The effect of the REG2 Anticoagulation System on thrombin generation kinetics: a pharmacodynamic and pharmacokinetic first-in-human study.

The REG2 Anticoagulation System consists of pegnivacogin, a subcutaneously administered aptamer factor IXa inhibitor, and its intravenous active control agent, anivamersen. Its effect on thrombin generation is unknown. A prospectively designed thrombin generation study was conducted within the phase 1 ascending dose study of REG2 to assess the effect of REG2 on thrombin generation kinetics. A total of 32 healthy volunteers were recruited into four cohorts of ascending dose pegnivacogin for the phase 1 study. In this pre-specified substudy, blood samples were drawn in the presence or absence of corn trypsin inhibitor at specified times within each dosing cohort. Thrombin generation was initiated with tissue factor and thrombin generation kinetics were measured using the Calibrated Automated Thrombogram (CAT). REG2 attenuated thrombin generation in a dose-dependent manner. All parameters of the CAT assay, except for lag time, showed a dose and concentration-dependent response to pegnivacogin [time to peak thrombin generation (PTm), endogenous thrombin potential, peak thrombin generation, and velocity index (VIx)]. Reversal of the effect of pegnivacogin with anivamersen demonstrated restoration of thrombin generation without rebound effect. This first-in-human study of the effect of the REG2 Anticoagulation System on thrombin generation demonstrates concentration-dependent suppression of thrombin generation that is reversible without rebound effect, as measured by the CAT assay.

Dose selection for a direct and selective factor IXa inhibitor and its complementary reversal agent: translating pharmacokinetic and pharmacodynamic properties of the REG1 system to clinical trial design.

We performed detailed pharmacokinetic and pharmacodynamic modeling of REG1, an anticoagulation system composed of the direct factor IXa (FIXa) inhibitor pegnivacogin (RB006) and its matched active control agent anivamersen (RB007), with a focus on level of target inhibition to translate phase 1 results to phase 2 dose selection. We modeled early-phase clinical data relating weight-adjusted pegnivacogin dose and plasma concentration to prolongation of the activated partial thromboplastin time (aPTT). Using an in vitro calibration curve, percent FIXa inhibition was determined and related to aPTT prolongation and pegnivacogin dose and concentration. Similar methods were applied to relate anivamersen dose and level of reversal of pegnivacogin anticoagulation. Combined early-phase data suggested that ≥0.75 mg/kg pegnivacogin was associated with >99% inhibition of FIX activity and prolongation of plasma aPTT values ≈2.5 times above baseline, leading to selection of a 1 mg/kg dose for a phase 2a elective percutaneous coronary intervention study to achieve a high intensity of anticoagulation and minimize intersubject variability. Phase 2 validated our predictions, demonstrating 1 mg/kg pegnivacogin yielded plasma concentrations ≈25 µg/ml and >99% inhibition of FIX activity. The relationship between the anivamersen to pegnivacogin dose ratio and degree of pegnivacogin reversal was also validated. Our approach decreased the need for extensive dose-response studies, reducing the duration, complexity and cost of clinical development. The 1 mg/kg pegnivacogin dose and a range of anivamersen dose ratios are being tested in the phase 2b RADAR study (NCT00932100).

Pharmacokinetic, bioavailability, and feasibility study of oral vinorelbine in patients with solid tumors.

