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R Cadórniga

Publications and source records attributed to R Cadórniga.

17 recordsLinked to original sources
PubMed2000

Enhancement of the mydriatic response to tropicamide by bioadhesive polymers.

The aim of this work was to evaluate how the addition of mucoadhesive polymers to aqueous solutions affects the ocular response of tropicamide (0.2%; w/v). The polymer solutions tested were carboxymethylcellulose sodium salt (CMC-Na; 1%; w/v), hyaluronic acid sodium salt (HA-Na; 0.1%; w/v) and polyacrylic acid (PAA; 0.2%; w/v). Polymeric solutions were compared to a nonviscous formulation (AS). In vitro mucoadhesion measurements were expressed as a percentage of the adhesion force mucin-mucin, considering this one as 100% mucoadhesion. The values ofmucoadhesion obtained were 172%, 127%, 103% and 87.6% for formulations with CMC, PAA, HA and AS, respectively. The mydriatic response of tropicamide was determined in adult male New Zealand rabbits, weighing 1.7-2 Kg, by pupil diameter measurements at different times after instillation. The area under the mydriatic response-time curve (AUC 0-6 hr) was interpreted as an indication of the bioavailability of tropicamide in each vehicle. The AUC 0-6 hr was related to the in vitro mucoadhesion for each formulation. Tropicamide solutions with CMC-Na and PAA resulted in mucoadhesion and AUC 0-6 hr values approximately 1.9 and 1.4 times higher than AS. Although the solution with HA-Na was less mucoadhesive than PAA, the hyaluronic acid solution resulted in a higher AUC mydriasis/time value. Formulations with HA-Na and PAA presented values of surface tension close to that observed in the lacrimal fluid, with the Imax (maximum pupil diameter) being higher than for CMC-Na and AS. Greater than 90% of the mydriatic effect disappeared 4.5 hr after instillation for PAA and AS. Nevertheless, the mydriatic effect remained up to 5.5 hr for HA-Na and CMC-Na. HA-Na solution enhanced the bioavailability oftropicamide, presenting a value of mucoadhesion similar to the reference mucin-mucin.

Acrylic Resins↗
PubMed1999

Stereoselective drug release from ketoprofen and ricobendazole matrix tablets.

Crystalline characteristics of racemic, pure R and S enantiomers and physical mixtures of Ketoprofen (KET) have been studied by DSC and X-ray diffractometry. Aqueous solubilities were 182.6 +/- 9.1 microg/ml for racemic KET, 259.6 +/- 6.6 microg/ml for R-KET, and 304.3 +/- 2.7 microg/ml for S-KET. Matrix tablets made with racemic and physical mixtures of KET show stereoselective drug release, which is faster for S-KET than for R-KET. This effect is more marked when the chiral excipient hydroxypropylmethylcellulose (HPMC) is used in place of the achiral Eudragit RL. Stereoselectivity of release is also affected by the amount of KET. Similar results were obtained when another chiral drug with low solubility, Ricobendazole (RBZ), is used. Depending on the excipient and drug dosage, more or less marked stereoselective drug release is obtained in RBZ matrix tablet formulations.

Albendazole↗
PubMed1998

Chronopharmacokinetics and calcium in the prevention of gentamicin-induced nephrotoxicity in rabbits.

The study used 36 New Zealand white rabbits organized into three groups of 12 animals each. Group I received gentamicin; Group II received joint administration of gentamicin and calcium chloride and Group III received gentamicin, calcium chloride and verapamil. All the drugs were administered over 16 day periods. Groups I and II were divided in two subgroups, one subgroup receiving the treatment in winter and the other in summer. The results obtained for Group I indicate that there is an influence of the seasonal period on the gentamicin elimination and/or distribution. Mean plasma levels of the antibiotic at steady-state as well as the amounts of gentamicin accumulated in renal tissue are higher in winter than in summer. On the other hand, when calcium was administrated with the antibiotic, no significant circannual variations were observed in the renal toxicity of gentamicin. Under our study conditions the presence of calcium diminishes gentamicin plasma levels and the amount accumulated in kidney. Calcium, probably, generated a diminution in renal damage and consequently gentamicin renal excretion increases. The differences between Group II and Group III are due to the effect of verapamil. This agent blocks the calcium channels reducing the calcium protective effect on the nephrotoxicity of gentamicin.

Animals↗
PubMed1995

Tableting characteristics of micro-aggregated egg albumin particles containing paracetamol.

