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Dive into the research topics where Juan J. García is active.

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Featured researches published by Juan J. García.


European Journal of Clinical Nutrition | 2002

Therapeutic effects of psyllium in type 2 diabetic patients

Matilde Sierra; Juan J. García; Nélida Fernández; M.J. Diez; Ángela P. Calle

Objective: The aim of this study was to evaluate the effects of psyllium in type 2 diabetic patients.Design: The study included three phases: phase 1 (1 week), phase 2 (treatment, 14 g fibre/day, 6 weeks) and phase 3 (4 weeks). At the end of each phase a clinical evaluation was performed after the ingestion of a test breakfast of 1824.2 kJ (436 kcal). Measurements included concentrations of blood glucose, insulin, fructosamine, GHbA1c, C-peptide and 24 h urinary glucose excretion. In addition, uric acid, cholesterol and several mineral and vitamin concentrations were also evaluated.Setting: The study was performed at the Department of Pharmacology, Toxicology and Nursing at the University of León (Spain).Subjects: Twenty type 2 diabetic patients (12 men and 8 women) participated in the study with a mean age of 67.4 y for men and 66 y for women. The mean body mass index of men was 28.2 kg/m2 and that of women 25.9 kg/m2.Results: Glucose absorption decreased significantly in the presence of psyllium (12.2%); this reduction is not associated with an important change in insulin levels (5%). GHbA1c, C-peptide and 24 h urinary glucose excretion decreased (3.8, 14.9 and 22.5%, respectively) during the treatment with fibre (no significant differences) as well as fructosamine (10.9%, significant differences). Psyllium also reduced total and LDL cholesterol (7.7 and 9.2%, respectively, significant differences), and uric acid (10%, significant difference). Minerals and vitamins did not show important changes, except sodium that increased significantly after psyllium administration.Conclusions: The results obtained indicate a beneficial therapeutic effect of psyllium (Plantaben®) in the metabolic control of type 2 diabetics as well as in lowering the risk of coronary heart disease. We also conclude that consumption of this fibre does not adversely affect either mineral or vitamin A and E concentrations. Finally, for a greater effectiveness, psyllium treatment should be individually evaluated.


European Journal of Clinical Nutrition | 2001

Effects of ispaghula husk and guar gum on postprandial glucose and insulin concentrations in healthy subjects

Matilde Sierra; Juan J. García; Nélida Fernández; M.J. Diez; Ángela P. Calle; Ana M. Sahagún

Objective: The aim of this study was to evaluate, under the same experimental conditions and in the same subjects, the effects of ispaghula husk and guar gum on postprandial glucose and insulin concentrations in healthy female subjects.Design: An oral glucose load with and without fiber was administered in the morning after an overnight fast. The study of the fiber effect was planned according to a randomized and cross-over design.Setting: The study was performed at the Department of Pharmacology, Toxicology and Nursing at the University of León (Spain).Subjects: Ten healthy female volunteers aged 30–48 y with normal body mass indices participated in this study.Results: A significant decrease in mean serum insulin concentrations was observed from 30 to 90 min in the presence of both fibers. The area under the insulin curve was significantly reduced by 36.1% for ispaghula husk and 39.4% for guar gum. The area under the glucose curve was reduced by 11.1% (significant difference) for ispaghula husk and 2.6% for guar gum (no significant difference).Conclusions: According to the results obtained in this study, the administration of ispaghula husk may be beneficial due to its ability to reduce glucose postprandial concentration and especially insulin requirements. Individualization of the treatment would be advisable due to large individual variations observed in glycemic and insulinemic postprandial responses.European Journal of Clinical Nutrition (2001) 55, 235–243


Journal of Liquid Chromatography & Related Technologies | 1990

Determination of levamisole by HPLC in plasma samples in the presence of heparin and pentobarbital

Juan J. García; M.J. Diez; Matilde Sierra; M. T. Terán

Abstract A method which allows for the isolation of levamisole in plasma samples of rabbit which contained pentobarbital and heparin as well, used as an anaesthetic and an anticoagulant respectively, is described in this paper. The subsequent quantification was carried out using a ion-pair high-performance liquid chromatographic method in a reversed and isocratic phase at room temperature, using a UV detection at 225 nm. In our conditions the retention time for the levamisole was about 2.15 minutes and the average percentage of recuperation was that of 73.62%.


