Midazolam and remifentanil by bolus injection for intensely stimulating procedures of brief duration: experience with awake laryngoscopy

IMPLICATIONS

The pharmacokinetic characteristics of midazolam and remifentanil administered by bolus injection may make them advantageous for providing brief, intense analgesia without prolonged respiratory depression. This application is particularly useful for awake, direct laryngoscopy.

Synthesis and preliminary evaluation of [18F]FEtP4A, a promising PET tracer for mapping acetylcholinesterase in vivo

N-[18F]Fluoroethyl-4-piperidyl acetate ([18F]FEtP4A), an analog of [11C]MP4A for mapping brain acetylcholineseterase (AchE) activity, was prepared by reacting 4-piperidyl acetate (P4A) with [18F]fluoroethyl bromide ([18F]FEtBr) using a newly developed automated system. Preliminary evaluation showed that the initial uptake of [18F]FEtP4A in the mouse brain was > 8% injected dose/g tissue. The distribution pattern of [18F]FEtP4A in the brain was striatum>cerebral cortex>cerebellum within 10-120 min post-injection, which reflected the distribution rank pattern of AchE activity in the brain. Moreover, chemical analysis of in vivo radioactive metabolites in the mouse brain indicated that 83% of [18F]FEtP4A was hydrolyzed to N-[18F]fluoroethyl-4-piperidinol ([18F]FEtP4OH) after 1 min intravenous injection. From these results, [18F]FEtP4A may become a promising PET tracer for mapping the AchE in vivo.

Phase I study of the cyclin-dependent kinase inhibitor flavopiridol in combination with paclitaxel in patients with advanced solid tumors

PURPOSE

Preclinical studies indicate that the cyclin-dependent kinase inhibitor flavopiridol potentiates the induction of apoptosis by paclitaxel, provided paclitaxel is followed by flavopiridol. We therefore designed a phase I clinical trial of sequential paclitaxel and flavopiridol.

PATIENTS AND METHODS

Paclitaxel was administered at a fixed dose, as either a 24- or 3-hour infusion on day 1, followed by a 24-hour infusion of flavopiridol on day 2. Doses of flavopiridol were escalated in successive cohorts according to a modified Fibonacci design. Flavopiridol pharmacokinetics were obtained on all patients.

RESULTS

Dose-limiting neutropenia developed with 24-hour paclitaxel doses of 135 and 100 mg/m(2) and flavopiridol doses of 10 and 20 mg/m(2), respectively. With 3-hour paclitaxel at 100 mg/m(2), flavopiridol could be escalated to 70 mg/m(2) without dose-limiting toxicity. With 3-hour paclitaxel next escalated to 135 mg/m(2), dose-limiting neutropenia and pulmonary toxicity occurred when flavopiridol was escalated to 94 mg/m(2). This did not correlate with any change in flavopiridol or paclitaxel pharmacokinetics. At a 3-hour paclitaxel dose of 175 mg/m(2), dose-limiting pulmonary toxicity occurred in only one patient at flavopiridol doses under 94 mg/m(2). Clinical activity was observed in patients with esophagus, lung, and prostate cancer, including patients who had progressed on paclitaxel.

CONCLUSION

The recommended phase II doses will be a 3-hour infusion of paclitaxel at 175 mg/m(2) on day 1 followed by a 24-hour infusion of flavopiridol at 70 mg/m(2) on day 2. Flavopiridol dose escalations to 80 mg/m(2) are possible. At these doses, toxicities are manageable and clinical activity is promising.

Piperine modulates permeability characteristics of intestine by inducing alterations in membrane dynamics: influence on brush border membrane fluidity, ultrastructure and enzyme kinetics

