The pharmacokinetics of vedaprofen and its enantiomers in dogs after single and multiple dosing

Vedaprofen is a chiral nonsteroidal anti-inflammatory drug that has been developed as a gel formulation for oral administration to dogs and horses. The pharmacokinetics of vedaprofen and its enantiomers were studied in beagle dogs after single (intravenous solution and oral gel) and multiple (oral gel) dosing at a dosage of 0.5 mg/kg body weight. Plasma concentrations of vedaprofen and its enantiomers were analysed by HPLC. The plasma protein binding of vedaprofen was studied by ultrafiltration. The absorption of vedaprofen was rapid (tmax 0.63 +/- 0.14 h) and almost complete after oral administration (bioavailability 86 +/- 7%). The terminal half-lives after intravenous and oral administration, 16.8 +/- 2.2 and 12.7 +/- 1.7 h respectively, were of the same order of magnitude. Enantioselective analysis showed that the R(-) enantiomer predominated in plasma. The change in the plasma time course of the plasma R(-)/S(+) enantiomer concentration ratio over time was similar after single intravenous and oral dosing, with R(-)/S(+) ratios in the AUC of 1.7 +/- 0.5 and 1.9 +/- 0.2 respectively. Plasma protein binding of vedaprofen and its enantiomers was high (> 99.5%). Vedaprofen is absorbed rapidly from the gastrointestinal tract, has a high bioavailability and does not accumulate in plasma in dogs following repeated oral administration.

Aspects of pharmacodynamics and biotransformation of the glucocorticoid resocortol butyrate

Aspects of the biotransformation and pharmacodynamics of the novel glucocorticoid resocortol butyrate (RCB) and its metabolites were assessed in vitro and in vivo in comparison with selected reference compounds. The main route of biotransformation of ((3)H)-RCB in the skin and the liver was 5alpha-reduction of the A-ring followed by reduction of the 3-carbonyl group. In the liver, metabolism was much more rapid than in the skin and 5beta-reduction also occurred. RCB had a relative binding affinity for the glucocorticoid receptor similar to that of triamcinolone acetonide, about 1.5 times that of dexamethasone, three times that of betamethasone valerate (BMV) and 10-14 times that of cortisol. The metabolites of RCB displayed only low to very low affinities for the receptor. The suppression of the hypothalamic-pituitary-adrenal axis was investigated in placebo- and positive-controlled studies in dogs by measurement of basal and corticotrophin-releasing hormone (CRH) stimulated plasma cortisol concentrations. The AUC of the plasma cortisol vs. time curve following CRH stimulation, a measure of adrenal suppression, was reduced significantly after topical application of BMV compared with the pretreatment values. The AUC in the RCB group was not reduced significantly. Adrenocorticotrophic hormone concentrations were not affected. Oral administration of RCB did not suppress adrenocortical function, whereas BMV induced almost complete suppression of basal and CRH-induced cortisol concentrations. The pharmacodynamics of RCB makes it a relatively safe glucocorticosteroid for topical application.

Pharmacokinetics of oestriol after repeated oral administration to dogs

The aim of the present study was to investigate the pharmacokinetics of oestriol in plasma in the dog after repeated oral administration of oestriol tablets, a preparation intended for the treatment of urinary incontinence in the bitch. The study was performed in six healthy, entire, adult female beagle dogs. The bitches were treated once daily with two tablets, containing 1 mg oestriol per tablet, for seven consecutive days (days 1-7). Blood samples were taken from the jugular vein before treatment, frequently on days 1, 3 and 7 of the treatment period and daily just before (C(trough)) and 1 h after dosing (C(t=1h)). During the washout period samples were taken at a 24 h interval up to four days post-treatment. Oestriol concentrations were determined in plasma by radioimmunoassay. Pharmacokinetic parameters, AUC, C(max) and t(max), were determined from the plasma concentration-time curves using non-compartmental methods. The between animal variation in C(max) and the AUC was high. Individual values of the C(max) varied from 206 pg/ml (day 1) to 1128 pg/ml (day 7) and the AUC(0-24h) from 789 pg x h/ml (day 1) to 5718 pg x h/ml (day 7). t(max) occurred within 1 h. The mean C(trough) value was slightly above the pre-treatment level ( 38+/-2 pg/ml vs. 18+/-5 pg/ml). Within 48 h after the last treatment the concentrations had returned to the pre-treatment values. C(max) and C(trough) did not increase during the treatment period, indicating that no accumulation occurred. A shoulder in the concentration-time curve around 8-12 h after treatment strongly suggested the existence of enterohepatic recirculation (EHR). The average relative contribution of the EHR to the AUC(0-24h) was estimated to be 22%, 38% and 44% on days 1, 3 and 7, respectively. These mean values were calculated from five animals per time point, because one dog failed to show EHR on days 1 and 3 and was therefore excluded from the calculations.

