Pharmacology of the pyrroloimidazole, SK&F 105809--I. Inhibition of inflammatory cytokine production and of 5-lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid

SK&F 105809 [2-(4- methylsulfinylphenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2- a] imidazole] was determined to be a prodrug for the sulfide metabolite SK&F 105561 [2-(4- methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2-a] imidazole] which inhibited interleukin-1 (IL-1) production in vitro and both 5-lipoxygenase (5-LO) and prostaglandin H (PGH) synthase activities in vitro and ex vivo. SK&F 105561 inhibited partially purified 5-LO with a half-maximal concentration (IC50) of 3 microM. This inhibition was reversible, independent of preincubation time, and dependent on the concentration of the substrate arachidonic acid. SK&F 105561 also inhibited purified PGH synthase with the potency dependent on the level of peroxidase activity. The IC50 was 100 microM in the absence of peroxidase activity, whereas an IC50 of 3 microM was observed in the presence of peroxidase activity. Using human monocytes, SK&F 105561 inhibited A23187-stimulated prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) production with IC50 values of 0.1 and 2 microM, respectively. In addition, IL-1 production by lipopolysaccharide-stimulated human monocytes was also inhibited (IC50 2 microM). Oral administration of SK&F 105809 to rats resulted in a dose-related generation of SK&F 105561 and in the inhibition of thromboxane B2 and LTB4 production ex vivo with a half-maximal dose (ED50) of 15 and 60 mg/kg, respectively. SK&F 105561 showed weak inhibitory activity on 12-lipoxygenase with an IC50 of greater than 200 microM. Neither SK&F 105561 nor SK&F 105809 inhibited the stimulated-turnover of arachidonic acid-containing phospholipids in human monocytes or the activity of cell-free phospholipases A2 and C. Moreover, neither SK&F 105561 nor SK&F 105809 antagonized the binding of LTB4 or leukotriene D4 to membrane receptors. From these results, SK&F 105561, the active principle of SK&F 105809, acts as an inhibitor of both inflammatory cytokine and eicosanoid production.     

SK&F 86002: a structurally novel anti-inflammatory agent that inhibits lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid

The effects of SK&F 86002 [5-(4-pyridyl)-6 (4-fluorophenyl)-2,3-dihydroimidazo (2,1-b) thiazole] on the generation of eicosanoids in vitro and on inflammatory responses in vivo are described and compared to other non-steroidal anti-inflammatory drugs. SK&F 86002 inhibited prostaglandin H2 (PGH2) synthase activity (IC50 120 microM) as well as prostanoid production by rat basophilic leukemia (RBL-1) cells (IC50 70 microM) and its sonicate (IC50 100 microM) and human monocytes (IC50 1 microM). In addition, SK&F 86002 inhibited the generation of dihydroxyeicosatetraenoic acid (diHETE) and 5-hydroxyeicosatetraenoic acid (5-HETE) by a high speed supernatant fraction of RBL-1 cells (IC50 10 microM). Cellular production of 5-lipoxygenase products was inhibited by SK&F 86002 as measured by leukotriene B4 (LTB4) generation from human neutrophils (IC50 20 microM), leukotriene C4 (LTC4) generation by human monocytes (IC50 20 microM), and 5-HETE production by RBL-1 cells (IC50 40 microM). The in vivo profile of anti-inflammatory activity of SK&F 86002 supports the dual inhibition of arachidonate metabolism as indicated by its activity in inflammation models that are insensitive to selective cyclooxygenase inhibitors. The responses of arachidonic-acid-induced edema in the mouse ear and rat paw, as well as the cell infiltration induced by carrageenan in the mouse peritoneum and by arachidonic acid in the rat air pouch, were inhibited by SK&F 86002 and phenidone but not by the selective cyclooxygenase inhibitors naproxen and indomethacin.     