Piperine (1-Piperoyl piperidine) is a major alkaloid of Piper nigrum Linn. and Piper longum Linn. It is shown to possess bioavailability-enhancing activity with various structurally and therapeutically diverse drugs. The mechanism of enhancing the bioavailability, is, however, not understood. We hypothesize that piperine's bioavailability-enhancing property may be attributed to increased absorption, which may be due to alteration in membrane lipid dynamics and change in the conformation of enzymes in the intestine. Results of membrane fluidity studies using an apolar fluorescent probe, pyrene (which measures the fluid properties of hydrocarbon core), showed an increase in intestinal brush border membrane (BBM) fluidity. Piperine also stimulated Leucine amino peptidase and Glycyl-glycine dipeptidase activity, due to the alteration in enzyme kinetics. This suggests that piperine could modulate the membrane dynamics due to its apolar nature by interacting with surrounding lipids and hydrophobic portions in the protein vicinity, which may decrease the tendency of membrane lipids to act as stearic constrains to enzyme proteins and thus modify enzyme conformation. Ultra structural studies with piperine showed an increase in microvilli length with a prominent increase in free ribosomes and ribosomes on the endoplasmic reticulum in enterocytes, suggesting that synthesis or turnover of cytoskeletal components or membrane proteins may be involved in the observed effect. In conclusion, it is suggested that piperine may be inducing alterations in membrane dynamics and permeation characteristics, along with induction in the synthesis of proteins associated with cytoskeletal function, resulting in an increase in the small intestine absorptive surface, thus assisting efficient permeation through the epithelial barrier.

End-stage renal failure reduces central clearance and prolongs the elimination half life of remifentanil

PURPOSE

To evaluate the pharmacokinetics of remifentanil in 13 end-stage renal failure patients compared to matched control patients with normal renal function.

METHODS

Remifentanil was infused for 20 min at a rate of 0.1 microg x kg(-1) x min(-1). Serial arterial blood samples (3 mL) were drawn at the start of infusion (zero), five, ten, 15, 20, 22.5, 25, 27.5, 30, 35, 40, 45, 50, 55 and 60 min. Blood samples were immediately preserved with citric acid and chilled on ice. High performance liquid chromatography-tandem mass spectrometry concentration assay was performed using GI 95779B internal standard.

RESULTS

A two-compartment pharmacokinetic model provided an adequate fit for individual patient data. There was no difference in the mean +/- SD distribution half life (t1/2) between the renal failure group (1.65 +/- 0.7 min) and the control group (1.58 +/- 0.54 min). There was a significant difference in the central clearance (Cl(c)) and elimination half life (t1/2) ss) between the renal failure group (28 +/- 7 mL x kg(-1) x min(-1) and 18.86 +/- 2.06 min, respectively) and the control group (46.3 +/- 13.8 mL x kg(-1) x min(-1) and 16.35 +/- 2.99 min, respectively). Remifentanil blood concentrations were significantly higher in the renal failure group than in the control group.

CONCLUSION

We have demonstrated a significant reduction in the Cl(c) and a prolongation of t1/2 ss of remifentanil in end-stage renal failure patients. While statistically significant, these variations in the pharmacokinetics of remifentanil were clinically modest and may be explained by a reduced volume of distribution in the period following hemodialysis.

Simple high-performance liquid chromatography method for the simultaneous determination of ketoconazole and piperine in rat plasma and hepatocyte culture

Piperine, a major alkaloid of black and long peppers has been reported to act as bioavailability enhancer of several drugs by inhibiting drug metabolising enzymes and/or by increasing oral absorption. Ketoconazole is a well established potent inhibitor of CYP 3A4 and P-glycoprotein. A simple and rapid HPLC method has been developed for the simultaneous analysis of ketoconazole and piperine in rat plasma and hepatocyte culture. Analysis was performed using a Symmetry C18 column (150x4.6 mm, 5 microm) and isocratic elution with 25 mM KH2PO4 (pH 4.5)-acetonitrile (50:50) with a flow-rate of 1 ml/min. Photodiode array detection was used to simultaneously monitor piperine at 340 nm and ketoconazole at 231 nm in a single sample. Calibration plots in spiked plasma, hepatocytes and William's medium E were linear over the range studied (10-2000 ng for both drugs). The detection limits for piperine and ketoconazole are 2 and 4 ng, respectively, and the limits of quantitation are 10 and 12 ng, respectively. Intra- and inter-assay variations were less than 8%.

Structure-activity relationships of new NAPAP-analogs

Several new analogs of the known thrombin inhibitor NAPAP were synthesized, in which the P2 glycine residue was substituted by natural and unnatural amino acids. The thrombin inhibitory potency was comparable to that of NAPAP. Several of the compounds had inhibition constants lower than 10 nM and a very high selectivity compared to trypsin, factor Xa and plasmin. In addition, analogs were prepared by alkylation of the N alpha-atom of the 4-amidinophenylalanine in P1 position, which showed a more than 10-fold lower thrombin inhibition. Furthermore, azaglycine was introduced instead of P2 glycine. For most of the inhibitors similar fast elimination rates were seen in rats after intravenous dosing, as found previously for NAPAP. Only some compounds, which contained a second basic group showed a slightly decreased cumulative biliary clearance.