PURPOSE: The feasibility of administering vinorelbine (Navelbine, Burroughs Wellcome Co, Research Triangle Park, NC), a semisynthetic vinca alkaloid with broad activity, as a liquid-filled gelatin capsule was evaluated in a bioavailability (F) and pharmacokinetic study. PATIENTS AND METHODS: Each of 17 cancer patients had pharmacokinetic studies performed after receiving vinorelbine 30 mg/m2 intravenously (IV), which is the maximum-tolerated dose (MTD) for weekly IV administration, and twice after receiving the oral formulation at a nominal dose of 100 mg/m2. Subsequently, these patients and 10 other subjects received the oral formulation at a dose of 100 mg/m2/wk to evaluate the feasibility of chronic oral administration. RESULTS: Plasma drug disposition was well described by a triphasic model. Mean central volume of distribution and steady-state volume of distribution (Vss) were large (0.66 +/- 0.46 L/kg and 20.02 +/- 8.55 L/kg, respectively); the mean harmonic terminal half-life (t1/2) was long (18 hours); and the high mean clearance (CI) rate (0.80 +/- 0.68 L/h/kg) approached hepatic blood flow. F was low (0.27 +/- 12), and absorption was rapid (mean time of maximum plasma concentration [Tmax], 0.91 +/- 0.22 hours). Absorption parameters after the first and second oral doses were similar, with mean F values of 0.27 +/- 0.14 and 0.25 +/- 0.11, respectively. Coefficients of variability (CVs) for F, maximum plasma concentration (Cmax), and Tmax were 32%, 42%, and 78%, respectively, indicating moderate intraindividual variability. The pharmacologic profile of this oral formulation indicates that there is a large first-pass effect. Neutropenia was the principal toxicity of oral vinorelbine. Grade 3 or 4 neutropenia occurred in 63% of patients, but only 11% developed neutropenia and infection. Nausea, vomiting, and diarrhea were also common with oral administration, but these effects were rarely severe and could be ameliorated by using a divided-dose schedule and/or prophylactic antiemetic and antidiarrheal agents. The mean nominal oral dose was 82 mg/m2, and the mean percentage of intended dose that was received was 92%. Although dose escalations were permitted for negligible toxicity, doses were not escalated to greater than 100 mg/m2/wk in any patient. Vinorelbine given as a liquid-filled gelatin capsule at 100 mg/m2 provided equivalent pharmacologic exposure as 30 mg/m2 IV. CONCLUSION: The oral administration of vinorelbine, specifically as a liquid-filled, soft gelatin capsule, is a feasible route of administration. Weekly oral dosing at 100 mg/m2 induces a consistent degree of myelosuppression, but the high frequency of grade 3 or 4 neutropenia, albeit brief and uncomplicated, warrants the recommendation of a slightly lower starting dose, ie, 80 mg/m2/d, for subsequent phase II evaluations, especially in heavily pretreated patients.

Inhibition of theophylline clearance by cimetidine but not ranitidine.

This study was designed to compare the effects of equivalent therapeutic doses of two H2 antagonists, cimetidine and ranitidine, on theophylline pharmacokinetics and to determine whether the previously described cimetidine-theophylline interaction is dose dependent. Twelve healthy adult men were given a 6-mg/kg intravenous aminophylline dose on four occasions. Subjects were randomly assigned four treatments: no treatment (control); cimetidine, 1,200 mg/day; cimetidine, 2,400 mg/day; and ranitidine, 300 mg/day. Cimetidine, 1,200 mg/day, significantly decreased theophylline clearance by 36% (range, 22% to 49%) and increased the mean elimination half-life from 5.7 hours (control) to 9.2 hours. A significant difference was not found between the two cimetidine dosages, indicating dose independence of the interaction over the dosage range studied. Ranitidine did not significantly alter theophylline pharmacokinetics. Theophylline plasma protein binding was not affected by any treatment. The relative effects of cimetidine and ranitidine on the elimination of cytochrome P-450 metabolized drugs such as theophylline indicate a useful property of ranitidine as compared with cimetidine.

Kinetic model for gentamicin dosing with the use of individual patient parameters.

Multiple-infusion dosing regimens for gentamicin were established for 84 patients with the use of individually calculated values of elimination kinetic parameters. Serum level-time data obtained after a single infusion were used to determine the patient's gentamicin half-life (t 1/2) and distribution volume. Patients with serum creatinine (Cr) less than 1.2 mg per 100 ml had t 1/2 (mean, 2.25 hr) and total body clearances (mean, 0.082 L/hr/kg) significantly different from those with Cr greater than or equal to 1.2 mg/100 ml (means, 5.3 and 0.039, respectively). Distribution volumes were not significantly different (means, 0.22 and 0.21 L/kg, respectively). Calculations of dosing intervals and infusion rates, based on each patient's kinetic parameters and desired steady-state peaks and nadirs, assumed a one-compartment model with first-order elimination and 1-hr constant-rate input at fixed intervals. Follow-up steady-state peak and nadir levels were measured in 63 of the regimens. Differences between predicted and measured peak levels averaged --0.05 mug/ml with 60% of the measured values falling within 1 mug/ml of that predicted. Predicted-measured nadir differences averaged --0.62 mug/ml (significantly different from zero) indicating slight bias in the model. Fifty-six percent of these nadirs were within 1 mug/ml of that predicted.

