Preclinical pharmacokinetic analysis of NOV-002, a glutathione disulfide mimetic

NOV-002 is a glutathione disulfide (GSSG) mimetic that is the subject of clinical investigation in oncology indications. GSSG is reduced by glutathione reductase (GR) to form glutathione (GSH), thereby maintaining redox homeostasis. The purpose of the study was to report the pharmacokinetic properties of NOV-002 and evaluate the effect that NOV-002 elicits in redox homeostasis. The pharmacokinetic analysis and tissue distribution of NOV-002 and GSH was evaluated in mice following a dose of 250 mg/kg, i.p. The redox potential and total protein thiol status was calculated. Here we show that NOV-002 is a substrate for GR and that GSH is a primary metabolite. Non-linear pharmacokinetic modeling predicted that the estimated absorption and elimination rate constants correspond to a half-life of ∼13 min with an AUC of 1.18 μg h/mL, a C_max of 2.16 μg/ml and a volume of distribution of 42.61 L/kg. In addition, measurement of the redox potential and total protein thiol status indicated the generation of a transient oxidative signal in the plasma compartment after administration of NOV-002. These results indicate that NOV-002 exerts kinetic and dynamic effects in mice consistent with the GSSG component as the active pharmacological constituent of the drug. A longer-lasting decrease in total plasma free thiol content was also seen, suggesting that the oxidative effect of the GSSG from NOV-002 was impacting redox homeostasis.     

Genuine antihyperalgesia by systemic diazepam revealed by experiments in GABAA receptor point-mutated mice

Ionotropic γ-aminobutyric acid (GABA_A) receptors control the relay of nociceptive signals at several levels of the neuraxis. Experiments with systemically applied benzodiazepines, which enhance the action of GABA at these receptors, have suggested both anti- and pronociceptive effects. The interpretation of such experiments has been notoriously difficult because of confounding sedation. Here, we have used genetically engineered mice, which carry specific benzodiazepine-insensitive GABA_A receptor subunits, to test whether diazepam, a frequently used classical benzodiazepine, exerts antihyperalgesia after systemic administration in the formalin test, a model of tonic nociception. In wild-type mice, systemic diazepam (3–30 mg/kg, p.o.) dose-dependently reduced the number of formalin-induced flinches during both phases of the test by about 40–70%. This antinociception was reversed by the benzodiazepine site antagonist flumazenil (10 mg/kg, i.p.), but fully retained in GABA_A receptor α1 point-mutated mice, which were resistant against the sedative action of diazepam. Experiments carried out in mice with two diazepam-insensitive subunits (α1/α2, α1/α3 and α1/α5 double point-mutated mice) allowed addressing the contribution of α2, α3 and α5 subunits to systemic diazepam-induced antihyperalgesia in the absence of sedation. The relative contributions of these subunits were α2 ≈ α3 > α5, and thus very similar to those found for intrathecal diazepam (0.09 mg/kg). Accordingly, SL-651498 (10 mg/kg, p.o.), an “anxioselective” benzodiazepine site agonist with preferential activity at α2/α3 subunits, significantly reduced formalin-induced flinching in wild-type mice. We conclude that systemic diazepam exerts a genuine antihyperalgesic effect, which depends on spinal GABA_A receptors containing α2 and/or α3 subunits.     

Inhibition of phosphatidylinositol-3 kinase γ reduces pruriceptive, inflammatory, and nociceptive responses induced by trypsin in mice

This study investigated the effects of pharmacological inhibition of phosphatidylinositol 3-kinase (PI3K)γ in the pruriceptive, inflammatory, and nociceptive responses induced by trypsin in mice. The animals were orally treated with the selective PI3Kγ inhibitor AS605240 (0.3-30 mg/kg) 30 minutes beforehand. In separate groups, AS605240 was given by intrathecal (i.t.) or intracerebroventricular (i.c.v.) routes. The control groups received saline at the same schedules. The effects of PI3K blocking were assessed in different experimental assays. The oral treatment with AS605240 produced a marked reduction of scratching behavior elicited by trypsin. Moreover, AS605240 (1 mg/kg) was able to produce a partial but significant inhibition of the scratching bouts elicited by CP 48/80. Interestingly, the i.c.v. and i.t. injection of AS605240 also reduced trypsin-induced itching. The oral administration of AS605240 was found effective in producing a significant and dose-dependent reduction of trypsin-induced paw edema and tumor necrosis factor α production, as well as the neutrophil recruitment, according to myeloperoxidase activity assessment. Likewise, oral AS605240 (1 mg/kg) promoted a significant reduction of spontaneous nociception induced by trypsin in the mouse paw. In contrast, the oral administration of AS605240 did not significantly modify capsaicin-evoked nociception, although this inhibitor was effective when dosed by i.c.v. route. Noteworthy, AS605240 (1 mg/kg) was able to prevent c-Fos and phospho-Akt immunopositivity at the spinal cord of trypsin-injected mice, either into the back of the neck or the paws. To conclude, PI3Kγ inhibition might well represent a valuable alternative for treating inflammatory and painful conditions, as well as pruritus.     

