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R Valiente

Publications and source records attributed to R Valiente.

13 recordsLinked to original sources
PubMed2001

Green and red light emission by upconversion from the near-IR in Yb(3+) doped CsMnBr3.

Direct near-IR excitation of Yb(3+) 2F(7/2)-->(2)F(5/2) levels at 10126, 10138, and 10596 cm(-1) in CsMnBr3:0.5%Yb(3+) leads to three types of luminescence at cryogenic temperatures: near-IR Yb(3+) emission and green and red upconverted luminescence. The green luminescence around 20 000 cm(-1) is identified as cooperative Yb(3+) pair upconversion. The broad red upconversion luminescence band centered at 14 700 cm(-1) is ascribed to the 4T(1g)-->6A(1g) transition of Mn(2+). Pulsed measurements indicate a sequence of ground-state absorption and excited-state absorption steps for the red upconversion process. One- and two-color excitation experiments support this, and we conclude that the red upconversion occurs by an exchange mechanism involving Yb(3+) and Mn(2+). The Yb(3+) 2F(5/2)-->(2)F(7/2) near-IR emission around 10 000 cm(-1) is also observed after Mn(2+) excitation at 21 838 cm(-1). This is indicative of a Mn(2+) 4T(1g)--> Yb(3+) 2F(5/2) relaxation process, which is a potential loss process for upconversion efficiency.

Journal Article↗
PubMed1995

Comparative bioavailability of a dispersible formulation of diclofenac and finding of double plasma peaks.

We carried out a comparative study of the bioavailability of a typical, enteric-coated diclofenac with regard to a new dispersible formulation whose faster dissolution results in an earlier onset of its analgesic effect. This randomized, crossover study was conducted in 12 healthy male volunteers, who received in fasting 100 mg of enteric-coated diclofenac (Dolotrén, FAES) and 100 mg of dispersible diclofenac (Dolotrén Dispersable, FAES), with one-week interval between both. Blood samples were taken at pre-established times during the 24 hours after dosing, and plasma concentrations of diclofenac were determined by HPLC. Possible adverse experiences were monitored with a check-list, and blood and urinalysis were performed for safety assessment. The dispersible formulation showed a relative extent of bioavailability between 78% and 99% (90% CI) for the AUC0-infinity, being the 90% CI for the Cmax 63%-129%. The time to Cmax (Tmax) was significantly shorter with the dispersible than with the enteric-coated formulation (95% CI for the difference = 1.5-4.25 hours) as the T0(lag) or time to measurable plasma concentrations (1.9-4.2 hours, 95% CI). A relevant feature in the study was the finding of a second peak at 2-2.5 hours post-dosing in 7 out of 11 profiles of subjects receiving the dispersible formulation. Both formulations were well tolerated in clinical and laboratory terms. In conclusion, the new dispersible formulation of diclofenac allows absorption to begin more rapidly and plasma peak is reached earlier, a fact that may be relevant to the analgesic treatment of acute pain.

Absorption↗
PubMed1992

Therapeutic effects of hidrosmin on chronic venous insufficiency of the lower limbs.

A double-blind, placebo-controlled trial was carried out to assess the effectiveness of a new synthetic bioflavonoid, hidrosmin, in patients with chronic venous insufficiency of the lower limbs. Fifty-seven patients, showing varicose veins and ankle swelling and suffering from local pain and heaviness of the legs, were allocated at random to receive treatment for 45 days with 1 capsule 3-times daily of either 200 mg hidrosmin (30 patients) or placebo (27 patients). Pain and heavy legs were assessed using rating scales; swelling was assessed by a photographic method. The results showed that hidrosmin produced a significant clinical improvement in all of the parameters evaluated; compared with placebo, there was a marked reduction in the main subjective symptoms accompanied by a 10% reduction in swelling. Apart from 1 patient who complained of epigastric pain, there were no reports of adverse events during the study period.

Adult↗
PubMed1989

Platelet GABA-aminotransferase in epileptic patients.

