Stereoselective pharmacokinetics of bisoprolol after intravenous and oral administration in beagle dogs

We report 81 of 107 cases of hemolytic uremic syndrome (HUS), admitted between July 1994 and February 1996, following an outbreak of Shigella dysenteriae type 1 dysentery in Kwazulu/Natal. All patients, excluding 1, were black with a mean age of 38 months (range 1-121); 50 (61.7%) were males. The mean duration of dysentery was 11.3 days (range 1-41) and HUS 15 days (range 1-91). Most patients had acute oliguric renal failure (90.1%), 42 (51.6%) required peritoneal dialysis. Complications included encephalopathy 30 (37.0%), convulsions 12 (14.8%) and hemiplegia 2 (2.3%), gastrointestinal perforation 8 (9.9%), protein losing enteropathy 26 (32.1%), toxic megacolon 4 (4.9%), rectal prolapse 5 (6.2%), hepatitis 11 (13.6%), myocarditis 5 (6.2%), congestive cardiac failure 3 (3.7%), cardiomyopathy 3 (3.7%), infective endocarditis 1 (1.2%), septicemia 15 (18.5%), disseminated intravascular coagulation 17 (21%). Leukemoid reactions were found in 74 (91.3%) patients, hyponatremia in 56 (69.1%), and hypoalbuminemia in 67 (82.7%). Stool culture for Shigella dysenteriae type I was positive in only 7 (8.6%) patients; Shiga toxin assays were not performed. Outcome was as follows: recovery 32 (39.5%), impaired renal function 8 (9.9%), chronic renal failure 26 (32.1%), end-stage renal disease 1 (1.2%), and death 14 (17.3%) patients.     

Application of a colon delivery capsule to 5-aminosalicylic acid and evaluation of the pharmacokinetic profile after oral administration to beagle dogs

Pressure-controlled colon delivery capsule (PCC) containing 5-aminosalicylic acid (5-ASA) for the treatment of inflammatory bowel disease (IBD) was prepared and evaluated by an in vivo experiment using beagle dogs. As a reference drug, sulfasalazine (SASP), prodrug of 5-ASA, was used as a plain gelatin capsule preparation. After the oral administration of SASP at the does of 25.0 mg/kg, the mean time when the plasma 5-ASA concentration reaches to its maximum (Tmax) was 9.0 hr. In the case of 5-ASA administered in PCC, at the doses of 12.5 and 25.0 mg/kg, Tmaxs were 5.3 and 5.3 hr, respectively. Although the time for the first appearance of 5-ASA into the systemic circulation was almost the same value between SASP capsule and PCC containing 5-ASA, longer Tmax was observed from SASP capsule than from PCC. These results suggest that this 5-ASA preparation would be an useful dosage form for the therapy of IBD from the point of avoiding the side effect of sulfapyridine, one of the metabolites of SASP.     

Benefit of oral zinc supplementation as an adjunct to zidovudine (AZT) therapy against opportunistic infections in AIDS

Zinc is perhaps the most important trace element for immune function. Congenital or acquired zinc deficiencies are associated with immune abnormalities and increased susceptibility to infectious diseases. AIDS subjects suffer from reduced zinc bioavailability, more severe in stage IV than in stage III. Such zinc deficiency causes, among other effects, a profound reduction in the biological activity of one of the thymic hormones, thymulin (zinc-facteur-timique-serique, ZnFTS). With these premises, zinc sulphate was administered orally at a daily dose of 200 mg for 30 days to AZT-treated stage III subjects with generalized lymphadenopathy (17 subjects) and stage IV subgroup C1 (12 subjects) AIDS patients. 18 stage III subjects with generalized lymphoadenopathy and 10 stage IV subgroup C1 subjects treated only with AZT served as controls. Zinc sulphate supplementation of stage III and in stage IV C1 patients was followed by an increase or a stabilization in the body weight and an increase of the number of CD4+ cells and the plasma level of active zinc-bound thymulin. The frequency of opportunistic infectious episodes in the 24 months following entry into the study was reduced after zinc supplementation in stage IV C1 subjects (11 infections vs 25 in controls) and delayed in stage III zinc-treated subjects (1 infection/24 months vs 13 infections/24 months in controls). The effect of zinc on opportunistic infections is restricted to infections due to Pneumocystis carinii and Candida, whereas no variations have been observed in the frequencies of cytomegalovirus and toxoplasma infections. These data may support the benefit of zinc as an adjunct to AZT therapy in AIDS pathology.     

