentrations of all tested fluoroquinolones were measured after using an application mode, in which one drop was given every 15 min between 0600 hours and 0800 hours, prior to operation. When applied by this mode, ciprofloxacin achieved a mean aqueous level of 0.380 (±0.328) μg · ml⁻¹ (range 0.033–1.388 μg · ml⁻¹), norfloxacin 0.182 (0.118) μg · ml⁻¹ (range 0.038–0.480 μg · ml⁻¹) and ofloxacin 0.564 (0.372) μg · ml⁻¹ (range 0.064–1.455 μg · ml⁻¹). These mean concentrations were above the minimum inhibitory concentration (MIC₉₀), concentrations required for inhibition of 90% of pathogen strains in vitro of gram-negative bacteria, such as Proteus mirabilis and Escherichia coli. Therapeutic values above the MIC₉₀ of Staphylococcus epidermidis, the pathogen causing eye infections most frequently, were reached by 67.5% of patients after ofloxacin and by 41% after ciprofloxacin, but never after norfloxacin treatment. Conclusion: Of the currently available topical fluoroquinolones, ofloxacin achieved the highest aqueous humour concentration. This fluoroquinolone may be an useful ophthalmic agent for topical antibacterial management, but it does not seem to be prophylactically effective against Streptococcus pneumoniae or Pseudomonas aeruginosa. Received: 22 April 1997 / Accepted: 8 June 1997     

<Emphasis Type="BoldItalic">In Vitro</Emphasis> Effects on MCF-7 Breast Cancer Cells Of Signal Transduction Inhibitor/Tamoxifen/Eicosapentaenoic Acid Combinations and their Simultaneous Delivery Across Skin

Purpose  To determine the in vitro effects of simultaneously administered LY29400, PD98059, tamoxifen and eicosapentaenoic acid (EPA) on breast cancer cells, and determine their transcutaneous delivery. Methods  Growth assays were performed on MCF-7 cells challenged with IC₅₀ and permeated concentrations of PD98059, LY294002 and tamoxifen firstly in isolation then combined. Permeation studies were performed using PD98059 and LY294002 (singly or simultaneously) in DMSO then fish oil, with enhancers. Immunocytochemical detection of phospho-MAPK, phospho-Akt, total COX-2 and Ki-67 was performed. Results  When applied singly, fluxes of PD98059 and LY294002 were 0.09 ± 0.008 and 0.14 ± 0.045 μg cm⁻² h⁻¹, respectively; applied simultaneously, 0.18 ± 0.045 and 0.49 ± 0.051 μg cm⁻² h⁻¹. Permeated concentrations of PD98059 and LY294002 reduced growth to 13.78 ± 0.63%. Fish oil plus 2.5% DMSO/ethanol allowed 5.96 ± 0.9 and 7.7 ± 1.2 μg cm⁻² of PD98059 and LY294002 to permeate after 48 h. Conclusions  PD98059 and LY294002 permeate excised skin at therapeutically useful rates, and also demonstrate growth inhibitory effects on MCF-7 cancer cells. Synergism was noted in co-transport across skin and activity against cancer cells. A formulation based on fish oil is potentially skin friendly; simultaneous permeation of EPA provides further anti-cancer action.     

Distribution and metabolism of N G-nitro-l-arginine methyl ester in patients with septic shock

