Partition coefficients of beta-blockers in bile salt/lecithin micelles as a tool to assess the role of mixed micelles in gastrointestinal absorption

The objective of this study was to develop non-invasive spectroscopic methods to quantify the partition coefficients of two beta-blockers, atenolol and nadolol, in aqueous solutions of bile salt micelles and to assess the effect of lecithin on the partition coefficients of amphiphilic drugs in mixed bile salt/lecithin micelles, which were used as a simple model for the naturally occurring mixed micelles in the gastrointestinal tract. The partition coefficients (Kp) at 25.0 +/- 0.1degreesC and at 0.1 M NaCl ionic strength were determined by spectrofluorimetry and by derivative spectrophotometry, by fitting equations that relate molar extinction coefficients and relative fluorescence intensities to the partition constant Kp. Drug partition was controlled by the: (i) drug properties, with the more soluble drug in water (atenolol) exhibiting smaller values of Kp, and with both drugs interacting more extensively in the protonated form; and by (ii) the bile salt monomers, with the dihydroxylic salts producing larger values of Kp for the beta-blockers, and with glycine conjugation of the bile acid increasing the values of Kp for the beta-blockers. Addition of lecithin to bile salt micelles decreases the values of Kp of the beta-blockers. Mixed micelles incorporate hydrophobic compounds due to their large size and the fluidity of their core, but amphiphilic drugs, for which the interactions are predominantly polar/electrostatic, are poorly incorporated in mixed micelles of bile salts/lecithin.

Effect of liposomes on the rate of alkaline hydrolysis of indomethacin and acemetacin

The anti-inflammatory, analgesic, and antipyretic drugs indomethacin (INDO) and acemetacin (ACE), extensively used for the treatment of diseases of degenerative or inflammatory character, exhibit marked gastric irritant action, have low water solubility at neutral pH, and decompose in alkali. Alternative formulations are being investigated to obtain products with lower toxicity and higher stability. Here we examine the effect of liposome charge on the rate of alkaline decomposition of INDO and ACE using micelles as reference. Binding of ACE and INDO to zwitterionic hexadecylphosphocholine (HDPC) micelles and phosphatidylcholine (PC) liposomes was analyzed using a two-phase separation model to quantify the effect of these aggregates on the rate of alkaline degradation. The substrate association constants to HDPC micelles were 1335 and 2192 M(-1) for INDO and ACE, respectively, whereas the corresponding values for PC vesicles were 612 and 3050 M(-1). The difference was attributed to the additional hydrophobicity of ACE. The inhibitory effect of HDPC micelles and PC vesicles was quantified by calculating the ratio between the rate constants in water (k(w)) and in the aggregate (k(m)). The values of the k(w)/k(m) ratios for INDO and ACE in HDPC micelles were, respectively, 80 and 42, and in PC liposomes these ratios were 21 and 3.7, respectively. Positively charged micelles of hexadecyltrimethylammonium chloride (CTAC) and vesicles containing varying proportions of dioctadecyldimethylammonium chloride (DODAC) and PC increase the rate of INDO and ACE alkaline decomposition. Vesicle effects were very sensitive to the DODAC/PC ratio, with rates increasing with the proportion of DODAC. The data were analyzed quantitatively using a pseudophase model with explicit consideration of ion exchange. The calculated second-order rate constants in micelles and vesicles were lower than that in water. The charge density in the liposome necessary to increase the entrapment efficiency and decrease drug decomposition can be modulated, by judicious choice of pH and ionic strength. These manipulations can lead to more stable formulation with increased efficiency in drug entrapment and controlled effects on drug stability.

Study of partition of nitrazepam in bile salt micelles and the role of lecithin

The effect of trihydroxy (sodium cholate and sodium glycocholate) and dihydroxy (sodium deoxycholate and sodium glycodeoxycholate) bile salt micelles on the spectrophotometric properties and on the solubility of nitrazepam in aqueous solution, at 25.0 degrees C and at ionic strength 0.1 M in sodium chloride, has been assessed. From the results obtained it was possible to calculate the partition coefficients (Kp) of nitrazepam between aqueous and micellar phases. The partition coefficients of nitrazepam have also been determined in mixed micelles of cholate or deoxycholate with lecithin (egg yolk phosphatidylcholine), which were used as a model of the gastrointestinal tract. Drug partition was found to depend on the bile acid (number of hydroxyl groups and conjugation with glycine), and our data indicate further that addition of lecithin to bile salt micelles decreases the values of the partition coefficients in the mixed micelles at physiological pH.

