Pharmacokinetics of eltoprazine in healthy male subjects after single dose oral and intravenous administration.

The kinetics, safety and tolerability of eltoprazine hydrochloride were studied in an open, cross-over, partially randomised design after single oral (8 mg) and intravenous (3 and 8 mg) doses to 12 healthy male subjects. After intravenous administration, the mean t1/2 ranged from 7 to 9 h, the MRT was 11 h, CL was 487 +/- 148 (3 mg dose) and 471 +/- 56 (8 mg dose) ml kg-1 h-1, while CLR was 226 +/- 124 (3 mg dose) and 189 +/- 38 (8 mg dose) ml kg-1 h-1. The Vss was 3.3 +/- 0.7 (3 mg dose) and 3.8 +/- 0.5 (8 mg dose) 1 kg-1. Cumulative renal excretion was 40%. The AUC and the cumulative urinary excretion were directly proportional to dose within the range of 3-8 mg. Values of tmax varied from 1 to 4 h after oral administration. The mean Cmax value was 24 ng ml-1 after an oral dose of 8 mg. The plasma elimination half-life after oral administration was 9.8 +/- 3.9 h. Absolute oral bioavailability was 110 +/- 32%. Dose-dependent somnolence was observed.     

Effect of food and various antacids on the absorption of tenoxicam.

1 Twelve healthy volunteers received a single oral dose of tenoxicam 20 mg on six occasions separated by 3 weeks. 2 The six occasions were: fasted overnight; postprandial; fasting and 15 ml aluminium hydroxide gel; postprandial and 15 ml aluminium hydroxide gel; fasting and 15 ml aluminium and magnesium hydroxide gel; postprandial and 15 ml aluminium and magnesium hydroxide gel. 3 Twenty plasma samples were collected over 15 days following dosing with tenoxicam. 4 The following kinetic parameters for plasma tenoxicam were compared: peak concentrations, time taken to reach peak concentrations, area under the plasma concentration-time curve (AUC) and half-life of elimination. 5 Food lengthened the time taken to reach peak tenoxicam concentrations (5.82 +/- 4.6 vs 1.84 +/- 1.0 h in the fasting state; P less than 0.02) and marginally reduced the peak concentrations achieved. AUC was not affected by any of the different regimens. 6 These effects of food on tenoxicam bioavailability are unlikely to be of clinical significance during chronic dosing with the drug.     

Pharmacokinetics of eltoprazine in the dog

Pharmacokinetics of eltoprazine in male and female beagle dogs was studied in two separate cross-over experiments after administration of different intravenous and oral doses. After intravenous administration of 0.5 mg.kg-1, the mean volume of distribution was 5.7 +/- 1.1 l.kg-1. Clearance was 25.5 +/- 1.4 ml.min-1.kg-1. About 25% of the doses was excreted in urine, resulting ina renal clearance of 6.1 +/- 1.4 ml.min-1.kg-1. The mean elimination half-life (t1/2) after intravenous dosing was about 2.6 h. After oral dosing the plasma peak levels (Cmax) were proportional with the dose. The mean time to reach Cmax (tmax) varied between 1.5 and 1.9 h, and t1/2 was about 2.4 h, which was not significantly different (p greater than 0.05) from the half-life obtained after intravenous dosing. Plasma pharmacokinetics after single and multiple dosing of 4 mg.kg-1 showed no difference. Absolute bioavailability was 67% +/- 20%.     

Sex-differences in the disposition of substituted benzamides: pharmacokinetics of a gastroprokinetic agent (4-amino-5-chloro-2-[2- (methylsulfinyl) ethoxy]-N-[2-(diethylamino)ethyl] benzamide hydrochloride) (ML-1035) in male and female New Zealand white rabbits.