Pharmacological profile of celecoxib, a specific cyclooxygenase-2 inhibitor

The pharmacological profile of celecoxib (CAS 169590-42-5, SC-58635), a specific cyclooxygenase-2 (COX-2) inhibitor, was investigated. Celecoxib inhibited COX-2-mediated prostaglandin E2 (PGE2) production in human dermal fibroblasts (IC50 = 91 nmol/l), whereas it was a weak inhibitor of COX-1-mediated PGE2 production in human lymphoma cells (IC50 = 2800 nmol/l). In in vivo studies, the effects of celecoxib were compared with those of nonsteroidal anti-inflammatory drugs (NSAIDs) in acute rat models of hyperalgesia and pyrexia. Celecoxib abrogated carrageenan-induced hyperalgesia in the hind paw accompanied by a decrease in PGE2 content in paw exudates and cerebrospinal fluid in a dose-related manner, with an ED30 = 0.81 mg/kg. Its analgesic potency was comparable to those of NSAIDs. In lipopolysaccharide-induced pyrexia, the anti-pyretic potency of celecoxib was equal to that of NSAIDs. On the other hand, in a gastric toxicity study in rats, single oral administration of celecoxib had no effect on gastric mucosa or mucosal PGE2 content at doses up to 200 mg/kg. Additionally, celecoxib did not inhibit thromboxane B2 production of calcium ionophore-stimulated peripheral blood of rats or arachidonic acid-induced aggregation of human platelets. These findings suggest that celecoxib might be a safe and effective alternative to NSAIDs for clinical use.     

The mixed lipoxygenase/cyclooxygenase inhibitor SK&F 105809 reduces cerebral edema after closed head injury in rat.

Closed head injury in rats induces edema formation, which is indicated by a decrease in cerebral specific gravity and an increase in water content. We previously described the activation of the eicosanoid metabolic cascade, namely, activation of PLA2 and accumulation of products of both 5-lipoxygenase (5-LO) and cyclo-oxygenase (CO) in the same model of head injury. The present study was designed to determine the effect of a novel drug, SK&F 105809, a dual inhibitor of 5-LO and CO on cerebral edema formation after head injury in rats. Rats, under ether anesthesia, were subjected to sham operation or trauma induced by weight-drop device impacting over the left calvarium. One group of traumatized rats received 0.9% saline and served as control and two other groups were treated with SK&F 105809, 20 or 30 mg/kg, i.p. immediately after the impact. In one group treatment was repeated additionally 2.5 h post-trauma. Four hours after trauma, rats were sacrificed and brain edema was evaluated. SK&F 105809 treated rats which received 30 mg/kg had significantly less brain edema, as measured by both gravimetry and water content, at 4 h after trauma. The lower dose, 20 mg/kg, had no effect. Our results suggest that treatment with a mixed 5-LO/CO inhibitor shortly after head injury will result in less brain edema and ultimately improved functional outcome.     

Effects of CI-930, a novel phosphodiesterase III inhibitor, on platelet aggregation and arachidonic acid metabolism

In the platelet-rich plasma of rabbits, 4,5-dihydro-6-[4-(1H-imidazol-1-yl)phenyl]-5-methyl-3(2H)-pyridazinone (CI-930) inhibited platelet aggregation triggered by AA, U-46619, ADP, collagen and PAF, with the IC50 values of 0.91, 0.73, 2.12, 2.35 and 7.15 mumols/L, respectively. The inhibitory effect of CI-930 on AA-induced aggregation was potentiated by PGE1, an adenylate cyclase activator, and antagonized by SQ-22536, an adenylate cyclase inhibitor. The contents of cAMP in washed rabbit platelets were increased by CI-930 5-50 mumols/L. In the concentration range of 0.5-500 mumols/L, CI-930 reduced the synthesis of TXB2 by either washed rat or rabbit platelets or rat pleural neutrophils. At the same time, CI-930 induced a dose-dependent increase of PGE2, PGF2a, and PGD2 biosynthesis by rat platelets and had no significant influence on the formation of 6-keto-PGF1a by the neutrophils. It is showed that CI-930 is an anti-platelet agent with a wide-spectrum activity and its anti-aggregating action may be exerted by dual mechanisms, both increasing cAMP contents and selectively inhibiting TXA2 synthesis in platelets.     

Pharmacological profile of a specific neutrophil elastase inhibitor,Sivelestat sodium hydrate

Imbalance between neutrophil elastase (NE) and its endogenous protease inhibitors has been considered to be one of possible mechanisms by which NE causes lung tissue destruction. It has been shown that the amount and/or activity of NE is increased in blood and bronchoalveolar lavage fluid in patients with acute lung injury. Accordingly, animals undergoing acute lung injury have increased NE activity such as in blood and bronchoalveolar lavage fluid. Sivelestat sodium hydrate (Sivelestat) is a synthetic inhibitor of NE with highly specificity to NE. Many studies have indicated that Sivelestat treatment improves inflammatory and edematous changes of lungs and survival as well as increased NE activity in several animal models of acute lung injury. Clinical studies have demonstrated that Sivelestat improves this injury that is associated with systemic inflammatory response syndrome. As compared with endogenous protease inhibitors that have high molecular mass, Sivelestat, a synthetic and low molecular weight elastase inhibitor, may be delivered to the inflammatory sites more easily and effectively and is considred to improve typical symptoms of acute lung injury. Clinical use of Sivelestat would further clarify the usefulness of this compound in clinical acute lung injury.     