Effect of zidovudine (AZT) on the structure and function of rat skeletal muscle

The role of the anti-HIV agent zidovudine (ZDV = AZT) in the generation of mitochondrial myopathies and subsequent skeletal muscle contractile deficiencies was evaluated in male rats given ZDV in drinking water (1 mg/mL). After 6 weeks, there was no difference in treadmill run time between experimental (n = 6) and control (n = 6) rats. ZDV did not affect tension output by the gastrocnemius-plantaris-soleus muscle group when stimulated in situ at frequencies of 15, 30, 45, and 75 tetani/min, nor did the drug affect the cytochrome oxidase activity of fast glycolytic, fast oxidative glycolytic, or slow oxidative fiber types after 6 or 15 weeks of treatment. A group of female rats, similarly evaluated after 6 weeks of ZDV at 1 (n = 4) or 2 (n = 4) mg/mL, also did not display any discernable deficiencies. However, when the data from all 10 control rats were compared with those of the 19 ZDV rats, the cytochrome oxidase activity of fast oxidative glycolytic muscle of the ZDV rats was significantly higher (35.0 +/- 1.36 versus 40.7 +/- 1.14 mumol.min-1.g-1; p < 0.05). No ultrastructural abnormalities were observed in 15-week ZDV-treated cardiac muscle or in any of the three skeletal muscle fiber types. These results suggest that ZDV-related myopathies observed in AIDS patients may be due to interactions between the drug and complications associated with HIV infection.     

Poly-(L-lactic) acid membranes in palatal surgery in beagle dogs: clinical and histologic evaluation

This article reports on the histologic findings from a larger study that was designed to investigate whether the attachment of scar tissue to underlying bone, which is normally found after palatal surgery, can be prevented by using biodegradable poly-(L-lactic) acid membranes. Von Langenbeck's procedure was simulated in 12-week-old beagle dogs without clefts. In one group normal wound healing was allowed. In two groups, membranes were inserted immediately after surgery or 3 weeks thereafter. Sham and control groups were also included. Histologic evaluation was carried out at regular intervals. Reports have been published on other aspects, such as clinical wound healing, contraction and maxillary arch development in beagle dogs following this treatment. After direct implantation of membranes, wound healing was retarded. Disintegration of the membranes started soon after implantation and remaining particles were surrounded by a fibroblastic sheath and a fibrous capsule. At sites where membrane particles persisted, attachment of the scar tissue to the underlying bone by Sharpey's fibers was prevented.     

Assessment of pituitary function after transsphenoidal hypophysectomy in beagle dogs

