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Biomedical subjects

José Luis Pedraz

Publications and source records attributed to José Luis Pedraz.

At least 19 recordsLinked to original sources
PubMed2006

Development and optimization of a novel sustained-release dextran tablet formulation for propranolol hydrochloride.

A novel oral controlled delivery system for propranolol hydrochloride (PPL) was developed and optimized. The in vitro dissolution profiles of sustained-release matrix tablets of racemic PPL were determined and compared with the United States Pharmacopeia (USP) tolerance specifications for Propranolol Hydrochloride Extended-Release Capsules. The influence of matrix forming agents (native dextran, hydroxypropyl methylcellulose (HPMC), cetyl alcohol) and binary mixtures of them on PPL release in vitro was investigated. A central composite design was applied to the optimization of a sustained-release tablet formulation. The sustained-release matrix tablets with good physical, mechanical and technological properties were obtained with a matrix excipient:PPL ratio of 60:40 (w/w), with a dextran:HPMC ratio of 4:1 (w/w) and with a cetyl alcohol amount of 15% (w/w). A comparative kinetic study of the present matrix tablets and commercial SUMIAL RETARD capsules (Spain) was established. The value for the similarity factor (f(2)=69.6) suggested that the dissolution profile of the present two sustained-release oral dosage forms are similar. Higuchi (diffusion) and Hixon-Crowell (erosion) kinetic profiles were achieved and this codependent mechanism of drug release was established.

Capsules↗
PubMed2006

Biocompatibility of alginate-poly-L-lysine microcapsules for cell therapy.

Cell microencapsulation holds promise for the treatment of many diseases by the continuous delivery of therapeutic products. The biocompatibility of the microcapsules and their biomaterials components is a critical issue for the long-term efficacy of this technology. The objective of this paper is to provide detailed information about the principal factors affecting the biocompatibility of alginates and alginate-poly-l-lysine microcapsules, which are the most frequently employed biomaterials and encapsulation devices for cell immobilization, respectively. Some of these factors include the alginate composition and purification, the selection of the polycation, the interactions between the alginates and the polycation, the microcapsule fabrication process, the uniformity of the devices and the implantation procedure. Improved knowledge will lead to the production of standardized transplantation-grade biomaterials and biocompatible microcapsules.

Alginates↗
PubMed2005

The role of pH dynamics and the Na+/H+ antiporter in the etiopathogenesis and treatment of cancer. Two faces of the same coin--one single nature.

Looked at from the genetic point-of-view cancer represents a daunting and, frankly, confusing multiplicity of diseases (at least 100) that require an equally large variety of therapeutic strategies and substances designed to treat the particular tumor. However, when analyzed phenotypically cancer is a relatively uniform disease of very conserved 'hallmark' behaviors across the entire spectrum of tissue and genetic differences [D. Hanahan, R.A. Weinberg, Hallmarks of cancer, Cell 100 (2000) 57-70]. This suggests that cancers do, indeed, share common biochemical and physiological characteristics that are independent of the varied genetic backgrounds, and that there may be a common mechanism underlying both the neoplastic transformation/progression side and the antineoplastic/therapy side of oncology. The challenge of modern oncology is to integrate all the diverse experimental data to create a physiological/metabolic/energetic paradigm that can unite our thinking in order to understand how both neoplastic progression and therapies function. This reductionist view gives the hope that, as in chemistry and physics, it will possible to identify common underlying driving forces that define a tumor and will permit, for the first time, the actual calculated manipulation of their state. That is, a rational therapeutic design. In the present review, we present evidence, obtained from a great number of studies, for a fundamental, underlying mechanism involved in the initiation and evolution of the neoplastic process. There is an ever growing body of evidence that all the important neoplastic phenotypes are driven by an alkalization of the transformed cell, a process which seems specific for transformed cells since the same alkalinization has no effect in cells that have not been transformed. Seen in that light, different fields of cancer research, from etiopathogenesis, cancer cell metabolism and neovascularization, to multiple drug resistance (MDR), selective apoptosis, modern cancer chemotherapy and the spontaneous regression of cancer (SRC) all appear to have in common a pivotal characteristic, the aberrant regulation of hydrogen ion dynamics [S. Harguindey, J.L. Pedraz, R. García Cañero, J. Pérez de Diego, E.J. Cragoe Jr., Hydrogen ion-dependent oncogenesis and parallel new avenues to cancer prevention and treatment using a H+-mediated unifying approach: pH-related and pH-unrelated mechanisms, Crit. Rev. Oncog. 6 (1) (1995) 1-33]. Cancer cells have an acid-base disturbance that is completely different than observed in normal tissues and that increases in correspondence with increasing neoplastic state: an interstitial acid microenvironment linked to an intracellular alkalosis.