The disposition of 4-amino-5-chloro-2-[2-(methylsulfinyl)ethoxy]-N- [2-(diethylamino)ethyl] benzamide hydrochloride (ML-1035) following intravenous (10 mg kg-1) and oral (200 mg kg-1) dosing was investigated in male and female New Zealand white rabbits. After intravenous dosing ML-1035 was eliminated with a half-life of 1.45 +/- 0.49 h in males and 0.79 +/- 0.08 h in females. Volume of distribution at steady-state was 2.08 +/- 0.98 l kg-1 in males and 9.11 +/- 5.86 l kg-1 in females. Clearance averaged 2.99 +/- 1.11 l h-1 kg-1 in males and 16.73 +/- 7.29 l h-1 kg-1 in females. All pharmacokinetic parameters were significantly different between males and females (p < 0.05). Absolute bioavailability after oral administration was 7.35 per cent for males and 12.31 per cent for females, suggesting that ML-1035 undergoes significant first-pass elimination. Plasma area under the curve for the metabolites of ML-1035 after both oral and intravenous administration were also different between the two sexes. These data suggest that the disposition of ML-1035 shows significant differences between male and female rabbits.     

Single-dose kinetics of an enteric-coated formulation of carbamazepine-10,11-epoxide, an active metabolite of carbamazepine

The kinetics of an enteric-coated formulation of carbamazepine-10,11-epoxide (CBZ-E) were studied in healthy subjects. A single oral dose of 100 mg of CBZ-E was given to eight subjects. Four of them were also given a single oral dose of 200 mg of CBZ-E. Plasma concentrations of CBZ-E and urinary excretion of the end metabolite trans-10,11-dihydroxy-10,11-dihydro-carbamazepine (trans-CBZ-diol) were determined by high performance liquid chromatography. Plasma kinetics of CBZ-E fitted an open one-compartment model with plasma elimination half-life of 7.4 +/- 1.8 h (mean +/- SD). The clearance was 105 +/- 17 ml/kg/h and the apparent volume of distribution 1.1 +/- 0.2 L/kg assuming complete bioavailability. There was no indication of dose-dependent elimination of CBZ-E. The recovery of trans-CBZ-diol in urine collected for 3 days was 67 +/- 9% of the given dose. This enteric-coated formulation may thus in the future be used for the evaluation of the clinical effects of CBZ-E in patients.     

Clinical pharmacology of prochlorperazine in healthy young males.

1. The pharmacokinetics and pharmacodynamics of prochlorperazine (PCZ) have been studied in healthy young males following single 12.5 mg i.v. and 50 mg oral doses, and during repeated doses (25 mg twice daily) for 14 days. 2. Oral bioavailability was low and an N-desmethyl metabolite was detected. Plasma clearance was high (0.98 1 kg-1 h) and the volume of distribution was large (12.9 1 kg-1) after i.v. dosing. 3. The terminal elimination half-life of PCZ was 9 +/- 1 h and 8 +/- 2 h after i.v. and single oral dosing, respectively. The urinary recoveries of drug and metabolite were low. 4. Accumulation of PCZ and its metabolite occurred following repeated dosing. The half-life at the end of 14 days therapy was 18 +/- 4 h. 5. Postural tachycardia, decreased salivary flow, impaired psychomotor function and a diminished level of arousal were observed after intravenous PCZ. Similar effects, but of lower magnitude were observed after single oral doses. During chronic dosing postural tachycardia and antihistaminic effects were observed, the latter not being observed after single doses. 6. After single intravenous dosing the maximal drug effects occurred 2-4 h after peak plasma drug concentrations for all measures except for plasma prolactin and self-scored restlessness 7. An antagonist action at dopamine (D2), muscarinic-cholinergic and alpha-adrenoceptors is postulated after single doses, with antihistaminic effects during chronic dosing, possibly indicating the presence of an active metabolite.     

The pharmacokinetics of mefloquine in man: lack of effect of mefloquine on antipyrine metabolism.

A method is described for the determination of the new antimalarial agent, mefloquine, in plasma and urine. After oral administration of 750 mg mefloquine to six volunteers, absorption, was apparently slow, with plasma mefloquine concentrations at 24 h (559 +/- 181 ng ml-1; mean +/- s.d.) higher than at 6 h (459 +/- 166 ng ml-1). The elimination half-life was 373 +/- 249 h, oral clearance was 5.09 +/- 2.7 1 h-1, and apparent volume of distribution was 35.7 +/- 30.7 l kg-1 (assuming 100% bioavailability). Mefloquine (750 mg) had no significant effect on salivary kinetics of antipyrine or on the metabolic clearance of antipyrine to its three main metabolites, 3-hydroxymethylantipyrine, 4-hydroxyantipyrine and norantipyrine, when antipyrine was administered either 2 h or 2 weeks after dosing with mefloquine.     

