Lenograstim: a review of its use in chemotherapy-induced neutropenia, for acceleration of neutrophil recovery following haematopoietic stem cell transplantation and in peripheral blood stem cell mobilization

Lenograstim (Granocyte?, Neutrogin?, Myelostim?) is a glycosylated recombinant human granulocyte colony-stimulating factor. This article reviews the pharmacological properties, therapeutic efficacy and tolerability of lenograstim, mainly focusing on its use in chemotherapy-induced neutropenia, acceleration of neutrophil recovery following haematopoietic stem cell transplantation (HSCT), and peripheral blood stem cell (PBSC) mobilization in patients with cancer and healthy donors. In randomized, multicentre trials in patients with solid tumours, lymphoma or multiple myeloma, the durations of chemotherapy-induced neutropenia, hospitalization for infection and intravenous antibacterial therapy were significantly shorter in patients receiving lenograstim prophylaxis than in those receiving placebo. The time to neutrophil recovery was also significantly shorter in patients with acute myeloid leukaemia or acute lymphoblastic leukaemia who received lenograstim than in those who received placebo or no treatment, according to the results of randomized, multicentre trials. In addition, lenograstim prophylaxis facilitated the administration of dose-intense or dose-dense chemotherapy regimens, with improved clinical outcomes seen in some trials. In patients with cancer undergoing HSCT, lenograstim accelerated neutrophil recovery post-HSCT and shortened the duration of hospitalization, according to the results of randomized, multicentre trials. Lenograstim effectively mobilized PBSCs in patients with cancer, demonstrating generally similar efficacy to filgrastim or molgramostim in five randomized trials (although lower dosages of lenograstim than filgrastim were administered in four of the trials). Lenograstim also provided effective PBSC mobilization in healthy donors and was more effective than filgrastim when both drugs were administered at a dosage of 10?μg/kg/day. The efficacy and safety of lenograstim for PBSC mobilization in healthy donors was supported by the results of a prospective, longer-term study involving almost 4000 healthy donors. Lenograstim was generally well tolerated across a variety of treatment settings, including PBSC mobilization in healthy donors, with bone pain being one of the most commonly reported adverse events. In conclusion, lenograstim remains an important option for use in chemotherapy-induced neutropenia, acceleration of neutrophil recovery following HSCT, and PBSC mobilization.     

Morphine-induced sensitization in mice: changes in locomotor activity by prior scheduled exposure to GABAA receptor agents

This study investigated the effects of a gamma-amino-butyric acid type A (GABAA) receptor agonist and antagonist on morphine-induced locomotor sensitization in male albino mice. Subcutaneous administration to mice of a high dose of morphine (30 mg/kg), but not lower doses (5, 10 and 20 mg/kg) increased locomotion. The maximum locomotor activity was achieved during a 20-min measurement period. The locomotor response to a low dose of morphine (5 mg/kg, subcutaneously) given on day 9 was enhanced in mice pretreated with morphine (7.5, 15 and 30 mg/kg/day x 3 days), indicating that sensitization had developed. Three-day intracerebroventricular (i.c.v.) administration of the GABAA receptor agonist, muscimol (0.025, 0.05, 0.1 and 0.2 microg/mouse/day) significantly decreased both morphine-induced motor stimulation and locomotor sensitization. On the other hand, a 3-day pretreatment with the GABAA-receptor antagonist, bicuculline (0.25, 0.5 and 1 microg/mouse/day) reduced morphine (15 mg/kg)-induced locomotor sensitization. Repeated i.c.v. injections of a lower dose of bicuculline (0.25 microg/mouse/day x 3 days) by itself also decreased morphine-induced locomotion. Furthermore, repeated i.c.v. administration of bicuculline (0.25, 0.5 and 1 microg/mouse/day x 3 days) decreased the effect of i.c.v. injection of muscimol (0.1 microg/mouse/day x 3 days) on locomotor activity induced by morphine (5 mg/kg) in both control and sensitized mice. The magnitude of this response was, however, variable. The results indicate that GABAA receptors might be involved in the acquisition of morphine-induced sensitization.     

