Pharmacokinetics of fosfosal in rats and dogs

Fosfosal (Disdolen) is a non acetyl derivative of salicylic acid with antiinflammatory and analgesic properties and a greater tolerance than acetylsalicylic acid and lysine acetylsalicylate. In the present work the pharmacokinetics of fosfosal have been studied after oral and intravenous administrations of 100 and 80 mg/kg in rats and dogs, respectively. Plasma concentrations of fosfosal and salicylic acid were determined by an HPLC method. After intravenous administration fosfosal plasma levels decreased rapidly showing a half-life of 2.7 min in rats and 6.7 min in dogs. Fosfosal in plasma is quickly hydrolyzed into salicylic acid producing high concentrations in few minutes after administration. The half-life of salicylic acid was 13.8 and 7.1 h for rats and dogs, respectively. After oral administration only salicylic acid was detected in plasma, indicating that fosfosal, when orally administered, behaves as a prodrug. From the comparison of the AUC for salicylic acid obtained after oral and intravenous administrations it can be deduced that fosfosal it totally absorbed in the two species studied.     

Metabolic fate of the new Ca++-channel blocking agent (+)-(2S,3S)-3-acetoxy-8-chloro-(2-(dimethylamino)ethyl)-2,3-dihydro- 2-(4-methoxyphenyl)-2,5-benzothiazepin-4-(5H)-one maleate. Distribution, excretion and protein binding in rats and dogs

Distribution, excretion and protein binding of (+)-(2S,3S)-3-acetoxy-8-chloro-(2-(dimethylamino)ethyl)-2,3-dihydro- 2-(4-methoxyphenyl)-2,5-benzothiazepin-4-(5H)-one maleate (TA-3090) in rats and dogs were investigated after oral (30 mg/kg (rats), 2 mg/kg(dogs] and intravenous (3 mg/kg (rats), 0.2 mg/kg (dogs) administration of 14C-TA-3090. Plasma level of radioactivity in rats reached plateau (6.04 micrograms equiv. of TA-3090 free base/ml) 1 h after oral administration. The plateau level continued at least up to 6 h. The plasma concentration of the unchanged drug (free base) reached the maximum (425 ng/ml) at 45 min after oral administration, and then decreased with a half-life of 1.16 h. Plasma level of radioactivity after intravenous administration to rats rose gradually up to 1 h and thereafter it was kept constant for 6 h. Plasma concentration of the unchanged drug decreased with half-lives of 0.43 h (alpha phase) and 1.33 h (beta phase) after intravenous administration. In dogs, the peak level of plasma radioactivity after oral administration was 227 ng/ml at 1 h. The Cmax, Tmax and t1/2 of unchanged drug were 31 ng/ml, 1.34 h and 4.13 h, respectively. The plasma levels of total radioactivity and unchanged drug after intravenous administration to dogs were 146 and 142 ng/ml at 1 min, respectively. The t1/2 of the plasma radioactivity were 0.02 h (alpha) and 4.02 h (beta). Those of unchanged drug were 0.03 h (alpha) and 1.66 h (beta).(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of moxisylyte in healthy volunteers after intravenous and oral administration.

The concentration-time profiles of metabolites of moxisylyte, an alpha-blocking agent, in the plasma and urine of 12 healthy volunteers were investigated after intravenous (iv) and oral (two formulations) administration. The study was conducted with an open, randomized Latin squares design. Plasma and urine levels of moxisylyte and its biotransformation products were assayed by a specific HPLC method with fluorescence detection. Plasma levels declined in a monophasic or biphasic pattern depending on the subject. Two metabolites, conjugated desacetylmoxisylyte (DAM) and conjugated monodesmethylated DAM (MDAM), were found in plasma and urine. Unconjugated DAM was found in plasma only after iv administration. The apparent elimination half-lives of unconjugated DAM, conjugated DAM, and MDAM were 0.86, 1.7, and 3 h, respectively. The total amounts of metabolites (expressed as the equivalent of DAM) excreted in the urine were 75% after i.v. administration and 68 and 69% after oral administration of the two formulations. Oral absorption appeared to be complete for the two treatments. There was no statistical difference between the two oral formulations studied.     