Pituitary function was assessed in healthy adult beagle dogs before and after hypophysectomy. Anterior pituitary function was tested by use of the combined anterior pituitary (CAP) function test, which consisted of sequential 30-sec intravenous injections of four hypothalamic releasing hormones, in the following order and doses: 1 microgram of corticotropin-releasing hormone (CRH)/kg, 1 microgram of growth hormone-releasing hormone (GHRH)/kg, 10 micrograms of gonadotropin-releasing hormone (GnRH)/kg, and 10 micrograms of thyrotropin-releasing hormone (TRH)/kg. Plasma samples were assayed for adrenocorticotropin (ACTH), cortisol, GH, luteinizing hormone (LH), and prolactin (PRL) at multiple times for 120 min after injection. Pars intermedia function was assessed by the alpha-melanotropin (alpha-MSH) response to the intravenous injection of the dopamine antagonist haloperidol in a dosage of 0.2 mg/kg. Posterior pituitary function was assessed by the plasma vasopressin (AVP) response to the intravenous infusion of 20% saline. Basal plasma ACTH, cortisol, thyroxine, LH. PRL, and AVP concentrations were significantly lower at 10 wk after hypophysectomy than before hypophysectomy. In the CAP test and the haloperidol test, the peaks for the plasma concentrations of ACTH, cortisol, GH, LH, PRL, and alpha-MSH occurred within 45 min after injection. At 2 and 10 wk after hypophysectomy, there were no responses of plasma GH, LH, PRL, and alpha-MSH to stimulation. In four of eight hypophysectomized dogs, there were also no plasma ACTH and cortisol responses, whereas in the other four dogs, plasma ACTH and cortisol responses were significantly attenuated. The basal plasma ACTH and cortisol concentrations were significantly lower in the corticotropic nonresponders than in the responders. Plasma AVP responses were completely abolished by hypophysectomy, although water intake by the dogs was normal. Histopathological examinations at 10 wk after hypophysectomy revealed that adrenocortical atrophy was much more pronounced in the corticotropic nonresponders than in the responders. No residual pituitary tissue was found along the ventral hypothalamic diencephalon. However, in all hypophysectomized dogs that were investigated, islets of pituitary cells were found embedded in fibrous tissue in the sella turcica. A significant positive correlation was found between the number of ACTH-immunopositive cells and the ACTH increment in the CAP test at 10 wk after hypophysectomy. It is concluded that 1) stimulation of the anterior pituitary with multiple hypophysiotropic hormones, stimulation of the pars intermedia with a dopamine antagonist, and stimulation of the neurohypophysis with hypertonic saline do not cause side effects that would prohibit routine use, 2) in the routine stimulation of the anterior pituitary and the pars intermedia, blood sampling can be confined to the first 45 min, 3) the ACTH and cortisol responses to hypophysiotropic stimulation are the most sensitive indicators for residual pituitary function after hypophysectomy, 4) small islets of pituitary cells in the sella turcica, containing corticotropic cells, are the most likely source of the attenuated corticotropic response that may occur after hypophysectomy, and 5) residual AVP release from the hypothalamus after hypophysectomy is sufficient to prevent diabetes insipidus, despite the fact that the AVP response to hypertonic saline infusion is completely abolished.     

In vivo characteristics of injectable poly(DL-lactic acid) microspheres for long-acting drug delivery

Poly(DL-lactic acid) (PLA) microspheres containing testosterone (T) were prepared by the solvent evaporation process to evaluate their physical properties such as size distribution, shape, drug content, in vivo controlled drug release, pharmacological influences on the prostate gland in castrated rats, and histopathological findings of tissues surrounding the implants. The in vivo release of T from PLA microspheres containing 30 mg of drug obtained with chloroform was continued over a 6-week period. This effect is attributed to high dispersibility of T in the device when obtained with chloroform. Both serum drug levels and prostate gland weight recovery suggested the effects of a long-acting drug delivery system. The histopathological findings showed that the devices used were completely degraded 10 weeks after injection.     

A physiologically based pharmacokinetic model of zidovudine (AZT) in the mouse: model development and scale-up to humans

After having been used in treating HIV infection for a decade, zidovudine (AZT) continues to be an essential component of antiretroviral regimens. Because antiviral responses and toxicity of AZT seem to be related to cells in specific target tissues, being able to understand and predict the distribution of AZT into different pharmacologically and toxicologically relevant tissues is therefore critically important to improving the efficacy and minimizing the toxicity of AZT therapy. This study was designed to develop a physiologically based pharmacokinetic model to help describe and predict the time course of AZT levels in different tissues. The model was developed in the mouse and then scaled up to predict human situations.     

Postmortem serum and tissue redistribution of fluoxetine and norfluoxetine in dogs following oral administration of fluoxetine hydrochloride (Prozac)