Mobilization of peripheral blood stem cells by granulocyte-colony stimulating factors: comparison of a standard dose of glycosylated and mutated granulocyte-colony stimulating factor in non-Hodgkin's lymphoma patients following CHOP therapy

The effects of granulocyte-colony stimulating factor (G-CSF) have been studied in several clinical settings. G-CSFs are widely used to stimulate the production of granulocytes and are well known to mobilize peripheral blood stem cells (PBSCs). However, very few studies have examined differences among G-CSFs. The aim of this study was to compare the mobilization of PBSCs induced by a standard dose of two G-CSFs following biweekly cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) therapy. Using a standard dose of G-CSF, we conducted a randomized, crossover trial that compared the efficacy of two kinds of G-CSF, glycosylated [lenograstim (2 micrograms/kg)] and mutated [nartograstim (1 microgram/kg)], on PBSC mobilization in 10 patients with non-Hodgkin's lymphoma after biweekly CHOP chemotherapy. Lenograstim (2 micrograms/kg) was more effective in shortening the duration of neutropenia than nartograstim (1 microgram/kg) (3.8 days vs. 5.0 days, p < 0.05, the number of days for the neutrophil count to reach 5 x 10(9)/l from nadir). The number of CD34+ cells and granulocyte-macrophage colony forming units (GM-CFU) was higher for lenograstim but no statistically significant difference between the two groups was found. Glycosylated G-CSF is more effective than mutated G-CSF in shortening the duration of neutropenia. As for the mobilization of CD34+ cells and the number of CFU-GM, there was a tendency to increase in the lenograstim group but no statistically significant differences were found.     

Antitumor effects of a podophyllotoxin derivative, VP 16-213

Single and combination chemotherapies of VP 16-213, a new antitumor agent were evaluated for its antitumor effect against several murine tumors. Dose-dependent antitumor effects were observed when VP 16-213 was administered via any of the three routes, i.p., i.v. and orally, on days 1 and 5 after i.p. or s.c. inoculation of Ehrlich carcinoma and sarcoma 180. The drug also proved effective against i.v. inoculated EL-LP-12 (subline of Ehrlich carcinoma), i.p. or s.c. inoculated P388 and B16 melanoma, i.p. inoculated colon 26, and s.c. inoculated colon 38 and Lewis lung carcinoma. However, oral administration of the drug was not effective against B16 melanoma, colon 26 and Lewis lung carcinoma despite the fact that the doses employed for this route was higher than those employed for i.v. and i.p. routes. The optimum dosing schedule was also investigated with oral administration of the drug against s.c. inoculated Ehrlich carcinoma. A single dose (day 1) or two doses (days 1 and 5) were more effective than three doses (days 1, 3 and 5) or five consecutive daily doses. VP 16-213 showed additive and more than additive effects in combination with the antitumor agents, cyclophosphamide, BCNU, mitomycin C or cisplatin against s.c. inoculated Ehrlich carcinoma and i.v. inoculated EL-LP-12.     

The influence of dextromethorphan on morphine analgesia in Swiss Webster mice is sex-specific

NMDA (N-methyl-d-aspartate) antagonists are known to enhance the analgesic effects of opioids. However, virtually, all studies of this phenomenon have been done using male subjects. Here, the noncompetitive NMDA receptor antagonist dextromethorphan (DEX) was tested over a range of doses (10-200 microg intracerebroventricularly [i.c.v.]) in male and female Swiss Webster mice in combination with 5 mg/kg intraperitoneal (i.p.) morphine. Males exhibited enhanced morphine analgesia following either 100 or 200 microg DEX, but there was no evidence of DEX-mediated potentiation in females at any dose. Instead, DEX attenuated morphine analgesia in females. We also evaluated the effect of 100 microg i.c.v. DEX with different doses of morphine (1, 5 and 10 mg/kg). Again, DEX significantly enhanced morphine analgesia in male mice and attenuated it in females. Next, ovariectomized (OVX) female mice were compared to males following 5 mg/kg i.p. morphine and 100 microg i.c.v. DEX. Male and OVX females exhibited equivalent maximal levels of analgesia following administration of DEX. Morphine analgesia was not enhanced by DEX in sham-treated females and OVX mice with estradiol treatment (5 microg i.p. once daily for 7 days) also did not show DEX enhancement. These experiments demonstrate that the ability of NMDA receptor antagonists to potentiate morphine analgesia is modulated by an estrogen-sensitive mechanism and suggest that sex differences may play a critical role toward a more general understanding of the potentiation of opioid-induced analgesia through NMDA receptor antagonists.     