Modulation of CNS pain circuitry by intravenous and sublingual doses of buprenorphine

Buprenorphine (BUP) is a partial agonist at μ-, δ- and ORL1 (opioid receptor-like)/nociceptin receptors and antagonist at the κ-opioid receptor site. BUP is known to have both analgesic as well as antihyperalgesic effects via its central activity, and is used in the treatment of moderate to severe chronic pain conditions. Recently, it was shown that intravenous (IV) administration of 0.2 mg/70 kg BUP modulates the blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) response to acute noxious stimuli in healthy human subjects. The present study extends these observations by investigating the effects of BUP dose and route of administration on central nervous system (CNS) pain circuitry. Specifically, the modulation of evoked pain BOLD responses and resting state functional connectivity was measured following IV (0.1 and 0.2 mg/70 kg) and sublingual (SL) (2 mg) BUP administration in healthy human subjects. While 0.1 mg/70 kg IV BUP is sub-analgesic, both 0.2 mg/70 kg IV BUP and 2.0 mg SL BUP are analgesic doses of the drug. Evoked BOLD responses were clearly modulated in a dose-dependent manner. The analgesic doses of BUP by both routes of administration yielded a potentiation in limbic/mesolimbic circuitry and attenuation in sensorimotor/sensory-discriminative circuitry. In addition, robust decreases in functional connectivity between the putamen and the sensorimotor/sensory-discriminative structures were observed at the two analgesic doses subsequent to measuring the maximum plasma BUP concentrations (C_max). The decreases in functional connectivity within the sensorimotor/sensory-discriminative circuitry were also observed to be dose-dependent in the IV administration cohorts. These reproducible and consistent functional CNS measures at clinically effective doses of BUP demonstrate the potential of evoked pain fMRI and resting-state functional connectivity as objective tools that can inform the process of dose selection. Such methods may be useful during early clinical phase evaluation of potential analgesics in drug development.     

Evaluation of Various Analogues of Tilorone Hydrochloride Against Venezuelan Equine Encephalitis Virus in Mice

The antiviral activity of tilorone hydrochloride and three of its analogues (11,002, 11,567, and 11,877) was assessed by oral and intraperitoneal (i.p.) administration to Venezuelan equine encephalitis (VEE) virus-infected mice. Significant increases in the percentage of survival (P < 0.01) were apparent after oral administration of tilorone and analogue 11,877 at dosages of 250 and 500 mg/kg. Neither tilorone nor 11,877 increased percentage of survival when dosages of 31.25 to 500 mg/kg were given by the i.p. route. Orally administered analogue 11,002 was effective against 100 mouse intracranial median lethal doses (MICLD₅₀) of VEE virus at doses at 250 to 1,000 mg/kg; doses of 31.25 to 250 mg/kg given i.p. were effective against 10 MICLD₅₀. Oral dosages of 250 to 1,000 mg of analogue 11,567 per kg were active against 100 MICLD₅₀ of virus. By the i.p. route, 250 mg of 11,567 per kg protected mice against 1,000 MICLD₅₀, and a dose of 125 mg/kg protected against 100 MICLD₅₀. Oral treatment of VEE infection with analogue 11,567 24 h after subcutaneous inoculation of VEE virus resulted in no significant increase in the percentage of survivors. All survivors of these studies were susceptible to rechallenge 21 days after the first inoculation of virus.     

