Pharmacokinetics and Absolute Bioavailability of Cyclosporin Following Intravenous and Abomasal Administration to Sheep

Abstract— Cyclosporin A pharmacokinetics were studied following intravenous and abomasal dosing in an open, crossover study in healthy, merino ewes. Five different doses of cyclosporin A were dispersed in milk and administered into the abomasum through a surgically inserted fistula which simulates oral administration. Cyclosporin A was well tolerated. Whole blood concentrations of cyclosporin A were measured by HPLC and mean clearance (0·45 ± 0·05 L h^?1 kg^?1), distribution volume (4·4 ± 2·0 L kg^?1), mean residence time (9·6 ± 4·1 h) and half-life (12·1 ± 3·1 h) were calculated. Negligible cyclosporin A was excreted in urine or bile. Area under the curve increased proportionally with doses up to 26·3 mg kg^?1, but was curvilinear above this dose. Abomasal bioavailability at 6·4 mg kg^?1 was 0·26 ± 0·09, and mean absorption time was 4·7 ± 11·1 h. Considerable pharmacokinetic variability was observed, particularly after abomasal administration. Cyclosporin A pharmacokinetics in sheep lie within the values reported in man after renal, bone marrow and cardiac transplantation.     

Cyclosporin Increases the CNS Sensitivity to the Hypnotic Effect of Phenobarbitone but not Ethanol in Rats

Abstract— The purpose of this investigation was to determine whether repetitive administration of cyclosporin affects the pharmacodynamics of phenobarbitone- and ethanol-induced anaesthesia. Sabra male rats received either cyclosporin (50 mg kg^?1 day^?1, i.m.) for four days, or the same volume of the vehicle. Two hours after the last cyclosporin dose, phenobarbitone or ethanol solutions were infused intravenously at a constant rate until the onset of anaesthesia. Repetitive treatment with cyclosporin increased the CNS sensitivity to the hypnotic action of phenobarbitone. This was evidenced by the lower CSF phenobarbitone concentration, at the onset of the hypnotic effect, in the cyclosporin-treated group vs control values (115 ± 4 vs 93 ± 7 mg L^?1, P = 0·01). However, the same pretreatment had no apparent effect on the pharmacodynamics of ethanol-induced sleep. It is suggested that anaesthesiologists must be alert to the possible increase in brain sensitivity when placing cyclosporin patients under anaesthesia with barbiturates.     

In-vivo Distribution and Erythrocyte Binding Characteristics of Cyclosporin in Renal Transplant Patients

The pharmacokinetic parameters of cyclosporin, a potent immunosuppressive agent, show large intra-and inter-individual variability, possibly because of the different analytical methods used. A recently developed cyclosporin-specific radioimmunoassay has been used to study the in-vivo distribution and binding characteristics of cyclosporin in whole blood, plasma and erythrocytes of fifteen renal transplant patients. The profiles of cyclosporin concentration-time curves after an oral dose of cyclosporin had either one peak (ten patients, group A) or two (five patients, group B). Essentially no difference was observed between the two groups in the relationship between equilibrium cyclosporin concentrations in erythrocyte and plasma as a function of whole-blood concentration. The equilibrium in-vivo cyclosporin concentrations in erythrocytes and plasma were, however, markedly lower than those previously observed under in-vitro conditions. The ratio of cyclosporin concentration in erythrocytes (C_E) to that in plasma (C_P) changed with time, in inverse proportion to the change in cyclosporin concentration in blood, over the range 0.63-2.80 in individual patients with an average of 1.36 ± 007 (mean ± s.e.m.) for group A and 1.42 ± 0.23 for group B. The apparent cyclosporin binding affinity (K_d) to erythrocytes under in-vivo conditions averaged 452.2 ± 47.6 nm (543.5 ± 57.2 ng mL^?1) for group A and 419.4 ± 41.2 nm (504.1 ± 49.5 ng mL^?1) for group B, whereas apparent cyclosporin binding capacity (B_max) of the blood cell averaged 0.83 ± 0.07 nmol mL^?1 for group A and 0.78 ± 0.07 nmol mL^?1 for group B. Significantly reduced average K_d (262.7 ± 40.2 nm or 315.8 ± 48.9 ng mL^?1, P < 001) and B_max (0.56 ± 008 nmol mL^?1, P < 005) values were observed during the period after T_max (4–12 h after the drug ingestion) in group A patients. Apparent K_d and B_max, determined by a nonlinear regression technique, were 131.6 ± 29.4 and 1088.0 ± 114.7 nm (158.2 ± 35.4 and 1307.8 ± 137.9 ng mL^?1) and 0.178 ± 0.024 and 0.814 ± 0.078 nmol mL^?1, respectively, during the 4–12 h period in group A patients. These findings reveal distinct differences in in-vivo distribution of cyclosporin and the binding characteristics of the compound to erythrocytes from those previously observed under in-vitro conditions. The significantly lower K_d of cyclosporin binding to erythrocytes during the elimination phase suggests a potential effect of cyclosporin-containing erythrocytes or of cyclosporin contained in erythrocytes during cyclosporin treatment.     