European Neuropsychopharmacology | 2005

Hydrosoluble fiber (Plantago ovata husk) and levodopa II: Experimental study of the pharmacokinetic interaction in the presence of carbidopa

Nélida Fernández; Demetrio Carriedo; Matilde Sierra; M. José Diez; Ana M. Sahagún; Ángela P. Calle; Aranzazu González; Juan J. García

Levodopa combined with carbidopa constitutes one of the most frequent medication in the treatment of Parkinsons disease. Plantago ovata husk (water-soluble fiber) improves levodopa absorption conditions, but when this drug is administered with carbidopa, fiber could reduce its effectiveness. The purpose of this study is to investigate whether the presence of P. ovata husk modifies in rabbits the bioavailability and other pharmacokinetic parameters of levodopa (20 mg/kg) when administered by the oral route with carbidopa (5 mg/kg). We have also studied whether pharmacokinetic modifications are fiber-dose dependent (100 and 400 mg/kg). When levodopa and carbidopa were administered with 100 mg/kg P. ovata husk, the value of AUC for levodopa diminishes 29.7% (sign, n=6, P<0.05) and Cmax 28.1% (sign, n=6, P<0.05) in relation to the values obtained when these drugs were administered without fiber. If the dose of fiber was 400 mg/kg, the decrease was smaller: 20.4% for AUC (no significant difference) and 24.6% for Cmax (sign, n=6, P<0.05), that may indicate an inhibitory action of AADC by the fiber or any of its partial hydrolysis products. On the other hand, since certain time on, levodopa concentrations are always higher in the groups that receive fiber: 210 min with 100 mg/kg and 150 min with 400 mg/kg. The administration of P. ovata husk with levodopa/carbidopa to patients with Parkinson disease could be beneficial and in particular in those patients who also suffer constipation due to an improvement of levodopa kinetic profile with higher final concentrations, a longer plasma half-life and lower Cmax.


European Neuropsychopharmacology | 2005

Hydrosoluble fiber (Plantago ovata husk) and levodopa I: experimental study of the pharmacokinetic interaction.

Juan J. García; Nélida Fernández; Demetrio Carriedo; M. José Diez; Ana M. Sahagún; Aranzazu González; Ángela P. Calle; Matilde Sierra

Fiber therapy could be used in patients with Parkinson disease to reduce the symptoms of gastrointestinal disorders; however, it could interact with levodopa reducing its effectiveness. In this experimental study we have investigated whether the presence of Plantago ovata husk (water-soluble fiber) modifies in rabbits the bioavailability and other pharmacokinetic parameters of levodopa (20 mg/kg) when administered by the oral route at the same time. We have also studied whether pharmacokinetic modifications are fiber-dose dependent (100 and 400 mg/kg). The extent of levodopa absorbed when administering 100 mg/kg of fiber (AUC=43.4 mug min ml(-1)) is approximately the same as when levodopa is administered alone (AUC=47.1 microg min ml(-1)); however, Cmax is lower (1.04 versus 1.43 microg ml(-1)). Results obtained indicate that fiber at the higher dose increases the extent of levodopa absorbed (AUC=62.2 microg min ml(-1)), being the value of Cmax similar (1.46 microg ml(-1)). The value of tmax increases from 10 min when levodopa is administered alone to 20 min when the animals receive fiber. On the other hand, since certain time on, levodopa concentrations are always higher in the groups that receive fiber: 60 min with 100 mg/kg fiber and 20 min with 400 mg/kg fiber. Fiber also increases the mean residence time (MRT). P. ovata husk administration with levodopa could be beneficial, not only in patients with constipation, due to: lower adverse reactions (lower values of Cmax) and longer and more stable effects (higher final concentrations and more time in the body).


Veterinary Journal | 2009

Pharmacokinetics of doxycycline in sheep after intravenous and oral administration

Luis José Castro; Ana M. Sahagún; M. José Diez; Nélida Fernández; Matilde Sierra; Juan J. García

The pharmacokinetics of doxycycline were investigated in sheep after oral (PO) and intravenous (IV) administration. The IV data were best described using a 2- (n = 5) or 3- (n = 6) compartmental open model. Mean pharmacokinetic parameters obtained using a 2-compartmental model included a volume of distribution at steady-state (V(ss)) of 1.759+/-0.3149L/kg, a total clearance (Cl) of 3.045+/-0.5264mL/kg/min and an elimination half-life (t(1/2beta)) of 7.027+/-1.128h. Comparative values obtained from the 3-compartmental mean values were: V(ss) of 1.801+/-0.3429L/kg, a Cl of 2.634+/-0.6376mL/kg/min and a t(1/2beta) of 12.11+/-2.060h. Mean residence time (MRT(0-infinity)) was 11.18+/-3.152h. After PO administration, the data were best described by a 2-compartment open model. The pharmacokinetic parameter mean values were: maximum plasma concentration (C(max)), 2.130+/-0.950microg/mL; time to reach C(max) (t(max)), 3.595+/-3.348h, and absorption half-life (t(1)/(2k)(01)), 36.28+/-14.57h. Non-compartmental parameter values were: C(max), 2.182+/-0.9117microg/mL; t(max), 3.432+/-3.307h; F, 35.77+/-10.20%, and mean absorption time (MAT(0-infinity)), 25.55+/-15.27h. These results suggest that PO administration of doxycycline could be useful as an antimicrobial drug in sheep.