Bioavailability of dihydroergotamine in man.

1 The pharmacokinetics of dihydroergotamine (DHE) in plasma were examined in six normotensive subjects after single acute doses of dihydroergotamine, 10 micrograms/kg i.v. and 10, 20 and 30 mg orally. 2 The mean apparent half-time of elimination was 2.37 +/- 0.29 h and plasma clearance of dHE was 1002 +/- 169 ml/min. 3 Mean apparent absorption of DHE determined from the 10 mg dose was 26.6 +/- 10% and ranged from 8.9 to 60.3%. The oral bioavailability after the 10, 20 and 30 mg doses averaged 0.47 +/- 0.07%, 0.59 +/- 0.13% and 0.52 +/- 0.14% respectively. Inter-patient variability in bioavailability was 6-fold. 4 The results indicate that pre-systemic 'first-pass' extraction of DHE is the main determinant of its oral bioavailability. Oral doses of the drug up to 30 mg do not saturate this extraction process resulting in apparently linear kinetics for the drug.     

Pharmacokinetics and efficacy of pirmenol hydrochloride in the treatment of ventricular dysrhythmia

Pirmenol hydrochloride (CI-845), a new antiarrhythmic agent available for both oral and intravenous administration, was given to seven patients with chronic ventricular dysrhythmia in an open-label fashion. After intravenous infusion of 150 mg over 30 min, the mean (+/- SD) peak plasma concentration achieved was 2.14 +/- 0.75 microgram/ml. The terminal elimination half-life, the volume of the central compartment, and the total body clearance averaged 6.5 h, 0.70 +/- 0.36 L/kg, and 3.0 +/- 2.6 ml/min/kg, respectively. After a single 150-mg oral dose, the peak plasma concentration of 1.3 +/- 0.55 microgram/ml was achieved 1 to 3 h after dosing. The mean apparent elimination half-life was 7.6 h. An estimated absorption lag time ranging from 14 to 37 min was observed in all but one patient. The mean absolute bioavailability for the oral dose was 87%. Dysrhythmia data were available in six patients. Complete (100%) suppression of ventricular ectopic beats occurred in four patients for 1/2 to 15 h after intravenous infusion, and in three patients for 7 to 25 h after oral dose. This suppression occurred with a plasma pirmenol level as low as 0.4 microgram/ml. No significant side effects were observed.     

The influence of aluminium hydroxide on the bioavailability of feprazone. Single dose study

The influence of aluminium hydroxide (given as a suspension, Aludrox) on the oral bioavailability of feprazone was tested. The degree and speed of absorption of feprazone from capsules (400 mg feprazone as a single dose; 8 volunteers) was investigated by determining plasma levels of feprazone and one of its metabolites using an HPLC method. No statistically significant change in feprazone kinetics caused by the antacid was evident. Cmax (means +/- SEM) decreased from 40.6 +/- 2.9 to 36.25 +/- 1.4 micrograms/ml; the mean area under the plasma level time curve was somewhat higher after additional administration of aluminium hydroxide (n. s.).     

Bioavailability of isradipine in young and old rats: effect of mode of administration

The bioavailability of isradipine has been examined in 7- and 52-week-old rats after oral (12.5 mg kg-1) or intravenous (2.5 mg kg-1) doses as a solution and administration of various doses (1.8-85.5 mg kg-1) in the diet. Serial plasma samples were obtained from each rat and the drug concentration was determined by radioimmunoassay. Absorption from the dose given by gavage was rapid but when administered in a drug diet mixture, isradipine appeared in the plasma slowly and in a manner reflecting the feeding pattern. Its absolute bioavailability from the drug-diet mixture averaged 3% over the dose range tested. By gavage its bioavailability was enhanced to 5% of dose with peak plasma values approximately 7 times higher than from a comparable dose in the diet. The low oral bioavailability of isradipine in the rat was most likely due to extensive first-pass metabolism. The decline in plasma concentrations was biexponential, with a mean terminal half-life of 3.6-3.7 h after oral or intravenous dosing. The pharmacokinetic characteristics of isradipine examined were independent of the age of the rat, except that its volume of distribution decreased with age. The older rats also showed a greater inter-animal variability in isradipine bioavailability from the drug-diet mixture.     