Absorption, distribution and excretion of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate in rats, dogs and monkeys

Absorption, distribution and excretion of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) were studied in rats, dogs and monkeys after administration of [14C]-MN-1695. MN-1695 was found to be well absorbed from the small intestine after oral administration in all species examined. Plasma level of unchanged MN-1695 reached a maximum at 1 to 4 h after oral administration of [14C]-MN-1695 in rats, dogs and monkeys. The mean elimination half-life of unchanged MN-1695 from plasma was about 3, 4 and 50 h in rats, dogs and monkeys, respectively. Tissue levels of radioactivity after oral administration of [14C]-MN-1695 in rats indicated that [14C]-MN-1695 was distributed throughout the body and the radioactivity in tissues disappeared with a rate similar to that in plasma. A stomach autoradiogram after intravenous administration of [14C]-MN-1695 in the rat revealed the radioactivity localized in the gastric mucosa where MN-1695 was assumed to exert its pharmacological activity. In pregnant rats, [14C]-MN-1695 was distributed to the fetus with levels similar to maternal blood levels. After oral administration of [14C]-MN-1695 in rats, 39 to 46% of the dose was excreted into the urine and 50 to 63% of the dose into the feces, within 96 h. In dogs, about 40% of the dose was excreted into the urine and about 50% of the dose into the feces, within 6 days after oral administration. In monkeys, within 14 days after oral administration, about 60 and 30% of the dose were excreted into the urine and feces, respectively, and the main excretion route was the urine.(ABSTRACT TRUNCATED AT 250 WORDS)     

Time-dependent, plasma-sulfate-independent kinetics of salicylamide in dogs

The mechanisms of the dose-dependent elimination kinetics of salicylamide in dogs were examined. Salicylamide was infused continuously over three consecutive 90-min periods. The rates of infusion during Periods I and III were the same. During Period II the infusion rate was 2.5-fold higher. Plasma concentrations of inorganic sulfate were kept constant by the administration of exogenous sulfate. The plasma concentrations of salicylamide, which reached steady state during Period I but not during II or III, were twice as high at the end of Period III than those at the end of Period I. Typical Michaelis-Menten kinetics do not explain these results. When salicylamide was given as 40 mg/kg single oral dose, clearance of an intravenous tracer dose of radiolabeled salicylamide was greatly reduced within 10 min but returned to baseline values by 240 min after the oral dose, despite persistently low plasma concentrations of inorganic sulfate. Therefore, dose- and time-dependent factors other than Michaelis-Menten kinetics, depletion of inorganic sulfate concentrations, and rate limitation of supply of "active sulfate" from plasma inorganic sulfate stores produce the dose- and time-dependent kinetics of salicylamide in the dog. Product inhibition of salicylamide sulfoconjugation remains a possible explanation.     

Effect of the renin response during renin inhibition: oral Ro 42-5892 in normal humans.

The effect of the new renin inhibitor Ro 42-5892 was evaluated in healthy volunteers after both intravenous and oral administration. In a preliminary study, 14 subjects received a 10-min infusion of Ro 42-5892 at doses ranging from 0.001 to 1 mg/kg. Plasma renin activity (PRA) and angiotensin (Ang) II levels were maximally suppressed in a dose-dependent manner at the end of the infusion. Plasma active renin concentration increased up to threefold. In a second study, 24 volunteers received placebo or 100, 600, or 1,200 mg of Ro 42-5892 p.o. in a single-blind, randomized fashion. Within 30 min after drug intake, PRA and plasma Ang I and Ang II levels fell to their nadir. Both Ang I and Ang II were measured specifically after extraction on phenylsilylsilica and separation by isocratic HPLC. The degree as well as the duration of inhibition were dose related. The decrease in plasma Ang lasted maximally for 2 h. Active renin increased dose dependently and remained elevated for more than 8 h after the 1,200 mg dose. A theoretical generation rate of Ang I was calculated for individual plasma samples assuming Michaelis-Menten kinetics for competitive inhibition and steady-state conditions. This calculated Ang I generation rate, based on plasma active renin concentrations and drug levels, closely correlated with actually measured Ang I and Ang II levels (r = 0.90, n = 88) over the whole 8 h time period. Thus, a sustained renin inhibition by Ro 42-5892, as indicated by increased plasma active renin levels, induces a much shorter fall in plasma Ang I and II apparently because of a rise in renin secretion.     