Safety and efficacy of the multidrug resistance inhibitor Incel (biricodar; VX-710) in combination with paclitaxel for advanced breast cancer refractory to paclitaxel

PURPOSE

VX-710 (biricodar, Incel) restores drug sensitivity to P-glycoprotein (MDR1) and multidrug resistance-associated protein (MRP1)-expressing cells. This Phase II study evaluated the safety/tolerability, pharmacokinetics, and efficacy of VX-710 plus paclitaxel in women with locally advanced or metastatic breast cancer who were refractory to prior paclitaxel therapy.

EXPERIMENTAL DESIGN

Eligible patients had paclitaxel-refractory disease defined as progressive disease after a minimum of two cycles of paclitaxel (weekly or 3-week schedule) or relapsed/progressive disease within 6 months of prior paclitaxel therapy. Patients received 80 mg/m(2) paclitaxel over 3 h starting 4 h after initiation of a 24-h continuous i.v. infusion of 120 mg/m(2)/h VX-710. Cycles were repeated every 3 weeks.

RESULTS

Thirty-seven patients received study treatment and 35 were evaluable for response. VX-710 + paclitaxel therapy was generally well tolerated. Myelosuppression was the principal toxicity, with a median nadir ANC cycle 1 of 0.76 x 10(9) cells/liter and a 40% overall incidence of Grade 4 neutropenia. Nonhematological side effects (asthenia, paresthesia, headache, myalgia, nausea, and diarrhea) were generally mild to moderate and reversible. Paclitaxel AUC (16.8 +/- 5.0 microg x h/ml) and clearance (5.1 +/- 1.3 liters/h/m(2)) during the first treatment cycle were comparable with standard 175 mg/m(2) paclitaxel administered in a 3-h schedule. Four patients achieved partial responses (three of the four had progressive disease on prior paclitaxel) with a mean response duration of 5.5 months.

CONCLUSIONS

The 11.4% (4 of 35) objective response rate observed in this study suggests that VX-710 can resensitize a subgroup of paclitaxel-refractory patients to paclitaxel. The safety and pharmacokinetics of the VX-710/pacitaxel regimen support further evaluation in breast cancer patients with initial paclitaxel therapy to prevent emergence of the MDR phenotype in recurrent disease.

[Pharmacological and clinical properties of levocabastine hydrochloride (eye drop and nasal spray), a selective H1 antagonist]

Levocabastine is a selective histamine H1-receptor antagonist exerting inhibitory effects on the release of chemical mediators from mast cells and on the chemotaxis of polymorphonuclear leukocytes and eosinophils. Both histamine and antigens induced conjunctivitis was inhibited by levocabastine in several allergy models. Levocabastine moderately inhibited histamine-release from guinea pig conjunctive induced by antigen-antibody reactions and prevented an increase in the vascular permeability of the conjunctive elicited by both histamine and antigen instillation. Symptoms of allergic rhinitis, which were induced by histamine, substance P and antigen, were also reduced by levocabastine. Levocabastine prevented an increase in the vascular permeability of nasal mucosa elicited by instillation of these three inducers. Furthermore, levocabastine has shown a large difference between the antiallergic dose and other non-specific pharmacological effective dose than that with other antiallergic drugs. The non-specific pharmacological effect of levocabastine reveals only blepharoptosis. With these pharmacological effects and topical usage, levocabastine was shown to be useful for allergic conjunctive and rhinitis in both seasonal and perennial clinical use.

Reduction of acute photodamage in skin by topical application of a novel PARP inhibitor