Influence of range of renal function and liver disease on predictability of creatinine clearance.

Several formulas for predicting creatinine clearance (Ccr) are used for adjusting drug dosages but limited data are available on their accuracy in patients with significant renal impairment or concurrent disease. We measured 144 Ccr in 103 patients and compared results using four predictive methods. Of nine common diseases in these patients, liver disease was associated with a large (p less than 0.02) prediction error (overprediction). After data from eight patients with liver disease were removed, there was good overall correlation between predicted and measured Ccr (r2 = 0.91 for each method) but only two of the methods (I and IV) were consistently accurate in all ranges of renal function. Methods for predicting Ccr should not be used in patients with liver disease.

Bidirectional interaction of valproate and lamotrigine in healthy subjects.

OBJECTIVE: To evaluate the steady-state pharmacokinetics of lamotrigine and valproate at three dosing levels of lamotrigine in normal volunteers receiving steady-state therapeutic doses of valproate. METHODS: This was an open-label, randomized, three-way crossover study of 18 normal male volunteers. Subjects received oral valproate (500 mg Depakote twice a day) throughout the study. Each subject subsequently received three oral dosage regimens of lamotrigine (50, 100, or 150 mg/day) for 1 week each, with a 2-week washout period between lamotrigine treatment periods. Valproate and lamotrigine trough plasma samples were determined by a capillary gas chromatography method and immunofluorometric assay, respectively. Urine samples were assayed for 11 valproate metabolites by gas chromatography/mass spectrometry. RESULTS: When compared to other studies in which lamotrigine was administered with no concurrent antiepileptic drug, concomitant valproate markedly increased the half-life of lamotrigine and decreased lamotrigine clearance, without substantial alteration in the linear kinetics of the drug. The addition of lamotrigine was associated with a small but significant 25% decrease in steady-state valproate plasma concentration. Oral clearance of valproate was increased (from 7.2 +/- 1.1 ml/hr/kg before lamotrigine treatment to 9.0 +/- 2.0 ml/hr/kg on day 28; p < 0.05). The formation clearance of the hepatotoxic valproate metabolites, 2-n-propyl-4-pentenoic acid (4-ene-valproate) and 2-propyl-2,4-pentadienoic acid [2(E),4-diene-valproate], was unaffected by lamotrigine administration. CONCLUSIONS: As a consequence of the interaction between lamotrigine and sodium valproate, a dosage reduction of lamotrigine should be considered in patients taking a combination of valproate and lamotrigine.

The clinical pharmacokinetics of vinorelbine (Navelbine).