Animals↗
PubMed2005

Preparation of sustained release hydrophilic matrices by melt granulation in a high-shear mixer.

PURPOSE: The objective of this work was to prepare theophylline sustained release matrix tablets based on the combination of hydroxypropyl methylcellulose (HPMC K4M and K100M) and different meltable binders by melt granulation in a high-shear mixer. METHODS: Dissolution profiles of each formulation were compared to those of TheoDur 200 mg tablets and the mean dissolution time (MDT) and similarity factor (f2 factor) were calculated. The matrices swelling behavior was investigated by texture analysis. RESULTS: The results obtained show that the type of excipient influenced the drug release rate. In particular, the dissolution rate was delayed when lipophilic binders were used and only formulations containing Gelucire 50/13 or PEG 6000 with HPMC K4M had a profile similar to the commercial formulation. The release mechanism of theophylline from the formulations was described by Peppas's equation showing a non-Fickian release mechanism. The investigation of matrices swelling behavior showed that the gel layer thickness increased continuously over the time period studied. Moreover, a correlation between gel layer thickness and strength with the percentage released was found. CONCLUSIONS: These results suggest that melt granulation could be an easy and fast method to formulate sustained release tablets.

Chemistry, Pharmaceutical↗
PubMed2005

Cefepime and continuous renal replacement therapy (CRRT): in vitro permeability of two CRRT membranes and pharmacokinetics in four critically ill patients.

BACKGROUND: Cefepime is a fourth-generation cephalosporin with a broad spectrum of antimicrobial activity against gram-positive and gram-negative micro-organisms. It is a useful option for treating infections in critically ill patients in intensive care due to its high degree of activity and its tolerability. OBJECTIVE: The aim of this study was to characterize in vitro the permeability to cefepime of 2 membranes frequently used in continuous renal replacement therapies (CRRTs). An in vivo study was also carried out to determine the pharmacokinetics of cefepime in critically ill patients undergoing CRRT. METHODS: In vitro procedures were conducted in 3 different fluids using polyacrylonitrile (AN69) or polysulfone (PS) membranes. Continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodialysis (CVVHD) were simulated. Four male patients undergoing CVVH or continuous venovenous hemodiafiltration, who received 2000 mg of cefepime intravenously every 8 hours, entered the in vivo study. Prefilter and ultrafiltrate samples were collected, and concentrations of cefepime were measured using high-performance liquid chromatography. The sieving coefficient (Sc), defined as the fraction of drug eliminated across the membrane, and the saturation coefficient (Sa), defined as the fraction of drug diffused through the membrane to the dialysate fluid, were analyzed. Pharmacokinetic parameters were determined according to a noncompartmental analysis. RESULTS: The patients ranged in age from 18 to 75 years and weighed from 65 to 80 kg. By analyzing Sc and Sa values in the in vitro procedures, no differences were detected in the permeability of AN69 or PS membranes to cefepime in CVVH or CVVHD. Sc/Sa values were between 0.93 and 1.03 in Ringer's lactate and in bovine albumin-containing Ringer's lactate samples, but Sc/Sa values were lower in plasma samples (0.82-0.95). In the in vivo portion of the study, the patients' mean (SD) Sc/Sa value was 0.76 (0.21) and correlated well with the fraction unbound to proteins (0.79 [0.09]). Clearance by CRRT (mean [SD]) was 29.0 (16.8)% of the total clearance. Serum elimination t(1/2) was 4.6 (0.9) hours, and the volume of distribution at steady state was 0.6 (0.3) L/kg (mean [SD] values). CONCLUSIONS: Cefepime was significantly removed by CRRT. No significant differences were found in the Sc or Sa of cefepime between AN69 and PS membranes used in the CVVH or CVVHD procedures. The clearance of cefepime by CRRT must be considered when dosing critically ill patients.