The ultraviolet (UV) components of sunlight induce damage to the DNA in skin cells, which is considered to be the initiating step in the harmful biological effects of UV radiation. Repair of DNA damage results in the formation of single-strand DNA breaks, which activate the nuclear poly(ADP-ribose) polymerase (PARP). Overactivation of PARP worsens the oxidative cell damage and impairs the energy metabolism, raising the possibility that moderation of PARP activation following DNA damage may protect skin cells from UV radiation. The topical effects of the novel PARP inhibitor O-(3-pyperidino-2-hydroxy-1-propyl) pyridine-3-carboxylic acid amidoxime monohydrochloride (BGP-15M) were investigated on UV-induced skin damage in a hairless mouse model. For evaluation of the UV-induced acute photodamage to the skin and the potential protective effect of BGP-15M, DNA injury was detected by measuring the formation of single-strand DNA breaks and counting the resulting sunburn (apoptotic) cells. The ADP-ribosylation of PARP was assessed by Western blot analysis and then quantified. In addition, the UV-induced immunosuppression was investigated by the immunostaining of tumor necrosis factor alpha and interleukin-10 expressions in epidermal cells. The signs of inflammation were examined clinically and histochemically. Besides its primary effect in decreasing the activity of nuclear PARP, topically applied BGP-15M proved to be protective against solar and artificial UV radiation-induced acute skin damage. The DNA injury was decreased (P<0.01). An inhibition of immunosuppression was observed by down-regulation of the epidermal production of cytokines IL-10 and TNFalpha. In the mouse skin, clinical or histological signs of UV-induced inflammation could not be observed. These data suggest that BGP-15M directly interferes with UV-induced cellular processes and modifies the activity of PARP. The effects provided by topical application of the new PARP-regulator BGP-15M indicate that it may be a novel type of agent in photoprotection of the skin.

The influence of remifentanil on the dynamic relationship between sevoflurane and surrogate anesthetic effect measures derived from the EEG

BACKGROUND

The authors modeled the influence of remifentanil on the dynamics of sevoflurane using three parameters derived from the electroencephalogram: 95% spectral edge frequency (SEF), canonical univariate parameter (CUP), and Bispectral Index (BIS).

METHODS

Thirty-six patients with American Society of Anesthesiologists physical status class I or II were recruited, of which 12 received a target remifentanil concentration of 0 ng/ml, eight 2 ng/ml, eight 4 ng/ml, and another eight 8 ng/ml. Next (before surgery), several step-wise changes in the end-tidal sevoflurane concentration (F(ET,sevo)) were performed. A data acquisition system simultaneously recorded F(ET,sevo), the raw electroencephalogram, BIS, and SEF. The authors used a combination of an effect compartment and an inhibitory sigmoid E(MAX) model to describe the relation between F(ET,sevo) and BIS, SEF, and CUP. Model parameters (t(1/2)k(e0), E(MAX), E(MIN), C(50), gamma, CUP weight factors) were estimated using the population data analysis program NONMEM. Significant remifentanil model parameter dependencies (P < 0.01) were determined.

RESULTS

Determined from SEF, remifentanil had no effect on t(1/2)k(e0) (1.91 +/- 0.26 min [mean +/- standard error]) but caused an increase in C(50) (baseline = 1.48 +/- 0.12%; 80% increase at 8 ng/ml) and decrease in E(MIN) (baseline = 10.8 +/- 0.6 Hz; 80% reduction at 8 ng/ml). Determined from CUP, remifentanil caused a dose-dependent decrease in t(1/2)k(e0) (baseline = 4.31 +/- 1.00 min; 60% decrease at 8 ng/ml), with no effect on C(50) (baseline = 0.88 +/- 0.13%). Determined from BIS, remifentanil caused a dose-dependent decrease in t(1/2)k(e0) (baseline value = 3.11 +/- 0.32 min; 40% decrease at 8 ng/ml), without affecting C(50) (baseline = 1.12 +/- 0.05%). Median R(2) values of the pooled data set were 0.815 for SEF, 0.933 for CUP (P < 0.01 vs. SEF), and 0.952 for BIS (P < 0.01 vs. SEF and CUP). Addition of remifentanil increased the R(2) values for CUP only.

CONCLUSIONS

Remifentanil accelerates sevoflurane blood-brain equilibration without affecting its hypnotic potency as determined from BIS and CUP. In terms of R(2), the authors' pharmacodynamic model describes the anesthetic-BIS relation best.