ADRENOCORTICOTROPHIC HORMONE-INDUCED HYPERTENSION IN THE RAT: EFFECTS OF THE ENDOTHELIN ANTAGONIST BOSENTAN

1. The effects of the endothelin antagonist bosentan on adrenocorticotrophic hormone (ACTH)-induced hypertension were examined in the conscious male Sprague-Dawley rat. 2. In order to confirm endothelin antagonism, 18 rats were randomly divided into two groups: receiving either (i) endothelin-1 (0.125, 0.25, 0.5 and 1 nmol/kg, i.v.); or (ii) endothelin-1 at these doses following bosentan (100 mg/kg gavage) and mean arterial pressure recorded (study A). Subsequently, 40 male rats (320 +/- 5 g) were randomly divided into four groups (n = 10): (i) Sham (0.9% saline, s.c.) + 5% acacia gum gavage; (ii) ACTH (500 micrograms/kg per day, s.c.) + 5% acacia gum gavage; (iii) Sham injection + bosentan (100 mg/kg per day) gavage; or (iv) ACTH + bosentan. Six control days (C1-C6) were followed by 11 treatment days (T0-T10). Systolic blood pressure, water intake, urine volume, food intake and bodyweight were measured every second day (study B). 3. Bosentan significantly attenuated the endothelin-1-induced blood pressure rise at 0.125 nmol/kg (P < 0.05), but not at higher doses. 4. Bosentan at a dose which attenuated endothelin-1-induced blood pressure increase had no effect on either blood pressure or metabolic parameters in ACTH-treated rats. 5. These results suggest that endothelin does not play a major role in ACTH-induced hypertension.     

Pharmacokinetics and hepatic disposition of bis[1-(ethoxycarbonyl)propyl]5-acetylamino-2,4,6-triiodoisophthalate in rats and isolated perfused rat livers.

Bis[1-(Ethoxycarbonyl)propyl]5-acetylamino-2,4,6- triiodoisophthalate+ (NC 68183) was designed as a new computed tomography imaging agent. The purpose of this study was to determine the pharmacokinetics and metabolism of NC 68183 in conscious rats and in the isolated perfused rat liver. Animals were i.v. dosed at 69 and 690 mg of iodine/kg. Blood samples were collected at 5, 15, 30, and 60 min, and 7 days after dosing. Tissue samples (liver, kidney, and spleen) were taken at 60 min and 7 days after dosing. NC 68183 was cleared from blood in first order kinetics following an i.v. administration of 69 mg I/kg. The volume of distribution (Vss) at steady state and elimination half-life (t(1/2)) were estimated as 24 ml and 11 min. The clearance of NC 68183 from blood was changed to zero-order kinetics following administration of 690 mg/kg, and its elimination rate was 16 microg I/ml.min. The liver and spleen were the only tissues to have the nanoparticle residue at day 7 following administration. NC 68183 (75 mg of agent, 35 mg of I) was injected into the isolated perfused rat liver system. Bile flow increased from 1.0 to 1.3 microl/min/g liver following administration. The biliary excretion rate maximum was estimated as 11 microg/min/g liver. The metabolite was identified using liquid chromatography/mass spectrometry as a monocarboxylic acid product, which exclusively excreted into the bile in a soluble iodinated metabolite. Pharmacokinetics data suggested that NC 68183 primarily resides in the blood pool following an i.v. administration with a plasma half-life appropriate for blood pool imaging.     

Lenograstim: an update of its pharmacological properties and use in chemotherapy-induced neutropenia and related clinical settings

Lenograstim is the glycosylated recombinant form of human granulocyte colony stimulating factor. The drug is used to reduce the risk of life-threatening infection in patients with neutropenia, particularly after cytotoxic chemotherapy. Lenograstim accelerates neutrophil recovery significantly after chemotherapy, with beneficial effects on clinical end-points such as incidence of laboratory-confirmed infection and length of hospital stay. Chemotherapy dose intensity has also been increased in patients receiving lenograstim, notably those with breast or small cell lung cancer, although improvements in tumour response and survival have not been demonstrated. Lenograstim also assists neutrophil recovery in patients undergoing bone marrow transplantation, and stimulates the production of peripheral blood stem cells (PBSCs) for autologous transfusion after aggressive chemotherapy. Lenograstim also mobilises CD34+ cells more efficiently in unit dose terms than filgrastim and has been used successfully to mobilise PBSCs from healthy donors for allogeneic transplantation. Randomised trials have shown increases in rates of disease remission after lenograstim therapy in patients with acute myeloid leukaemia, with no evidence of stimulation of malignant blasts. The drug has also shown potential in the mobilisation of nonmalignant PBSCs for autotransplantation in patients with chronic myeloid leukaemia. Other studies show efficacy of lenograstim in patients with acute lymphoblastic leukaemia, aplastic anaemia, in children with severe chronic neutropenia and in the reversal of neutropenia related to antiviral therapy in patients with AIDS, although data are not extensive. Cost analyses of lenograstim have been carried out from a hospital perspective, although results have been inconclusive. Cost-effectiveness or cost-benefit data are lacking at present. Lenograstim is well tolerated, with bone pain and injection site reactions being reported most frequently in clinical trials. Conclusions: Lenograstim has been confirmed as a valuable adjunct to minimise the haematological toxicity of myelosuppressive chemotherapy in patients with malignant disease. The drug also enhances neutrophil recovery in patients undergoing stem cell rescue, and assists PBSC mobilisation. Data indicate clinical benefit with lenograstim in myeloid disorders, with no evidence of malignant blast cell proliferation. Further studies are required to assess more fully the pharmacoeconomic implications of the use of lenograstim and other recombinant growth factors, to provide more data on the efficacy of the drug in the management of disease-related neutropenia, and to clarify fully its position relative to filgrastim.     