Objective: The pharmacokinetics of N ^G-nitro-l-arginine methyl ester (l-NAME), an inhibitor of nitric oxide (NO) synthesis, was investigated in patients with septic shock. Methods: Blood was sampled at intervals before, during and after 12-h infusion of l-NAME 1 mg · kg⁻¹ · h⁻¹ in nine septic shock patients for determination of plasma concentrations by high-performance liquid chromatography (HPLC). In three patients the renal clearance of the drug was determined. Results: Incubation of l-NAME with plasma and blood in vitro revealed hydrolysis to N ^G-nitro-l-arginine (l-NOARG), the active inhibitor of NO synthesis. l-NOARG did not undergo further degradation. Continuous intravenous infusion of 1 mg · kg⁻¹ · h⁻¹ of l-NAME for 12 h in patients with septic shock increased blood pressure and resulted in increasing plasma concentrations of l-NOARG (C_max 6.2 μg · ml⁻¹ at 12 h) whereas l-NAME concentrations reached a plateau within 1.5 h (C_max 1.0 μg · ml⁻¹). After the infusion was stopped l-NAME disappeared from the plasma rapidly (half-life 19.2 min) whereas l-NOARG concentration declined slowly (half-life 22.9 h). The calculated volume of distribution for l-NAME was 0.45 l · kg⁻¹ body weight and 1.96 l · kg⁻¹ for l-NOARG. The renal clearance for l-NOARG was 3.5% of total body clearance for l-NOARG, whereas l-NAME could not be detected in urine. Conclusion: We conclude that vasoconstriction with l-NAME in septic patients may result from hydrolysis to l-NOARG, the active inhibitor of NO synthesis. The long plasma half-life and large volume of distribution for l-NOARG suggests extensive distribution to extravascular tissues. Since renal excretion is minimal, elimination of the metabolite l-NOARG follows other pathways. Received: 13 March 1998 / Accepted in revised form: 30 June 1998     

Anti-inflammatory activity of the constituents of the roots of <Emphasis Type="Italic">Aralia continentalis</Emphasis>

To assess the anti-inflammatory activity of the constituents of the roots of Aralia continentalis, ent-pimara-8(14),15-diene-19-oic acid (continentalic acid, pimaradienoic acid, compound I), 7β-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (compound II), 7-oxo-ent-pimara-8(14),15-diene-19-oic acid (compound III), 15α,16α-epoxy-17-hydroxy-ent-kauran-19-oic acid (compound IV) and ent-kaura-16-en-19-oic acid (kaurenoic acid, compound V), their inhibitory effects against cyclooxygenase-2 (COX-2)-catalyzed PGE₂ and inducible nitric oxide synthase (iNOS)-catalyzed NO production by lipopolysaccharide-treated RAW 264.7 cells were examined. Among the compounds tested, compound III and V moderately inhibited NO production. In addition, compound III weakly inhibited PGE₂ production, while treatment with compounds II and IV at concentrations of up to 100 μM had no significant effects. Conversely, compound I only weakly inhibited PGE₂ and NO production. To elucidate the mechanism by which these changes occurred, the iNOS down-regulating capacity of compound III was investigated. Western blot analysis and an electrophoretic mobility shift assay demonstrated that compound III weakly inhibited COX-2 and iNOS expression at 50–100 μM, and inhibited NF-κB activation. When in vivo anti-inflammatory activities of compounds I, III and V were examined, intraperitoneal injection of 4–100 mg/kg of compound I and V significantly inhibited carrageenaninduced paw edema in mice, whereas compound III did not. Taken together, the results of this study suggest that some constituents of A. continentalis, especially compounds I, III and V, exert significant anti-inflammatory activity, which suggests that these constituents contribute, at least in part, to the anti-inflammatory action of the roots of A. continentalis.     

Inhibition of cyclooxygenase-2 and inducible nitric oxide synthase by silymarin in proliferating mesenchymal stem cells: comparison with glutathione modifiers

Silymarin, a mixture of flavonolignans, is extracted from milk thistle (Silybum marianum) and has a strong antioxidant activity and exhibits anticarcinogenic, anti-inflammatory, and cytoprotective effects. In this study we attempted to determine whether silymarin and the glutathione modifiers, buthionine sulfoxamine (BSO) and N-acetylcysteine (NAC), are involved in regulation of cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) in proliferating mesenchymal stem cells (MSCs). Cellular glutathione was manipulated during a 14-day culture using BSO, NAC and silymarin. At intervals of 2, 7 and 14 days, cells were collected and COX-2 and iNOS levels were measured. In parallel, generation of cellular H₂O₂ and glutathione were measured. Supplementation of the culture media with BSO caused a dose-dependent decrease in MSC proliferation, whereas NAC or silymarin elevated the proliferation (p < 0.05). Treatment of MSC with NAC or silymarin caused a significant decrease in COX-2 levels. However, COX-2 levels in cells treated with high levels of NAC (1.0 mM) were significantly lower than those in MSCs treated with high levels of silymarin (100 μM). BSO (1.0 and 5.0 μM) caused a significant increase in COX-2 on days 2, 7 and 14. BSO caused a significant increase in iNOS, whereas NAC or silymarin decreased cellular iNOS. Overall result show that glutathione, iNOS and COX-2 in proliferating MSCs are affected by silymarin treatment. It appears that glutathione is the main target of silymarin, and in consequence iNOS and COX-2 are affected in response to silymarin treatment.     