Repaglinide: a review of its therapeutic use in type 2 diabetes mellitus

Repaglinide, a carbamoylmethyl benzoic acid derivative, is the first of a new class of oral antidiabetic agents designed to normalise postprandial glucose excursions in patients with type 2 diabetes mellitus. Like the sulphonylureas, repaglinide reduces blood glucose by stimulating insulin release from pancreatic beta-cells, but differs from these and other antidiabetic agents in its structure, binding profile, duration of action and mode of excretion. In clinical trials of up to 1-year's duration, repaglinide maintained or improved glycaemic control in patients with type 2 diabetes mellitus. In comparative, 1-year, double-blind, randomised trials (n = 256 to 544), patients receiving repaglinide (0.5 to 4mg before 3 daily meals) achieved similar glycaemic control to that in patients receiving glibenclamide (glyburide) < or = 15 mg/day and greater control than patients receiving glipizide < or = 15 mg/day. Changes from baseline in glycosylated haemoglobin and fasting blood glucose levels were similar between patients receiving repaglinide and glibenclamide in all studies; however, repaglinide was slightly better than glibenclamide in reducing postprandial blood glucose in I short term study (n = 192). Patients can vary their meal timetable with repaglinide: the glucose-lowering efficacy of repaglinide was similar for patients consuming 2, 3 or 4 meals a day. Repaglinide showed additive effects when used in combination with other oral antidiabetic agents including metformin, troglitazone, rosiglitazone and pioglitazone, and intermediate-acting insulin (NPH) given at bedtime. In 1-year trials, the most common adverse events reported in repaglinide recipients (n = 1,228) were hypoglycaemia (16%), upper respiratory tract infection (10%), rhinitis (7%), bronchitis (6%) and headache (9%). The overall incidence of hypoglycaemia was similar to that recorded in patients receiving glibenclamide, glipizide or gliclazide (n = 597) [18%]; however, the incidence of serious hypoglycaemia appears to be slightly higher in sulphonylurea recipients. Unlike glibenclamide, the risk of hypoglycaemia in patients receiving repaglinide was not increased when a meal was missed in 1 trial. In conclusion, repaglinide is a useful addition to the other currently available treatments for type 2 diabetes mellitus. Preprandial repaglinide has displayed antihyperglycaemic efficacy at least equal to that of various sulphonylureas and is associated with a reduced risk of serious hypoglycaemia. It is well tolerated in a wide range of patients, including the elderly, even if a meal is missed. Furthermore, glycaemic control is improved when repaglinide is used in combination with metformin. Thus, repaglinide should be considered for use in any patient with type 2 diabetes mellitus whose blood glucose cannot be controlled by diet or exercise alone, or as an adjunct in patients whose glucose levels are inadequately controlled on metformin alone.

Safety and efficacy of the multidrug-resistance inhibitor biricodar (VX-710) with concurrent doxorubicin in patients with anthracycline-resistant advanced soft tissue sarcoma

PURPOSE

Incel (biricodar, VX-710) restores drug sensitivity to P-glycoprotein and multidrug resistance-associated protein-1-expressing cells. This Phase I/II study evaluated the safety/tolerability, pharmacokinetics, and efficacy of VX-710 plus doxorubicin in patients with inoperable, locally advanced or metastatic, anthracycline-resistant/refractory, soft tissue sarcoma.

EXPERIMENTAL DESIGN

In Phase I, i.v. bolus doxorubicin at 60, 75, or 67.5 mg/m(2) was administered 8 h after initiation of a 72-h continuous i.v. (CIV) infusion of VX-710 (120 mg/m(2)/h) to cohorts of patients to establish a maximum tolerated dose. For efficacy evaluations in Phase II, eligible patients had inoperable, locally advanced or metastatic, anthracycline-resistant/refractory soft tissue sarcoma; < or =225 mg/m(2) cumulative prior doxorubicin; and adequate hematological, liver, and kidney function. Cycles were repeated every 3 weeks.

RESULTS

Fourteen patients were enrolled in Phase I. Myelosuppression was the dose-limiting toxicity with 75 and then 67.5 mg/m(2) doxorubicin, and the maximum tolerated dose was established at 60 mg/m(2) with VX-710, 120 mg/m(2)/h, 72-h CIV. VX-710 had no apparent effect on doxorubicin pharmacokinetics. Twenty-nine patients enrolled in Phase II were treated with VX-710, 120 mg/m(2)/h 72-h CIV, and 60 mg/m(2) doxorubicin. Among 26 evaluable patients, minimal activity was noted among 11 patients with gastrointestinal stromal tumors (GISTs); however, in 15 patients with anthracycline-resistant sarcomas of other histologies, 2 achieved partial responses and 7 patients had disease stabilization with an overall median progression-free interval of 3.4 months.