Pharmacokinetics of palifermin administered as the standard dose and as a collapsed dose in patients with hematologic malignancies

STUDY OBJECTIVE: To assess the pharmacokinetic profile of palifermin after intravenous dosing with either a collapsed dose of 180 microg/kg/day for 1 day or a standard dose of 60 microg/kg/day for 3 days, before and after myeloablative chemoradiotherapy and peripheral blood progenitor cell (PBPC) transplantation. DESIGN: Prospective, open-label pharmacokinetic study. SETTING: University-affiliated hematology and oncology center. PATIENTS: Twenty-five adult patients with hematologic malignancies receiving myeloablative therapy; 13 were in the standard-dose group, and 12 were in the collapsed-dose group. INTERVENTION: Patients received total-body irradiation (study days -8 to -5), etoposide (day -4), cyclophosphamide (day -2), and PBPC transplantation (day 0). Standard-dose palifermin was administered on days -11, -10, -9, 0, 1, and 2; collapsed-dose palifermin was administered on days -11 and 0. MEASUREMENTS AND MAIN RESULTS: Baseline demographic and clinical characteristics were recorded. Blood samples were obtained for pharmacokinetic assessment, presence of palifermin antibodies, and routine chemistry and hematology panels. Adverse events were documented daily. For both dosing groups, palifermin concentrations declined rapidly (>or= 98%) in the first 30 minutes and increased slightly between 1 and 4 hours after dosing, with a terminal decay phase. For standard-dose palifermin, mean values for area under the serum concentration-time curve (AUC) were within 15% between doses 1 and 3 and within 1% between doses 1 and 4. For collapsed-dose palifermin, mean AUC values and other pharmacokinetic parameters were within 2% between doses 1 and 2. Mean AUC on days -11 and 0 were approximately 4-fold higher for collapseddose palifermin than for standard-dose palifermin. Both dosing regimens were well tolerated. CONCLUSIONS: Our results were consistent with approximately dose-linear pharmacokinetics for the two dosing regimens, with no observed accumulation. A randomized, controlled study is warranted to assess the safety and efficacy of collapsed-dose palifermin, which may provide a more convenient administration schedule.     

Central effect of histamine and peripheral effect of histidine on the formalin-induced pain response in mice

1. The present study was designed to investigate the role of brain histamine in modulating pain transmission in mice. 2. In conscious mice implanted with an intracerebroventricular (i.c.v.) cannula, the effects of i.v.c. injections of normal saline (control) and low and high doses histamine (2 and 40 microg/mouse, respectively) were investigated on the duration of paw licking and biting induced by subcutaneous (s.c.) injection of formalin (20 microL; 5%) into the plantar surface of the left hindpaw. 3. To clarify the involvement of histidine in the pain response, the effects of intraperitoneal (i.p.) injections of low and high doses of histidine (50 and 1000 mg/kg, respectively) alone or before i.c.v. injection of histamine were also examined. 4. Intraplantar injection of formalin induced a biphasic pain response (first phase: 0-5 min after injection; second phase: 20-40 min after injection). 5. Histamine (2 microg/mouse, i.c.v.) had no effect on the first phase of the pain response, but suppressed the second phase. The higher dose of histamine (40 microg/mouse, i.c.v.) suppressed both phases of the pain response. 6. Histidine, at 50 mg/kg, i.p., had no effect on the pain response, but the higher dose (1000 mg/kg, i.p.) suppressed the both phases of the pain response. 7. Pretreatment with the low dose of histidine (50 mg/kg, i.p.) prior to administration of 2 microg/mouse, i.c.v., histamine did not change the antinociception induced by low-dose histamine. However, pretreatment with the high dose of histidine (1000 mg/kg, i.p.) prior to 2 microg/mouse, i.c.v., histamine produced antinociception that resembled that seen following administration of the high dose of either histidine or histamine. Pretreatment with the low dose of histidine (50 mg/kg, i.p.) prior to administration of 40 microg/mouse, i.c.v., histamine has no effect on the pain response following high-dose histamine. Pretreatment with 1000 mg/kg, i.p., histidine prior to administration of 40 microg/mouse, i.c.v., histamine strongly suppressed both phases of the formalin-induced pain response, particularly the second phase. 8. The results of the present study indicate that: (i) activation of brain histamine produces antinociception in the mouse formalin test; (ii) peripheral loading with a high dose of histidine (1000 mg/kg, i.p.) alone exerts the same effect as that seen following 40 microg/mouse, i.c.v., histamine; and (iii) pretreatment with a high dose of histidine potentiates central histamine-induced antinociception.     