Reduced kallikrein excretion by liposome-encapsulated cyclosporin in the rat

Abstract— Different phospholipids and methods of preparation were used to produce cyclosporin encapsulated in liposomes. The optimal formulation of cyclosporin-liposome was compared to the oily cyclosporin after intraperitoneal administration of 25 mg kg^?1 body weight to rats. Urinary kallikrein excretion was significantly reduced with the liposomal form. The abrupt increase of kallikrein excretion after the tenth day with the control oil preparation suggests that cyclosporin toxicity could be present at the tubular level, and the encapsulation of cyclosporin in liposomes reduces tubular damage.     

Anti-ulcer Activity of Cromakalim (BRL 34915), a Potassium-channel Opener,Against Experimentally Induced Gastric and Duodenal Ulcers in Rats and Guinea-pigs

The effect of cromakalim, a potassium-channel opener, was studied on pylorus ligation-induced, aspirin-induced and water-immersion plus restraint stress-induced gastric ulcers in rats and on histamine-induced duodenal ulcer in guinea-pigs. Pretreatment with cromakalim (50–500 μg kg^?1, p.o.) resulted in a significant reduction in the incidence of gastric and duodenal ulceration in each model. The anti-ulcer activity of cromakalim was comparable with that of cimetidine. Cromakalim at 100, 250 and 500 μg kg^?1 caused a reduction in the volume of the gastric content in pylorus-ligated rats, and a dose of 250 μg kg^?1 resulted in a significant reduction in total acidity (28.81 ± 11.73 mEq L^?1, P < 0.02) in the pylorus ligation model. A significant reduction in total acid output was observed at doses of 250 μg kg^?1 (84.27 ± 22.33 mEqH+, P < 0.02) and 500 μg kg^?1 (120.17 ± 24.49 mEq H+, P < 001) in pylorus-ligated rats. A significant reduction in the ulcer index in pylorus-ligated rats was observed at all cromakalim doses: 50 μg kg^?1 (0.23 ± 009, P < 0.05), 100 μg kg^?1 (0.15 ± 0009, P < 0.02), 250 μg kg^?1 (0.12 ± 0.05, P < 0.01) and 500 μg kg^?1 (0.14 ± 0.03, P < 0.02). A significant reduction in the ulcer index of aspirin-treated rats was also observed at all cromakalim dose levels: 50 μg kg^?1 (0.39 ± 0.03. P < 0.01), 100 μg kg^?1 (0.28 ± 0.06, P < 0.01), 250 μg kg^?1 (0.22 ± 0.04, P < 0.001) and 500 μg kg^?1 (0.28 ± 0.03, P < 0.01). In the water-immersion plus restraint stress-induced gastric ulcer model, cromakalim significantly reduced gastric ulceration at all the dose levels: 50 μg kg^?1 (28.2 ± 2.12, P < 0.001), 100 μg kg^?1 (20.24 ± 1.71, P < 0.01), 250 μg kg^?1 (19.95 ± 1.46, P < 0.001) and 500 μg kg^?1 (21.61 ± 3.00, P < 0.001) but there was no consistent reduction of gastric bleeding. In addition to gastric ulcers, duodenal lesions were also reduced by pretreatment with cromakalim at all dose levels: 50 μg kg^?1 (97.87 ± 20.03 mm², P < 0.02). 100 μg kg^?1 (70.72 ± 12.82 mm², P < 0.02), 250 μg kg^?1 (48.32 ± 8.42 mm², P < 0.01) and 500 μg kg^?1 (55.50 ± 12.50 mm², P < 0.01). Cromakalim at a dose of 100 μg kg^?1 also reduced total acidity (99.36 ± 9.12 mEq L^?1, P < 0.02) and total acid output (172.22 ± 45.33 mEq of H+, P < 0.05) in this model. These findings demonstrate the anti-ulcer activity of cromakalim in different experimental models and suggest its potential use in ulcer therapy.     