Cardiovascular profile of duloxetine, a dual reuptake inhibitor of serotonin and norepinephrine

This analysis assessed the effects of duloxetine, a dual reuptake inhibitor of serotonin and norepinephrine, on indices of cardiovascular safety, including heart rate, blood pressure (BP), and electrocardiograms (ECGs), in a large group of clinical trial patients with depression. Data were available from 8 double-blind, randomized, placebo-controlled (n = 777), and active comparator-controlled depression trials. Duloxetine (n = 1139) doses ranged from 40 to 120 mg/d, and fluoxetine (n = 70) and paroxetine (n = 359) were administered at a dose of 20 mg/d. Patients were treated for 8 to 9 weeks. There was a significant increase for duloxetine compared with placebo for heart rate (1.6 vs. -0.6 beats per minute) and for systolic BP (1.0 vs. -1.2 mm Hg); the difference for diastolic BP (1.1 vs. 0.3) was not significant. There were no significant differences between duloxetine and placebo treatment groups in the incidence of sustained (at least 3 consecutive visits) elevations in systolic (duloxetine 1.0%, placebo 0.4%), diastolic (duloxetine 0.4%, placebo 0.4%), or either (duloxetine 1.3%, placebo 0.8%) BP. Moreover, the effect of duloxetine on mean changes in supine systolic and diastolic BP was not significantly different from that of fluoxetine or paroxetine. Drug-placebo differences in mean changes in electrocardiograms (eg, QTc, PR, and QRS intervals) were neither statistically nor clinically significant, with the exception that duloxetine 120 mg/d had significant decreases in PR and QRS intervals compared with placebo. These data demonstrate that duloxetine has modest effects on heart rate and BP and no clinically meaningful effect on electrocardiogram profiles in a relatively healthy cohort of clinical trial patients. The cardiovascular effects of duloxetine appear to be comparable with medications considered to be first-line options for depression.     

Pharmacological profile of opicapone,a thirdgeneration nitrocatechol catechol-O-methyl transferase inhibitor,in the rat

Background and Purpose

Catechol-O-methyltransferase (COMT) is an important target in the levodopa treatment of Parkinson''s disease; however, the inhibitors available have problems, and not all patients benefit from their efficacy. Opicapone was developed to overcome those limitations. In this study, opicapone''s pharmacological properties were evaluated as well as its potential cytotoxic effects.

Experimental Approach

The pharmacodynamic effects of opicapone were explored by evaluating rat COMT activity and levodopa pharmacokinetics, in the periphery through microdialysis and in whole brain. The potential cytotoxicity risk of opicapone was explored in human hepatocytes by assessing cellular ATP content and mitochondrial membrane potential.

Key Results

Opicapone inhibited rat peripheral COMT with ED₅₀ values below 1.4 mg⋅kg⁻¹ up to 6 h post-administration. The effect was sustained over the first 8 h and by 24 h COMT had not returned to control values. A single administration of opicapone resulted in increased and sustained plasma levodopa levels with a concomitant reduction in 3-O-methyldopa from 2 h up to 24 h post-administration, while tolcapone produced significant effects only at 2 h post-administration. The effects of opicapone on brain catecholamines after levodopa administration were sustained up to 24 h post-administration. Opicapone was also the least potent compound in decreasing both the mitochondrial membrane potential and the ATP content in human primary hepatocytes after a 24 h incubation period.

Conclusions and Implications

Opicapone has a prolonged inhibitory effect on peripheral COMT, which extends the bioavailability of levodopa, without inducing toxicity. Thus, it exhibits some improved properties compared to the currently available COMT inhibitors.     