Vinorelbine (Navelbine; Burroughs Wellcome Co, Research Triangle Park, NC; Pierre Fabre Médicament, Paris, France) is a semisynthetic vinca alkaloid agent that has been structurally modified on the catharanthine nucleus to impart increased lipophilicity. As a result, vinorelbine appears to possess a higher therapeutic index and different pharmacokinetic properties from other marketed vinca alkaloids. Vinorelbine has been quantified in biologic matrices by measurement of total radioactivity, radioimmunoassay, and high-performance liquid chromatography. Because it is specific for the parent drug, high-performance liquid chromatography has generated the most reliable pharmacokinetic data. Vinorelbine is highly bound to platelets and lymphocytes, and is also bound to alpha 1-acid glycoprotein, albumin, and lipoproteins. The drug undergoes significant metabolism and elimination via the liver and metabolites are excreted primarily in the bile. Two likely vinorelbine metabolites, vinorelbine N-oxide and deacetylvinorelbine, have been isolated and identified in human urine and very low concentrations appeared in plasma. Urinary excretion of unchanged drug accounts for less than 20% of an intravenous dose, with fecal elimination accounting for an additional 30% to 60%. The pharmacokinetic profile of vinorelbine after intravenous bolus or infusion is characterized by triexponential decay. Initial rapid decay is due primarily to distribution into tissues in the peripheral compartments. There is a prolonged terminal phase due to relatively slow efflux of the drug from peripheral compartments, which results in a long terminal phase half-life, with average values ranging from 27.7 to 43.6 hours. Plasma clearance of vinorelbine is high, approaching hepatic blood flow in humans, and its volume of distribution is large, indicating extensive extravascular distribution. In comparison to vinblastine or vincristine, vinorelbine has a higher clearance and a larger volume of distribution than either drug, and a half-life shorter than vinblastine but longer than vincristine. There is no relationship between the age of the patient and the pharmacokinetic parameters of vinorelbine, and coadministration of cisplatin does not appear to influence the pharmacokinetics of vinorelbine. Vinorelbine is the first vinca alkaloid to show promising efficacy following oral administration, and this has led to the development of a liquid-filled, soft-gelatin capsule dosage form. The absolute bioavailability of vinorelbine from this dosage form was 27% when intravenous doses of 30 mg/m2 were compared with oral doses of 100 mg/m2.

Factors associated with nephrotoxicity and clinical outcome in patients receiving amikacin.

Data from 60 patients treated with amikacin were analyzed for factors associated with nephrotoxicity. In 42 of these patients, data were examined for factors associated with clinical outcome. Variables evaluated included patient weight, age, sex, serum creatinine level, creatinine clearance, duration of therapy, total dose, mean daily dose, organism minimum inhibitory concentration (MIC), mean peak levels, mean trough levels, mean area under the serum concentration-time curve (AUC), total AUC, mean AUC greater than MIC, total AUC greater than MIC, mean Schumacher's intensity factor (IF), total IF, In (mean maximum concentration [Cmax]/MIC). Model-dependent pharmacokinetic parameters were calculated by computer based on a one-compartment model. When the parameters were examined individually, duration of therapy and total AUC correlated significantly (P less than .05) with nephrotoxicity. In contrast, a stepwise discriminant function analysis identified only duration of therapy (P less than .001) as an important factor. Based on this model and on Bayes' theorem, the predictive accuracy of identifying "nephrotoxic" patients increased from 0.17 to 0.39. When examined individually, mean IF, MIC, total dose, mean daily dose, and ln (mean Cmax/MIC) correlated significantly (P less than .05) with cure. In contrast, a simultaneous multivariable analysis identified IF, MIC, and total dose according to one model and ln (mean Cmax/MIC) according to a second statistical model of parameters selected to have the greatest prospective value. Based on Bayes' theorem and the first model, the predictive accuracy of identifying patients not cured increased from 0.19 to 0.83. For the second model, the predictive accuracy increased from 0.19 to 0.50.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of oral and transdermal triprolidine.

In this open, nonrandomized, three-way crossover study, six healthy male volunteers received single doses of triprolidine (TPL) hydrochloride syrup orally (2.5 mg) and wore transdermal TPL patches (5 mg and 10 mg doses) to compare the pharmacokinetic profiles and dose tolerance of the two formulations. A washout period of at least 1 week was scheduled between the three dosing periods. Blood samples were collected at defined times, and plasma concentrations were determined using a radioimmunoassay. Maximum plasma drug concentration (Cmax) decreased from 5.6 +/- 2.9 ng/mL (mean +/- SD) with oral dosing to 2.0 +/- 1.0 ng/mL and 4.2 +/- 2.0 ng/mL following 5 mg and 10 mg transdermal doses, respectively. Time to reach peak concentration (tmax) increased from 2.0 +/- 1.2 hours with oral dosing to 12.0 +/- 5.9 and 14.3 +/- 9.9 hours following 5 mg and 10 mg transdermal doses, respectively. The differences between AUC0-alpha values with the oral syrup and the 5 mg and 10 mg transdermal doses were not significant when normalized to 2.09 mg (TPL base). The bioavailabilities of the 5 mg and 10 mg transdermal doses relative to the oral 2.09 mg doses were 0.89 +/- 0.32 and 1.04 +/- 0.33, respectively. Mild erythema and pruritus were the most common adverse effects secondary to TPL transdermal application. Drowsiness observed following oral TPL, was not evident following either transdermal dose. The results of this study, therefore, indicate that TPL can be absorbed transdermally, providing consistent plasma concentrations.