Metabolism of 2-ethylhexanoic acid administered orally or dermally to the female Fischer 344 rat1

1. Excretion balance studies were conducted with 2-ethylhexanoic acid (EHA) in the female Fischer 344 rat following single high (1?g kg) or low (0.1?g kg) oral doses of \[2- Chexyl]EHA,following repeated oraldosing with unlabelled EHA and a final\ [C]EHAoral dose at the low dose level, following dermal exposure with a high (1?g kg) and low (0.1?g kg) applied dose of \ [C]EHA, and following a 1?mg kg i.v. dose of \ [C]EHA. 2. Oral, i.v. and dermal doses were eliminated rapidly, predominantly in the urine during the first 24 h following dosing. 3. After oral dosing of 0.1?g kg, the mean peak blood level was 85.1 mu?g equivalents EHA g. Maximum blood concentrations were detected at either 15 or 30 min in individual animals. After dermal application of 0.1?g kg, the mean peak blood level of 7.9 mu?g equivalents EHA?g was attained at 8 h. 4. Occlusive dermal exposure caused damage to the epidermis in the first 24 h after application and resulted in dermal absorption of 70% relative to i.v. dosing, based on the ratio of percent dose in excreta. 5. Dermal application followed by prompt washing of the skin resulted in recovery of 101.9% from the skin surface and 0.2% in the excreta. 6. The major urinary metabolites were the glucuronide of EHA, 2-ethyl-1,6- hexanedioic acid (namely 2-ethyladipic acid), 2-ethyl-5-hydroxyhexanoic acid, 2-ethyl-6- hydroxyhexanoicacidandethylketohexanoicacid.Evidencefor metabolismvia beta -oxidation was alsofound,consistent with the incorporationofEHAinto normalcellular intermediary metabolism.     

Lack of evidence for tachykinin NK1 receptor-mediated neutrophil accumulation in the rat cutaneous microvasculature by thermal injury

The effect of the non-peptide selective tachykinin NK1 receptor antagonist SR140333 has been investigated on oedema formation and neutrophil accumulation induced by thermal injury (50 degrees C for 5 min), mustard oil, substance P, the tachykinin NK1 agonist GR73632, and interleukin-1beta in the abdominal skin of the anaesthetised rat. SR140333 significantly inhibited (120 nmol/kg i.v.) or prevented (240 nmol/kg i.v.) the early oedema formation (0-10 min) induced by thermal injury. However, a dosing strategy which blocked NK1 receptors for 5 h (SR140333, 240 nmol/kg i.v. + 240 nmol/kg s.c.) failed to influence neutrophil accumulation measured 5 h after thermal injury. Thus, the neurogenic component mediated by NK1 receptors is important to elicit the early oedema formation, but does not influence subsequent neutrophil accumulation. Topical application of mustard oil (2%), a neurogenic inflammation stimulant, caused NK1 receptor-mediated early neurogenic plasma extravasation, but did not induce cutaneous neutrophil accumulation over 5 h. Substance P and GR73632 at high doses (1 nmol/site) also failed to elicit neutrophil accumulation. Neutrophil accumulation induced by interleukin-1beta (0.03-3 pmol i.d.) was not affected by SR140333 pretreatment. In conclusion, despite an early pronounced tachykinin NK1 receptor-dependent oedema response after thermal injury, the results suggest that subsequent neutrophil accumulation is not mediated by NK1 receptors. Furthermore, we have not obtained any evidence to suggest that either endogenous or exogenous tachykinins can directly induce neutrophil accumulation in the rat cutaneous microvasculature.     

Kinetics and disposition of hexarelin, a peptidic growth hormone secretagogue, in rats.