Pharmacology of the pyrroloimidazole, SK&F 105809--II. Antiinflammatory activity and inhibition of mediator production in vivo

SK&F 105809 [2-(4-methylsulfinylphenyl)-3-(4-pyridyl)- 6,7-dihydro-[5H]-pyrrolo[1,2,a] imidazole] demonstrated unique antiinflammatory activities in murine models that are resistant to selective cyclooxygenase (CO) inhibitors. Both edema and inflammatory cell infiltration induced by the topical application of arachidonic acid to the mouse ear were decreased by SK&F 105809 (ED50 values of 44 mg/kg, p.o.). Polymorphonuclear leukocyte (PMN) infiltration following the intraperitoneal injection of either monosodium urate crystal or carrageenan was inhibited with ED50 values of 64 and 72 mg/kg, p.o., respectively. These inflammatory responses were unaffected by the selective cyclooxygenase inhibitor naproxen. SK&F 105809 also inhibited leukotriene B4 (LTB4) and prostaglandin E2 production in vivo in arachidonic acid-induced inflammatory exudates (ED50 values of 41 and 15 mg/kg, p.o., respectively). The inhibition of LTB4 production preceded the inhibition of PMN infiltration. The impact of inhibition of both 5-lipoxygenase (5-LO) and CO was seen with platelet-activating factor-induced vascular permeability which was inhibited markedly by SK&F 105809. However, the 5-LO inhibitor, phenidone, only strongly inhibited when coadministered with the selective CO inhibitor, indomethacin. In spite of a short half-life (14-18 min) for both SK&F 105809 and the active metabolite SK&F 105561 [2-(4- methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2-a] imidazole], the pharmacological activity lasted at least 1.5 hr. The biochemical evidence of inhibition of interleukin-1 (IL-1) production and 5-LO and CO activity, in vitro, by the metabolite (SK&F 105561) seen in the companion paper (Marshall PJ, Griswold DE, Breton J. Webb EF, Hillegass LM, Sarau HM, Newton J Jr, Lee JC, Bender PE and Hanna N, Pharmacology of the pyrroloimidazole, SK&F 105809--I. Inhibition of inflammatory cytokine production and of 5-lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid. Biochem Pharmacol 42: 813-824, 1991) and inhibition of the fluid and cellular phases of the inflammatory response, in vivo, by SK&F 105809 suggest that this compound possesses a unique profile of activity.     

Pharmacological profile of PMS777, a new AChE inhibitor with PAF antagonistic activity

The key pathophysiological mechanisms in Alzheimer's disease involve the selective loss of cholinergic neurons and pro-inflammatory mediator-related chronic inflammatory responses in the brain, therefore interventions of these processes are crucial to the treatment of this disease. In the present study, the pharmacological profile of PMS777, a new acetylcholinesterase (AChE) inhibitor with platelet-activating factor (PAF) antagonistic activity, has been evaluated in vitro and in vivo. PMS777 (1-100 microM) dose-dependently inhibited PAF-induced rabbit platelet aggregation by competing with [3H]PAF for its receptor on platelets, and protected a human neuroblastoma cell line SH-SY5Y against PAF-induced neurotoxicity. Moreover, it markedly inhibited brain AChE activity in mice and showed a modest selectivity for AChE (AChE: IC50=2.48+/-0.12 microM; butyrylcholinesterase: IC50=4.47+/-0.15 microM). Ex vivo, PMS777 (5, 10, 20 or 40 mg/kg i.p.) reduced brain AChE activity in a dose-dependent manner. In-vivo studies revealed that PMS777 (0.25, 0.5, 1, 2.5 or 5 mg/kg i.p.) could reverse scopolamine-induced memory retrieval deficits in mice, and displayed a typical bell-shaped dose-response relationship. Taken together, these results demonstrate that PMS777 possesses dual activities for PAF receptor antagonism and AChE inhibition, suggesting that this compound may be a promising lead compound for further investigation related to the treatment for Alzheimer's disease.     