Plasma pharmacokinetics and urinary and biliary excretion of a new potent tripeptide HIV-1 protease inhibitor,KNI-272, in rats after intravenous administration

The pharmacokinetic (PK) characteristics of KNI-272, a potent and selective HIV-1 protease inhibitor, were evaluated in rats after intravenous (IV) administration. The effect of dose on KNI-272 plasma kinetics, and the urinary and biliary elimination kinetics of KNI-272, were examined. After IV administration of 10.0 mg kg^?1 KNI-272, the mean terminal elimination half-life, t_1/2λz, was 3.49 ± 0.19 (SE) h, the total plasma clearance, CL_tot, was 15.1 ± 1.2 mL min^?1 and the distribution volume at steady state, V_d,ss, was 3790±280 mL kg^?1. On the other hand, after 1.0mg kg^?1 IV administration, t_d,ss, was 3.04±0.11 h, CL_tot was 15.9±0.2mL min^?1, and V_d,ss was 6950±600 mL kg^?1. The PK parameters of KNI-272 after IV administration showed that the disposition of KNI-272 in the rat plasma is linear within the dose range from 1.0 to 10.0mg kg^?1. Using an equilibrium dialysis method, the plasma binding of KNI-272 was measured in vitro. The free fractions were 17.7 ± 0.6%, 12.1±1.5%, and 13.8 ± 1.4% at the total concentration ranges of 9.898 ± 0.097 μg mL^?1, 0.888 ± 0.008 μg mL^?1, and 0.470±0.55 μg mL^?1, respectively. The percentages of the dose excreted into the urine and bile as the unchanged form were 1.20 ± 1.06% and 1.61 ± 0.32% at 1.0mg kg^?1 dose, and 0.164 ± 0.083% and 1.42 ± 0.26% at 10.0 mg kg^?1 dose, respectively. The renal clearance (CL_R) and the biliary clearance (CL_B) were calculated to be 0.191 and 0.256mL min^?1 for 1.0mg kg^?1, and 0.0248 and 0.215 mL min^?1 for 10.0 mg kg^?1, respectively. When comparing these values with the CL_tot values, the urinary and biliary excretion of KNI-272 are minor disposition routes.     

Simple HPLC Determination of the Concentrations of Epiroprim in the Serum and Brains of Mice

Epiroprim, an analogue of trimethoprim, has been shown to potentiate the efficacy of dapsone in experimental parasitic infections. A simple and accurate HPLC method has been developed to estimate epiroprim in serum and brain Blood and brains from mice were sampled 0, 30, 75, 120 and 240 min after 50 or 100 mg kg^?1 oral gavage. The drug and added internal standard metoprine in serum and brain supernatant were isolated by solid-phase extraction (Supelclean LC-SCX). The HPLC system consisted of a 150 × 4.6 mm Hypersil 5 μm ODS column. The mobile phases contained various proportions of acetonitrile, methanol and phosphate buffer (0.1 M). Peaks were detected by UV absorbance at 210 run. Serum concentrations (mean ± s.e.m.) of epiroprim were highest at 30 min for both 50 and 100 mg kg^?1 doses, 173 ± 20 and 207 ± 25 ng mL^?1, respectively, falling to 8 ± 5 and 18 ±6 ng mL^?1, respectively, at 240 min. Epiroprim concentrations in the brain correlated well with those in the serum, with levels of 223 ±69 and 265 ±21 ng g^?1 falling to 10 ± 10 and 31 ± 11 ng g^?1, respectively. Epiroprim is rapidly absorbed and distributed to the brain.     

Pharmacokinetics and pharmacodynamics of morphine-3-glucuronide in rats and its influence on the antinociceptive effect of morphine

In this study the pharmacokinetics and pharmacodynamics of morphine-3-glucuronide (M3G) were investigated in rats after i.v. administration as a bolus dose (86.7 μmol kg^?1) and as a constant rate infusion (2.9 μmol h^?1) over 5 days. After the bolus dose, the clearance (Cl) was 12.1 ± 0.6 ml min ^?1* kg, the volume of distribution at steady state (V_ss) 1.68 ± 0.89 1 kg^?1, the half-life of the first phase 13.2 ± 1.8 min and the halflife of the second phase 11.6 ± 7.7 h. After the constant rate infusion, Cl was 10.5 ± 1.7 ml min^?1*kg. The antagonistic effect of M3G on the antinociceptive effect of a bolus dose of morphine (35 μmol kg^?1) was tested during steady state concentrations of M3G on day 4 and to M3G naïve rats. No antinociceptive, hyperalgesic or withdrawal effects were observed as a result of M3G administration, but a significantly lower antinociceptive effect of morphine was found in the M3G infusion group compared to the control group. Systemically administered M3G antagonized the antinociceptive effect of morphine, but this cannot be the only explanation to the tolerance development observed after morphine administration.     