Disopyramide pharmacokinetics in patients with acute myocardial infarction

To study the effects of acute myocardial infarction on the pharmacokinetics of disopyramide a single oral dose of disopyramide base (200 mg) was administered to 6 patients with myocardial infarction both in the acute (Study I) and recovery (Study II) phases. An intravenous tracer dose of 14C-disopyramide (2.5 micrograms/0.3 mg) was given simultaneously with the oral dose. On the basis of the intravenous tracer data, the volume of distribution, binding to plasma proteins, total plasma clearance, renal clearance and elimination half-life of disopyramide and mono-N-dealkyl disopyramide were the same in Studies I and II. The peak serum concentrations of disopyramide after oral dosing in Studies I and II were 2.6 +/- 1.2 (SEM) and 6.4 +/- 1.9 microgram/ml, respectively (p less than 0.05), the peak times 3.29 +/- 1.22 and 1.21 +/- 0.39 h (N.S.) and the AUCINF 38.0 +/- 7.7 and 60.7 +/- 9.9 micrograms . h . ml-1 (p less than 0.05). The recovery of disopyramide in urine over 3 days averaged 46% and 47% of dose, and that of mono-N-dealkyl disopyramide 22% and 16% of the dose, respectively. Thus, the gastrointestinal absorption of disopyramide was disturbed, resulting in low plasma concentrations after oral dosing, whereas the elimination of disopyramide was unaltered in the acute phase of myocardial infarction.     

Pharmacokinetics of dexloxiglumide after administration of single and repeat oral escalating doses in healthy young males