Pharmacological profile of parecoxib: a novel, potent injectable selective cyclooxygenase-2 inhibitor

The antinociceptive, anti-inflammatory, antipyretic effects along with gastric safety profile of parecoxib, a novel, potent selective cyclooxygenase-2 inhibiting prodrug, and those of ketorolac, a nonselective cyclooxygenase inhibitor, were evaluated in various animal models. Parecoxib (up to 20 mg/kg, i.v.) had no effect in two acute pain models, namely, the acetic acid-induced writhing (visceral pain) and the formalin test (tonic pain). However, ketorolac (up to 10 mg/kg, i.v.) showed marked antinociceptive effects in these models. In the models of carrageenan-provoked inflammatory hyperalgesia and inflammation, and in lipopolysaccharide-induced pyrexia, parecoxib significantly reversed all the behavioral changes and it was found to be more potent than ketorolac. Further, ketorolac (10 mg/kg, i.v.) produced visible gastric lesions with prominent petechiae and hemorrhagic streaks. However, parecoxib was without any effect on gastric mucosa. The present results showed that the cyclooxygenase-2 inhibitor, parecoxib, when administered parenterally, has potent antihyperalgesic, anti-inflammatory, antipyretic effects and has a better safety profile than with ketorolac, with sparing of cyclooxygenase-1 in the stomach in these animal models.     

Human metabolism of lapatinib, a dual kinase inhibitor: implications for hepatotoxicity

Lapatinib (Tykerb, Tyverb) is an important orally active dual tyrosine kinase inhibitor efficacious in combination therapy for patients with progressive human epidermal receptor 2-overexpressing metastatic breast cancer. However, clinically significant liver injury, which may be associated with lapatinib metabolic activation, has been reported. We describe the metabolism and excretion of [(14)C]lapatinib in six healthy human volunteers after a single oral dose of 250 mg and the potential relationships between metabolism and clinical hepatotoxicity. Overall, elimination showed high intersubject variability, with fecal elimination being the predominant pathway, representing a median of 92% of the dose with lapatinib as the largest component (approximate median 27% of the dose). In plasma, approximately 50% of the observed radioactivity was attributed to metabolites. Analysis of a 4-h pooled plasma extract identified seven metabolites related by an N- and α-carbon oxidation cascade. Fecal metabolites derived from three prominent pathways: N- and α-carbon oxidation, fluorobenzyl oxidative cleavage, and hydroxypyridine formation. Several of the lapatinib metabolites can undoubtedly be linked to reactive species such as aldehydes or quinone imines. In addition to the contribution of these potentially reactive metabolites as suspects in clinical liver injury, the role of other disposition factors, including interaction with drug transporters, pharmacogenetics, or magnitude of the therapeutic dose, should not be discounted.     

Pharmacological profile of SL 59.1227, a novel inhibitor of the sodium/hydrogen exchanger

1. The NHE1 isoform of the Na(+)/H(+) exchanger plays an important role in the regulation of intracellular pH and in cardiac cell injury caused by ischaemia and reperfusion. SL 59.1227 is a novel imidazolypiperidine Na(+)/H(+) antiport inhibitor which is structurally unrelated to previously described acylguanidine inhibitors such as cariporide. 2. Recovery of pH(i) following an intracellular acid load was measured in CCL39-derived PS120 variant cells, selectively expressing either NHE1 or NHE2 isoforms of the Na(+)/H(+) exchanger. pH(i) recovery was potently and selectively slowed by SL 59.1227 in NHE1-expressing cells (IC(50) 3.3+/-1.3 nM) versus NHE2-expressing cells (2.3+/-1.0 microM). The respective IC(50) values for cariporide were 103+/-28 nM (NHE1) and 73+/-46 microM (NHE2). 3. In anaesthetized rats following left coronary artery occlusion (7 min) and reperfusion (10 min) SL 59.1227 (10 - 100 microg kg(-1) min(-1) i.v.) inhibited ischaemia-mediated ventricular tachycardia (71 - 100%) and reperfusion-induced ventricular fibrillation (75 - 87%) and prevented mortality. Bolus i.v. administration of SL 59.1227 (1 mg kg(-1)) produced anti-arrhythmic effects when administered either before or during ischaemia. 4. Cardiac infarct size was determined in anaesthetized rabbits following left coronary artery occlusion (30 min) and reperfusion (120 min). Infarct size measured as a percentage of the area at risk was 36.2+/-3.4% (control group) versus 15.3+/-3.9% (SL 59.1227 0.6 mg kg(-1) i.v.). 5. SL 59.1227 is the first example of a potent and NHE1-selective non-acylguanidine Na(+)/H(+) exchanger inhibitor. It possesses marked cardioprotective properties.     