Natural Products: Anti-hyperalgesic Effect of an Ethanolic Extract of Propolis in Mice and Rats

Propolis, or bee glue, which contains a complex mixture of secondary metabolites, has long been used in many countries for the management of several diseases. The purpose of this study was to evaluate, by means of several pharmacological models, the anti-hyperalgesic effect of propolis collected in the south of Brazil. The abdominal constrictions induced in mice by intraperitoneal injection of acetic acid (0.6%), kaolin (50 mg kg^?1) or zymosan (40 mg kg^?1) were inhibited to different extents by an extract of propolis (1–60 mg kg^?1) administered intraperitoneally 30 min earlier; mean ID50 (concentrations resulting in 50% inhibition) values were 2.7, 10.8 and 10.7 mg kg^?1, respectively, and maximum inhibition was 58 ± 5, 57 ± 10 and 51 ± 5%, respectively. Given orally (25–200 mg kg^?1, 1 h previously) propolis also inhibited the abdominal constrictions induced by acetic acid (maximum inhibition 43 ±5%). When injected intraperitoneally (3–60 mg kg^?1, 30 min previously), propolis attenuated both the neurogenic (first phase) and inflammatory (second phase) pain responses and paw oedema caused by intraplantar injection of formalin (2.5%); maximum inhibition was 32 ±5, 43 ±6 and 19 ±2%, respectively. Oral administration of propolis (25–200 mg kg^?1, 1 h previously) inhibited both phases and reduced the oedema formation associated with the second phase of the formalin test (maximum inhibition 22±5, 33 ±6 and 26±3%) and extract of propolis (3–30 mg kg^?1 i.p. or 25–100 mg kg^?1 p.o., respectively 30 min and 1 h previously) significantly inhibited capsaicin-induced pain with maximum inhibition of 39±8 and 41 ±8%, respectively. When assessed in the Randall–Sellito test of pain, the extract of propolis (3–30 mg kg^?1, i.p., 30 min previously) significantly reversed the hyperalgesia induced by intraplantar injection of bradykinin (3 nmol per paw) in rats (P < 0.01). In contrast with morphine the extract of propolis (. 100 mg kg^?1, 30 min previously) was ineffective when assessed in the tail-flick and hot-plate thermal assays. Naloxone (5 mg kg^?1 i.p.) reversed (P < 0.01) the effect of morphine (5 mg kg^?1 s.c.) by 70 and 94% respectively in the first and second phases of the formalin test, but did not interfere with the analgesic effect of propolis (10 mg kg^?1 i.p., 30 min previously). These results show that ethanolic extract of propolis, given systemically, has significant anti-hyperalgesic action when assessed in chemical, but not thermal, models of nociception in mice and rats. Its analgesic action seems to be unrelated to release or activation of the opioid system.     

Niosomes encapsulating paclitaxel for oral bioavailability enhancement: preparation,characterization, pharmacokinetics and biodistribution

Abstract

In this study, niosome formulations were prepared and evaluated for their effects on improving the oral bioavailability of paclitaxel (PCT). Niosomes were prepared from Span 40 and coated with bioadhesive carbopol polymers. The niosomes encapsulated 98.7%?±?0.8 of the initially added PCT and their size ranged from 133?±?6?nm to 320?±?6?nm. The stability of Carbopol 974P coated niosomes in bile salts was better than uncoated niosomes. Extended release of PCT was observed. After oral administration of formulations to Wistar rats, higher drug plasma concentrations were observed for niosomes comparing to PCT suspension. The high PCT accumulation in intestine and liver obtained after Carbopol 974P coated niosomes administration indicated their potential regarding effective treatment of localized carcinomas in intestine and liver. The relative bioavailability of PCT was increased 3.8- and 1.4-fold by uncoated and Carbopol 974P coated niosomes emphasizing the ability of niosomes on improving the oral bioavailability of PCT.     