A pharmacodynamic and pharmacokinetic study with vedaprofen in an equine model of acute nonimmune inflammation

The pharmacodynamics and enantioselective pharmacokinetics of vedaprofen were studied in six ponies in a two period cross-over study, in which a mild acute inflammatory reaction was induced by carrageenan soaked sponges implanted subcutaneously in the neck. Vedaprofen, administered intravenously at a dosage of 1 mg/kg, produced significant and prolonged inhibition of ex vivo serum thromboxane B2 (TXB2) synthesis and short-lived inhibition of exudate prostaglandin E2 (PGE2) and TXB2 synthesis. Vedaprofen also partially inhibited oedematous swelling and leucocyte infiltration into exudate. Vedaprofen displayed enantioselective pharmacokinetics, plasma concentrations of the R(-) enantiomer exceeding those of S(+) vedaprofen. The plasma concentration ratio, R:S, increased from 69:31 at 5 min to 96:4 at 3 h and plasma mean AUC values were 7524 and 1639 ng x h/mL, respectively. Volume of distribution was greater for S(+) vedaprofen, whilst elimination half-life (t(1/2beta)) and mean residence time were greater for R(-) vedaprofen. The penetration of vedaprofen into inflammatory exudate was also enantioselective. For R(-) and S(+) vedaprofen maximum concentration (Cmax) values were 2950 and 1534 ng/mL, respectively, and corresponding AUC values were 9755 and 4400 ng x h/mL. Vedaprofen was highly protein bound (greater than 99%) in both plasma and exudate. The significance of these data for the therapeutic use of vedaprofen is discussed.

Effects of long-term administration of pituitary-derived bovine growth hormone and estradiol on growth in steers

Sixty-three Friesian steers (9 mo old, 257 kg; n = 15 or 16/treatment) were employed in a 2 x 2 factorial to test bovine growth hormone (bGH) and estradiol (Compudose implant). Steers received daily subcutaneous injections of vehicle or bGH (40 micrograms/kg body weight) for 22 wk. Steers were slaughtered 8 wk after the end of bGH treatment (wk 30). Steers had ad libitum access to silage plus a fixed amount (4 to 5.5 kg/d) of concentrate. Average daily gain (ADG) and feed conversion efficiency (FCE) improved (P less than .05) in response both to bGH and to estradiol during wk 0 to 22. Although bGH did not affect ADG or FCE during wk 23 to 30, estradiol improved (P less than .05) them; bGH and estradiol appeared additive (nonsignificant interactions) during wk 0 to 22. At slaughter, estradiol increased (P less than .05) carcass weight and carcass and leg length while decreasing (P less than .05) conformation score and percentage of kidney, knob and channel fat (KHP); bGH decreased (P less than .05) KHP. Although both bGH and estradiol increased (P less than .01) plasma GH, their effects were not additive. Both bGH and estradiol increased (P less than .01) plasma somatomedin-C and decreased (P less than .01) plasma urea nitrogen concentrations; effects were additive. Estradiol, but not bGH, increased (P less than .05) plasma glucose, whereas neither bGH nor estradiol altered plasma creatinine and nonesterified fatty acids. In summary, both bGH and estradiol improved growth and FCE, and their effects appeared to be additive. It is likely that some of their effects were mediated by somatomedin-C.