CONCLUSION

Anthracycline resistance in GISTs appears to be independent of P-glycoprotein or multidrug resistance-associated protein-1 resistance mechanisms. However, the combination of VX-710 and doxorubicin resulted in objective responses or disease stabilization in patients with strictly defined anthracycline-refractory non-GIST sarcomas, which warrants further evaluation.

Multiple-dose, safety, pharmacokinetics, and pharmacodynamics of a new selective estrogen receptor modulator, ERA-923, in healthy postmenopausal women

ERA-923 is a new selective estrogen receptor modulator under clinical investigation for use in tamoxifen refractory metastatic breast cancer. This study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of once-daily oral ERA-923 (10-200 mg) for 28 days in healthy postmenopausal females. ERA-923 was well tolerated, and adverse events were mild and reversible. No clinically significant changes in laboratory values were found with ERA-923 versus placebo. ERA-923 appeared to undergo extensive metabolism and enterohepatic recirculation. In addition, pharmacokinetic analysis showed that a high-fat breakfast increased the extent of absorption. ERA-923-dosed subjects had no uterine or ovarian changes when evaluated with transvaginal ultrasound and compared to placebo subjects. Overall, ERA-923 was safe and well tolerated in postmenopausal women dosed for 28 days.

Differentiation between isomeric oxidative metabolites of a piperidine-containing drug by liquid chromatography-tandem mass spectrometry with stable-isotope tracer technique

This report describes the application of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to differentiation of hydroxylations and N-oxidations and of two different aliphatic hydroxylations in the investigation of the metabolism of pibutidine hydrochloride, a novel H2 antagonist, the structure of which includes a piperidine ring. Pibutidine metabolites in urine samples from adult male volunteers after oral administration of pibutidine hydrochloride were separated by reversed-phase LC and ionized using an electrospray ionization (ESI) interface. A hydroxylated form of pibutidine was distinguished from the N-oxide by comparison of their product ion spectra, although their mass-to-charge ratios of protonated molecules were identical. Further, two hydroxylated compounds were present in rat microsomal incubation mixtures with pibutidine. The distinction between their positions of hydroxylation (beta- and gamma-carbon hydroxylation) on the piperidine ring was studied using [piperidine-2H10] pibutidine as incubation substrate. The production of the beta-hydroxylated form was accompanied by the elimination of three 2H, resulting from a mechanism including the formation of iminium/enamine. The participation of the iminium ion intermediate in the beta-hydroxylation was confirmed by the observation that a cyanide adduct of pibutidine was formed instead of the beta-hydroxylated form when another incubation was performed in the presence of cyanide.

4-(Phenylsulfonyl)piperidines: novel, selective, and bioavailable 5-HT(2A) receptor antagonists

On the basis of a spirocyclic ether screening lead, a series of acyclic sulfones have been identified as high-affinity, selective 5-HT(2A) receptor antagonists. Bioavailability lacking in the parent, 1-(2-(2,4-difluorophenyl)ethyl)-4-(phenylsulfonyl)piperidine (12), was introduced by using stability toward rat liver microsomes as a predictor of bioavailability. By this means, the 4-cyano- and 4-carboxamidophenylsulfonyl derivatives 26 and 31 were identified as orally bioavailable, brain-penetrant analogues suitable for evaluation in animal models. Bioavailability was also attainable by N substitution leading to the N-phenacyl derivative 35. IKr activity detected through counterscreening was reduced to insignificant levels in vivo with the latter compound.

A chemokine receptor CCR-1 antagonist reduces renal fibrosis after unilateral ureter ligation

The expression of chemokines and their receptors is thought to contribute to leukocyte infiltration and progressive renal fibrosis after unilateral ureter obstruction (UUO). We hypothesized that blocking the chemokine receptor CCR1 using the nonpeptide antagonist BX471 could reduce leukocyte infiltration and renal fibrosis after UUO. UUO kidneys from BX471-treated mice (day 0-10 and day 6-10) revealed a 40-60% reduction of interstitial macrophage and lymphocyte infiltrate compared with controls. Treated mice also showed a marked reduction of CCR1 and CCR5 mRNA levels, and FACS analysis showed a comparable reduction of CD8+/CCR5+ T cells. Markers of renal fibrosis, such as interstitial fibroblasts, interstitial volume, mRNA and protein expression for collagen I, were all significantly reduced by BX471-treatment compared with vehicle controls. By contrast treatment was ineffective when the drug was supplied only from days 0 to 5. In summary, blockade of CCR1 substantially reduces cell accumulation and renal fibrosis after UUO. Most interestingly, late onset of treatment is also effective. We therefore conclude that CCR1 blockade may represent a new therapeutic strategy for reducing cellular infiltration and renal fibrosis as major factors in the progression to end-stage renal failure.