The effect of pharmacokinetic/pharmacodynamic (PK/PD) parameters of gatifloxacin on its bactericidal activity and resistance selectivity against clinical isolates of Streptococcus pneumoniae

The impact of the pharmacokinetic/pharmacodynamic (PK/PD) parameters (the 24h area under the concentration-time curve [AUC_24h]/minimum inhibitory concentration [MIC] and maximum concentration in serum [C_max]/MIC ratio) after single oral dosing of gatifloxacin on its bactericidal activity and resistance selectivity against quinolone-susceptible clinical isolates of Streptococcus pneumoniae J-69 was investigated using an in vitro PK model. The MICs of gatifloxacin, levofloxacin, and ciprofloxacin were 0.25, 1, and 1µg/ml, respectively. When the range of AUC_24h/MIC ratios was varied from 9.0 to 36 with a constant C_max/MIC ratio of 3.4, the bactericidal activity was correlated with the AUC_24h/MIC ratios. Eradication was observed at an AUC_24h/MIC ratio of 36. On the other hand, the resistance selectivity was associated with the C_max/MIC ratio. Mutant strains were selected at a C_max/MIC ratio of 0.84, but not 1.7 with a constant AUC_24h/MIC ratio of 9.0. These results suggested that an AUC_24h/MIC ratio of 36 and a C_max/MIC ratio of 1.7 might be possible benchmarks to show enough bacterial eradication and prevention of emergence of resistant strains to gatifloxacin, respectively. When the serum concentrations after clinical oral dosing of gatifloxacin (200mg b.i.d.), levofloxacin (100mg t.i.d.), and ciprofloxacin (200mg t.i.d.) were simulated, the bactericidal activity of gatifloxacin was higher than those of levofloxacin and ciprofloxacin. Moreover, no resistant strain was obtained by the exposure to gatifloxacin and levofloxacin, whereas ciprofloxacin selected resistant strains. The clinically relevant oral dosage of gatifloxacin was anticipated to result in a high AUC_24h/MIC₉₀ ratio of 81 and a C_max/MIC₉₀ ratio of 4.4, suggesting that this agent is clinically effective in the treatment of pneumococcal infections.     

Oral administration of the p38α MAPK inhibitor,UR13870, inhibits affective pain behavior after spinal cord injury

The p38α mitogenous activated protein kinase (MAPK) cell signaling pathway is a key mechanism of microglia activation and has been studied as a target for neuropathic pain. The effect of UR13870, a p38α MAPK inhibitor, on microglia expression in the anterior cingulate cortex (ACC) and spinal dorsal horn was addressed after T9 contusion spinal cord injury (SCI) in the rat, in addition to behavioral testing of pain-related aversion and anxiety. Administration of intravenous UR13870 (1 mg/kg i.v.) and pregabalin (30 mg/kg i.v.) reduced place escape avoidance paradigm (PEAP) but did not affect open-field anxiety behavior 42 days after SCI. PEAP behavior was also reduced in animals administered daily with oral UR13870 (10 mg/kg p.o.) and preserved spinal tissue 28 days after SCI. Although UR13870 (10 mg/kg p.o.) failed to reduce OX-42 and glial fibrillar acid protein immunoreactivity within the spinal dorsal horn, a reduction toward the control level was observed close to the SCI site. In the anterior cingulate cortex (ACC), a significant increase in OX-42 immunoreactivity was identified after SCI. UR13870 (10 mg/kg p.o.) treatment significantly reduced OX-42, metabotropic glutamate type 5 receptor (mGluR5), and NMDA (N-methyl-d-aspartate) 2B subunit receptor (NR2B) expression in the ACC after SCI. To conclude, oral treatment with a p38α MAPK inhibitor reduces the affective behavioral component of pain after SCI in association with a reduction of microglia and specific glutamate receptors within the ACC. Nevertheless the role of neuroinflammatory processes within the vicinity of the SCI site in the development of affective neuropathic pain cannot be excluded.     