Acrylic Resins↗
PubMed2005

[Pharmacokinetic/pharmacodynamic analysis of antibiotic therapy in dentistry and stomatology].

INTRODUCTION: This study evaluates the efficacy of various antimicrobial treatments for orofacial infections on the basis of pharmacokinetic/pharmacodynamic (PK/PD) criteria. METHODS: A complete a literature search was undertaken to establish the MIC90 values of the five microorganisms most frequently isolated in odontogenic infections and the pharmacokinetic parameters of 13 antibiotics used in these infections. Pharmacokinetic simulations were then carried out with mean population parameters and efficacy indexes were calculated for the 47 treatment regimens analyzed. For drugs showing time-dependent antibacterial killing, the time above MIC (t > MIC) was calculated. For drugs with concentration-dependent bactericidal activity, the AUC/MIC was calculated. RESULTS: Amoxicillin-clavulanic (500 mg/8 h or 1000 mg/12 h) and clindamycin (300 mg/6 h) in the time-dependent killing group and moxifloxacin (400 mg/24 h) in the concentration-dependent group showed adequate efficacy indexes against the five pathogens considered to be the most commonly implicated in odontogenic infections. The spiramycin plus metronidazole combination, present in the commercial formulation Rhodogyl, did not reach satisfactory PK/PD indexes. CONCLUSION: PK/PD indexes, which are useful predictors of the potential efficacy of antibacterial therapy, were used with ontogenic infections in the present study. The PK/PD simulations showed that amoxicillin-clavulanic, clindamycin and moxifloxacin were the most suitable antibiotics for this kind of infection. Clinical trials are required to confirm that this methodology is useful in these pathologic processes.

Algorithms↗
PubMed2005

Influence of renal function on the pharmacokinetics of piperacillin/tazobactam in intensive care unit patients during continuous venovenous hemofiltration.

The pharmacokinetics of piperacillin/tazobactam (4 g/0.5 g every 6 or 8 hours, by 20-minute intravenous infusion) were studied in 14 patients with acute renal failure who underwent continuous venovenous hemofiltration with AN69 membranes. Patients were grouped according to severity (CL(CR) < or =10 mL/min, 10 < CL(CR) < or =50 mL/min, and CL(CR) > 50 mL/min). A noncompartmental analysis was performed. The sieving coefficient (0.78 +/- 0.28) was similar to the unbound fraction (0.65 +/- 0.24) for tazobactam, but it was significantly different (0.34 +/- 0.25) from the unbound fraction (0.78 +/- 0.14) for piperacillin. Extracorporeal clearance was 37.0% +/- 28.8%, 12.7% +/- 12.6%, and 2.8% +/- 3.2% for piperacillin in each group and 62.5% +/- 44.9%, 35.4% +/- 17.0%, and 13.1% +/- 8.0% for tazobactam. No patients presented tazobactam accumulation. In patients with CL(CR) < 50 mL/min, t(%)ss >MIC90 values were 100% for a panel of 19 pathogens, but in those with CL(CR) > 50 mL/min, t(%)ss >MIC90 indexes were 55.5% and 16.6% for pathogens with MIC90 values of 32 and 64. The extracorporeal clearance of piperacillin/tazobactam is clinically significant in patients with CL(CR) > 50 mL/min, in which the risk of underdosing and clinical failure is important and extra doses are required.