Estimate the time varying brain receptor occupancy in PET imaging experiments using non-linear fixed and mixed effect modeling approach

Positron-Emission Tomography (PET) is an imaging technology currently used in drug development as a non-invasive measure of drug distribution and interaction with biochemical target system. The level of receptor occupancy achieved by a compound can be estimated by comparing time-activity measurements in an experiment done using tracer alone with the activity measured when the tracer is given following administration of unlabelled compound. The effective use of this surrogate marker as an enabling tool for drug development requires the definition of a model linking the brain receptor occupancy with the fluctuation of plasma concentrations. However, the predictive performance of such a model is strongly related to the precision on the estimate of receptor occupancy evaluated in PET scans collected at different times following drug treatment. Several methods have been proposed for the analysis and the quantification of the ligand-receptor interactions investigated from PET data. The aim of the present study is to evaluate alternative parameter estimation strategies based on the use of non-linear mixed effect models allowing to account for intra and inter-subject variability on the time-activity and for covariates potentially explaining this variability. A comparison of the different modeling approaches is presented using real data. The results of this comparison indicates that the mixed effect approach with a primary model partitioning the variance in term of Inter-Individual Variability (IIV) and Inter-Occasion Variability (IOV) and a second stage model relating the changes on binding potential to the dose of unlabelled drug is definitely the preferred approach.

Pharmacokinetics and pharmacological effect of lerisetron, a new 5-HT3 antagonist, in rats

The pharmacokinetics of lerisetron, a novel 5HT(3) antagonist, are studied together with its efficacy in inhibiting the serotonin (5-HT)-evoked transient bradycardia reflex (von Bezold-Jarisch reflex) in Sprague Dawley rats. [(14)C]Lerisetron (50, 100, and 200 microg/kg) was given to rats by intravenous (iv) injection and plasma levels of unchanged (UL) and total (unchanged + changed, TL) drug were measured by liquid chromatography with radioactivity monitoring and scintillation counting, respectively. Linearity of UL and TL pharmacokinetics over the dose range was established by noncompartmental analysis. Protein binding of lerisetron was measured in vitro by ultrafiltration. The unbound fraction was 14.4 +/- 1.4%. A nonlinear mixed effects ("population") bicompartmental pharmacokinetic analysis showed that volume of distribution and clearance (CL) were high for both forms of the drug, but CL was significantly smaller for TL [(mean +/- SEM) 0.014 +/- 0.03 L/min for UL versus 0.006 +/- 0.03 L/min for TL, p < 0.05)]. Large interindividual variabilities were observed for both forms. The response to lerisetron administration (inhibition of bradycardia) was evaluated at different doses (2, 3, 5, 6, and 10 microg/kg, iv) at times 2-180 min after dose administration and related to simulated concentrations. Inhibition was 100% 5 min after the 10-microg/kg dose and, 3 h later, it was still > 10%. Response to lerisetron was dose related in the range studied. Pharmacodynamic parameters were estimated by a sigmoid E(max) naive-pooled model. The parameters were also different between the two forms: EC(50) was 0.44 ng/mL (CV = 5.9%) for UL and 0.88 ng/mL (CV = 4.9%) for TL. We conclude that UL and TL pharmacokinetics were linear and that the differences in the kinetics and dynamics between the two forms suggest the presence of at least one metabolite.

Modeling the pharmacokinetics and pharmacodynamics of a unique oral hypoglycemic agent using neural networks

PURPOSE

To develop a predictive population pharmacokinetic/ pharmacodynamic (PK/PD) model for repaglinide (REP), an oral hypoglycemic agent, using artificial neural networks (ANNs).

METHODS

REP, glucose concentrations, and demographic data from a dose ranging Phase 2 trial were divided into a training set (70%) and a test set (30%). NeuroShell Predictor was used to create predictive PK and PK/PD models using population covariates: evaluate the relative significance of different covariates; and simulate the effect of covariates on the PK/PD of REP. Predictive performance was evaluated by calculating root mean square error and mean error for the training and test sets. These values were compared to naive averaging (NA) and randomly generated numbers (RN).