Effect of cyclosporine on drug transport and pharmacokinetics of nifedipine

Nifedipine (NFP) is an anti-hypersensitive drug and a well-known substrate of cytochrome P450 3A4 (CYP3A4), while cyclosporine (CSP) is a potent p-glycoprotein (P-gp) inhibitor. P-gp is a drug transporter, which determines the absorption and bioavailability of many drugs that are substrates for P-gp. Drugs that induce or inhibit P-gp may have a profound effect on the absorption and pharmacokinetics (PK) of drugs transported by P-gp within the body, possibly compromising their bioavailability. But the role of P-gp in the NFP efflux and its impact on PK profile is not known. Hence in our present study we attempted to investigate the effect of CSP on oral absorption and PK of NFP. Rhodamine 123 (Rho 123), a known P-gp substrate was used as a positive control. Male Wistar rats (350–400 g) were used for the study. Rats were divided into 4 groups (n = 6 each); one group was treated with vehicle (cremophor) followed by NFP (0.2 mg/kg; i.v. bolus) and the other group with CSP (10 mg/kg; i.v.) followed by NFP. Group 3 and 4 were treated with vehicle (cremophor) followed by Rho 123 (0.2 mg/kg, i.v.) and CSP (10 mg/kg; i.v.) followed by Rho 123 (0.2 mg/kg, i.v.) respectively. The blood samples were collected at 0, 5, 10, 15, 30, 60, 90, 120, 180 and 240 min after NFP administration. NFP concentrations in plasma were analyzed by LC–MS–MS and Rho 123 was analyzed by fluorimetric detector. NFP efflux was significantly decreased in CSP treated rats (49.1% decrease, P < 0.05), while NFP concentration in plasma were not changed. However the decrease in NFP efflux did not show any significant changes in NFP PK parameters (T_max; 2.0 vs. 2.5 min, C_max; 0.084 vs. 0.076 μg/ml, T_1/2; 84.0 vs. 91.4 min, AUC_0–t; 4.183 vs. 3.467 μg h/ml, AUC_∞; 5.915 vs. 4.769 μg h/ml, AUMC_0–t; 224.073 vs. 173.063 μg h/ml, AUMC_∞; 776.871 vs. 575.038 μg h/ml, MRT_0–t; 53.608 vs. 49.538 μg h/ml, MRT_∞; 118.194 vs. 115.246 μg h/ml, CL_tot; 0.0375 vs. 0.0433 l/h, Vd_ss; 3.999 vs. 4.641 l in NFP alone vs. CSP + NFP groups respectively). Thus the results indicate that NFP would belong to a group of P-gp substrate. The decrease in efflux of NFP by CSP, through inhibition of P-gp, into the intestinal lumen did not show any impact on PK. This could be due to the activity of other transporters and/or CYP3A4 may have more limiting role than P-gp on NFP metabolism and disposition that is why inhibiting P-gp did not lead to increase the bioavailability and PK alterations.     

Pharmacological activation of 5-HT7 receptors reduces nerve injury-induced mechanical and thermal hypersensitivity

The involvement of the 5-HT₇ receptor in nociception and pain, particularly chronic pain (i.e., neuropathic pain), has been poorly investigated. In the present study, we examined whether the 5-HT₇ receptor participates in some modulatory control of nerve injury-evoked mechanical hypersensitivity and thermal (heat) hyperalgesia in mice. Activation of 5-HT₇ receptors by systemic administration of the selective 5-HT₇ receptor agonist AS-19 (1 and 10 mg/kg) exerted a clear-cut reduction of mechanical and thermal hypersensitivities that were reversed by co-administering the selective 5-HT₇ receptor antagonist SB-258719. Interestingly, blocking of 5-HT₇ receptors with SB-258719 (2.5 and 10 mg/kg) enhanced mechanical (but not thermal) hypersensitivity in nerve-injured mice and induced mechanical hypersensitivity in sham-operated mice. Effectiveness of the treatment with a 5-HT₇ receptor agonist was maintained after repeated systemic administration: no tolerance to the antiallodynic and antihyperalgesic effects was developed following treatment with the selective 5-HT₇ receptor agonist E-57431 (10 mg/kg) twice daily for 11 days. The 5-HT₇ receptor co-localized with GABAergic cells in the dorsal horn of the spinal cord, suggesting that the activation of spinal inhibitory GABAergic interneurons could contribute to the analgesic effects of 5-HT₇ receptor agonists. In addition, a significant increase of 5-HT₇ receptors was found by immunohistochemistry in the ipsilateral dorsal horn of the spinal cord after nerve injury, suggesting a “pain”-triggered regulation of receptor expression. These results support the idea that the 5-HT₇ receptor subtype is involved in the control of pain and point to a new potential use of 5-HT₇ receptor agonists for the treatment of neuropathic pain.     

Effect of soybean administration on the pharmacokinetics of carbamazepine and omeprazole in rats

Influence of soybean administration on the bioavailability of carbamazepine and omeprazole was studied after single dose administration of soybean (10 g/kg p.o.) or after chronic administration of soybean (50% w/w mixed with normal feed) for 15 days in rats. Carbamazepine was administered orally at a dose of 10 mg/kg and omeprazole at a dose of 20 mg/kg. Soybean decreased the bioavailability of carbamazepine after both single dose and chronic administration. It produced a significant decrease in C_max, T_max, AUC_0–t of carbamazepine after single dose administration and increased the plasma clearance and V_d along with decrease in C_max, T_max, AUC_0–t and AUC_{0– ∞} after chronic administration. On the contrary, soybean administration increased the bioavailability of omeprazole by producing an increase in C_max, AUC_0–t and AUC_{0– ∞} and a decrease in V_d after single dose administration and a decrease in plasma clearance along with increase in C_max, AUC_0–t and AUC_{0– ∞} after chronic administration. The half‐life of omeprazole was also increased after both acute and chronic administration of soybean. It was concluded that soybean decreases the bioavailability of carbamazepine and increases the bioavailability of omeprazole after both single dose and chronic administration.     