The extrapulmonary effects of increasing doses of formoterol in patients with asthma

Objective: To assess the cardiovascular and metabolic responses to increasing doses of formoterol administered from a dry powder inhaler. Methods: Twenty patients with mild to moderate asthma were given 12, 24, 48 and 96 μg of formoterol or a matched placebo on separate days. The doses were administered using a randomised, cross-over, double-blind design. The effects on heart rate, blood pressure, electromechanical systole (QS₂I), the electrocardiographic QTc interval, plasma potassium (K); blood glucose and FEV₁ were assessed prior to, and for 9 h following each dose. Results: There was no difference between the maximum effects of formoterol 12 μg and placebo; the 24 μg dose significantly decreased plasma K (−0.2 mmol · l⁻¹) and increased blood glucose (1.8 mmol · l⁻¹) compared to placebo. The two highest doses affected most of the variables with the 96 μg dose being significantly different from placebo for all indices, heart rate (9 beats · min⁻¹), systol BP (4 mmHg), diastolic BP (−3 mmHg), QS₂I (−11 ms), QTc (17 ms), plasma K (−0.5 mmol · l⁻¹) and blood glucose (2.6 mmol · l⁻¹). All doses of formoterol increased FEV₁. Conclusion: Although there were dose-dependent effects on the extrapulmonary measurements, only the effects at the highest dose may be of clinical significance. Received: 17 June 1997 / Accepted in revised form: 12 November 1997     

Pharmacokinetics and pharmacodynamics of acetazolamide in patients with transient intraocular pressure elevation

Objective: To characterize the pharmacokinetics and pharmacodynamics of acetazolamide in patients with transient intraocular pressure (IOP) elevation and to provide individual patients with the optimal dosage regimen for this drug. Methods: We studied 17 patients with transient IOP elevation, who were given 62.5–500 mg acetazolamide orally as single or repetitive doses. Plasma acetazolamide concentration and IOP were measured at approximately 1, 3, 5, and 9 h after the last acetazolamide administration. Pharmacokinetics and pharmacodynamics were analyzed by nonlinear mixed-effect modeling using the program NONMEM. Results: The plasma concentration profile of acetazolamide was characterized by a one-compartment model with first-order absorption. The apparent oral clearance was related to the creatine clearance (CCR) which was estimated by the Cockcroft and Gault equation, as follows: 0.0468 · CCR l · h⁻¹. The estimated apparent oral volume of distribution, first-order absorption rate constant, and absorption lag time were 0.231 l · kg⁻¹, 0.821 · h⁻¹, and 0.497 h, respectively. IOP after oral acetazolamide administration was characterized by an E_max model. The maximal effect in lowering the IOP (E_max) was 7.2 mmHg, and the concentration corresponding to 50% of the maximal effect (EC₅₀) was 1.64 μg · ml⁻¹. As 70% of E_max was achieved at a plasma concentration of 4 μg · ml⁻¹, this concentration was considered satisfactory for lowering IOP. The recommended dosage was calculated so that the minimum plasma concentration at steady state exceeded this target concentration; 250 mg t.i.d., 125 mg t.i.d., 125 mg b.i.d., and 125 mg once daily for the patients with CCR values of 70, 50, 30, and 10 ml · min⁻¹, respectively. Conclusion: Measuring plasma concentrations of acetazolamide and subsequent pharmacokinetic and pharmacodynamic analyses are useful for estimating its concentration-dependent effectiveness in lowering the IOP in individual patients. The dosage regimen presented in this study is expected to improve the benefits of acetazolamide pharmacotherapy in most elderly patients with transient rises in IOP following intraocular surgery. Received: 10 April 1997 / Accepted in revised form: 21 October 1997     

Adrenocortical activity with repeated administration of one-daily inhaled fluticasone propionate and budesonide in asthmatic adults