RESULTS

Covariates found to have an influence on PK of REP include dose, gender. race, age, and weight. Covariates affecting the glucose response included dose, gender, and weight. These differences are not expected to be clinically significant.

CONCLUSIONS

We came to the following three conclusions: 1) ANNs are more precise than NA and RN for both PK and PD; 2) the bias was acceptable for ANNs as compared with NA and RN; and 3) neural networks offer a quick and simple method for predicting, for identifying significant covariates, and for generating hypotheses.

Extended radioligand binding profile of iloperidone: a broad spectrum dopamine/serotonin/norepinephrine receptor antagonist for the management of psychotic disorders

Iloperidone is a novel psychotropic compound currently undergoing Phase III trials. Its affinity for human dopamine and 5-HT(2A) and 5-HT(2C) receptors has been reported previously. This report presents the affinity of iloperidone for a largely extended number of human neurotransmitter receptors. In a few instances human receptors were not available and receptor studies were performed on tissues from laboratory animals. The present data, supplemented with those of, indicate that iloperidone displays high affinity (K(I) < 10 nM) for norepinephrine alpha(1)-adrenoceptors, dopamine D(3) and serotonin 5-HT(2A) receptors. Intermediate affinity (10-100 nM) was found for norepinephrine alpha(2C)-adrenoceptors, dopamine D(2A) and D(4) receptors and serotonin 5-HT(1A), 5-HT(1B), 5-HT(2C) and 5-HT(6) receptors. The affinity for all other receptors was below 100 nM, including norepinephrine alpha(2A), alpha(2B), beta(1), and beta(2), muscarine M(1)-M(5), histamine H(1), dopamine D(1) and D(5), CCK(A) and CCK(B), 5-HT(7), dopamine and norepinephrine transporters. Thus, iloperidone targets a selective set of dopamine, norepinephrine and serotonin receptor subtypes. The affinity for this particular set of receptors indicates that iloperidone has the potential to be a broad spectrum antipsychotic, with efficacy against positive, negative, depressive and cognitive symptoms of schizophrenia, and a low propensity to induce side effects.

Pharmacokinetics of remifentanil in anesthetized pediatric patients undergoing elective surgery or diagnostic procedures

Remifentanil hydrochloride is an ultra-short-acting opioid that undergoes rapid metabolism by tissue and plasma esterases. We aimed to characterize the pharmacokinetics and determine the hemodynamic profile of remifentanil after a single-bolus dose in children aged 0 to 18 yr. Forty-two children undergoing elective surgical procedures received remifentanil 5 microg/kg infused over 1 min. Patients were divided into age groups as follows: young infants (< or =2 mo), older infants (> 2 mo to < 2 yr), young children (2 to < 7 yr), older children (7 to < 13 yr), adolescents (13 to < 16 yr), and young adults (16 to < 18 yr). Arterial blood samples were collected and analyzed by mass spectroscopy to determine remifentanil pharmacokinetic profiles. Hemodynamic measurements for remifentanil's effect were made after the infusion. Methods of statistical analysis included analysis of variance and linear regression, with significance at P < or = 0.05. Complete remifentanil pharmacokinetic data were obtained from 34 patients. The volume of distribution was largest in the infants < 2 mo (mean, 452 mL/kg) and decreased to means of 223 to 308 mL/kg in the older patients. There was a more rapid clearance in the infants < 2 mo of age (90 mL. kg(-1). min(-1)) and infants 2 mo to 2 yr (92 mL. kg(-1). min(-1)) than in the other groups (means, 46 to 76 mL. kg(-1). min(-1)). The half-life was similar in all age groups, with means of 3.4 to 5.7 min. Seven subjects (17%) developed hypotension related to the remifentanil bolus. Remifentanil showed an extremely rapid elimination similar to that in adults. The fast clearance rates observed in neonates and infants, as well as the lack of age-related changes in half-life, are in sharp contrast to the pharmacokinetic profile of other opioids. Remifentanil in a bolus dose of 5 microg/kg may cause hypotension in anesthetized children.

IMPLICATIONS

The pharmacokinetics of remifentanil were studied in children from birth to 18 yr. Remifentanil was found to have age-related changes in clearance and volume of distribution, but not half-life. The increased clearance observed in young infants is in contrast to other opioids.