Pharmacokinetics of a new derivative of partricin A (SPA-S-753) in rodents

Pharmacokinetics of a new semisynthetic polyene antibiotic (N-dimethylaminoacetyl-partricin A 2-dimethylaminoethylamide) in the form of its diaspartate salt (code SPA-S-753) was studied in rats and mice following intravenous injection and in rats following oral administration at different dose levels. In rats the urinary and biliary recovery after intravenous administration was also determined. Rats and mice received a single intravenous injection of 1.25 and 2.5 mg/kg of SPA-S-753 (about 1-2 mg/kg of free base) or 1 mg/kg of amphotericin B as reference drug. Blood samples were obtained at 5 min to 96 h after injection. The half-lives at the elimination phase in serum were 21.3, 26.5, 10.8 h in rats and 11.7, 13.7, 19.8 h in mice, respectively, for 1.25 and 2.5 mg/kg of SPA-S-753 and 1 mg/kg of amphotericin B. The values of AUC(0-infinity) for SPA-S-753 were about 5 times higher in rats and twice higher in mice than those for amphotericin B. Rats received also a single oral dose of 200 or 500 mg/kg of SPA-S-753. Serum samples were obtained at 0.5-96 h after dosing. The compound is poorly absorbed by the oral route. The mean cumulative urinary recovery of SPA-S-753 at 48 h after intravenous injection of 1.25 mg/kg in rats accounts only for 0.5% of the dose, while the cumulative recovery from the bile at 10 h after 2.5 mg/kg i.v. administration in rats accounts for 5.5% of the dose.     

Oral topotecan: Bioavailability,pharmacokinetics and impact of ABCG2 genotyping in Chinese patients with advanced cancers

Oral topotecan (Hycamtin^®) has been recently approved for the treatment of relapsed small cell lung cancer (SCLC) in 2007, however, the bioavailability and pharmacokinetic data of topotecan for Chinese patients is still limited. Xinze^® is a new and the only capsule formulation of topotecan used in China that is similar to Hycamtin^®. The current study aimed to investigate the absolute bioavailability and pharmacokinetics of Xinze^® in Chinese patients with advanced cancers. On day 1, an IV dose of 1.5 mg/m²/d as a 30 min continuous infusion was administered. Patients took the oral topotecan at one of two dose levels: 1.5 mg/m²/d (six patients) or 1.9 mg/m²/d (seven patients) on day 2. Plasma pharmacokinetics of total topotecan and topotecan in the lactone form were performed on both days using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS). Single-nucleotide polymorphisms (SNPs) identified in exon 5 (421C>A) and in exon 2 (34G>A) in ATP-binding cassette sub-family G member 2 (ABCG2) were analyzed by direct sequencing. Safety assessments were performed throughout the study. The maximum plasma concentration (C_max) reached at 1–2 h and the elimination half-life time (T_1/2) was approximately 4.2 h after oral administration. The absolute bioavailability of total topotecan in the 1.5 mg/m²/d and 1.9 mg/m²/d groups averaged 41.23 ± 11.8% and 36.00 ± 14.8%, respectively. The patients with heterozygous SNPs had essentially the same bioavailability and pharmacokinetics. The bioavailability of topotecan after oral administration illustrates good systemic exposure at dosages of 1.5 mg/m²/d and 1.9 mg/m²/d over a five-day schedule in Chinese patients. On a dose-normalized basis, the values of C_max and AUC_0–t for total topotecan in Chinese patients were higher than in Caucasians following oral and intravenous administration, while the T_1/2 was consistent.     