Assessment of hair and bone accumulation of beryllium by mice exposed to contaminated dusts

This study looks at the accumulation of Be in the hair and bones of mice to understand both the use of hair as a bioindicator of exposure to Be and accumulation in bones as a means to evaluate the translocation of Be. We exposed two groups of mice (C3H/HeJ) to 250 µg m^?3 of two different particles sizes of Be metal (fine and intermediate; Be‐F and Be‐I) during 3 weeks of nose‐only inhalation exposure. A control group was exposed to HEPA‐filtered air. Mice were sacrificed either 1 or 3 weeks after the end of exposure. Mice were shaved and the bones were extracted. For washed hair, the results of mice sacrificed one week after the end of exposure were 8.3 ± 1.4 µg kg^?1 hair for the control group, 114 ± 42 µg kg^?1 hair for the Be‐I group, and 159 ± 65 µg kg^?1 hair for the Be‐F group. Results for Be‐F mice sacrificed 3 weeks after the end of exposure showed an average Be concentration in washed hair of 419 ± 100 µg kg^?1, thus suggesting that excretion of Be in hair increases with time. Be concentration in bones was 6 ± 3 µg kg^?1 dry bone tissues for the control group, compared with 24 ± 7 µg kg^?1 for Be‐I and 34 ± 6 or 43 ± 8 µg kg^?1 for Be‐F in mice sacrificed 1 or 3 weeks after the end of exposure. These results demonstrate the potential of using hair and bone as bioindicators of Be exposure. Copyright © 2009 John Wiley & Sons, Ltd.     

Pharmacokinetics and Cardiovascular Effects of YM-21095, a Novel Renin Inhibitor,in Dogs and Monkeys

Abstract— The pharmacokinetics and cardiovascular effects of YM-21095 ((2 RS), (3S)-3-[N^α-[1,4-dioxo-4-morpholino-2-(1-naphthylmethyl)-butyl]-l-histidylamino]-4-cyclohexyl-1-[(1-methyl-5-tetrazolyl)thio]-2-butanol), a potent renin inhibitor, have been studied in beagle dogs and squirrel monkeys. Plasma levels of YM-21095 after 3 mg kg^?1 intravenous dosing to dogs declined biphasically and fitted a two-compartment model. Kinetics were as follows: t½α = 4·9±0·2 min, t½β = 2·76±0·79 h, Vd_ss = 3·86±1·04 L kg^?1, plasma clearance = 2·22 ± 0·39 L kg^?1, and AUC= 1445 ± 266 ng h mL^?1. After 30 mg kg^?1 oral dose, maximum plasma concentration, t_max and AUC of YM-21095 were 28·8 ± 9·6 ng mL^?1, 0·25 h and 23·6 ± 7·7 ng h mL^?1, respectively. Systemic bioavailability as determined on the basis of the ratio of AUC after intravenous and oral dose was 0·16 ± 0·04%. In conscious, sodium-depleted monkeys, YM-21095 at an oral dose of 30 mg kg^?1 lowered systolic blood pressure and inhibited plasma renin activity without affecting heart rate and plasma aldosterone concentration. Maximum plasma concentration of YM-21095 after 30 mg kg^?1 oral dose to monkeys was 71·8 ± 41·5 ng mL^?1, which was reached 0·5 h after the dose. At equihypotensive doses, captopril and nicardipine increased plasma renin activity markedly and slightly, respectively. These results suggest that oral absorption of YM-21095 is low in dogs and monkeys, and YM-21095 shows a blood pressure lowering effect by inhibiting plasma renin activity in sodium-depleted monkeys.     

Antinociceptive Effect of the Hydroalcoholic Extract of Bauhinia splendens Stems in Mice