Antemortem serum and postmortem serum and tissues were evaluated to determine if postmortem redistribution of the antidepressant, fluoxetine (Prozac) and its major active metabolite, norfluoxetine, occurred in dogs following oral administration of fluoxetine hydrochloride. Beagle dogs (four males) received daily oral doses of 10 mg fluoxetine/kg for five days. Antemortem serum concentrations of fluoxetine and norfluoxetine were determined 3 and 24 h following administration of the first four daily doses of fluoxetine and 3 h after the fifth dose in order to monitor for steady-state serum concentrations of parent and metabolite prior to postmortem serum concentration determinations. Antemortem serum concentrations of fluoxetine and norfluoxetine 3 h postdose on Day 5 ranged from 530 to 1210 ng/mL and 1460 to 1980 ng/ mL, respectively. Immediately following the 3 h blood sample on Day 5, each dog was euthanized. Serum concentrations of fluoxetine and norfluoxetine were determined from blood samples collected from the vena cava, heart, and clotted blood within the heart at 2 h after death in two dogs and 12 h after death in the remaining two dogs. Similarly, tissue concentrations of fluoxetine and norfluoxetine in heart, liver, and lung were determined 2 and 12 h postmortem. Serum concentrations of fluoxetine and norfluoxetine from the vena cava and heart 2 h postmortem were 2.2- to 6.0-fold and 2.3- to 3.6-fold higher, respectively, than antemortem serum concentrations. Similarly, serum concentrations of fluoxetine and norfluoxetine from vena cava and heart 12 h postmortem were 1.3- to 3.5-fold and 1.7- to 3.3-fold higher, respectively, than antemortem serum concentrations. However, 2-h and 12-h postmortem serum concentrations of fluoxetine and norfluoxetine from clotted blood within the heart were equal to or less than levels determined in antemortem serum. Results from 2-h and 12-h postmortem average tissue concentrations of fluoxetine and norfluoxetine in heart, liver, and lung demonstrated that fluoxetine and norfluoxetine concentrations in myocardium were similar 2 h and 12 h postmortem. However, in liver, fluoxetine concentrations decreased 39% and norfluoxetine concentrations decreased 23% from 2 h to 12 h postmortem. Even greater postmortem decreases in fluoxetine and norfluoxetine concentrations were observed in lung. Fluoxetine and norfluoxetine concentrations in lung decreased 49% and 39%, respectively, from 2 h to 12 h postmortem. In conclusion, this study demonstrated that fluoxetine and norfluoxetine undergo postmortem redistribution in the dog. Furthermore, postmortem serum concentrations appear to be dependent on the sample site and the degree of coagulation of the blood. Finally, postmortem decreases in concentrations of fluoxetine and norfluoxetine in liver and lung may, in part, explain the observed increase in serum concentrations at 2 and 12 h postmortem.     

In vivo disposition of p-substituted phenols in the young rat after intraperitoneal and dermal administration

The objective of this study was to examine the 120-hr disposition of phenol and four p-substituted congeners after ip and dermal administration in the 29-day-old female rat. The dermal absorption was very high (66-80% of the dose) for phenol, cyanophenol, heptyloxyphenol and nitrophenol, but minimal for hydroxybenzoic acid (2%). The major portion of the dose for all of the phenols not absorbed dermally in 24 hr was washed from the skin. Only minor amounts (1-2%) were detected in the treated skin at 120 hr. Urinary excretion was the predominant means of elimination for these phenols and occurred primarily within 24 hr after dermal and ip administration. However, the excretion of heptytoxyphenol after administration by both routes differed from that of the other compounds, with more of it detected in the faeces. The profile of metabolites in urine (collected at 12-24 hr) from the animals dermally treated with phenol, cyanophenol, heptyloxyphenol and nitrophenol showed only peaks that eluted earlier than the parent compound, which suggests that conjugates or more polar metabolites were formed and excreted. The difference in dermal absorption between hydroxybenzoic acid and the other phenols may be due to potential ionization of the p-substituted carboxylic acid group of hydroxybenzoic acid. This suggests that, at least for the phenols examined in this study, physicochemical characteristics other than just lipophilicity can affect in vivo dermal absorption.     

Controlled release of thyrotropin releasing hormone from microspheres: evaluation of release profiles and pharmacokinetics after subcutaneous administration

The drug-release kinetics of thyrotropin releasing hormone (TRH) containing copoly(dl-lactic/glycolic acid) (PLGA) microspheres were evaluated both in vitro and in vivo. The drug was encapsulated in PLGA using an in-water drying method through a water in oil in water emulsion. The drug release from the PLGA microspheres in vitro correlated well with that in vivo, and pseudo-zero-order release kinetics were observed. The pharmacokinetics of TRH following administration of this controlled-release parenteral dosage form have been also examined in rats. Following a transient increase in the plasma level due to an initial burst, steady-state plasma levels were observed. The duration of drug release estimated from the plasma level was comparable with the results in the in vitro and in vivo release studies. The steady-state plasma levels correlated well with the levels predicted from the pharmacokinetic parameters following a single subcutaneous or intravenous injection of TRH solution. The results of this study confirm the previously reported in vivo sustained release of TRH achieved with this drug-delivery system.     