Pharmacological profile of FR260330, a novel orally active inducible nitric oxide synthase inhibitor

In this study, we examined effects of a newly synthesized chemical compound, FR260330, (2E)-3-(4-chlorophenyl)-N-[(1S)-2-oxo-2-{[2-oxo-2-(4-{[6-(trifluoromethyl)-4-pyrimidinyl]oxy}-1-piperidinyl)ethyl]amino}-1-(2-pyridinylmethyl)ethyl]acrylamide on nitric oxide (NO) production in rat splenocytes and human colon cancer cell line, DLD-1 cells. FR260330 inhibited NOx production dose dependently in both cells. In lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) treated murine macrophage cell line, RAW264.7, Western blot analysis with gel filtration chromatography revealed FR260330 might prevent dimerization of inducible nitric oxide synthase (iNOS), but had no effect on the expression of iNOS protein. Furthermore, oral administration of FR260330 reduced NOx production dose dependently in plasma from rats exposed to LPS (IC50=1.6 mg/kg). Meanwhile, higher dose (100 mg/kg) of oral administration of FR260330 did not change mean arterial blood pressure in rats. These results suggest that FR260330 might be a useful therapeutical approach to various inflammatory diseases, in which superoxide or peroxynitrite formed from iNOS-derived NO are involved.     

Pharmacological profile of KR-33028, a highly selective inhibitor of Na+/H+ exchanger

We evaluated the cardioprotective effects of 4-cyano (benzo[b]thiophene-2-carbonyl)guanidine (KR-33028), a recently developed inhibitor of the Na+/H+ exchanger (NHE), on hypoxia-induced H9c2 cell death and on perfused rat hearts subjected to ischemia/reperfusion. KR-33028 inhibited in a concentration-dependent manner the recovery from acidosis induced by an NH4Cl prepulse in PS120 fibroblast cells expressing the human NHE-1 isoform (IC50: 2.59 microM). Treatment with KR-33028 (1-10 microM) significantly decreased hypoxia-induced necrotic cell death and apoptotic cell death in H9c2 cells. KR-33028 significantly inhibited hypoxia-induced increases in cytosolic and mitochondrial Ca2+ level and cytochrome c release, and recovered hypoxia-induced Delta psi(m) reduction. In the perfused rat hearts subjected to 30 min of ischemia and 30 min of reperfusion, KR-33028 (1-10 microM) improved cardiac contractility, decreased lactate dehydrogenase release, and increased content of tissue ATP, creatine phosphate and glycogen in a concentration-dependent manner. In addition, KR-33028 did not produce significant acute or subacute toxicity in the rats at doses tested. Our results suggest that a novel NHE-1 inhibitor KR-33028 possesses potent cardioprotective effects with minimal toxicity and that the effects may be mediated by inhibition of intracellular Ca2+ overload and mitochondrial cell death pathway.     

Pharmacological studies with SK&F 94120, a novel positive inotropic agent with vasodilator activity

The pharmacological properties of SK&F 94120 on the cardiovascular system have been studied in laboratory animal species. The compound was shown to have positive inotropic activity on hearts from guinea-pig, cat, dog and marmoset in-vitro and in cat and dog in-vivo. These responses in-vivo occurred in association with minimal changes in heart rate. Positive inotropic activity was not caused by SK&F 94120 in rat or hamster hearts in-vitro, thereby indicating a species dependence in myocardial response. SK&F 94120 was shown to have vasodilator activity in cats in-vivo. Detailed studies carried out on anaesthetized cats indicated that the compound caused a balanced dilatation of both resistance and capacitance blood vessels. Haemodynamic studies in anaesthetized cats indicated that, as a consequence of the positive inotropic and vasodilator actions, SK&F 94120 causes significant increases in cardiac output and stroke volume. Studies in conscious dogs showed the compound to be active as a positive inotrope after oral administration. The above properties suggest that this compound possesses useful haemodynamic properties for the treatment of congestive heart failure.     

Pharmacokinetics,metabolism, and excretion of nefopam,a dual reuptake inhibitor in healthy male volunteers

1.?The disposition of nefopam, a serotonin–norepinephrine reuptake inhibitor, was characterized in eight healthy male volunteers following a single oral dose of 75?mg [¹⁴C]-nefopam (100 μCi). Blood, urine, and feces were sampled for 168 h post-dose.

2.?Mean (±?SD) maximum blood and plasma radioactivity concentrations were 359?±?34.2 and 638?±?64.7 ngEq free base/g, respectively, at 2 h post-dose. Recovery of radioactive dose was complete (mean 92.6%); a mean of 79.3% and 13.4% of the dose was recovered in urine and feces, respectively.