The analgesic effect of the hydroalcoholic extract of the stems of Bauhinia splendens (Leguminosae) has been investigated in chemical and thermal models of nociception in mice. The hydroalcoholic extract of B. splendens, 3–60 mg kg^? intraperitoneally or 50–400 mg kg^? orally, caused dose-related, and long-lasting (up to 3 h) inhibition of acetic acid-induced abdominal constriction in mice, with ID50 values of 3.2 and 177.6 mg kg^? and maximum inhibition of 95 ± 2 and 61 ± 6%, respectively. In the formalin test, the extract given intraperitoneally (1.60 mg kg^?) or orally (50–400 mg kg^?) caused graded inhibition of both phases of formalin-induced pain, being about 5- to 6-fold more potent in attenuating the second phase of pain. The calculated mean ID50 values for the first and the second phases were 11.5 and 2.5 mg kg^?, respectively, for intraperitoneal administration and > 200 and 70 mg kg^?, respectively, for oral administration; the percentages of maximum inhibition for the first and the second phases were 68 ± 6 and 99 ± 1, respectively, for intraperitoneal administration and 37 ± 6 and 69 ± 9, respectively, for oral administration. However, at the same doses the extract did not significantly affect the oedematogenic response induced by formalin. The treatment of animals with naloxone (5 mg kg^?, i.p.) completely reversed the analgesic effect caused by morphine (5 mg kg^?, s.c), but had no effect against the antinociceptive effect of the hydroalcoholic extract of B. splendens (60 mg kg^?, i.p.) when assessed against acetic acid-induced abdominal constrictions. Furthermore, the extract, in contrast with morphine, had no analgesic effect in the hot-plate test. These data show that the hydroalcoholic extract of B. splendens has significant analgesic action when assessed against several models of pain. The mechanism underlying its analgesic effect still remains unknown, but seems to be unrelated to interaction with opioid systems.     

Evaluation of the anti-inflammatory activity of N,N′-bis(3-dimethylamino-1-phenyl-propylidene)hydrazine dihydrochloride

This study investigated the anti-inflammatory effect of N, N′-bis(3-dimethylamino-1-phenyl-propylidene)hydrazine dihydrochloride, D1, on carrageenan-induced edema. In addition, its effect on hyaluronidase-induced vascular permeability was also tested. D1 was synthesized, and anti-inflammatory activity was determined by carrageenan-induced hind paw edema in rats (n?=?30) at 50, 100, and 200?mg kg^?1 doses of D1 and also a 25?mg kg^?1 dose of indomethacin. The effects of D1 and indomethacin on hyaluronidase-induced capillary permeability were investigated in rabbits (n?=?18) at a 100?mg kg^?1 dose of D1 and 25?mg kg^?1 dose of indomethacin. D1 inhibited carrageenan-induced inflammation by 40, 20, and 10% at 50, 100, and 200?mg kg^?1 doses after 1?h. The inhibitions were 22.5, 32.7, 28.6% and 15.6, 33.4, 8.9% at 2?h and 3?h, respectively. The inhibitions due to indomethacin (25?mg kg^?1 dose) were 67.5, 87.8, and 91.1%, at 1?h, 2?h, and 3?h, respectively. The subcutaneous spreading areas of Trypan blue at 1, 5, 30, and 60?min after subcutaneous injection of hyaluronidase were 172.6?±?41.6, 210.2?±?39.7, 363?±?50, and 400.2?±?46.7?mm² in the D1 (100?mg kg^?1) treated group. The spreading areas at these time periods were 38.8?±?3.7, 48.2?±?4.5, 100.6?±?6.9, and 119.8?±?22.5?mm² in the indomethacin treated group. Our results showed that D1 inhibits carrageenan-induced inflammation in rats. A tendency to decrease the capillary permeability suggested that the mechanism of action of the anti-inflammatory effect of D1 may partly depend on inhibition of the hyaluronidase enzyme.     

The pharmacokinetics and absolute bioavailability of selegiline in the dog

Selegiline is beneficial to Parkinsonian patients as an adjunct to levodopa therapy. Currently no pharmacokinetic data are available for selegiline in the literature, mainly due to lack of analytical methods that can measure concentrations below 10 ng mL^?1 in plasma. A sensitive fluorimetric assay based on inhibition of rat brain monoamine oxidase-B (MAO-B) in vitro has been developed to measure selegiline in plasma as low as 0.25 ng mL^?1. The pharmacokinetics of selegiline were investigated following intravenous and oral administration to four female mongrel dogs. Each dog received 1 mg kg^?1 selegiline in solution via gavage or by an intravenous route separated by one week. The mean terminal half-life, volume of distribution of the central compartment, and systemic clearance of selegiline were 60.24 ± 9.56 min, 6.56 ± 0.56 L kg^?1, and 159.91 ± 19.28 mL min^?1 kg^?1, respectively. After oral administration selegiline appeared to be absorbed rapidly with a t_max and C_max of 25 ± 5.8 min and 5.2 ± 1.36 ng mL^?1, respectively. The absolute bioavailability of selegiline in the dog was 8.51 ± 3.31%.     