OBJECTIVE: To assess the pharmacokinetics, safety and tolerability of dexloxiglumide, a new CCK1 receptor antagonist currently under development for the treatment of the constipation-predominant irritable bowel syndrome. SUBJECTS AND METHODS: Twelve volunteers were enrolled in the present study and received orally 100, 200 and 400 mg of dexloxiglumide as tablets as a single dose followed by repeated t.i.d. doses for 7 days according to a randomized, double-blind, double-dummy complete crossover design. Plasma and urine were collected before drug administration and up to 72 h after dosing. Dexloxiglumide plasma and urinary concentration, determined using validated HPLC methods with UV detection, were used for the pharmacokinetic analysis by standard noncompartmental methods. In addition, dexloxiglumide safety and tolerability were evaluated throughout the study period by performing standard laboratory tests, by recording vital signs and ECGs and by monitoring the occurrence and severity of adverse events. RESULTS: After a single oral administration, dexloxiglumide was rapidly bioavailable with mean t(max) ranging from 0.9 - 1.6 h at all doses. The mean peak plasma concentrations (Cmax) were 1.7+/-0.6, 5.4+/-1.7, and 11.9+/-4.7 microg/ml, and the mean area under the plasma concentration-time curves (AUC) were 4.4+/-3.3, 8.6+/-3.6, and 18.3+/-5.9 microg x h/ml at the 3 doses, respectively. Apparent plasma clearance (CL/F) was 30.8+/-13.9, 27.2+/-10.6, and 21.1+/-8.6 l/h at the 3 doses, respectively. The apparent elimination half-life from plasma (t1/2) ranged from 2.6 - 3.3 h at the 3 doses. The excretion of unchanged dexloxiglumide in 0 - 72 h urine accounted for approximately 1% of the administered dose and this was true for all doses. Dexloxiglumide renal clearance (CLR) averaged 0.4+/-0.4, 0.4+/-0.2, and 0.3+/-0.3 l/h for the 3 doses, respectively. After the last dose of the repeated dosing period dexloxiglumide Cmax occurred at 1.1 - 1.6 h after drug administration and averaged 2.4+/-1.3, 7.1+/-2.9, and 15.3+/-2.7 microg/ml for the 3 doses, respectively. The AUC values averaged 5.9+/-3.0, 16.0+/-8.8, and 50.8+/-38.1 microg x h/ml, respectively. The area under the plasma concentration-time curve calculated at steady state within a dosing interval (AUCss) averaged 4.6+/-1.6, 11.3+/-3.6, and 28.4+/-8.2 microg x h/ml, whereas CL/F averaged 20.3+/-8.3, 16.3+/-9.0, and 10.3+/-5.0 l/h at the 3 doses, respectively. Dexloxiglumide t1/2 could not be accurately calculated due to the high inter-subject variability and to sustained dexloxiglumide plasma concentrations that precluded the identification ofthe terminal phase of the plasma concentration-time profiles. However, it appeared that dexloxiglumide t1/2 was considerably prolonged at the dose of 400 mg. CLR averaged 0.4+/-0.4, 0.3+/-0.3, and 0.3+/-0.1 l/h for the 3 doses, respectively. After a single dose, the plasma pharmacokinetics of dexloxiglumide were dose-independent in the dose range 100 - 400 mg. After repeated dose the pharmacokinetics of dexloxiglumide were virtually dose-independent in the dose range 100 - 200 mg. A slight deviation from linear pharmacokinetics was found with a dose of 400 mg. Dexloxiglumide plasma pharmacokinetics were also time-independent in the dose range 100 - 200 mg with a deviation from expectation based on the superimposition principle with a dose of 400 mg. Dexloxiglumide urinary excretion and renal clearance were both dose- and time-independent in the dose range 100 - 400 mg. The safety and tolerability of dexloxiglumide administered to healthy young males was good up to the maximum investigated dose of 400 mg both after single and after repeated doses. CONCLUSIONS: The safety and pharmacokinetic profile of dexloxiglumide when the drug is administered as single and repeated doses in the dose range 100 - 400 mg provides the rationale for the choice of the treatment schedule (200 mg t.i.d.) for the efficacy trials in patients with (constipation-predominant) irritable bowel syndrome.     

Clonidine kinetics in man--evidence for dose dependency and changed pharmacokinetics during chronic therapy.

1 Clonidine kinetics were studied in 21 patients with essential hypertension. All received two bolus i.v. injections in the mean dose range of (0.78--3.36 micrograms kg-1) and one single oral dose (mean dose 1.7--2.3 micrograms kg-1) on separate occasions. The kinetics were also studied in some of these patients after multiple therapeutic oral dose (mean dose 1.1 or 1.9 micrograms kg-1) twice daily during a dosage interval after 6--12 months monotherapy with clonidine. The multiple oral dosage was based on the therapeutic response. 2 With increasing i.v. doses the rate constants (alpha, beta) decreased and the plasma clearance was reduced by 74% (9.94--2.61 ml min-1 kg-1) indicating dose-dependent kinetics. The volume of distribution (Vd beta) did not change with dose in contrast to the volume of the plasma compartment (Vc) which was increased at the highest doses. 3 The single oral dose kinetics agreed with the i.v. kinetics at comparable dose. The bioavailability was 90%. 4 During multiple oral dosing the elimination rate constants decreased compared to the single dose. The plasma clearance increased (7.18 ml min-1 kg-1) compared to the corresponding single dose (4.17 ml min-1 kg-1). The latter change was probably caused by the decrease in bioavailability to about 65%. 5 The pharmacodynamic properties of the drug could explain the changes in pharmacokinetics with increased dose and during multiple doses.     