Objective: The aim of this study was to evaluate the steady-state effects of once-daily inhaled fluticasone propionate (FP) and budesonide (BUD) on adrenocortical activity in asthmatic patients. Methods: Ten asthmatic patients with a mean age of 31.2 years, a mean forced expiratory volume in 1 s (FEV₁) of 91% predicted and a forced mid-expiratory flow (FEF_25–75) of 62.3% predicted were studied in a single-blind randomised crossover design comparing placebo (PL), FP (375 μg per day and 750 μg per day) and BUD (400 μg per day and 800 μg per day) all given once daily for 4 days at each dose via a pressurised metered dose inhaler (pMDI) at 0800 hours. After 4 days of treatment, plasma cortisol was measured at 0800 hours (24 h after the last dose) and a 10-h overnight urine collection was taken, 14 h after the last dose (2200–0800 hours) for analysis of cortisol and creatinine excretion. Results: Plasma cortisol levels (nmol · l⁻¹, as geometric mean) at 0800 hours demonstrated a significant difference between the highest doses of FP and BUD (424.1 vs 510.3 nmol · l⁻¹, respectively) but not between the low doses (506.8 vs 514.9 nmol · l⁻¹; PL 532.2 nmol · l⁻¹). For the highest dose FP (750 μg) this equated to 20% suppression of 0800 hours plasma cortisol. Likewise, for overnight urinary cortisol output (nmol · 10 h⁻¹, as geometric mean), there was a significant difference at the high doses of FP and BUD (25.5 vs 38.2 nmol · 10 h⁻¹), but not at the low doses 31.3 vs 34.8 nmol · 10 h⁻¹; PL 32.0 nmol · 10 h⁻¹. For the overnight urinary cortisol/creatinine ratio (nmol · mmol⁻¹, as geometric mean) there was a similar trend; 4.5 vs 6.1 nmol · mmol⁻¹ for high dose and 5.6 vs 6.3 nmol · mmol⁻¹ for low dose; PL 5.9 nmol · mmol⁻¹. Conclusion: Repeated doses of FP 750 μg once daily caused greater adrenal suppression than BUD 800 μg once daily, when comparing effects on plasma cortisol levels at 0800 hours, 24 h after the last dose, as well as effects on overnight urinary cortisol output. Neither FP 375 μg once daily nor BUD 400 μg once daily produced detectable adrenal suppression. Received: 29 April 1997 / Accepted in revised form: 5 July 1997     

The relevance of inhibitor-substrate interactions when measuring neuropathy target esterase inhibition

Neuropathy target esterase (NTE), thought to be the target for organophosphate polyneuropathy, is operationally defined as that neural phenyl valerate esterase resistant to paraoxon (40 μM) and sensitive to mipafox (50 μM; 20 min, pH 8.0, 37°C). The time course of inhibition of particulate paraoxon pretreated esterases by mipafox showed that the lines indicating the rate of inhibition did not pass through the log 100% activity when extrapolated at zero time. Slopes of inhibition of NTE were not linearly related to the concentration of mipafox. Kinetic parameters derived from Wilkinson type plots were: K _a=49–199 μM, k ₊₂=0.24–0.64 min⁻¹ and k _a=3.1–5.0 mM⁻¹m⁻¹. When mipafox was removed (either by dilution or centrifugation) before the addition of phenyl valerate intercepts below 100% disappeared. We confirm that the formation of Michaelis complex between NTE and mipafox is not prevented by phenyl valerate and that inhibition proceeds after addition of phenyl valerate. We compared inhibitions obtained with experiments by using the traditional method (sequential incubation with inhibitors and phenyl valerate) to those obtained with a method where mipafox is removed before the addition of substrate. When calculating fixed-time 50% inhibitory concentrations (IC₅₀s) of some inhibitors for NTE, the longer the hydrolysis time, the lower were the IC₅₀s. Therefore, the inhibitory potency of certain NTE inhibitors, is accurately assessed only when calculating second-order rate constants (k _a). Received: 22 June 1999 / Accepted: 2 November 1999     