In vivo evaluation of dosage forms: application of gamma scintigraphy to non-enteral routes of administration

The trend to deliver drugs to defined areas of the body involves sophisticated carriers systems. In addition to the in vitro drug release profile one must be aware of the in vivo behaviour of the dosage form and the drug. Gamma scintigraphy is an elegant way to gain insights of the actual in vivo distribution pattern of dosage forms. This technique relies on the use of radioactive tracers included into the medicament and selected so as to enable an optimum detection by a gamma ray camera. The choice of a convenient label enables the in vivo determination of the targeting of the formulation administered through a large number of routes. The present paper reviews applications of gamma scintigraphy for the evaluation of dosage forms administered by the parenteral, rectal, buccal, nasal, pulmonary, and ophthalmic routes.     

Systemic and histopathologic changes in Beagle dogs after chronic daily oral administration of synthetic (ethinyl estradiol) or natural (estradiol) estrogens, with special reference to the kidney and thyroid

ABSTRACT Four groups of 3 male and 3 female sexually mature Beagle dogs were treated daily po with either ethinyl estradiol (EE) or estradiol (E2). A fifth group of 4 males and 4 females acted as a control group. Three groups of dogs were treated with EE: One group was treated at dose levels of 2.0, 1.5, and 1.0 mg/kg for 6 mo; the other 2 groups received either 0.5 mg/kg or 1.0 mg/kg for 1 yr. The fourth group was treated with 5.0 mg/kg E2 for 1 yr. Results obtained for the clinical, hematological, and biochemical parameters and the histopathologic findings of most organs and tissues in EE- and E2-treated dogs were essentially comparable to those documented in the literature for dogs treated with synthetic or natural estrogens. Chronic treatment with EE or E2 induced similar effects, with the exception of mesothelial proliferation of the genital serosa, which was observed in EE-treated dogs only. Additional new estrogen-related findings were observed in the kidneys and thyroid glands of EE- and E2-treated dogs. Increased interstitial fibrous tissue occurred at the corticomedullary junction and in the outer cortex of the kidney. It appeared to originate primarily from the perivascular fibrous tissue of branches of the renal arteries and veins. Extension of this lesion into the renal parenchyma resulted in secondary atrophic changes of tubules and glomeruli. The treatment relationship and specific characteristics of this renal alteration differentiated it from other chronic renal interstitial and vascular diseases. Squamous metaplasia of urogenital tract epithelia, including renal cortical tubule epithelium, occurred as expected in both EE- and E2-treated dogs. Unexpectedly, squamous metaplasia of thyroid follicular epithelium also occurred. It was present in scattered follicles of both EE- and E2-treated dogs. The renal and thyroid changes did not alter clinicopathological function tests for either of these organs. These 2 new findings extend the list of estrogen-related effects in the dog.     

Fractional absorption of L-carnitine after oral administration in rats: evaluation of absorption site and dose dependency

We evaluated the fractional absorption of L-carnitine, a gamma-amino acid essential cofactor for the transfer of long-chain fatty acids, in rats in vivo after oral administration to determine its absorption behavior. At both low (0.05 micromol/rat) and high (100 micromol/rat) doses, L-carnitine was recovered only from the region of the cecum and below at 10 h after administration. During a major shift in distribution from cecum at 10 h to feces at 24 h, there was no significant change in the total recovery at each dose, suggesting that L-carnitine absorption is negligible in the cecum and the large intestine (colon and rectum). However, the recovery of L-carnitine was incomplete and the fraction recovered was larger at the high dose than at the low dose. The fractions absorbed were estimated to be 96.7 and 33.0% for the low and high doses, respectively, as these were the fractions that disappeared from the gastrointestinal tract. These values were comparable with 100 and 42%, respectively, of bioavailability values by the pharmacokinetic analysis of plasma concentration data in our preceding study [Matsuda et al., Biopharmaceutics & Drug Disposition, in press]. These results suggest that L-carnitine is significantly absorbed only in the small intestine, without undergoing first-pass degradation, and in a dose-dependent manner presumably due to the involvement of saturable transport by L-carnitine carriers. Consistent with the suggestions in vivo, L-carnitine absorption in the closed intestinal loop in situ was concentration-dependent in the small intestine but not in the large intestine, and the apparent membrane permeability in the large intestine was smaller by an order of magnitude than that of passive transport in the small intestine. These findings support our preceding kinetic modeling strategy assuming the small intestine to be the sole absorption site, and should be of help in guiding studies on development of more efficient oral L-carnitine delivery strategies.     