Implantable slow release cyclosporin A (CYA) delivery system to thoracic lymph duct

An implant from which cyclosporin A (CyA) is slowly released has been prepared and the immunosuppressive effect of such a CyA implant was studied with an allogenic rat heart transplantation model system. The implant was made of a biodegradable polymer of L-lactic acid (PLA) and/or co-polymer of L-lactic acid and glycolic acid (PLGA) as the base. The synthetic nonionic surfactant, HCO-60 (polyoxyethylated, 60μmol, castor oil derivative), was used as an additive. By changing the contents of the polymer and HCO-60, the release rate of CyA was adjusted. To determine the kind and formulation of the base, the lipophilic dye, Sudan Black (SB), was used as a model drug for CyA. Implants made of PLGA and HCO-60 (10:15) released more than 45% of SB within 6 days, whereas PLA implants released less than 15%. Based on these results, an implant containing CyA from which 70 ± 9.7% of the formulated CyA was released within 6 days was prepared. The size of the implant was 2 mm (o.d.)× 15 mm length. The immunosuppressive activities of CyA administered as an implant attached to the thoracic duct were evaluated with an allogenic rat heart transplantation model system. As a control, a placebo implant was used. The CyA implant showed a cardiac graft survival period of 9.8 ± 1.3 (mean ±S.D.) and 21.0 ± 9.6 days at 20 and 35 mg/kg, respectively, which is significantly longer than that of the placebo implant rat group (7.6 ± 0.9 days). These results demonstrate the possibility of local immunosuppression at the thoracic lymph in immunosuppressive therapy with CyA.     

Mesulergine antagonism towards the fluoxetine anti-immobility effect in the forced swimming test in mice

Abstract— The anti-immobility effect of fluoxetine (40 mg kg^?1) in the forced swimming test in mice was antagonized by the 5-HT_1c/2 antagonist mesulergine (7·5 mg kg^?1) and the dopamine D₂ antagonist (±)-sulpiride (12.5 mg kg^?1) but not by the 5-HT_2/1C antagonist ritanserine (2 mg kg^?1), the 5-HT_1A/1B antagonist (–)-propranolol (20 mg kg^?1) or the 5-HT₃ antagonist DAU 6215 (0·1 mg kg^?1). All compounds were administered intraperitoneally (i.p.) 6 min before fluoxetine, given i.p. 30 min before testing. The anti-immobility effect of fluoxetine was also prevented by pretreat-ment with p-chlorophenylalanine (300 mg kg^?1 twice daily for 3 days) which produced an 80% reduction of 5-HT in brain. The results suggest that fluoxetine reduces immobility time in mice forced to swim, by acting indirectly through a mesulergine-sensitive site, probably the 5-HT_1C receptor.     

Cirsimarin and Cirsimaritin,Flavonoids of Microtea debilis (Phytolaccaceae) with Adenosine Antagonistic Properties in Rats: Leads for New Therapeutics in Acute Renal Failure

In traditional medicine Microtea debilis is used against proteinuria. In ligand-binding studies extracts of Microtea debilis have been shown to inhibit the binding of [³H]1,3-dipropyl-8-cyclopentylxanthine ([³H]DPCPX) to adenosine-A₁ receptors in rat forebrain membranes. Subsequently, cirsimarin, a flavonoid, was isolated as the active component and was shown to function as adenosine antagonist at the adenosine-A₁ receptor in-vitro. In this study we have investigated the adenosine-A₂ receptor activity of cirsimarin the in-vivo inhibition of the effects of adenosine by cirsimarin in rats, the absorption of cirsimarin and the inhibition of the binding of [³H]DPCPX to the adenosine-A₁ receptor by urine samples obtained after oral administration of crude extract of Microtea debilis, cirsimarin or cirsimaritin to rats. Cirsimarin inhibited the binding of [³H]5′-N-ethylcarboxamidoadenosine ([³H]NECA) to adenosine-A₂ receptors in rat striatum with an inhibition constant, K_i, of 6.5 ± 0.3 μm . The decrease of heart rate and blood pressure induced by adenosine was significantly inhibited by cirsimarin. After oral administration of 8 and 80 mg kg^?1 cirsimarin, the compound could not be detected in either plasma or urine, but the presence of cirsimaritin was established. By use of β-glucuronidase, glucuronides of cirsimaritin were also detected in the urine. The concentrations of cirsimaritin in the plasma were 0.126 ± 0.04, 0.138 ± 0.015, and 0.120 ± 0.022 μm , respectively, 2, 5 and 12 h after administration of 8 mg kg^?1 cirsimarin. The concentrations of cirsimaritin in the urine at the same times after administration of the same dose were 205 ± 1.86, 5.05 ± 2.6 and 2.06 ± 0.09 μm , respectively. The inhibition of the binding of [³H]DPCPX to the adenosine-A₁ receptor by urine samples collected 2, 5 and 12 h after oral administration of 8 mg kg^?1 cirsimarin or a crude extract of Microtea debilis containing approximately 8 mg kg^?1 cirsimarin and 2.8 mg kg^?1 cirsimaritin, or 6.8 mg kg^?1 cirsimaritin, was not significantly different from that of urine samples collected from untreated rats, in contrast with urine samples collected 1 and 2 days after oral administration of 80 mg kg^?1 cirsimarin. Approximately 3% of the cirsimarin was excreted in the urine as cirsimaritin. The results indicate that in the kidney and urinary tract the concentrations of cirsimaritin produced after ingestion of more than 8 mg kg^?1 cirsimarin can be high enough to inhibit the interaction of adenosine with its receptors; this might explain the effectiveness of Microtea debilis preparations against proteinuria in traditional medicine.     