Effect of different growth hormone-releasing factors on the concentrations of growth hormone, insulin and metabolites in the plasma of sheep maintained in positive and negative energy balance

Three experiments were conducted to compare the ability of different preparations of growth hormone-releasing factor (GRF) to stimulate GH secretion in sheep maintained in positive and negative energy balance. In experiment 1 five sheep were injected (i.v.) with three preparations of human pancreatic GRF (hpGRF-44, hpGRF-40, hpGRF-29-NH2) and one preparation of rat hypothalamic GRF (rhGRF-29-NH2) all at 98.0 pmol/kg, or control vehicle, in a Latin square design when the animals either had free access to food or were fed half their maintenance requirements. Analysis of plasma samples, obtained before and for 150 min after injection, revealed that the reduced food intake resulted in the expected changes in body weight and circulating GH, insulin, glucose, urea and non-esterified fatty acids. The maximum post-injection concentrations of GH did not differ between either the two levels of feeding or the four GRF preparations but the mean post-injection concentration of GH was significantly higher for all GRF treatments on the restricted ration (P less than 0.001). The mean post-injection response to rhGRF-29-NH2 was less than that obtained with hpGRF-44 for sheep with food available ad libitum (P less than 0.05) and was clearly more persistent for all GRF treatments in animals fed the reduced diet (P less than 0.001). In experiment 2 the same five sheep were injected i.v. with rhGRF-29-NH2 (98.0 pmol/kg) when they had free access to food and after food had been withdrawn for 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of hyperprolactinemia on the accessory sexual organs of the male rat

The growth-promoting effect of prolactin on the ventral prostate lobe, the anterior prostate lobe (or coagulating gland), and seminal vesicles has been studied before, during and after puberty in rats up to 5 months of age. Pituitaries from female rats were grafted under the renal capsule of 23-26-day-old male rats. Within 1/2 month substantial (five- to ten-fold) hyperprolactinemia occurred followed by a gradual decline; levels were still high 4 months after grafting. A statistically significant increase in the weight of the seminal vesicles and the ventral and anterior prostate lobes was observed 1 month after implantation. This effect was only maintained for the seminal vesicles during the next 3 months. Hyperprolactinemia did not influence testosterone metabolism. In the ventral prostate lobe, 1 month after grafting, the nuclear androgen receptor content increased, whereas the cytosolic androgen receptor content decreased. These results suggest that the growth-promoting effect of prolactin, on the ventral prostate lobe of the rat, is brought about by an increased translocation of the androgen receptor.

Effect of long-term hyperprolactinemia on the prolactin receptor content of the rat ventral prostate

The rat ventral prostate contains prolactin receptors, and during sexual maturation prolactin stimulates the growth of this gland. The aim of the present investigation was to evaluate whether prolactin is involved in the regulation of the number of its own receptor sites in the rat ventral prostate. To this end, the content of prolactin receptors was estimated in prostate membranes of control and chronically hyperprolactinemic rats both before and after in vitro desaturation with 4 M MgCl2. Hyperprolactinemia resulted in a 40% increase in the number of available prolactin receptors (P less than 0.05). In vitro desaturation of receptors resulted in loss of 84% of protein and 36 +/- 6% and 52 +/- 6% of prolactin receptors from ventral prostate membranes of control and hyperprolactinemic rats respectively (P less than 0.05). We have concluded that the rat ventral prostate membranes are not suited to in vitro desaturation of prolactin receptors with MgCl2. From the increase in the number of available prolactin receptors after hyperprolactinemia we have concluded that prolactin is involved in the regulation of the number of its own receptors in the rat ventral prostate.