A fast and reliable spectroscopic method for the determination of membrane--water partition coefficients of organic compounds

Partition coefficients (Kp) between egg yolk phosphatidylcholine multilamellar vesicles and water were determined for two nonsteroidal anti-inflammatory drugs (indomethacin and acemetacin) using two independent methodologies: derivative spectrophotometry and variation of the experimental acidity constant in the presence of increasing vesicle concentration. Second-derivative spectrophotometry allowed for total elimination of background signal effects arising from lipid vesicles, without the need for separation techniques that may disturb equilibrium states. By using a model based on a simple partition, the values of K(T)p can be obtained directly; furthermore, by performing determinations at two different pH values it is possible to calculate partition coefficients for the neutral and negatively charged forms of the drugs (K(AH)p and K(A)p). In the other methodology, values of apparent acidity constants (K(app)) were determined by spectrophotometry at different pH values and different lipid concentrations, and an increase in K(app) with decreasing lipid concentration was observed for both drugs, and from this dependence it was possible to calculate K(AH)p and K(A-)p for each drug. These values were used as a check for those obtained by derivative spectroscopy, which has proven to be a reliable and more expeditious method to obtain K(AH)p and K(A-)p .

Patients in Europe evaluate general practice care: an international comparison

BACKGROUND

Patients' evaluations can be used to improve health care and compare general practice in different health systems.

AIM

To identify aspects of general practice that are generally evaluated positively by patients and to compare opinions of patients in different European countries on actual care provision.

METHOD

An internationally-validated questionnaire was distributed to and completed by patients in 10 European countries. A stratified sample of 36 practices per country, with at least 1080 patients per country, was included. A set of 23 validated questions on evaluations of different aspects of care was used, as well as questions on age, sex, overall health status, and frequency of visiting the GP.

RESULTS

The patient sample included 17,391 patients in 10 different countries; the average response rate was 79% (range = 67% to 89%). In general, patients visiting their general practitioner (GP) were very positive about the care provided. For most of the 23 selected aspects of care more than 80% viewed care as good or excellent; in particular, keeping records confidential, GP listening to patients, time during consultations, and quick services in case of urgent problems were evaluated positively. Patients were relatively negative about organisational aspects of care. The evaluations in different countries were largely similar, with some interesting differences; for instance, service and organisational aspects were evaluated more positively in fee-for-service health systems.

CONCLUSIONS

Patients in Europe are positive about general practice but improvements in practice management in some countries are requested. More research is needed to study the complex field of differences in expectations and evaluations between countries with different health systems.

Doctor-patient concordance and patient initiative during episodes of low back pain

Doctor-patient concordance and patient initiative were examined in a prospective network interview study, with telephone follow-up, of a cohort of 100 patients presenting with low back pain to their family physician. The average overall rate of concordance was 60% (95% CI = 53 to 66), with the highest rates for radiographic imaging studies and sick leave. No correlation was found between concordance and patient parameters. Subjects initiated an average of two (95% CI = 1.7 to 2.3) diagnostic or therapeutic procedures, the most common of which were for medications (40%), followed by bed rest (26%) and back school (22%). One out of every six subjects initiated a referral to a complementary therapist. Positive correlation was found between patient initiatives and pain severity (P = 0.022) and disability (P = 0.02). There was a negative correlation between the subjects' initiatives and their belief that the physician understood the cause of their pain and its influence on their life (P = 0.02). Overall, those patients who described more pain or disability sought more types of diagnostic and therapeutic measures, while those who felt they had been understood sought less.

Phenolic acids and derivatives: studies on the relationship among structure, radical scavenging activity, and physicochemical parameters

The antiradical activity of caffeic acid (1), dihydrocaffeic acid (5), and their corresponding n-alkyl esters was evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(*)) method. Dihydrocaffeic acid (5) was the most potent compound, having an antiradical effect higher than that of (+/-)-alpha-tocopherol, whereas caffeic acid (1) was less efficient. Esterification of the carboxyl group of dihydrocaffeic acid (5) had a dramatic effect on its antiradical potency, but similar effects were not observed for caffeic acid (1) derivatives. The n-alkyl esters of both phenolic series had similar potencies, and their antiradical activities were independent of the alkyl chain length. Dose-dependent scavenger effects were found in both series. Acid-base properties of the compounds, evaluated by using potentiometry and spectrophotometry, showed that the catechol moiety had pK(a2) and pK(a3) values of 9. 24-9.02 and 11.38-10.99 in the dihydrocaffeic series and 8.48-8.24 and 11.38-11.07 in the caffeic series, respectively. Antiradical activity and pK(a) values of the compounds were not related.

Abnormal myocardial phosphorus-31 nuclear magnetic resonance spectroscopy in women with chest pain but normal coronary angiograms

BACKGROUND

After hospitalization for chest pain, women are more likely than men to have normal coronary-artery angiograms. In such women, myocardial ischemia in the absence of clinically significant coronary-artery obstruction has long been suspected. Most methods for the detection of the metabolic effects of myocardial ischemia are highly invasive. Phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy is a noninvasive technique that can directly measure high-energy phosphates in the myocardium and identify metabolic evidence of ischemia.

METHODS

We enrolled 35 women who were hospitalized for chest pain but who had no angiographically significant coronary-artery obstructions and 12 age- and weight-matched control women with no evidence of heart disease. Myocardial high-energy phosphates were measured with 31P-NMR spectroscopy at 1.5 tesla before, during, and after isometric handgrip exercise at a level that was 30 percent of the maximal voluntary grip strength. We measured the change in the ratio of phosphocreatine to ATP during exercise.