Pharmacokinetics of intravenous ATP in cancer patients

Objective: To characterise the pharmacokinetics of adenosine 5′-triphosphate (ATP) in patients with lung cancer after i.v. administration of different ATP dosages. Methods: Twenty-eight patients received a total of 176 i.v. ATP courses of 30 h. Fifty-two infusions were given as low-dose infusions of 25–40 μg kg⁻¹ min⁻¹, 47 as middle-dose infusions of 45–60 μg kg⁻¹ min⁻¹ and 77 as high-dose infusions of 65–75 μg kg⁻¹ min⁻¹ ATP. Kinetic data of ATP concentrations in erythrocytes were available from 124 ATP courses. Results are expressed as mean ± SEM. Results: Most ATP courses in cancer patients were without side effects (64%), and side effects occurring in the remaining courses were mild and transient, resolving within minutes after decreasing the infusion rate. Baseline ATP concentration in erythrocytes was 1554 ± 51 μmol l⁻¹. ATP plateau levels at 24 h were significantly increased by 53 ± 3, 56 ± 3 and 69 ± 2% after low-dose, middle-dose and high-dose ATP infusions, respectively. At the same time, significant increases in plasma uric acid concentrations were observed: 0.06 ± 0.01, 0.11 ± 0.01 and 0.16 ± 0.01 mmol l⁻¹, respectively. The mean half-time for disappearance of ATP from erythrocytes, measured in five patients, was 5.9 ± 0.5 h. Conclusions: During constant i.v. infusion of ATP in lung cancer patients, ATP is taken up by erythrocytes and reaches dose-dependent plateau levels 50–70% above basal concentrations at approximately 24 h. Received: 7 July 1999 / Accepted in revised form: 30 December 1999     

Influence of beta-blockers on melatonin release

Objective: Melatonin is a mediator in the establishment of the circadian rhythm of biological processes. It is produced in the pineal gland mainly during the night by stimulation of adrenergic beta₁- and alpha₁-receptors. Sleep disturbances are common side-effects of beta-blockers. The influence of specific beta-blockade as well as that of combined alpha-and beta-blockade on melatonin production has not been investigated in humans before. Methods: We performed a randomized, double-blind, placebo-controlled, cross-over study in 15 healthy volunteers. Subjects received single oral doses of 40 mg (R)-propranolol, 40 mg (S)-propranolol, 50 mg (R)-atenolol, 50 mg (S)-atenolol, 25 mg (R,S)-carvedilol, 120 mg (R,S)-verapamil or placebo at 1800 hours. Urine was collected between 2200 hours and 0600 hours, and 6-sulfatoxy-melatonin (aMT6s), the main metabolite of melatonin which is almost completely eliminated in urine, was determined by radioimmunoassay (RIA). Results: Mean nocturnal excretion of aMT6s in urine after intake of the drugs was as follows (in μg): placebo 26; (R)-propranolol 24 (−7%, NS); (S)-propranolol 5 (−80%, P < 0.001); (R)-atenolol 27 (+7%, NS); (S)-atenolol 4 (−86%, P < 0.01); (R,S)-carvedilol 23 (−10%, NS); (R,S)-verapamil 29 (+14%, NS). These data show that only the specifically beta-blocking (S)-enantiomers of propranolol and atenolol decrease the nocturnal production of melatonin whereas the non-beta-blocking (R)-enantiomers have no effect. Unexpectedly, (R,S)-carvedilol which inhibits both alpha- and beta-adrenoceptors does not decrease melatonin production. Conclusion: These findings indicate that beta-blockers decrease melatonin release via specific inhibition of adrenergic beta₁-receptors. Since lower nocturnal melatonin levels might be the reason for sleep disturbances, further clinical studies should investigate whether or not oral administration of melatonin might avoid this well-known side-effect of beta-blockers. The reason why (R,S)-carvedilol does not influence melatonin production remains to be determined. Received: 10 August 1998 / Accepted in revised form: 25 November 1998     

Pharmacokinetics and tolerability of oral iloprost in thromboangiitis obliterans patients