The effects of food and divided dosing on the bioavailability of oral vinorelbine.

The effects of food and divided dosing on the bioavailability of a liquid-filled gelatin capsule formulation of vinorelbine (Navelbine), a semisynthetic vinca alkaloid with broad clinical activity, was evaluated in patients with advanced solid tumors. A group of 13 patients were randomized to treatment with the oral formulation at the recommended phase II dose of 80 mg/m2 per week either in the fasting state or after ingestion of a standard meal. Patients were treated 1 week later in the alternate state relative to their first dose. The effects of divided dosing were assessed during the 3rd week, at which time vinorelbine was administered in two divided doses. After the completion of pharmacokinetic and bioavailability studies, patients received the oral formulation at a dose of 80 mg/m2 per week in two divided doses to evaluate the feasibility of chronic oral drug administration. Both manipulations resulted in small, albeit statistically significant, reductions in the relative bioavailability of this oral formulation. The relative bioavailability decreased by 22 +/- 28% when treatment followed the ingestion of a standard meal, possibly due to a delay in gastrointestinal transit time. The mean time of maximum plasma concentration (Tmax) increased from 1.3 +/- 1.6 h in the fasting state to 2.5 +/- 1.6 h in the fed state, although this difference was not statistically significant. Similarly, the relative bioavailability declined by 16 +/- 51% when vinorelbine was administered in two divided doses. An analysis of dose proportionality revealed disproportionate increases in dose-normalized Cmax and AUC values with single oral doses above 120 mg, which may account for this phenomenon. The high clearance of vinorelbine, which approaches hepatic blood flow, and the lack of dose proportionality after oral administration, indicate that there is a large first-pass effect which may be saturable, or nonlinear, above single doses of 120 mg. In addition, the toxicological and pharmacological characteristics of oral vinorelbine indicate that treatment after a standard meal or on a divided dosing schedule is safe. Chronic oral administration of the agent in two divided doses was also well tolerated. However, the small reduction in the relative bioavailability following the ingestion of a standard meal and with divided dosing suggest the need for further pharmacodynamic studies to determine if reductions in drug exposure of this magnitude may portend diminished antitumor activity.

Pharmacokinetics and safety of lamotrigine (Lamictal) in patients with epilepsy.

In a double-blind parallel study, patients with epilepsy on stable regimen of antiepileptic drugs (AEDs) were given lamotrigine (8 pts) or placebo (3 pts). Patients were sequentially dosed with 100, 200 and 300 mg/day given as a b.i.d. regimen. After steady state was achieved, timed plasma lamotrigine levels were obtained post dose. No medical, psychogenic, neurologic, or hematologic changes were observed and no subjective effects were detected as a result of treatment with lamotrigine. No changes in heart rhythm or blood pressure were observed related to lamotrigine. Pharmacokinetic parameters were calculated using 1-compartment and non-compartment models. The results were similar using both models. Area under the plasma concentration vs. time curves increased linearly with dose. Mean half life (13.5 h), volume of distribution (1.36 l/kg) and clearance (1.27 ml/min/kg) were similar to previously reported results and did not change with increasing dose. These findings indicate that lamotrigine pharmacokinetics can be described by the 1-compartment model, has linear kinetics, and does not induce its own metabolism in patients on concomitant AEDs.

Automated dissolution testing of combination drug product using high-pressure liquid chromatography.