To document the disposition of hexarelin, a peptidyl growth hormone secretagogue, male Sprague-Dawley rats received a 5-microg/kg bolus i.v. dose or three single s.c. doses of 5, 10, and 50 microg/kg. To assess hexarelin tissue distribution and excretion, rats were given 1 microg/kg of [(3)H]hexarelin (9.4 Ci/mmol). Metabolism of [(3)H]hexarelin was assessed in bile duct-exteriorized rats given 50 microg/kg where radiolabeled hexarelin biliary and urinary excretion was quantified. After its i.v. injection, hexarelin displayed a half-life of 75.9 +/- 9.3 min, a systemic clearance of 7.6 +/- 0.7 ml/min/kg, and a volume of distribution at steady state of 744 +/- 81 ml/kg. After s.c. administration, the area under the curve (477-3826 pmol.min/ml) estimated with increasing doses confirmed the absence of hexarelin accumulation. Clearance/F (12-15 ml/min/kg) and volume of distribution/F (1208-1222 ml/kg) were dose independent. Hexarelin bioavailability given s.c. was 64%. The highest radioactivity levels were detected in the kidney, liver, and duodenum. The pattern of hexarelin excretion was similar after i.v. or s.c. administrations. Total radioactivity in bile, urine, and feces corresponded to 60, 22, and 10% of the dose, respectively. Of the radioactivity excreted in bile and urine, 90 and 71% was unchanged hexarelin, respectively. These results suggest that: 1) the kinetics of hexarelin appear to be first order up to 50 microg/kg; 2) hexarelin is rapidly absorbed after s.c. administration; 3) biliary excretion is the primary route of hexarelin elimination; and 4) the high recovery of unchanged peptide in bile and urine demonstrates hexarelin stability toward proteolytic enzymes.     

Role of potassium channels in the antinociception induced by agonists of alpha2-adrenoceptors

1. The effect of the administration of pertussis toxin (PTX) as well as modulators of different subtypes of K+ channels on the antinociception induced by clonidine and guanabenz was evaluated in the mouse hot plate test. 2. Pretreatment with pertussis toxin (0.25 microg per mouse i.c.v.) 7 days before the hot-plate test, prevented the antinociception induced by both clonidine (0.08-0.2 mg kg(-1), s.c.) and guanabenz (0.1-0.5 mg kg(-1), s.c.). 3. The administration of the K(ATP) channel openers minoxidil (10 microg per mouse, i.c.v.), pinacidil (25 microg per mouse, i.c.v.) and diazoxide (100 mg kg(-1), p.o.) potentiated the antinociception produced by clonidine and guanabenz whereas the K(ATP) channel blocker gliquidone (6 microg per mouse, i.c.v.) prevented the alpha2 adrenoceptor agonist-induced analgesia. 4. Pretreatment with an antisense oligonucleotide (aODN) to mKv1.1, a voltage-gated K+ channel, at the dose of 2.0 nmol per single i.c.v. injection, prevented the antinociception induced by both clonidine and guanabenz in comparison with degenerate oligonucleotide (dODN)-treated mice. 5. The administration of the Ca2+-gated K+ channel blocker apamin (0.5-2.0 ng per mouse, i.c.v.) never modified clonidine and guanabenz analgesia. 6. At the highest effective doses, none of the drugs used modified animals' gross behaviour nor impaired motor coordination, as revealed by the rota-rod test. 7. The present data demonstrate that both K(ATP) and mKv1.1 K+ channels represent an important step in the transduction mechanism underlying central antinociception induced by activation of alpha2 adrenoceptors.     

Cardiovascular effects of SL65.0472, a 5-HT receptor antagonist

In this study, we describe the cardiovascular effects of SL65.0472 (7-fluoro-2-oxo-4-[2-[4-(thieno[3,2-c] pyridin-4-yl) piperazin-l-yl] ethyl]-1, 2-dihydroquinoline-1-acetamide), a novel 5-hydroxytryptamine (5-HT) receptor antagonist developed for the treatment of cardiovascular disease, in several in vivo models. The haemodynamic profile of SL65.0472 was evaluated in anaesthetised dogs. Following i.v. bolus doses of 0.03 mg/kg i.v. and 0.3 mg/kg, no significant changes in cardiac output, contractility or rate, systemic and pulmonary pressures, regional blood flows and vascular resistances or electrocardiogram were noted. After 1 mg/kg i.v. SL65.0472 significantly reduced arterial blood pressure. In conscious spontaneously hypertensive rats administration of SL65.0472 0.5 mg/kg p.o. had no effect on mean arterial blood pressure or heart rate. Vasoconstriction produced by 5-HT results primarily from the stimulation of two receptor subtypes, 5-HT(1B) and 5-HT(2A) receptors. In anaesthetised dogs SL65.0472 antagonised sumatriptan-induced decreases in saphenous vein diameter (5-HT(1B)-receptor mediated) with an ID(50) of 10.1 microg/kg i.v. (95% c.l. 8.3-12.4). In anaesthetised pithed rats SL65.0472 inhibited 5-HT pressor responses (5HT(2A)-receptor mediated) with ID(50) values of 1.38 microg/kg i.v. (95% c.l. 1.15-1.64) and 31.1 microg/kg p.o. (95% c.l. 22.6-42.6). The duration of the 5-HT(2A)-receptor antagonist effect of SL65.0472 following oral administration was evaluated in conscious rats. SL65.0472 (0.1 mg/kg p.o.) markedly inhibited 5-HT pressor responses 1 and 6 h after administration. Therefore, in vivo, SL65.0472 potently antagonises vasoconstriction mediated by 5-HT(1B) and 5-HT(2A) receptors but has minimal direct haemodynamic effects.     