The tableting characteristics of micro-aggregated egg albumin particles containing paracetamol were evaluated and compared with non-micro-encapsulated paracetamol and coagulated egg albumin particles. Mean yield pressure values of micro-aggregated egg albumin particles containing paracetamol and coagulated egg albumin particles were 30.5 and 49.3 MPa, respectively, which were lower than the mean yield pressure obtained for paracetamol (97.5 MPa). Paracetamol tablets obtained with micro-aggregated egg albumin particles did not show the capping characteristic of conventional paracetamol tablets. Crushing strength of paracetamol tablets obtained with egg micro-aggegated particles was similar to that obtained using paracetamol granulated with povidone and gelatin as binders at 3 and 6% (w/w) concentrations. Drug release from the paracetamol tablets depends on the choice of excipients. Crospovidone showed good protective characteristics for the tableting of micro-aggregated particles. Crushing strength of paracetamol tablets formed from egg albumin-coated particles could be increased using crospovidone or microcrystalline cellulose as fillers and was decreased by the use of magnesium stearate. Nevertheless, magnesium stearate was useful to decrease the ejection force.

Acetaminophen↗
PubMed1995

Effect of dissolution profile and (-)-alpha-bisabolol on the gastrotoxicity of acetylsalicylic acid.

The effect of particle size and (-)-alpha-bisabolol on the gastric toxicity produced by acetylsalicylic acid (AAS) was studied in rats. AAS crystals of size 0.5-0.4, 0.2-0.05 mm and AAS pellets were administered orally (dose 200 mg/kg) to rats. The effect of particle size on gastric toxicity was not significant (P < 0.05). Small AAS crystals (0.2-0.05 mm) were granulated with ethanol to produce pellets (0.5-0.4 mm). The resultant pellets were less ulcerogenic than AAS crystals (P < 0.05). The pelletization process improves the wetting process of AAS crystals and for this reason produces a faster dissolution profile of AAS. When (-)-alpha-bisabolol, a natural essential oil obtained from camomile oil, was administered orally (dose 0.8-80 mg/kg) with AAS (dose 200 mg/kg), a significant (P < 0.05) protective effect was found. Some possible mechanisms of protection are suggested for (-)-alpha-bisabolol.

Animals↗
PubMed1994

Comparison of assay methods by second-derivative spectroscopy, colorimetry and fluorescence spectroscopy of salicylic acid in aspirin preparations with a high-performance liquid chromatographic method.

Second-derivative spectroscopy, colorimetry and fluorescence spectroscopy have been compared with a high-performance liquid chromatographic (HPLC) method for the assay of salicylic acid in preparations of aspirin. Results are presented for the linearity, sensitivity and reproducibility of these methods. The second-derivative spectroscopic and the HPLC methods were acceptable in terms of linearity, sensitivity and inter-day reproducibility and were convenient for the routine analysis of salicylic acid in aspirin preparations.

Aspirin↗
PubMed1990

Pharmacokinetics of cefroxadine after infusion to healthy volunteers.

The pharmacokinetics of cefroxadine in healthy human volunteers was studied in plasma and urine, after an infusion administration of 1 g of this drug for 0.5 h. Blood and urine samples were microbiologically quantified by diffusion on solid gelose using Bacillus Subtilis ATCC 6633 as the test organism. Plasma and urine profiles were fitted to a reduced two-compartment model not having inactivating biotransformation as a route of elimination. The parameters of distribution for this model show a rapid disposition (t1/2 alpha = 0.28 h) and an average volume of the central compartment of 0.15 +/- 0.04 l/kg (range 0.20-0.09). The dominant terminal half-life (beta-phase) was 1.17 +/- 0.26 h (range 0.90-1.67). The total body volume 0.41 +/- 0.09 l/kg (range 0.30-0.52) indicates that there is no diffusion of the antibiotic into intracellular fluids of poorly perfused tissues due to its high elimination rate.

Adult↗
PubMed1984

Pharmacokinetic study of vincamine teprosilate.

The results obtained by the authors in the pharmacokinetic study of vincamine teprosilate after oral and i.v. administration to young healthy volunteers and after oral administration to patients aged 68 to 84 years are presented. The description of the assay for each administration route is reported in the protocol. Plasma levels of vincamine teprosilate were assayed by reverse phase HPLC with spectrofluorimetric detection. The data obtained after i.v. administration made it possible to define the pharmacokinetic model and to estimate parameters. Concentration-time data were adapted to a biocompartmental open model with alpha value of 2.9080 and beta value 0.1047. In oral administration, the overlapping of the fast disposition phase and the absorption phase led to an apparent monocompartmental fit; in both young and aged volunteers, the absorption rate constants as well as the elimination rate constants were calculated. In both groups no significant differences in tmax values were found and no latency period was noticed . Cmax values were similar in both groups of patients; the lower distribution volume in aged volunteers compared to younger ones contributed to this finding. Differences in absorption rate constants in aged and young volunteers (0.53 h-1 and 0.73 h-1 respectively) are analysed. Vincamine teprosilate bioavailability after oral administration was found to be 20 +/- 5%. Possible vincamine teprosilate dose dependence kinetics are suggested.