Pharmacokinetics of enrofloxacin after intravenous, intramuscular and oral administration in houbara bustard (Chlamydotis undulata macqueenii)

The in-vitro activity of enrofloxacin against 117 strains of bacteria isolated from bustards was determined. Minimum inhibitory concentrations for 72% of the Proteus spp., E. coli, Salmonella spp. and Klebsiella spp. (n = 61) and for 48% of the Streptococci spp. and Staphylococci spp. (n = 31) were < or = 0.5 microg/mL. The minimum inhibitory concentration (MIC) of 76% of Pseudomonas spp. (n = 25) was < or = 2 microg/mL. Fourteen strains were resistant to concentrations > or = 128 microg/mL. The elimination half-lives (t1/2 elim beta) (mean +/- SEM) of 10 mg/kg enrofloxacin in eight houbara bustards (Chlamydotis undulata) were 6.80 +/- 0.79, 6.39 +/- 1.49 and 5.63 +/- 0.54 h after oral (p.o.), intramuscular (i.m.) and intravenous (i.v.) administration, respectively. Enrofloxacin was rapidly absorbed from the bustard gastro-intestinal tract and maximum plasma concentrations of 1.84 +/- 0.16 microg/mL were achieved after 0.66 +/- 0.05 h. Maximum plasma concentration after i.m. administration of 10 mg/kg was 2.75 +/- 0.11 microg/mL at 1.72 +/- 0.19 h. Maximum plasma concentration after i.m. administration of 15 mg/kg in two birds was 4.86 microg/mL. Bioavailability was 97.3 +/- 13.7% and 62.7 +/- 11.1% after i.m. and oral administration, respectively. Plasma concentrations of enrofloxacin > or = 0.5 microg/mL were maintained for at least 12 h for all routes at 10 mg/kg and for 24 h after i.m. administration at 15 mg/kg. Plasma enrofloxacin concentrations were monitored during the first 3 days of treatment in five houbara bustards and kori bustards (Ardeotis kori) with bacterial infections receiving a single daily i.m. injection of 10 mg/kg for 3 days. The mean plasma enrofloxacin concentrations in the clinical cases at 27 and 51 h (3.69 and 3.86 microg/mL) and at 48 h (0.70 microg/mL) were significantly higher compared with the 3 h and 24 h time intervals from clinically normal birds. The maximum plasma concentration (Cmax)/MIC ratio was ranked i.v. (10/mg/kg) > i.m. (15 mg/kg) > i.m. (10 mg/kg) > oral (10 mg/kg), but it was only higher than 8:1 for i.v. and i.m. administrations of enrofloxacin at 10 mg/kg and 15 mg/kg, respectively, against a low MIC (0.5 microg/mL). A dosage regimen of 10 mg/kg repeated every 12 h, or 15 mg/kg repeated every 24 h, would be expected to give blood concentrations above 0. 5 microg/mL and hence provide therapeutic response in the bustard against a wide range of bacterial infections.     

Kinetics of trans- and cis-resveratrol (3,4',5-trihydroxystilbene) after red wine oral administration in rats

Kinetics of trans- and cis-resveratrol (3,4',5-trihydroxystilbene), a natural compound from grape products, have been evaluated in rats after oral administration of red wine. Resveratrol concentrations were measured in plasma, heart, liver and kidneys. Tissue concentrations showed a significant cardiac bioavailability and strong affinity for liver and kidneys.