Plasma profiles of lycopene after single oral and intravenous administrations in dogs

The objectives of this study were to identify the factors limiting the absorption of purified lycopene after oral administration, and to comparatively assess plasma data sets after single oral and intravenous administrations in dogs to define the conditions for performing an absolute bioavailability study. Solubility of purified lycopene (all-trans, 93.5%) was determined in media simulating the conditions in the fasted and in the fed upper gastrointestinal lumen. After evaluating the plasma levels achieved following single administrations of purified lycopene powder to fasted and fed dogs at escalating doses (75-750 mg), a crossover study was performed in four fed female mongrel dogs at two phases. In phase I, one soft gelatine capsule (10 mg lycopene) with 500 mL milk was administered orally. In phase II, 500 mL milk was administered orally and 250 mL 5% dextrose containing 5 mg lycopene in the form of a binary system with hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) was administered intravenously over 3.5 h. In-vitro and preliminary canine studies confirmed that, after oral administration of lycopene in solid form, arrival of lycopene into the systemic circulation was limited by lymphatic transport and, in addition, if the administered dose was higher than approximately 2 mg, by intralumenal solubility. During the first 50 h after single administrations to fed dogs, lycopene plasma levels were lower after intravenous than after oral administration. This could have been related to capacity limited elimination of lycopene and/or route-dependent disposition kinetics. Estimation of the amount of lycopene reaching the systemic circulation after oral and after intravenous administration requires separate estimations of total body clearance of lycopene.     

Metabolism and pharmacokinetics of cinobufagin

1. The metabolic fate of cinobufagin, a major component of the cardiotonic Senso, has been studied after i.v. administration to rats. Two metabolites were detected in rat serum and shown by n.m.r. and mass spectroscopy to be desacetylcinobufagin (I) and 3-epidesacetylcinobufagin (II). 2. Inhibitory activities of I and II on guinea-pig heart Na+/K+-ATPase were less than that of cinobufagin. 3. Serum or plasma levels of cinobufagin, I and II in rats, cats and dogs were determined by h.p.l.c. after i.v. and/or oral administration of cinobufagin. After i.v. administration, cinobufagin, I and II appeared in rat serum, but in dog and cat plasma only unchanged cinobufagin was present. After oral administration, only II was detected in rat serum, but neither cinobufagin nor either of its metabolites (I and II) were found in cat and dog serum.     

Studies of metabolic pathways of trimebutine by simultaneous administration of trimebutine and its deuterium-labeled metabolite

Trimebutine maleate (I), (+-)-2-dimethylamino-2-phenylbutyl 3,4,5-trimethoxybenzoate hydrogen maleate, and a deuterium-labeled sample of its hydrolyzed metabolite, 2-dimethylamino-2-phenylbutanol-d3 (II-d3), were simultaneously administered to experimental animals at an oral dose of 10 or 50 mumol/kg, and distribution ratios of the two alternative initial metabolic steps, i.e., ester hydrolysis and N-demethylation, were estimated by determining the composition of the urinary alcohol-moiety metabolites, II, and its mono- and di-demethylated metabolites, III and IV, by GC/MS. In dogs, the order of quantities of the metabolites from II-d3 was II much greater than III much greater than IV, showing predominance of conjugation over N-demethylation. However, this order was reversed when the amounts of the metabolites from I were compared, indicating that I was preferentially metabolized by N-demethylation followed by ester hydrolysis and conjugation in this order. In rats, a considerable proportion of I was presumed to be metabolized by ester hydrolysis before N-demethylation. In in vitro experiments employing the liver microsomes and homogenates of liver and small intestine from rats and dogs, it was found that both ester-hydrolizing and N-demethylating activities were higher in rats than in dogs, and the conjugating activity was higher in dogs than in rats. It was also found that I, having a high lipophilicity, was more susceptible to N-demethylation than less lipophilic II. These results from the in vitro experiments could account for the species differences in the distribution ratio of the metabolic pathways of I in vivo.     