Pharmacokinetics and bioavailability of viqualine, a new antidepressant

A high performance liquid chromatographic assay was developed for plasma and urine levels measurement of viqualine. The assay was used to study the disposition of 25 mg intravenous and oral single doses in five healthy subjects. Two exponential terms were required to describe the disposition of the drug after intravenous and oral administration. The bioavailability of oral viqualine averaged 80%. The mean apparent half-life was 12.1 +/- 1.9 and 11.9 +/- 1.4 h (mean +/- s.e.m., n = 5) after 25 mg I.V. and oral dose respectively. The apparent volume of distribution (Vdss) were 1578 +/- 132 1 (after I.V. administration) and 1572 +/- 201 1 (after oral administration). The body and renal clearances were respectively 1.56 +/- 0.31 1.h-1. kg-1 and 1.57 +/- 0.31 1.h-1. kg-1, after 25 mg bolus I.V.     

Glyceryl-1-nitrate pharmacokinetics in healthy volunteers.

The plasma kinetics and urinary excretion of glyceryl-1-nitrate (G-1-N), a metabolite of glyceryl trinitrate with antianginal potential, were investigated in 10 healthy male volunteers, after intravenous infusion and oral administration of 20 mg G-1-N. The apparent volume of G-1-N distribution was 601 corresponding to 0.761 kg-1 body weight, on average. It is suggested that total body water is the principal biological correlate of the hydrophilic drug. Mean intravenous clearance was 283 ml min-1 or 3.61 ml min-1 kg-1. The average of elimination half-lives were 2.50 +/- 0.36 (s.d.) h after the intravenous and 2.54 +/- 0.40 (s.d.) h after the oral dose. Inter-subject variances of pharmacokinetic parameters were low compared to variances reported for glyceryl trinitrate. The coefficient of intra-subject variation of the elimination half-lives was 8.8%. 5.5% (i.v.) and 5.4% (p.o.) of the administered dose were excreted into urine up to 48 h after the administration. 1% (i.v.) and 1.5% (p.o.) were in the conjugated form. The oral dose was rapidly and almost completely absorbed. The oral bioavailability on the basis of areas under the curve amounted to 88.6% on the average. For clinical use, owing to its high oral bioavailability, long residence in the body, inactivation by metabolic conversion, and good predictability of kinetic parameters, G-1-N offers advantage over glyceryl trinitrate.     

Study of the bioavailability of pindolol in malabsorption syndromes.

Pindolol kinetics and bioavailability were studied after a single dose (oral 5 mg; intravenous 3 mg) in nine patients with malabsorption (two with villous atrophies, seven with short bowel syndromes) and in six healthy volunteers. After oral administration no significant differences were observed in bioavailability (59.4 +/- 6.2% in patients vs 79.5 +/- 8.6% in controls) and for most plasma and urinary pharmacokinetic parameters between the experimental and control groups as a whole. However, detailed analysis revealed decreased absorption for pindolol in two out of nine patients. After i.v. administration, apparent distribution volume was smaller (V: 2.10 +/- 0.25 l kg-1 vs 3.05 +/- 0.31 l kg-1) and global elimination constant was larger (ke: 1.43 +/- 0.46 h-1 vs 0.56 +/- 0.10 h-1), in patients with malabsorption than in controls (P less than 0.05). The smaller weight of patients and pharmacokinetic modifications due to the pathology could account for this.     

Application of stable isotope methodology to study the pharmacokinetics, bioavailability and metabolism of nitrendipine after i.v. and p.o. administration.

1. The pharmacokinetics, bioavailability and metabolism of nitrendipine were studied in six healthy volunteers (three females, three males) using [13C4]-nitrendipine as a biological internal standard. In the first study the drug was administered simultaneously by the i.v. [13C4] and p.o. (solution) routes and in a second study two oral preparations (13C4-solution and commercial tablet) were administered, also simultaneously. 2. The mean terminal elimination half-life was 8.3 +/- 3.2 h (range 3.4 to 16 h) with no differences between the intravenous and oral route of administration. Total plasma clearance averaged 18.7 +/- 0.6 ml min-1 kg-1 and volume of distribution at steady state 5.4 +/- 2.4 1 kg-1. 3. Following oral administration of nitrendipine solution the percentage of dose absorbed was 88.4 +/- 16.0% based on urinary excretion of metabolites. Despite its almost complete absorption, absolute bioavailability of the solution was only 22.6 +/- 6.7% due to extensive presystemic elimination. The bioavailability of the commercial tablet relative to the solution was 82.2 +/- 20.3%. 4. Both after i.v. and oral administration the drug was extensively metabolized with less than 0.5% of the dose excreted as unchanged drug in urine. Cleavage of the two ester functions in position 3 and 5, respectively, to carboxylic acids and further hydroxylation of the methyl groups in position 2 and 6 of the pyridine ring to the corresponding hydroxymethyl carboxylic acids constituted the major urinary metabolites accounting for 35.0 +/- 16.5% (i.v.) and 32.8 +/- 20.4% (p.o.), respectively, of the dose administered. 5. Binding of nitrendipine to plasma proteins was high with a fraction unbound of only 0.02 +/- 0.012 (range 0.011 to 0.036).     