Platelet GABA-aminotransferase (GABA-T) activity was determined in 12 adults (six healthy volunteers and six long-term treated epileptic patients) and 17 children (six non-epileptic, and 11 long-term treated epileptic patients). Platelet GABA-T activity was about 60% higher in the epileptic patients than in the controls, both in adults (14.7 +/- 8.6 versus 8.8 +/- 3.5 pmol/min/mg of protein,) and children (13.1 +/- 4.8 versus 8.3 +/- 3.3 pmol/min/mg of protein, p less than 0.05). The relationship between this increase and either epilepsy or anti-epileptic treatment should be clarified in further studies.

4-Aminobutyrate Transaminase↗
PubMedDate not supplied

Poor correlation between single-dose data and steady-state kinetics for phenobarbitone, primidone, carbamazepine and sodium valproate in children during monotherapy. Possible reasons for the lack of correlation.

An investigation was performed to determine the relationship between the serum drug concentration/dose ratio at 24 hours following a first dose and that at steady-state for phenobarbitone, primidone (as phenobarbitone and as primidone), carbamazepine and sodium valproate, in order to assess the utility of this method in clinical practice. The drugs were given as monotherapy to 63 children for the treatment of epilepsy or febrile convulsions. The correlation between concentration/dose ratios, instead of between serum concentrations, was investigated with the aim of allowing the use of variable doses. The correlation coefficients were: r = 0.30 for phenobarbitone; r = 0.05 for phenobarbitone derived from primidone; r = 0.38 for primidone; r = 0.19 for carbamazepine; and r = 0.52 for sodium valproate. None of these correlation coefficients differed statistically from 0. These low correlation coefficients contrast with the acceptable results found by other authors for other drugs, indicating that several factors may have a greater influence on this correlation than earlier investigations suggest. The poor correlation obtained emphasises the need for clinical verification of mathematical models based on theoretical considerations which do not always apply in practice.

Age Factors↗
PubMedDate not supplied

[Comparative bioavailability and pharmacokinetics of Dolotren retard and Dolotren].

A randomized crossover study was designed in order to evaluate the bioequivalence of a sustained-release preparation (DR) of diclofenac sodium (Dolotrén RETARD) with respect to an enteric coated (D) tablet (Dolotren). For this purpose the bioavailability of both formulations, orally administered in single and multiple doses, was determined. Nine healthy volunteers were included in this study, receiving 100 mg of D and 100 mg of DR, firstly in single dose and then for 15 days b.i.d. for D group and once a day for DR group. For the analytical determination of diclofenac, blood samples at established time intervals, the day of the single dose and the 3rd, 7th and 15th day of multiple dose administration, were taken. The following kinetic parameters were determined: Cmac, tmax, alpha and beta, clearance, ka, area under the curve and absolute and relative bioavailability. When administered both endovenous and orally, the great interindividual variability in the kinetic characteristics of diclofenac sodium is evidenced. The lag time (tlag) for DR is 0.4 h, shorter than for D (2.2 h), which indicates a faster absorption in the upper sections of the gastrointestinal tract. Also tmax was shorter for Dr (1.9 h) than for D (4.3 h). Cmax obtained with D was higher tan with DR. The diclofenac sodium elimination process from plasma is significantly slower with DR than with D (t1/2 beta = 18.1 h and 2.5 h, respectively). In consequence, quantifiable plasmatic levels are maintained for at least 24 hours after administration of DR, but not of D. Absolute bioavailability of both preparations is about 80%, with great interindividual variations. Significant differences between the two preparations could not be demonstrated. Relative bioavailability between DR and D was 91.5%. None of the preparations when administered in repeated doses, D every 12 hours and DR every 24 hours, produced accumulation, neither their pharmacokinetic characteristics changed. Clinical and biological tolerance of both preparations were excellent, at doses used and for the period of time studied. Dolotren Retard is absorbed orally faster than Dolotren and maintains plasmatic levels longer, which allows it to be administered once a day, with a lesser incidence of undesirable effects related to Cmax.

Administration, Oral↗