A comparison of the acute haemodynamic effects of nisoldipine and nifedipine during treatment with atenolol in patients with coronary artery disease

1. The acute haemodynamic effects of intravenous nisoldipine (1, 2, 4 microg kg(-1)) and nifedipine (2.5, 5, 10 microg kg(-1)) were compared in a randomised, within-patient crossover study. Fifteen male patients with stable angina pectoris treated with atenolol were studied after undergoing routine cardiac catheterisation. 2. Nisoldipine caused a dose-related fall in systemic vascular resistance (maximum 22%) associated with an increase in heart rate and cardiac index (18%) and a fall in mean arterial pressure (7%). 3. By contrast, nifedipine was associated with a significant increase in heart rate but systemic vascular resistance, cardiac index and mean arterial pressure remained unaltered. 4. At doses with equivalent effects on heart rate (2 microg kg(-1) nisoldipine; 10 microg kg(-1) nifedipine) acute dosing with nisoldipine caused a significantly greater fall in systemic vascular resistance and increase in cardiac index, whilst nifedipine caused a greater reduction in stroke volume index and left ventricular stroke work index. 5. The results suggest that, when combined with atenolol, acute dosing with nisoldipine may have a more complementary haemodynamic profile than nifedipine. The implications of this finding for chronic oral dosing in patients with impaired left ventricular function should be evaluated.     

Low-dose effects of ammonium perchlorate on the hypothalamic-pituitary-thyroid axis of adult male rats pretreated with PCB126.

The objective of this research was to characterize the disturbances in the hypothalamic-pituitary-thyroid (HPT) axis resulting from exposure to a binary mixture, 3,3',4,4',5-pentachlorobiphenyl (PCB126) and perchlorate (ClO(4)(-)), known to cause hypothyroidism by different modes of action. Two studies were conducted to determine the HPT axis effects of ClO(4)(-) on adult male Sprague-Dawley rats pretreated with PCB126. In dosing study I, rats were administered a single oral dose of PCB126 (0, 7.5, or 75 microg/kg) on day 0 and 9 days later ClO(4)(-) (0, 0.01, 0.1, or 1 mg/kg day) was added to the drinking water until euthanasia on day 22. Significant dose-dependent trends were found for all thyroid function indices measured following ClO(4)(-) in drinking water for 14 days. Seventy-five micrograms PCB126/kg resulted in a significant increase in hepatic T(4)-glucuronide formation, causing a decline in serum thyroxine and fT(4), and resulting in increased serum thyroid-stimulating hormone (TSH). Serum TSH was also increased in animals that received 7.5 microg PCB126/kg; no other HPT axis alterations were found in these animals. When pretreated with PCB126, the ClO(4)(-) dose trends disappeared, suggesting a less than additive effect on the HPT axis. In dosing study II, animals were given lower doses of PCB126 (0, 0.075, 0.75, or 7.5 microg/kg) on day 0, and followed with ClO(4)(-) (0 or 0.01 mg/kg day) in drinking water beginning on day 1 and continuing for several days to explore transient HPT axis effects. No statistical effects were seen for PCB126 or ClO(4)(-) alone, and no perturbations were found when administered sequentially in dosing study II. In conclusion, these studies demonstrate that HPT axis disturbances following exposure to ClO(4)(-) are less than additive when pretreated with relatively high doses of PCB126. At relatively low doses, at or near the no-observed-effect-level for PCB126 and ClO(4)(-), no interactions between the chemicals occur.     

Effect of potassium channel modulators in mouse forced swimming test.