An automated high-pressure liquid chromatographic (HPLC) system compatible with any standard tablet dissolution apparatus was developed. This system allowed the individual drug concentrations within a product to be determined simultaneously, even when the drugs had similar structures and UV spectra. This automated system permitted unattended sampling and concentration determination at predetermined time intervals. The dissolution medium was pumped continuously through a fixed-volume, microprocessor-controlled injector and returned to the USP rotating-basket dissolution apparatus. No corrections for the changing dissolution medium volume were necessary since each injection onto a reversed-phase HPLC column consumed just 10 microliter of medium. Dissolution tests were performed on three brands of trisulfapyrimidines tablets. Sample injections were made automatically at 5.1-min intervals for approximately 2 hr. Dissolution profiles were determined for each drug in each product. Statistically significant differences were found in the mean concentration-time values between drugs within a drug product and between the drug products.

High-pressure liquid chromatographic assay for chloramphenicol, chloramphenicol-3-monosuccinate, and chloramphenicol-1-monosuccinate.

A high-pressure liquid chromatographic method for the sensitive and rapid determination of chloramphenicol, chloramphenicol-3-monosuccinate, and chloramphenicol-1-monosuccinate is presented. The procedure utilizes a reversed-phase chromatographic column with UV absorption detection. The assay is useful for monitoring patients receiving chloramphenicol, determining the pharmacokinetics of parenteral chloramphenicol sodium succinate, and certifying sterile chloramphenicol sodium succinate.

Pharmacokinetics of RheothRx injection in healthy male volunteers.

The objectives of this study were to evaluate the safety and tolerability of RheothRx (poloxamer 188) injection administered as an intravenous (i.v.) infusion to healthy male volunteers and to determine the pharmacokinetic profile of poloxamer 188. Thirty-six healthy male volunteers were enrolled in a randomized, double-blind, placebo-controlled, dose-escalation trial for RheothRx injection. The volunteers were randomized to three treatment groups (12 per treatment group, with eight receiving active therapy and four receiving placebo). In each treatment group, volunteers received RheothRx injection or placebo as an i.v. infusion on two occasions at least 3 weeks apart to make a total of six doses being studied (10, 30, and 45 mg/kg/h for 72 h, 60 mg/kg/h for 43.3 to 72 h, 60 and 90 mg/kg/h for 24 h). Serial plasma samples were collected during and up to 36 h after the end of the infusions; urine was collected over intervals from the start of the infusion until 36 h after the infusions were terminated. Plasma and urine samples were assayed for poloxamer 188 by gel-permeation chromatography. Pharmacokinetic parameter values were calculated by noncompartmental and compartmental methods. Poloxamer 188 was eliminated primarily by renal excretion. Estimates of clearance, elimination rate constant, and apparent volume of distribution at steady state values were independent of infusion rate. Poloxamer 188 displayed no apparent infusion rate dependence in its pharmacokinetics.

Antipyrine kinetics following partial blood exchange with Fluosol-DA in the rat.

The effects of partial blood exchange with Fluosol-DA on hepatic microsomal oxidative metabolism have been studied in the rat. Antipyrine clearance (Cl) was used as an in-vivo measure of the activity of the mixed function oxidase system. Rats were partially exchanged with Fluosol-DA and dosed with antipyrine at selected time intervals following exchange. No change in antipyrine Cl was observed at 0.5 h, but there was a statistically significant decrease at 24 h and then an increase by more than 50% relative to control at 48 and 72 h. These data indicate that the effects of Fluosol-DA on hepatic function are time-dependent and that Fluosol-DA has the potential both to inhibit and to enhance hepatic metabolism. The possibility of altered hepatic metabolism should be considered when patients transfused with Fluosol-DA are given drugs primarily metabolized by the mixed function oxidase system.

Variable first-pass elimination of propranolol following single and multiple oral doses in hypertensive patients.