Contraception | 2000

Influence of two dietary fibers in the oral bioavailability and other pharmacokinetic parameters of ethinyloestradiol.

Juan J. García; Nélida Fernández; M. José Diez; Ana M. Sahagún; Aranzazu González; M. Luisa Alonso; Carlos Prieto; Ángela P. Calle; Matilde Sierra

Dietary fibers are widely used in hypoglycaemic, hypolipidemic, slimming diets. It is probable that their ingestion coincides with the oral administration of drugs and a modification of their pharmacokinetics can appear. In the present study, the influence of two soluble fibers (guar gum and psyllium) was evaluated on the pharmacokinetics of ethinyloestradiol (EE) when they were administered together to female rabbits via the oral route. Three groups of rabbits were used. All animals received 1 mg/kg of EE; this compound was administered alone in the control group and with 3.5 g of guar gum or psyllium in the other two groups. When guar gum was administered, there was a decrease in the extent of EE absorbed, but no change was observed in the rate of absorption. When psyllium was administered, the extent of EE absorbed increased slightly and the rate of absorption was slower.


Journal of Chromatography B: Biomedical Sciences and Applications | 1993

Rapid high-performance liquid chromatographic assay of ethynyloestradiol in rabbit plasma.

Nélida Fernández; Juan J. García; M.J. Diez; M. T. Terán; Matilde Sierra

A method for the determination of ethynyloestradiol in samples of rabbit plasma containing pentobarbital and heparin, the former used as an anaesthetic and the latter as an anticoagulant, has been developed. Quantification was carried out using a reversed-phase high-performance liquid chromatographic (HPLC) method in isocratic mode at room temperature, with electrochemical detection at an applied potential of +1 V vs. Ag/AgCl. Under these conditions, the retention time for ethynyloestradiol was ca. 2.9 min, the average recovery from plasma was 74.5%, and the limit of detection was 10 pg, corresponding to a plasma concentration of 50 pg/ml using 1 ml of plasma. Natural oestrogens, oestriol, oestradiol and oestrone showed peaks that did not interfere with ethynyloestradiol, and retention times of ca. 0.8, 2.4 and 3.4 min, respectively.


Contraception | 1997

Study of the pharmacokinetic interaction between ethinylestradiol and amoxicillin in rabbits

Nélida Fernández; Matilde Sierra; M.J. Diez; T. Terán; P. Pereda; Juan J. García

Several antibiotics have been implicated in oral contraception failure when they are administered at the same time as the oral contraceptive (OC) pill. In the present paper, a study about amoxicillin-ethinylestradiol (EE2) pharmacokinetic potential interaction was studied. Two rabbit groups were utilized, the first group received amoxicillin (10 mg/kg) and EE2 (30, 50 and 100 micrograms/kg, respectively), both by intravenous (i.v.) route. The second group received amoxicillin (oral route, 10 mg/kg/day) and EE2 (i.v. route, 100 mu/kg) on day 1, 4 and 8 of antibiotic treatment, respectively. After compartmental (two-compartment open model) and non-compartmental analysis of plasma concentrations, the statistical study (ANOVA p < or = 0.05) revealed that the presence of amoxicillin did not modify the EE2 distribution and elimination pharmacokinetic parameters (by comparison with those obtained in a previous study where EE2 was administered alone). There also were no significant differences with the time of amoxicillin oral treatment.


BioMed Research International | 2013

Hypoglycemic and Hypolipidemic Potential of a High Fiber Diet in Healthy versus Diabetic Rabbits

Raquel Díez; Juan J. García; M. José Diez; Matilde Sierra; Ana M. Sahagún; Ángela P. Calle; Nélida Fernández

The aim of this study was to investigate potential hypoglycaemic and hypolipidemic effects of Plantago ovata husk included in the diet, in healthy and diabetic rabbits. We also examined the effects of this fiber in other biochemical parameters. Two groups of 18 rabbits were used. The first group was fed with standard chow and the second with chow supplemented with Plantago ovata husk (3.5 mg/kg/day). On day 14 diabetes mellitus was induced by the intravenous administration of alloxan (80 mg/kg). After an oral glucose load (3 g), glucose, insulin, and other biochemical parameters were determined on day 14 (healthy rabbits) and on day 28 (diabetic rabbits). In healthy rabbits, fiber did not modify glucose or insulin levels but decreased significantly total cholesterol, LDL-cholesterol, atherogenic index, and glycosylated hemoglobin. In diabetic rabbits, fiber was more beneficial in mild diabetics than in severe diabetics with significant decreases in glucose levels and increases in insulin concentrations. In these animals fiber caused an important reduction in cholesterol, indicating a beneficial effect of Plantago ovata husk in diabetic rabbits. Although further studies in patients are necessary, we think that Plantago ovata husk offers interesting perspectives to be administered to patients with diabetes mellitus.

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