Endocrinological studies with (7 alpha, 17 alpha)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-yn-3-one (Org OD 14)

A novel steroid, (7 alpha, 17 alpha)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-yn-3-one (Org OD 14), is described which has concomitant weak estrogenic, progestational and androgenic activities. This hormonal profile was demonstrated using various endocrinological tests and the results were evaluated in terms of well-known reference compounds. It has been well established that combinations of estrogens, androgens and progestagens exert positive or synergistic effects on certain target organs, e.g. the hypothalamic-pituitary axis, and antagonistic or complementary effects on others, e.g. on the endometrium. Org OD 14 with estrogenic, androgenic and progestational activities can therefore be expected to induce complex effects on various target organs. This explains the observed effects of the compound on hypothalamic-pituitary axis, bone-loss, endometrium and sexual behaviour.

Comparison of the metabolism of testosterone undecanoate and testosterone in the gastrointestinal wall of the rat in vitro and in vivo

The metabolism of testosterone undecanoate (TU) and testosterone (T) is studied in the gastrointestinal wall of the rat in vitro. A comparison is made with the in vivo metabolism of these compounds in the rat. The major metabolite first appearing during incubation of TU with the small intestine is T. Incubation of TU or T with the small intestine reveals a great similarity between the metabolite patterns obtained. This is also the case with the patterns derived from portal vein plasma upon oral administration of TU and T. Incubation of different parts of the gastrointestinal tract with TU or T shows that the greatest metabolic activity is located in the wall of the small intestine. Unlike T, TU is metabolized only to a small extent in the wall of the stomach and the large intestine.

Lymphatic absorption and metabolism of orally administered testosterone undecanoate in man

[3H]-testosterone undecanoate ([3H]TU) was administered orally to 4 patients with a thoracic duct catheter after neck dissection surgery. Appearance of radioactivity in lymph, plasma and urine was measured at different times. Metabolites of TU in these fluids were investigated. Peak levels of radioactivity appeared simultaneously in lymph and plasma (2.5-5 h after administration) while the excretion in urine was highest approximately 2 h after the plasma and lymph peak. The main compounds appearing in the lymph were TU and 5alpha-dihydrotestosterone undecanoate (5alpha-DHTU), but 5beta-DHTU could not be detected. In plasma almost all metabolites were probably conjugated. During the first 24 h approximately 40% of the administered radioactivity was excreted in the urine. The total amount of radioactivity excreted in the urine during the first week was 45-48%. The predominant urinary metabolites were testosterone- and androsterone-glucuronide. The results indicate that TU is metabolized partly in the intestinal wall. The remaining TU and newly-formed 5alpha-DHTU, at least partly, are absorbed via the lymphatic system.

Testosterone undecanoate: a new orally active androgen

Oral testosterone undecanoate (TU) in arachis oil has been evaluated with a view to its possible use as a means of androgen replacement therapy. A single 100 mg dose was found to elevate plasma androgen levels and urinary 17-ketosteroid excretion in 6 normal men. Ninety mg/day and 60 mg/day doses taken by a hypogonadal man resulted in sustained levels of androgen which appeared physiological when measured by radioimmunoassay without chromatography. However, upon separation of the steroids by chromatography it was found that much of the androgen present was in fact dihydrotestosterone not testosterone. Both TU and dihydrotestosterone undecanoate were detected in plasma by gas chromatography and it is suggested that the ester is absorbed as such from the intestine and the unesterified steroid subsequently released by hydrolysis. The convenience of oral administration, the resulting prolonged elevated plasma androgen levels and the probable lack of deleterious effects on the liver may render oral TU of value where androgen replacement therapy is indicated.

The pharmacology and metabolism of testosterone undecanoate (TU), a new orally active androgen

Testosterone undecanoate (TU), either dissolved in arachis oil or as micro-crystal suspension, displays androgenic activity on oral administration to rats in the Hershberger test. The solution in arachis oil is more active than the crystal suspension. When [3H]TU is administered orally to rats, most of it is metabolized in the intestinal wall. The majority of the metabolites probably lose their undecanoate group and are absorbed via the portal vein. The non-metabolized [3H]TU and at least two metabolites are absorbed exclusively via the lymphatic system. One of these metabolites has been identified as 5alpha-dihydrotestosterone undecanoate (5alpha-DHTU). TU has no harmful effects on the liver of the rabbits on oral administration.