Effect of itraconazole on the pharmacokinetics of diclofenac in beagle dogs

The objective of this study was to investigate the potential effect of itraconazole on the pharmacokinetics of diclofenac potassium in beagle dogs after oral coadministration. Five male beagle dogs received a single oral 50 mg dose of diclofenac potassium alone in phase I, and along with a single oral 100 mg dose of itraconazole in phase II. Blood samples obtained for 8.0 hours post dose were analysed for diclofenac concentration using a validated high performance liquid chromatography (HPLC) assay method. The area under plasma concentration-time curve (AUC(0aa)), maximum plasma concentration (C(max)), time to reach C(max) (T(max)) and elimination half-life (t(1/2)), were calculated for diclofenac before and after itraconazole administration. The coadministration of itraconazole with diclofenac potassium has resulted in a significant reduction in AUC(0aa) and C(max) of diclofenac, which was about 31 and 42%; respectively. No statistically significant differences were observed for T(max) and t(1/2) of diclofenac between the two phases. Therefore, it could be concluded that oral coadministration of itraconazole may have the potential to affect the absorption of diclofenac as indicated by the significant reduction in its AUC and C(max) in beagle dogs.     

Bioavailability and pharmacokinetics of S-propargyl-L-cysteine, a novel cardioprotective agent, after single and multiple doses in Beagle dogs

As a novel hydrogen sulfide-modulated agent, S-propargyl-L-cysteine (SPRC) is proven to be a potent cardioprotective candidate. Bioavailability and pharmacokinetics of SPRC (20?mg/kg) in beagle dogs after oral and intravenous administrations were investigated in this study. Plasma concentrations of SPRC were measured by a LC-MS/MS method. Intravenous administration of SPRC (single dose) to beagle dogs gave a mean plasma half-life of 14.7?h, mean clearance of 0.4?ml min?1 kg?1 and mean apparent volume of distribution of 0.56?L/kg. Single oral administration was completely, fast absorbed (T(max)= 0.33?±?0.20?h) with a mean absolute availability of 112% and mean plasma half-life of 16.5?h. Multiple oral administration (once daily for 10 consecutive days) of SPRC to dogs resulted in steady state plasma drug concentration being reached after seven doses and didn't cause obvious accumulation. No significant difference was found between the single and multiple pharmacokinetic parameters.     

GLC determination of plasma drug levels after oral administration of clorazepate potassium salts.

Plasma nordiazepam levels resulting from the oral administration of clorazepate potassium salts were determined by a sensitive GLC assay. Nordiazepam and the internal standard (diazepam) were selectively extracted into ether at pH 9.2, hydrolyzed to their respective benzophenones, and quantified by electron-capture detection. The assay was used in a comparative bioavailability study of single equimolar oral doses of monopotassium and dipotassium salts of clorazepate in dogs. Both clorazepate salts were rapidly absorbed and exhibited mean peak total drug levels after 1 hr. Clorazepate levels accounted for about 50% of the total drug levels present. No statistical difference in the plasma drug levels of clorazepate mono- and dipotassium salts and the metabolite was found in dogs.     

The pharmacokinetics of pranoprofen in humans

The pharmacokinetics of pranoprofen, 2-(5H-[1]benzopyrano[2,3-b]pyridin-7-yl) propionic acid (I) in humans were examined. 1-O-Acylglucuronide of I (II) and its isomer (III) were isolated from the human urine after oral administration of I. The stability of II was tested in order to establish the suitable conditions for the storage and handling of biological samples. Maximum stability of II was found at pH 3-4. Unchanged drugs, II and III were detected in the human plasma after oral administration of I. Plasma concentrations of these compounds reached the maximum at 1-2 h after the administration and thereafter decreased biphasically. From the urinary sample, 1-O-acylglucoside of I (IV) was detected in addition to unchanged drugs, II and III. Within 24 h after dosing, 1.3, 84.0, 7.0 and 0.6% of the dose were excreted as I, II, III and IV, respectively and the total urinary excretion amounted to 92.9% in term of unchanged drug.     