ONO-8130, a selective prostanoid EP1 receptor antagonist, relieves bladder pain in mice with cyclophosphamide-induced cystitis

Given the previous evidence for involvement of prostanoid EP1 receptors in facilitation of the bladder afferent nerve activity and micturition reflex, the present study investigated the effect of ONO-8130, a selective EP1 receptor antagonist, on cystitis-related bladder pain in mice. Cystitis in mice was produced by intraperitoneal administration of cyclophosphamide at 300 mg/kg. Bladder pain-like nociceptive behavior and referred hyperalgesia were assessed in conscious mice. Phosphorylation of extracellular signal-regulated kinase (ERK) in the L6 spinal cord was determined by immunohistochemistry in anesthetized mice. Cyclophosphamide treatment caused bladder pain-like nociceptive behavior and referred hyperalgesia accompanying cystitis symptoms, including increased bladder weight and vascular permeability and upregulation of cyclooxygenase-2 in the bladder tissue. Oral preadministration of ONO-8130 at 0.3-30 mg/kg strongly prevented both the bladder pain-like behavior and referred hyperalgesia in a dose-dependent manner, but had slight effect on the increased bladder weight and vascular permeability. Oral ONO-8130 at 30 mg/kg also reversed the established cystitis-related bladder pain. Intravesical administration of prostaglandin E₂ caused prompt phosphorylation of ERK in the L6 spinal cord, an effect blocked by ONO-8130. Our findings strongly suggest that the prostaglandin E₂/EP1 system participates in processing of cystitis-related bladder pain, and that EP1 antagonists including ONO-8130 are useful for treatment of bladder pain, particularly in interstitial cystitis.     

Evidence for the involvement of the serotonergic, noradrenergic, and dopaminergic systems in the antidepressant-like action of riparin III obtained from Aniba riparia (Nees) Mez (Lauraceae) in mice

Previous work has shown that intraperitoneal administration of riparin III (ripIII) reduces immobility time in the forced swimming test (FST), which suggests potential antidepressant activity. As the mechanism of action is not completely understood, this study is aimed at investigating the antidepressant‐like action of ripIII. Following intraperitoneal administration of ripIII at doses of 25 and 50 mg/kg, there were decreases in the immobility time in the FST and tail suspension test without accompanying changes in ambulation (data not shown). The pretreatment of mice with sulpiride (50 mg/kg, i.p.), prazosin (1 mg/kg, i.p.), yohimbine (1 mg/kg, i.p.), and p‐chlorophenylalanine (PCPA, 100 mg/kg, i.p. for, four consecutive days) significantly prevented the anti‐immobility effect of ripIII in the FST. On the other hand, the anti‐immobility effect of ripIII (50 mg/kg, v.o.) was not altered by pretreatment of mice with SCH23390 (15 μg/kg, i.p.) Furthermore, ripIII potentiated the sleeping latency and sleeping time of the pentobarbital‐induced sleeping time test and also potentiated apomorphine (16 mg/kg, i.p.)‐induced hypothermia in mice. In conclusion, the present study provides evidence that the antidepressant‐like effect of ripIII is dependent on its interaction with the serotonergic, noradrenergic (α₁‐ and α₂‐ receptors), and dopaminergic (dopamine D₂ receptors) systems.     

Heart rate reduction with ivabradine increases ischaemia-induced ventricular fibrillation threshold: role of myocyte structure and myocardial perfusion

Aims

We showed previously that ivabradine (IVA), a selective inhibitor of the cardiac pacemaker I_f current, achieved protection against ischaemia-induced ventricular fibrillation (VF) in pigs by increasing the VF threshold (VFT). This was correlated to the heart rate reduction (HRR), the limitation of monophasic action potential shortening and the reduction of the hypoxic area. This study investigated myocyte ultrastructure and regional myocardial blood flow (RMBF), potentially involved in these cardioprotective effects of IVA.

Methods and results

Myocardial ischaemia was induced in pigs by total 1-min occlusion of the left anterior descending coronary artery following i.v. administration of saline (n = 6) or IVA (0.25 mg/kg, n = 6). Electrophysiological and haemodynamic parameters, the hypoxic area and the presence of myocyte ultrastructural lesions were evaluated. The RMBF was assessed using positron emission tomography following ischaemia/reperfusion in IVA (0.25 mg/kg, i.v., n = 6) or vagal stimulation (n = 4) groups. Compared with saline, IVA induced a 32% HRR (p < 0.01), a 2.9-fold increase in the VFT (p < 0.001) and a reduction of the hypoxic area without any change in left ventricular dP/dt_max. IVA preserved cardiomyocyte morphology, particularly mitochondrial ultrastructure. Compared with baseline, RMBF during reperfusion was increased in the hypoxic area following IVA administration (+218% vs. +97%, p < 0.05) or vagal stimulation (+195% vs. +127%, p < 0.05). This increase was sharply reduced by atrial pacing in IVA-group.