3.?Three main radioactive peaks were observed in plasma (metabolites M2 A-D, M61, and M63). Intact [¹⁴C]-nefopam was less than 5% of the total radioactivity in plasma. In urine, the major metabolites were M63, M2 A-D, and M51 which accounted for 22.9%, 9.8%, and 8.1% of the dose, respectively. An unknown entity, M55, was the major metabolite in feces (4.6% of dose). Excretion of unchanged [¹⁴C]-nefopam was minimal.     

Pharmacological characterization of cinnamophilin, a novel dual inhibitor of thromboxane synthase and thromboxane A2 receptor.

1. The pharmacological effects of cinnamophilin, a new lignan, isolated from Cinnamomum philippinense, was determined in vitro in human platelet, rat isolated aorta and guinea-pig isolated trachea and in vivo in mice and guinea-pigs. 2. Cinnamophilin inhibited dose-dependently human platelet-rich plasma (PRP) aggregation induced by arachidonic acid (AA), collagen and U-46619 with IC50 of 5.0 +/- 0.4, 5.6 +/- 0.6 and 3.0 +/- 0.4 microM, respectively. The second wave of ADP- or adrenaline-induced platelet aggregation was inhibited by cinnamophilin, while the first wave was only slightly inhibited by cinnamophilin above 30 microM. 3. Cinnamophilin was found to be a thromboxane A2 (TXA2) receptor blocking agent in human platelet, rat aorta and guinea-pig trachea as revealed by its competitive antagonism of U-46619-induced aggregation of human-PRP, contraction of rat aortic rings and guinea-pig tracheal rings with pA2 values of 7.3 +/- 0.2, 6.3 +/- 0.1 and 5.2 +/- 0.2, respectively. 4. [3H]-inositol monophosphate formation and the rise of intracellular Ca2+ caused by U-46619 in human platelet was suppressed by cinnamophilin (10 microM). 5. Cinnamophilin induced a dose-dependent inhibition of thromboxane B2 (TXB2) formation, while the prostaglandin E2 (PGE2) formation was increased. Cinnamophilin did not affect unstimulated platelet adenosine 3':5'-cyclic monophosphate (cyclic AMP) levels. When the platelets were challenged with AA, a dose-dependent rise in cyclic AMP was observed. Dazoxiben (a pure TX synthase inhibitor) and SQ 29548 (a pure TXA2 receptor antagonist) did not affect cyclic AMP levels in AA-treated platelets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacological profile and therapeutic potential of BM-573, a combined thromboxane receptor antagonist and synthase inhibitor

BM-573 (N-terbutyl-N'-[2-(4'-methylphenylamino)-5-nitro-benzenesulfonyl]urea), a torsemide derivative, is a novel non-carboxylic dual TXA2 synthase inhibitor and receptor antagonist. The pharmacological profile of the drug is characterized by a higher affinity for the thromboxane receptor than that of SQ-29548, one of the most powerful antagonists described to date, by a complete prevention of human platelet aggregation induced by arachidonic acid at a lower dose than either torsemide or sulotroban, and by a significantly prolonged closure time measured by the platelet function analyser (PFA-100). Moreover, at the concentrations of 1 and 10 microM, BM-573 completely prevented production of TXB2 by human platelets activated by 0.6 mM of arachidonic acid. BM-573 prevents rat fundus contraction induced by U-46619 but not by prostacyclin or other prostaglandins. Despite possessing a chemical structure very similar to that of a diuretic torsemide, BM-573 has no diuretic activity. BM-573 does not prolong bleeding time and, unlike some of the other sulfonylureas, has no effect on blood glucose levels. In vivo, BM-573 appears to have antiplatelet and antithrombotic activities since it reduced thrombus weight and prolonged the time to abdominal aorta occlusion induced by ferric chloride. BM-573 also relaxed rat aorta and guinea pig trachea precontracted with U-46619. In pigs, BM-573 completely antagonized pulmonary hypertensive effects of U-46619 and reduced the early phase of pulmonary hypertension in models of endotoxic shock and pulmonary embolism. Finally, BM-573 protected pigs from myocardial infarction induced by coronary thrombosis. These results suggest that BM-573 should be viewed as a promising therapeutic agent in the treatment of pulmonary hypertension and syndromes associated with platelet activation.