Pharmacokinetic study of intravenous and oral idarubicin in cancer patients

Idarubicin (4-demethoxydaunorubicin) is a new anthracycline analogue which lacks the methoxyl group at the C-4 position of the aglycone moiety. The present study was undertaken to investigate the pharmacokinetics and bioavailability of idarubicin in man. The drug was administered at 3-week intervals to six patients by both intravenous and oral routes. Doses used were 13-15 mg/m2 intravenous and 45 mg/m2 p.o. Plasma levels of unchanged idarubicin and of its metabolite idarubicinal were assayed by high performance liquid chromatography (HPLC). After intravenous administration the plasma levels of the unchanged drug declined very rapidly reaching the sensitivity limits of the analytical method (1-2 ng/ml) 24 h after dosing. Plasma levels of idarubicinal reached a peak of about 10 ng/ml within two hours then decreased very slowly with a plasma t1/2 of about 2.5 days. After the oral dose of 45 mg/m2, the plasma level patterns of both parent compound and the idarubicinal were roughly similar to those after 15 mg/m2 intravenous except for the obvious difference linked to the absorption of idarubicin. The absorption of oral idarubicin was rapid and, in terms of area under curve of the metabolite, the availability after oral administration can be estimated as about 30% of the dose. The urine findings reflected the plasma situation. The metabolite levels were much higher and longer lasting than those of the parent compound. Urinary recovery after intravenous (16% of the dose in four days) and oral administration (approximately 5% of the dose) confirmed the 30% absorption estimated on the basis of plasma levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Single and multiple dose pharmacokinetics of sultosilic acid in humans

Single and multiple oral doses of Sultosilic acid were administered to four healthy volunteers. Plasma and Urine levels of unchanged Sultosilic acid (I) and its major metabolite (II) were measured. I and II were extracted from plasma and urine with chloroform after ion-pair formation and analysed by HPLC using a U.V. detector. Sultosilic acid was well absorbed and the plasma concentrations declined bioexponentially with mean half-lives of 1.9 h (fast disappearance phase, alpha) and 17.6 h (slow disappearance phase, beta) for I and 2.0 h (alpha) and 17.0 h (beta) for II. Renal clearances of I and II were 50.5 ml/min and 74.8 ml/min respectively. 60% of the administered dose was excreted in urine, 28% unchanged (I), the remainder as carboxylic derivative (II). Minimal drug concentrations in plasma in the range of those detected in steady state conditions were already found within the first day of treatment.     

A single and multiple dose pharmacokinetic and metabolism study of meclofenamate sodium

A single and multiple oral dose administration study of meclofenamate sodium (Meclomen) was conducted in ten healthy male volunteers. An initial 300 mg oral dose on day 1 was followed by a 100 mg every 8 h dosage regimen on study days 4 through 18. Intensive plasma and urine sample collection was carried out over the first three study days, and for 120 h following administration of the final dose on day 18. Plasma and urine specimens were analyzed by a specific HPLC assay for unconjugated meclofenamic acid and metabolites I and II of meclofenamic acid before and after sample incubation with beta-glucuronidase. Meclofenamic acid was rapidly absorbed following oral dose administration. Concentrations of meclofenamic acid existed primarily as unconjugated drug in plasma, with only a small amount present in the conjugated form. Meclofenamic acid was rapidly eliminated, with an elimination half-life of approximately 1.3 h. This resulted in no detectable accumulation upon multiple dose administration. Metabolite I, which is one-fifth as active as meclofenamic acid in in vitro inhibition of cyclooxygenase, was present in unconjugated form at steady state in concentrations approximately 50 per cent of those of meclofenamic acid, as unconjugated drug. The majority of metabolite I in plasma existed as glucuronide conjugate. Metabolite II, which is inactive, was present in very significant concentrations in unconjugated form. Plasma protein binding determinations conducted on meclofenamic acid and metabolite I indicated that the free fraction of metabolite I was 8.7 to 10.9 times higher than that of meclofenamic acid. When the lower activity and lower steady state concentrations, but higher free fraction, are considered, it would appear that metabolite I may contribute significantly to the in vivo inhibition of cyclooxygenase activity seen after administration of meclofenamic acid.     

The objective and timing of drug disposition studies, appendix II. Plasma concentrations of oxyphenbutazone in dogs given oxyphenbutazone or the calcium or sodium salts of its phosphate ester.

Plasma levels of oxyphenbutazone were measured in beagle dogs following oral administration of oxyphenbutazone and salts of oxyphenbutazone phosphate. Dosage with sodium and calcium salts of oxyphenbutazone phosphate produced higher oxyphenbutazone plasma levels than dosage with oxyphenbutazone itself. Oxyphenbutazone phosphate was not detected in plasma following oral dosing with salts of oxyphenbutazone phosphate but was found in plasma following intramuscular administration of oxyphenbutazone phosphate sodium salt. A metabolite, oxyphenbutazone glucuronide, was found in plasma of dogs following administration of either oxyphenbutazone or salts of oxyphenbutazone phosphate.     