Conclusion

IVA exerts a cardioprotection from ischaemia-induced VF by increasing RMBF and preserving cardiomyocyte and mitochondrial ultrastructure, which opens new perspectives regarding potential targets that would be involved in the anti-ischaemic effects of IVA.     

Development and validation of an HPLC-UV-visible method for sunitinib quantification in human plasma

Background

Sunitinib malate is a novel oral multitargeted tyrosine kinase inhibitor with antitumor and antiangiogenic activities. Only mass spectrometry detection is currently available to determine sunitinib in human plasma. The purpose of this study was to develop a simple and sensitive high-performance liquid chromatographic method with UV-Visible detection for quantification of sunitinib concentrations in human plasma.

Methods

After a liquid-liquid extraction with ethyl acetate, sunitinib and ranitidine (internal standard) are separated on cyanopropyl column using a simple binary mobile phase of ammonium acetate buffer (20 mM; pH 6.8):acetonitrile (55:45,v/v). Samples were eluted isocratically at a flow rate of 1 mL/min throughout the 10 min run. Dual wavelength mode was used, with ranitidine monitored at 255 nm, and sunitinib at 431 nm.

Results

The calibration was linear in the range 20-200 ng/mL. Inter- and intra-day coefficients of variation were less than 7%. This method is sensitive, accurate and selective. It has been successfully implemented to monitor trough sunitinib concentrations in plasma samples (n = 39) from 14 unselected cancer patients treated with the recommended once daily dose of 50 mg or less.

Conclusion

This method can be used in routine clinical practice to monitor plasma sunitinib concentrations in cancer patients treated with once daily administration.     

Serum concentration and cardiovascular effects of salbutamol after oral and rectal administration in healthy volunteers

In order to evaluate rectal administration of salbutamol (SB), five healthy volunteers were dosed orally and rectally with racemic SB (0–1 mg/kg) solution. Compared with the oral SB, the rectal SB gave significantly higher serum SB concentration immediately after dosing but slightly lower levels in the elimination phase. The C_BMX following rectal administration was 17–9 ng/ml (17–0 ng/ml for oral administration), the t_max 0–67 h (1–5 h for oral administration) and the AUC 98–2 ng/ml/h (100 ng/ml/h for oral administration). Heart rate also rose more rapidly to a maximum of 70% above baseline values after rectal dosing. The rate continued to be twice larger than after oral dosing for up to 5 h. The concentration versus response curves indicated that rectal SB was more effective than oral SB at increasing heart rate at the same SB concentration in serum. A plausible explanation for this phenomenon might be a difference in the stereo–selective first–pass metabolism of the two enantiomers. Therefore, the rectal dose of SB administered as a suppository for prophylactic treatment of asthma should be lower than that used orally.     

An Open,Randomized, Single-Center,Crossover Pharmacokinetic Study of Meropenem after Intraperitoneal and Intravenous Administration in Patients Receiving Automated Peritoneal Dialysis

The objective of this study was to determine the pharmacokinetic profile of meropenem in automated peritoneal dialysis (APD) patients. In 6 patients without peritonitis, a single dose of 0.5 g of meropenem was applied intraperitoneally (i.p.) or intravenously (i.v.) and concentrations in serum and dialysate were measured at specified intervals over 24 h with high-performance liquid chromatography-mass spectrometry. The mean maximum concentrations of meropenem in serum (C_max) were 27.2 mg/liter (standard deviation [SD], ±6.9) and 10.1 mg/liter (SD, ±2.5) and in dialysate were 3.6 mg/liter (SD, ±2.3) and 185.8 mg/liter (SD, ±18.7) after i.v. and i.p. administrations, respectively. The mean areas under the curve from 0 to 24 (AUC_0–24) of meropenem in serum were 173.5 mg · h/liter (SD, ±29.7) and 141.4 mg · h/liter (SD, ±37.5) (P = 0.046) and in dialysate were 42.6 mg · h/liter (SD, ±20.0) and 623.4 mg · h/liter (SD, ±84.1) (P = 0.028) after i.v. and i.p. administrations, respectively. The ratios for dialysate exposure over plasma exposure after i.v. and i.p. treatments were 0.2 (SD, ±0.1) and 4.6 (SD, ±0.9), respectively (P = 0.031). A mean target value of 40% T>MIC (time for which the free meropenem concentration exceeds the MIC) for clinically relevant pathogens with EUCAST susceptibility breakpoints of 2 mg/liter was reached in serum after i.p. and i.v. administrations and in dialysate after i.p. but not after i.v. administration. The present data indicate that low i.p. exposure limits the i.v. use of meropenem for PD-associated peritonitis. In contrast, i.p. administration not only results in superior concentrations in dialysate but also might be used to treat systemic infections.     