Aged↗
PubMed2005

Meropenem and continuous renal replacement therapy: in vitro permeability of 2 continuous renal replacement therapy membranes and influence of patient renal function on the pharmacokinetics in critically ill patients.

The pharmacokinetics of meropenem were characterized in 20 patients with different degrees of renal function who underwent continuous renal replacement therapy. Previously, no differences were detected in vitro in the removal of meropenem by continuous venovenous hemofiltration or continuous venovenous hemodialysis or when AN69 or polysulfone membranes were compared. In patients, no significant differences in the sieving coefficient or the saturation coefficient with the renal function were found, and the mean sieving coefficient/saturation coefficient value (0.80 +/- 0.12) was similar to the unbound fraction (0.79 +/- 0.08). An increase in total clearance and a decrease in elimination half-life were observed to the extent that the patient's creatinine clearance was higher. Likewise, the contribution of continuous renal replacement therapy to total clearance diminished in patients with less renal impairment. The results suggest that the renal function of the patient may influence meropenem pharmacokinetics during continuous renal replacement therapy. The lower trough plasma levels observed in nonrenal patients would not lead to adequate time during which serum drug concentrations are above the minimum inhibitory concentration values in many infections.

Acrylic Resins↗
PubMed2004

History, challenges and perspectives of cell microencapsulation.

Cell microencapsulation continues to hold significant promise for biotechnology and medicine. The controlled, and continuous, delivery of therapeutic products to the host by immunoisolated cells is a potentially cost-effective method to treat a wide range of diseases. Although there are several issues that need to be addressed, including capsule manufacture, properties and performance, in the past few years, a stepwise analysis on the essential obstacles and limitations has brought the whole technology closer to a realistic proposal for clinical application. This paper summarizes the current situation in the cell encapsulation field and discusses the main events that have occurred along the way.

Cell Transplantation↗
PubMed2004

The search for new beta-cell sources.

Type 1 diabetes affects an estimated 150 million people worldwide and results from an autoimmune-mediated destruction of insulin-producing beta-cells. In the United States alone more than 16 million people are affected by this disease and it is estimated that spending for diabetes management accounts for one out of every eight healthcare dollars. In this context, scientists are proposing novel therapeutic strategies that might allow a perfect glycemic control of most patients with diabetes.

Animals↗
PubMed2003

Drug delivery in biotechnology: present and future.

Drug delivery is becoming a whole interdisciplinary and independent field of research and is gaining the attention of pharmaceutical makers, medical doctors and industry. A targeted and safe drug delivery could improve the performance of some classical medicines already on the market and, moreover, will have implications for the development and success of new therapeutic strategies, such as peptide and protein delivery, glycoprotein administration, gene therapy and RNA interference. Many innovative technologies for effective drug delivery have been developed, including implants, nanotechnology, cell and peptide encapsulation, microfabrication, chemical modification and others. On the long way from the clinic to market, however, several issues will have to be addressed, including suitable scientific development, specific financial support as a result of altered scientific policy, government regulations and market forces.

Biotechnology↗
PubMed2003

Cell microencapsulation technology for biomedical purposes: novel insights and challenges.

The aim of cell microencapsulation technology is to treat multiple diseases in the absence of immunosuppression. Using this technique, cells are immobilized within carefully designed capsules that allow the long-term function of the graft. Although the potential impact of this field is likely to be wide-ranging, the past few years have seen several 'firsts' that have brought the whole technology much closer to a realistic clinical application.

Animals↗
PubMed2003

Controversies over stem cell research.

Much interest and effort has focused on the therapeutic potential of stem cell technology to treat presently intractable diseases. However, this scientific promise has been accompanied by important issues, including ethical hurdles, political policies and dilemmas concerning cell-source selection (embryonic versus adult stem cells). Although the contribution of stem cells to medical research seems enormous, many countries now face complex ethical and regulatory questions, which could represent a significant limitation to medical progress and could take years to overcome.