The disposition of orally administered propranolol has been studied in twelve patients with mild to moderate hypertension. Each patient received single doses of 40, 80, and 160 mg. Serial blood samples were obtained and quantitated using a sensitive gas chromatographic analytical technique. Ten of the twelve patients received 40 mg doses of propranolol every 6 hours for 5 doses. Blood samples were obtained after administration of the first, second, third, and fifth doses. Substantial intersubject variability in the areas under the bloodconcentration-time profiles (AUC) was observed. Evidence for a nonlinear first-pass effect was not obtained in all patients. The patients displaying a nonlinear relationship between dose and AUC for single propranolol doses consistently showed a similar relationship during multiple dosing. Blood levels obtained following the evening dose (08h00 to 14h00) appeared to be lower than expected based on multiple-dosing pharmacokinetic principles. These findings suggest that monitoring propranolol blood levels is the most viable way to ascertain therapeutic concentrations of this drug.

A phase 1 ascending dose study of a subcutaneously administered factor IXa inhibitor and its active control agent.

BACKGROUND: The REG2 anticoagulation system consists of pegnivacogin, a subcutaneously administered aptamer factor IXa inhibitor, and its intravenous control agent, anivamersen. OBJECTIVES: To assess the safety, tolerability and pharmacokinetic and pharmacodynamic responses of REG2. PATIENTS/METHODS: In this phase 1a study, 36 healthy volunteers were enrolled into five cohorts and given one dose of pegnivacogin. Cohorts 1 (n = 6) and 1A (n = 4) received 0.5 mg kg(-1); cohort 2 (n = 6) received 1.0 mg kg(-1); cohort 3 (n = 6) received 3.0 mg kg(-1); and cohort 4 (n = 8) received 2.0 mg kg(-1) . In cohorts 1-3, two subjects were randomized to placebo. Cohort 4 subjects were subsequently randomized to single-dose (n = 4) or multidose (n = 4) anivamersen. RESULTS: The mean maximum observed concentrations of pegnivacogin in cohorts 1, 1A, 2 and 3 at median time were 5.16 µg mL(-1) at 84 h, 5.19 µg mL(-1) at 72 h, 9.32 µg mL(-1) at 90 h, and 32.5 µg mL(-1) at 84 h, respectively. The maximum relative activated partial thromboplastin time and time needed to achieve this were 1.18 at 2 days, 1.16 at 2 days, 1.27 at 3 days, and 1.85 at 2 days, respectively. The calculated mean half-life and mean residence times of pegnivacogin were 6.12 days and 9.6 days, respectively. There was rapid reversal with intravenous anivamersen, although subsequent reaccumulation of pegnivacogin was observed. CONCLUSIONS: In our first-in-human study, REG2 was well tolerated and provided dose-proportional anticoagulation for several days after a single subcutaneous dose, with complete, although transient, reversal by its control agent. This study demonstrates the first application of a subcutaneously administered aptamer, and represents a potential advance in aptamer therapeutics.

High-performance liquid chromatographic determination of carbaryl and 1-naphthol in biological fluids.

A simple and sensitive method for the simultaneous analysis of carbaryl and 1-naphthol in whole blood by reversed-phase high-performance liquid chromatography and fluorescence detection is described. Spiked blood (heparinized) containing an internal standard was hemolyzed and extracted with ethyl acetate. After centrifugation the extractant was removed and taken to dryness. Reconstitution and subsequent high-performance liquid chromatography-fluorescence analysis yielded linear standard curves for carbaryl and 1-naphthol. Linear response vs. concentration profiles were obtained for carbaryl and 1-naphthol extracted from buffer solutions as well. A simple chemical hydrolysis study of carbaryl is included to illustrate the effectiveness of the extraction procedure and assay.

Pitfalls and valid approaches to pharmacokinetic analysis of mean concentration data following intravenous administration.

Pharmacokinetic analysis fo arithmetic mean concentration data can lead us to selection of an inappropriate deterministic compartmental model and biased pharmacokinetic parameter estimates. The terminal phase disposition rate constant estimated by fitting a deterministic model to mean data is in all cases an underestimate of the expected value of this rate constant. The area under the mean data curve calculated via the linear trapezoidal rule from time zero to the last detectable concentration sampling point is equal to the mean of the individual subject areas under the curve for the same time span. This equality supports the use of mean data for determination of model-independent pharmacokinetic parameters.