Administration, Oral↗
PubMed1984

[Pharmacokinetics of cadmium-109 in blood and brain structures of the rat].

Pharmacokinetics of cadmium chloride (109Cd) in blood and cerebral structures in male Wistar rats is studied. Blood kinetics is obtained after intravenous administration of 20 microCi 109Cd; the element is distributed according to an open bicompartimental model with a high alpha deposition constant. The half-life of the alpha-phase is 0.043 hours and the half-life of the beta-phase is 5.54 hours. The kinetics of 109Cd in cerebral structures is calculated after injection of a total amount of 1 microCi in both lateral ventricles. Cadmium radionuclide in cerebral structures of the rat is rapidly fixed from the cerebral fluid, but released slowly. The structure of major accumulation is striatum and that of minor accumulation is cerebellum.

Animals↗
PubMed1982

[Data on the biochemical significance of nickel].

Pharmacokinetics of nickel chloride (63Ni) in blood and cerebral structures in male Wistar Rats is studied. After intravenous administration of 100 microCi 63 Ni, the trace element is distributed after an open bicompartmental model with a high alfa deposition constant, and the point obtained at 20 min. is considered in phase alfa. The kinetics of 63Ni in cerebral structures after the intracerebroventricular administration shows that hypocampus is the structure that most quickly reaches its maximal concentration. Mesencephalon shows slower penetration. Hypothalamus and hypocampus present greater accumulation of the radionucleide as compared with cortex and cerebellum which present a minor one. Insulin secretion of isolated and perfused rat pancreas from animals ingesting nickel in drink water after the stimulus with 16.7 mM glucose, is greater (53,35 ng immunoreactive insulin/min) than in control animals (30,42 ng immunoreactive insulin/min). In in vivo experiments, after a stimulus with 0,5 g glucose/Kg rat, for the 200 micrograms Ni/ml drinking water and control groups, there was an insulin secretion of 14 microunits insulin/ml and 2 microunits insulin/ml respectively. The normal plasmatic levels of insulin do not show any difference in both, nickel drinking water and controls. Nickel ion in drinking water induces the accumulation of calcium and zinc by the rat pancreas from 2.7 to 4 micrograms/mg protein and from 0.8 to 1.3 micrograms mg protein respectively. Both ions are essential cations for pancreatic physiological function and the synthesis of insulin.

Animals↗
PubMed1979

Penetration of antibiotic into interstitial tissue fluid following parenteral administration of lysine cephalexin.

Serum and interstitial fluid levels of antibiotic have been measured at various times following i.m. administration of equivalent doses of lysine cephalexin and sodium ampicillin, in a cross-over design, to dogs fitted with s.c. implanted silastic "tissue cages" and the results subjected to pharmacokinetic analysis. Serum concentrations of cephalexin were consistently higher than those of ampicillin and elimination half-lives were calculated as 1.73 h and 0.87 h, respectively. The rate of appearance of cephalexin in the interstitial fluid (Ka 1.741 h-1 was faster than that for ampicillin (Ka 0.946 h-1) and the maximum concentration obtained also proved to be higher. The half-life of cephalexin in the interstitial fluid (6.79 h) was almost four times longer than that in serum whereas that of ampicillin (2.03 h) was only a little more than twice as long. As a consequence a greater concentration and retention in interstitial fluid was obtained with cephalexin at all times tested. Since the interstitial fluid levels of cephalexin were still relatively high 8-12 h after the administration of a single dose repeated administration of lysine cephalexin 2 or 3 times daily is expected to result in a beneficial accumulation of cephalexin in the interstitial fluid.

Ampicillin↗
PubMed1977

Pharmacokinetic study of fosfomycin and its bioavailability.

The pharmacokinetics of fosfomycin in humans was studied in six young healthy volunteers after intravenous administration of 500 mg fosfomycin and after the same dose in oral administration in three different formulations. It was proven that fosfomycin follows a bicompartmental pattern, for which the disposition constants, the biological half-lives for the fast and slow phases, and the distribution constants were calculated. The renal excretion constant was evaluated making determinations of fosfomycin in the urine, and this constant together with the elimination constant allowed us to determine the extrarenal elimination. The concentration and quantity of the drug in the central and peripheral compartments were calculated and tabulated for different periods of time. An analogous behavior was obtained with the three formulations that were orally administered, with an average bioavailability of 37% in relation to the intravenous bioavailability, as evaluated by means of the accumulative renal excretion.

Administration, Oral↗