Pharmacokinetics of a novel retinoid AGN 190168 and its metabolite AGN 190299 after intravenous administration of AGN 190168 to rats

The pharmacokinetics of AGN 190168, a novel synthetic retinoid, and its major metabolite, AGN 190299, in rat blood after intravenous administration was investigated. Approximately 4.4 mg kg^?1 (high dose) or 0.49 mg kg^?1 (low dose) of AGN 190168 was administered to rats via the femoral vein. Blood was collected from the femoral artery at various time points during an 8 h period. Blood concentrations of AGN 190168 and AGN 190299 were determined by a specific and sensitive high-pressure liquid chromatographic (HPLC) method. AGN 190168 was rapidly metabolized in rats. The only detectable drug-related species in the blood was AGN 190299. Therefore, only pharmacokinetics of AGN 190299 were calculated. Elimination of AGN 190299 appeared to be non-linear after administration of the high dose, and linear after administration of the low dose. The maximum elimination rate (V_max) and the concentration at half of the V_max (k_m), as estimated by a Michaelis—Menten one-compartment model, were 7.58 ± 2.42 μg min^?1 (mean ± SD) and 6.10 ± 1.58 μg mL^?1, respectively. The value of the area under the blood concentration time curve (AUC) was 9.54 ± 1.68 μg h mL^?1 after administration of the high dose and 0.594 ± 0.095 μg h mL^?1 after administration of the low dose. The clearance value was 7.79 ± 1.20 mL min^?1 kg^?1 after the high dose, statistically significantly different from that after the low dose (p < 0.05), 14.0 ± 2.2 mL min^?1 kg^?1. The terminal half-life (t_1/2) was 1.25 ± 0.74 h for the high-dose group and 0.95 ± 0.16 h for the low-dose group. Study results demonstrate rapid systemic metabolism of AGN 190168 to AGN 190299, non-linear pharmacokinetics of AGN 190299 after the 4.4 mg kg^?1 dose, and the lack of difference in disposition profiles between sexes after intravenous administration of AGN 190168 to rats.     

Gastrointestinal Effects of Diazepam-withdrawal are Linked to Activation of Central Cholecystokinin-ergic Pathways in Rats

Abstract— The influence of flumazenil-precipitated diazepam withdrawal on intestinal myoelectric activity and colonic transit was evaluated, in diazepam-dependent rats. Administered intraperitoneally, flumazenil (15 mg kg^?1) induced a strong stimulation of the duodenal spiking activity lasting 197 ± 20 min, and accelerated colonic transit corresponding to a significantly (P < 0·05) increased value of the geometric centre (3.52 ± 0.23 vs 2·44 ± 0·1 for the control). Both devazepide and L365260 administered intracerebroventricularly at a dose of 10 μg kg^?1 abolished the flumazenil-induced withdrawal effect on the duodenum, whereas at a lower dose (1 μg kg^?1) only L365260 was able to antagonize this effect. In the same way, devazepide, loxiglumide and L365260 suppressed the effect of precipitated withdrawal on colonic transit when administered intracerebroventricularly at a dose of 10 μg kg^?1, whereas similar blockade was obtained at a dose of 5 μg kg^?I with L365260, and 10 ng kg^?1 with PD135–158. It is concluded that in rats precipitated diazepam-withdrawal altered intestinal motility and colonic transit and that these effects are mediated by central release of cholecystokinin (CCK) or activation of CCK-ergic neurons.