Plasma androgen levels in men after oral administration of testosterone or testosterone undecanoate

Plasma testosterone and androstenedione levels in men were measured after oral administration of free testosterone and testosterone undecanoate. Both androgens were determined by simultaneous, specific radioimmunoassays after separation and isolation by thin layer chromatography. While free unesterified testosterone had no effect on plasma androgen levels, a striking increase of both testosterone and androstenedione levels was noted after administration of testosterone undecanoate, which is otherwise only achieved by parenteral testosterone application. This effect of testosterone undecanoate is probably due to absorption via the lymph rather than via the portal vessels so that peripheral circulation is reached before metabolism in the liver. Testosterone undecanoate promises to be an effective medication for oral androgen replacement.

Metabolites of lynestrenol acetate in the bile of rats after intravenous administration; a comparison with lynestrenol

Some aspects of the metabolism of lynestrenol acetate, an orally active contraceptive compound, were studied in female rats. Lynestrenol acetate is stable in gastric and intestinal juice in vitro. After intravenous administration of lynestrenol acetate and lynestrenol with a -14C label in the nucleus approximately 40% of the administered radioactivity was excreted in the bile within 90 min. After administration of lynestrenol acetate labelled in the ester group, 6% of the radioactivity was found in the bile. This means that the greater part of the lynestrenol acetate had lost its acetate group during the process of metabolism. There was an important difference between the autoradiograms of the thin layer patterns of post-hydrolysis extracts after administration of [4-14C]lynestrenol acetate and those after administration of [1'-14C]lynestrenol acetate and [4-14C]lynestrenol: the major metabolite of [4-14C]lynestrenol acetate did not appear on the autoradiograms of [1'--14C]lynestrenol acetate and [4-14C]lynestrenol. This indicates that lynestrenol acetate was altered in the nucleus in the presence of the acetate group. The acetate group itself was removed, either when the alterations took place, or after it had been completed. The results of IR, NMR and mass spectrometry analysis indicate the introduction of a 15alpha hydroxyl group. Results of gas-liquid chromatography and thin layer chromatography indicate that a second important metabolic is 19-nor-17alpha-pregn-20-yne-3alpha, 17beta-diol. The main conclusions are: 1. A part of the lynestrenol acetate is metabolized and excreted in the bile, the acetate group still being present. 2. Lynestrenol acetate is to some extent metabolized via another pathway than lynestrenol. This indicates that esterification of a steroid can lead to deviation from the metabolic pathway of the free original steroid.

Comparative studies on the binding of 131 I-labelled and unlabelled insulin to rat diaphragm in vitro

Rat hemidiaphragms were incubated with either unlabelled or 131I and 127I-labelled insulin of varying degrees of iodination (0.08–1.4 I/mole). With all types of insulin the percentage disappearance of immunoreactive insulin (IRI) was found to exceed the percentage uptake of radioactive label by the tissue by a factor of 10. This discrepancy is attributed to degradation of labelled hormone taken up by the tissue, degradation of the hormone within the medium and reduced tissue-binding of iodinated insulin molecules.

Even after incubation for 15 min, fixation of labelled insulin to the diaphragm appeared to coincide with a return-flow of TCA-soluble labelled fragments into the medium. Washing of the diaphragm for 10 min resulted in a 30% loss of tissue-bound radioactivity. After incubation with unlabelled insulin less than 1% of the tissue-bound IRI could be recovered in the washing medium.

After correction for IRI degradation within the medium, the binding of iodo-insulin 1.4 I/mole to the diaphragm amounted to 56% of that of the unlabelled insulin. Since the biological activity at this degree of iodination appeared to be reduced by over 50% of the immunologic activity, it is suggested that the decreased activity of iodo-insulins may be due to the reduced affinity of the hormone to specific receptor sites involved in the initiation of the biological response.

The results of this study indicate that accumulation of the radioactive label of 131I-labelled insulin in incubated diaphragms gives no reliable quantitative index for the binding of either labelled or unlabelled insulin to this tissue.