Objective: Iloprost is a potent PGI₂ mimetic, which has been shown to be therapeutically effective in several vascular disorders. Due to its rapid clearance from the central compartment, iloprost is administered mainly by i.v. infusion, which limits its use to hospitalized patients. In order to improve pharmacotherapeutic use of this PGI₂ mimetic, an oral extended-release (ER) dosage form has been developed, which should mimic plasma level profiles as observed after i.v. infusion and serve as a therapeutic equivalent. Methods: This trial was performed to investigate the tolerability and pharmacokinetics of iloprost administered perorally, compared with i.v. infusion, in 12 patients suffering from thromboangiitis obliterans (TAO). A dose titration was carried out for 1 week with i.v. iloprost, followed by a p.o. titration and treatment phase of 3 weeks' duration. Pharmacokinetics was investigated at the individually tolerated dose levels; i.e., on days 5–7 (i.v. infusion at 2, 2.5 and 3 ng · kg⁻¹ · min⁻¹), and twice during p.o. treatment after b.i.d. administration of 50, 100, 150, 200 or 300 μg. Results: Individual tolerability of iloprost varied: 7 patients out of 12 tolerated the maximum i.v. dose of 3 ng · kg⁻¹ · min⁻¹; six tolerated the maximum oral dose of 600 μg. No patients withdrew from the study due to adverse events. Flush and headache were the most common adverse events and seemed to be related to the study drug. After i.v. infusion of iloprost, dose-normalized (3 ng · kg⁻¹ · min⁻¹), steady-state plasma levels were 260 pg · ml⁻¹. Terminal half-life was 0.57 h. Total clearance ranged from 8 to 17 ml · min⁻¹ · kg⁻¹. Peroral administration of the ER formulation resulted in dose-dependent C_max and AUC values. AUC values of the first and second daily dose interval, i.e., 0–5 h and 5–11 h after first dosing, were almost identical. Absolute bioavailability was 24%, with the exception of two patients who tolerated only 50 μg b.i.d. and exhibited a bioavailability of approx. 60%. The AUC values observed in weeks 2 and 4 were identical, demonstrating low day-to-day variability of iloprost plasma level profiles in TAO patients. Conclusion: Based upon pharmacokinetic data, the ER formulation provides an equivalent to the i.v. infusion of iloprost and broadens the range of therapy to non-hospitalized patients. The availability of capsules with 50 and 100 μg iloprost enables individual dose titration and pharmacotherapy. Beneficial effects, as observed with i.v. iloprost in TAO patients, should therefore be achievable by peroral pharmacotherapy using the new ER formulation. Received: 18 July 1996 / Accepted in revised form: 2 April 1997     

Anti-oxidative and inhibitory activities on nitric oxide (NO) and prostaglandin E<Subscript>2</Subscript> (COX-2) production of flavonoids from seeds of <Emphasis Type="Italic">Prunus tomentosa</Emphasis> Thunberg

Chemical investigation of the 80% Me₂CO extract from the seeds of Prunus tomentosa led to the isolation and identification of six flavonoids: kaempferol (1), kaempferol 3-O-α-L-rhamnopyranoside (2; afzelin), kaempferol 3-O-β-D-(6-acetyl)-glucopyranosyl(1→4)-α-L-rhamnopyranoside (3; multiflorin A), kaempferol 3-O-β-D-glucopyranosyl(1→4)-α-L-rhamnopyranoside (4; multiflorin B), quercetin 3-O-α-L-rhamnopyranoside (5; quercitrin), and quercetin 3-O-β-D-glucopyranosyl (1→4)-α-L-rhamnopyranoside (6; multinoside A). Anti-oxidative and inhibitory activities on nitric oxide (NO) and prostaglandin E₂ production in interferon-γ (INF-γ) and lipopolysaccharide (LPS)-activated RAW 264.7 cells in vitro (COX-2) of the isolated compounds were evaluated. Compounds 1, 5, and 6 exhibited potent anti-oxidative activity in the DPPH radical scavenging assay with IC₅₀ values of 57.2, 59.4, and 54.3 μg/mL respectively. The positive control, ascorbic acid, had an IC₅₀ of 55.5 μg/mL. Compounds 1, 5, and 6 also reduced COX-2 levels in a dose dependent manner with IC₅₀ values of 10.2, 8.7, and 9.6 μg/mL respectively, with the positive control, indomethacin, having an IC₅₀ of 5.1 μg/mL. All six compounds inhibited NO production in a dose dependent manner with IC₅₀ values of 35.1, 42.8, 40.0, 44.8, 43.7, and 43.9 μg/mL respectively, while the positive control, L-NMMA, had an IC₅₀ of 42.1 μg/mL.