Pharmacokinetics of D(+)-usnic acid in rabbits after intravenous and oral administration.

The pharmacokinetics of D(+)-usnic acid--a lichen antitubercular, antitumor, and enzyme-inhibiting agent--was studied in rabbits following intravenous or oral administration of 5 and 20 mg/kg body weight doses, respectively. Plasma samples were collected at different time intervals, and usnic acid was determined by HPLC. Plasma usnic acid levels following intravenous administration showed a triexponential elimination with a mean +/- SD terminal half-life of 10.7 +/- 4.6 hr. The volume of distribution of the central compartment and systemic clearance were 43.9 +/- 21.3 ml/kg and 12.2 +/- 3.0 ml/hr/kg, respectively. Pharmacokinetic parameters obtained, based on compartmental and noncompartmental approaches, were comparable. Plasma concentration data obtained after oral administration were analyzed using a noncompartmental method. Peak plasma level (Cmax) of 32.5 +/- 6.8 micrograms/ml was achieved in 12.2 +/- 3.8 hr (tmax). Mean absolute bioavailability of usnic acid following oral administration was 77.8%.     

Metabolic disposition of 6-ethyl-3-(1H-tetrazol-5-yl)-chromone, a new antiallergic agent, in the rat, guinea-pig, rabbit, dog and monkey.

1. [14C]Ethyltetrazolylchromone ([14C]ETC) was promptly absorbed from the rat small intestine by the portal route. 2. The maximum plasma concn. of unchanged drug after oral administration (10 mg/kg) was highest in dogs (456 microgram/ml), followed by monkeys (287 microgram/ml), guinea-pigs (146 microgram/ml) and rats (55 microgram/ml), and lowest in rabbits (09 microgram/ml). The half-life of the drug in plasma varied with the species, ranging from 13 to 133 h. The drug was highly bound to plasma protein. In dogs and rats, the plasma 14C was predominantly the unchanged drug, whereas in guinea-pigs, rabbits and monkeys it was mainly metabolites. 3. At 10 min after oral administration of the drug to rats there was a wide distribution of the 14C in the tissues. At this time, the 14C concn. were the highest in stomach, followed by kidney, liver, plasma, heart and lung, and lowest in brain. 4. Almost all administered 14C was eliminated from the body in 72 h. The major route of excretion was via the urine except with guinea-pigs, in which animal the 14C was almost equally divided between urine and faeces. 5. only trace amounts of the unchanged drug were found in urine and bile. The major urinary metabolites were as follows: I (1-hydroxyethyl ETC), II (acetyl ETC), III (IIIa, 2-hydroxyethyl ETC) and IV (1,2-dihydroxyethyl ETC) in rats, I and VI (5-carboxymethylsalicylic acid) in guinea-pigs, I, III (IIIb, carboxymethyl ETC) and VII (ETC-N-1-glucuronide) in rabbits, I and VII in dogs, and I and IV in monkeys.     

Metabolism of thymoxamine. I. Studies with 14C-thymoxamine in rats

Thymoxamine is rapidly and completely absorbed in rats. It is a prodrug which does not enter the systemic circulation in its unchanged form. After either oral or intravenous administration it undergoes rapid and intense metabolism involving four biotransformation reactions: Enzymatic hydrolysis to the corresponding phenol (metabolite I), Monodemethylation to metabolite II, Sulfate conjugation of I and II (metabolites III and IV) and Conjugation of I and II with glucuronic acid (metabolites V and VI). With these 6 metabolites identified approximately 95% of the radioactivity can be accounted for in plasma, urine and bile. Whereas the systemic availability of I and II is low, III and IV show high bioavailability. Metabolites I to IV are pharmacologically active, while III and IV are less potent than I and II. The radioactivity distribution in tissues is different after oral and intravenous administration consistent with the higher portion of unconjugated metabolites in the body after administration by parenteral route. Although 60% of the labelled compounds is eliminated via bile, the radioactive compounds are almost completely excreted in the urine after both routes of administration. This demonstrates complete reabsorption of the biliary metabolites. Secondary peaks of radioactivity in plasma and organs at 4 hours are explained by the participation of the metabolites in the enterohepatic circulation.