High-performance liquid chromatographic assay of the aldose reductase inhibitor spiro-(2-fluoro-9H-fluorene-9,4'-imidazolidine)-2',5'-dione (AL01567) in plasma and urine and its pharmacokinetics in humans

Two selective high-performance liquid chromatographic (HPLC) methods have been developed for the quantitative determination of spiro-(2-fluoro-9H-fluorene-9,4'-imidazolidine)-2',5'-dione (AL01567; 1) in plasma and urine, with an assay sensitivity of 0.25 micrograms/mL for plasma and 0.13 micrograms/mL for urine. The plasma assay procedure involved precipitation of proteins with acetonitrile followed by dilution with water. The diluted supernatant was analyzed on an ODS column eluting with acetonitrile:0.5% phosphoric acid (30:70) adjusted to pH 7.2 with concentrated ammonium hydroxide. The urine assay procedure involved extraction of 1 with 10% n-butanol in hexane, followed by back extraction with 0.05 M sodium hydroxide. The basic extract was neutralized and analyzed on a phenyl column eluting with acetonitrile:10 mM potassium phosphate (30:70; monobasic, pH 5.6). The pharmacokinetics of 1 was investigated in humans following single and multiple oral doses. The elimination half-life from 12 normal subjects following single 100-400-mg oral doses was independent of dose, and the overall mean half-life was 66 +/- 9 h. The overall mean oral clearance (assuming a bioavailability of 100%) was 11 +/- 3 mL/min, and the mean apparent volume of distribution was 59 +/- 13 L. The mean urinary recovery of intact drug during the first 24 h after dosing was 1.2 +/- 0.4% of the administered dose. During once daily 100-mg oral dosing of 1 to five subjects for 21 d, plasma concentrations of 1 reached apparent steady-state by 7 d.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bioavailability and mammary excretion of bisphenol a in Sprague-Dawley rats.

This study reports the absolute oral bioavailability and mammary excretion of bisphenol A in rats. The oral bioavailability was determined after administration of relatively low iv (0.1 mg/kg) and oral (10 mg/kg) doses of bisphenol A to rats. After iv injection, serum levels of bisphenol A declined biexponentially, with the mean initial distribution and terminal elimination half-lives being 6.1 +/- 1.3 min and 52.5 +/- 2.4 min, respectively. The systemic clearance (Cls) and the steady-state volume of distribution (Vss) averaged 107.9 +/- 28.7 m/min/kg and 5.6 +/- 2.4 L/kg, respectively. Upon oral administration, the maximum serum concentration (Cmax) and the time to reach the maximum concentration (Tmax) were 14.7 +/- 10.9 ng/ml and 0.2 +/- 0.2 h, respectively. The apparent terminal elimination half-life of bisphenol A (21.3 +/- 7.4 h) after oral administration was significantly longer than that after iv injection, indicating the flip-flop of the absorption and elimination rates. The absolute oral bioavailability of bisphenol A was low (5.3 +/- 2.1%). To determine the extent of mammary excretion, bisphenol A was given by simultaneous iv bolus injection plus infusion to steady state at low, medium, and high doses. The steady-state serum levels of bisphenol A were linearly increased with higher dosing rates. The systemic clearance (mean range, 119.2-154.1 ml/min/kg) remained unaltered over the dosing rate studied. The levels of bisphenol A in milk exceeded those in serum, with the steady-state milk to serum concentration ratio being 2.4-2.7.