Preclinical pharmacology and pharmacokinetics of the anti-hepatitis virus agent 2''-fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil in mice and rats.

The preclinical pharmacology and pharmacokinetics of 2'-fluoro-5-ethyl-1-beta-D-arabinofuranosyluracil (FEAU), a selective inhibitor of herpesvirus and hepatitis virus replication, were investigated in the mouse and rat. Following intravenous (i.v.) or oral (p.o.) administration, FEAU was cleared from the plasma primarily unchanged, with a terminal half-life of 58 to 80 min in the mouse and 63 to 78 min in the rat. The steady-state volumes of distribution times bioavailabilities of FEAU were approximately 2.1 and 3.4 times the total body water volumes after p.o. administration of 10 mg of drug per kg of body weight in mice and rats, respectively. A comparison of the area under the concentration-time curve after i.v. and p.o. FEAU administration indicated that the p.o. dose was completely absorbed in both species. When tritiated FEAU was used in mice, 35.0% of the i.v. dose and 33.5% of the p.o. dose were excreted in urine as unchanged FEAU, 8.1% (i.v. dose) and 9.2% (p.o. dose) were excreted as tritiated water, and 15.6% (i.v. dose) and 18.1% (p.o. dose) were excreted as unknown metabolite(s) in urine within 24 h of dosing. Only 1.24% (i.v. dose) and 2.6% (p.o. dose) of the total doses were found in urine as 3H2O when the FEAU dose was increased to 50 mg/kg. However, a higher percentage of the total dose (59.6% for the i.v. dose and 61.3% for the p.o. dose) was recovered within 24 h as intact FEAU in rat urine, less than 1.4% (i.v. dose) and 2.7% (p.o. dose) of the total dose were found to be 3H2O, and 5.6% (i.v. dose) and 6.7% (p.o. dose) of the total dose were excreted as known metabolite(s). The distribution ratios for total radioactivity in tissue relative to those in plasma were 0.5 to 1.3 in spleen, testes, muscle, and liver during the first hour after a 10-mg/kg dose in rats. Of the total FEAU radioactivity administered, only 1.38% was excreted in bile as unchanged FEAU. No FEAU glucuronide metabolite was detected. Tissue concentrations of 0.15 to 0.6 microM at 6 h after dosing are in the range of the effective antiviral concentration for FEAU. In conclusion, FEAU administered p.o. to mice and rats was well absorbed; FEAU was rapidly distributed into tissues and remained above in vitro antiviral concentrations for more than 6 h; in mice, [3H]FEAU showed metabolism-mediated tritium exchange with water; and in rats, FEAU was less extensively metabolized than in mice and clearance was primarily via renal processes, mainly in the form of unchanged FEAU.     

Absorption, disposition, and urinary metabolism of 14C-rifabutin in rats.

14C-rifabutin was given orally (25 mg/kg) and intravenously (i.v.) (10 mg/kg) to female Sprague-Dawley rats. Radioactivity was eliminated by both the renal and fecal routes, amounting to 44.49 and 43.39% of the dose, respectively, in urine and feces at 96 h after the oral dose and to 47.81 and 40.76% of the dose, respectively, in urine and feces after the i.v. dose. Differences between the two routes of administration were negligible. Tissue distribution of radioactivity after the oral dose was investigated by the combustion technique. At 2 h, the highest concentration of radioactivity was observed in the liver, followed by the lung, abdominal adipose tissue, and spleen, whereas at 72 h, the sequence was abdominal adipose tissue, liver, spleen, bone marrow, and lung. Brain levels of radioactivity were very low. The results of whole-body autoradiography after i.v. administration confirmed the above. Whole-body autoradiography of pregnant rats showed higher concentrations of radioactivity in the uterus than in the placenta and trace levels in the fetuses up to 8 h. Radioactivity was absent in the amniotic fluid. The urinary metabolism was studied by radio-high-pressure liquid chromatography. Rifabutin accounted for 7.4 and 7.2% of the dose in 0- to 48-h urine after oral and i.v. administration, respectively. Metabolites 31-OH rifabutin and 25-O-deacetyl rifabutin amounted to 4.3 and 1.6% of the dose, respectively, after oral administration and to 2.6 and 0.7% of the dose, respectively, after i.v. administration. The remaining urinary radioactivity was mainly due to polar compounds.