Adult↗
PubMed2003

A glimmer of hope for diabetics?

Diabetes affects 150 million people worldwide and results from abnormal function of pancreatic islets. The scarcity of human tissue donors has focused interest in developing renewable sources of insulin-producing cells appropriate for engraftment. Advances in stem cell technology and transdifferentiation techniques have provided powerful tools to study pancreatic development, function and disease. Recent results from these two approaches could have significant implications for future therapies of diabetes.

Cell Differentiation↗
PubMed2003

In vivo pharmacokinetic-pharmacodynamic relationship and in vitro equivalence of two oral furosemide tablet formulations.

A randomized, cross-over, open study of bioequivalence between two different furosemide (CAS 54-31-9) formulations was performed; simultaneously, diuretic effects (urine output, sodium, potassium and chloride excretion) were also compared. Both products meet the British Pharmacopoeia specification and the results of a previous in vitro comparative study ensure equivalence of the two dissolution curves. Twenty-four healthy volunteers (male/female) participated in the bioequivalence study. Each treatment was given as a single 40-mg tablet following an overnight fast. Furosemide concentrations in plasma (measured by HPLC) and electrolyte amounts in urine were determined up to 12 h after treatment. The pharmacokinetic parameters AUC0-infinity, Cmax and Cmax/AUC0-infinity were tested for bioequivalence after ln-transformation of data and ratios of tmax were evaluated nonparametrically. The parametric analysis revealed the following test/reference ratios and their 90% confidence intervals (90% CI): 1.06 (0.94-1.19) for AUC0-infinity, 1.12 (0.96-1.31) for Cmax, and 1.06 (0.97-1.16) for Cmax/AUC0-infinity. The 90% CI for tmax was 0.55-1.00. Bioequivalence between both formulations was concluded for all parameters except for tmax. No significant diuretic differences between both formulations (test and reference) were observed after drug administration in relation to the baseline period. Systolic and diastolic blood pressure and heart rate showed a similar time-course after the drug administration and there were no differences between both formulations. Both products were well tolerated. It can be concluded that both formulations are equivalent in vitro and in vivo.

Adult↗
PubMed2002

Release of salbutamol sulphate and ketoprofen enantiomers from matrices containing HPMC and cellulose derivatives.

We studied the release of salbutamol and ketoprofen enantiomers from HPMC K100M matrices containing two types of cellulose derivatives: cellulose tris (3,5-dimethylphenylcarbamate) and cellulose tris (2,3-dichlorophenylcarbamate), chiral excipients used as stationary phases for liquid chromatography. These matrices provided an extended release of both drugs. Ketoprofen release from formulations elaborated with cellulose tris (2,3-dichlorophenylcarbamate) was by anomalous transport, because the value of n (release exponent of the diffusion equation) ranged between 0.60-0.68, whereas for all other formulations the value of exponent n ranged from 0.50-0.54. The drug thus diffuses through the matrix and is released following a quasi-Fickian diffusion mechanism (stereoselective process). The matrices preferentially retained R-salbutamol and S-ketoprofen and cellulose tris (3,5-dimethylphenylcarbamate) showed more capacity of chiral discrimination for both drugs than cellulose tris (2,3-dichlorophenylcarbamate). Moreover, we observed that stereoselectivity is dependent on the amount of chiral excipient in the formulation. Diffusion tests confirmed the chiral interaction between drugs and cellulose derivatives observed in the dissolution assays except for matrices elaborated with ketoprofen and cellulose tris (2,3-dichlorophenylcarbamate), where the low stereoselectivity observed with the matrices is due to the presence of HPMC K100M. We conclude that the inclusion of these cellulose derivatives in HPMC matrices does not result in a relevant stereoselectivity with respect to the two drugs studied.

Albuterol↗