1. The effect of intracerebroventricular (i.c.v.) administration of different potassium channel blockers (tetraethylammonium, apamin, charybdotoxin, gliquidone), potassium channel openers (pinacidil, minoxidil, cromakalim) and aODN to mKv1.1 on immobility time was evaluated in the mouse forced swimming test, an animal model of depression. 2. Tetraethylammonium (TEA; 5 microg per mouse i.c.v.), apamin (3 ng per mouse i.c.v.), charybdotoxin (1 microg per mouse i.c.v.) and gliquidone (6 microg per mouse i.c.v.) administered 20 min before the test produced anti-immobility comparable to that induced by the tricyclic antidepressants amitriptyline (15 mg kg(-1) s.c.) and imipramine (30 mg kg(-1) s.c.). 3. By contrast pinacidil (10-20 microg per mouse i.c.v.), minoxidil (10-20 microg per mouse i.c.v.) and cromakalim (20-30 microg per mouse i.c.v.) increased immobility time when administered in the same experimental conditions. 4. Repeated administration of an antisense oligonucleotide (aODN) to the mKv1.1 gene (1 and 3 nmol per single i.c.v. injection) produced a dose-dependent increase in immobility time of mice 72 h after the last injection. At day 7, the increasing effect produced by aODN disappeared. A degenerate mKv1.1 oligonucleotide (dODN), used as control, did not produce any effect in comparison with saline- and vector-treated mice. 5. At the highest effective dose, potassium channels modulators and the mKv1.1 aODN did not impair motor coordination, as revealed by the rota rod test, nor did they modify spontaneous motility as revealed by the Animex apparatus. 6. These results suggest that modulation of potassium channels plays an important role in the regulation of immobility time in the mouse forced swimming test.     

Single- and multiple-dose pharmacokinetics of exendin-4 in rhesus monkeys

A radioimmunoassay (RIA) for the measurement of exendin-4 concentration in rhesus monkeys serum was developed and validated. The radioimmunoassay described here was sensitive, linear, accurate, precise, and reproducible. Range of the assay was 25-2000 pg/ml. Using this method we characterized the pharmacokinetics and accumulation of exendin-4 in rhesus monkeys. Following s.c. administration at doses rate of 1, 3 and 10 microg/kg, average C(max) ranged from 2.26+/-0.15 to 22.72+/-1.54 ng/ml, and AUC(0-infinity) ranged from 3.43+/-0.05 to 47.1+/-0.10 ng h/ml. As compared to the i.v. administration at a single dose of 3 microg/kg, the absolute bioavailability after s.c. administration were estimated to be 67.3+/-5.3, 75.1+/-4.7 and 72.7+/-8.4% for 1, 3 and 10 microg/kg dose, respectively. After daily s.c. administration at 10 microg/kg for 7 consecutive days, the accumulation ratio was approximately to 1.0, indicating no accumulation upon multiple doses in the monkeys.     

The broad-spectrum anti-emetic activity of AS-8112, a novel dopamine D2, D3 and 5-HT3 receptors antagonist

The anti-emetic and pharmacological profile of AS-8112 ((R)-5-bromo-N-(1-ethyl-4-methylhexahydro-1H-1,4-diazepin-6-yl)-2-methoxy-6-methylamino-3-pyridinecarboxamide.2 fumarate), a novel and potent dopamine D2, D3 and 5-hydroxytryptamine-3 (5-HT3) receptors ligand, was investigated in the present study. In guinea-pig isolated colon, AS-8112 produced a rightward shift of the concentration-response curves of 2-methyl-5HT, a 5-HT3 receptor agonist (pA2 value of 7.04). Other 5-HT3 receptor antagonists also produced such a shift in the following antagonistic-potency order: granisetron> ondansetron=AS-8112>metoclopramide. In mice, AS-8112 (1.0 - 3.0 mg kg(-1) s.c.) potently inhibited hypothermia induced by the dopamine D3 receptor agonist; R(+)-7-OH-DPAT (R(+)-7-hydroxy-2-(N,N-di-n-propylamino)tetraline) (0.3 mg kg(-1) s.c.). Domperidone and haloperidol, which have affinity for dopamine D3 receptor, also inhibited R(+)-7-OH-DPAT-induced hypothermia. In ferrets or dogs, AS-8112 dose-dependently inhibited emesis induced by R(+)-7-OH-DPAT, apomorphine, morphine or cisplatin with ID50 values of 2.22 microg kg(-1) s.c., 10.5 microg kg(-1) s.c., 14.2 microg kg(-1) i.v. and 17.6 microg kg(-1) i.v., respectively. Moreover, oral administration of AS-8112 significantly inhibited emesis induced by these emetogens. AS-8112 (0.3 mg kg(-1) i.v.) significantly inhibited emesis induced by cyclophosphamide and doxorubicin. In conclusion, AS-8112 is a potent dopamine D2, D3 and 5-HT3 receptors antagonist, and a novel anti-emetic agent with a broad-spectrum of anti-emetic activity. These results suggest that this compound is worthy of clinical investigation.