RESULTS

Seven (20 percent) of the 35 women with chest pain and no angiographically significant stenosis had decreases in the phosphocreatine:ATP ratio during exercise that were more than 2 SD below the mean value in the control subjects without chest pain. There were no significant differences between the two groups with respect to hemodynamic variables at rest and during exercise, risk factors for ischemic heart disease, findings on magnetic resonance imaging and radionuclide perfusion studies of the heart, or changes in brachial flow during the infusion of acetylcholine.

CONCLUSIONS

Our results provide direct evidence of an abnormal metabolic response to handgrip exercise in at least some women with chest pain consistent with the occurrence of myocardial ischemia but no angiographically significant coronary stenoses. The most likely cause is microvascular coronary artery disease.

Acid-base properties and solubility of pindolol, diazepam and chlordiazepoxide in SDS micelles

The effect of sodium dodecyl sulphate (SDS) on the acid-base properties and on the solubility of a beta-blocker (pindolol) and of two benzodiazepines (diazepam and chlordiazepoxide) has been assessed. The study was performed by potentiometric and spectrophotometric determinations of the acidity constants and by spectrophotometric evaluation of the solubilities of the pharmaceutical drugs in aqueous solution and in solutions to which was added SDS with concentrations below and above the critical micelle concentration (cmc), at 25 degrees C and at an ionic strength 0.1 M (NaCl). The effect of the organized assemblies on the pKa values was quantified by the application of two theoretical models that differ in the inclusion of ionic exchange between positively charged species in solution. These models have allowed the determination of the binding constants for drug/micelle and yielded values in good agreement with those obtained by the solubility method, and in addition provide a more detailed picture of the effect of drug charge on its partition. The results can be taken to evidence different interaction modes of the drugs with the SDS micelles.

A new look at low back complaints in primary care: a RAMBAM Israeli Family Practice Research Network study

BACKGROUND

Low back pain (LBP) is one of the most frequent reasons patients seek consultations in primary care, and it is a major cause of disability. Our research examines the natural history of LBP and the prediction of chronicity in the context of patients presenting to family medicine clinics.

METHODS

We performed a prospective cohort study of new episodes of LBP within the framework of a national family practice research network. The setting was 28 primary care family practice clinics located throughout Israel. Of 238 eligible subjects, 219 (92%) completed the study.

RESULTS

During the 2-month study period, 2 subjects were referred to the emergency department and discharged, and 2 others were hospitalized. Forty-five percent did not require bed rest, and 38% of the employed were not absent from work. Seventy-one percent showed improvement in functional status; however, only 37% noted complete pain relief. Clinical and demographic data usually did not predict LBP-episode outcomes. The strongest predictors of chronicity were depression, history of job change due to LBP in the past, history of back contusion, lack of social support, family delegitimization of patient's pain, dissatisfaction with first office visit, family history of LBP or other chronic pain, coping style, and unemployment.

CONCLUSIONS

The cohort patients displayed a relatively benign natural history of LBP, matched by benign clinical behavior from their physicians. In Israeli primary health care, acute LBP is infrequently associated with hospitalization or prolonged work absenteeism. Although most patients have functional improvement, pain often lingers. Almost all predictors of chronicity are psychosocial.

Fluorimetric and solubility studies of nadolol and atenolol in SDS micelles

The effect of sodium dodecyl sulfate (SDS) micelles on the spectrofluorimetric intensities and on the solubility of two beta-blockers (atenolol and nadolol) were studied at 25.0 +/- 0.1 degrees C and I = 0.1 M NaCl. From the dependence of these physical properties on SDS concentration it was possible to calculate the binding constants drug-micelle, and it was found that both techniques yield similar results for the binding constants, and that are in agreement with those calculated from the effect of micelles on the apparent acidity constants of the beta-blockers.

Tetracycline, oxytetracycline and chlortetracycline determination by flow injection potentiometry

This paper describes tetracycline (TCH), oxytetracycline (OTCH) and chlortetracycline (CTCH) determination by flow injection potentiometry. In the flow system proposed TC samples are inserted in a carrier solution and converged with a Cu(II) solution of known concentration; the Cu(II) decrease due to its complexation with tetracyclines (TC) was monitored. The detector used was a homogeneous crystalline CuS/Ag2S double membrane tubular electrode with increased sensitivity. The present system allows tetracyclines determinations within a 48.1-4.8 x 10(3) ppm for TCH, 49.1-4.9 x 10(3) ppm for OTCH and 51.5-5.1 x 10(3) ppm for CTCH and a precision better than 0.4% for the three TC species. This procedure accomplishes 150-200 samples h(-1) with a Cu(II) consumption of about 13 microg determination(-1).

A report from the Second International Forum for Primary Care Research on Low Back Pain. Reexamining priorities

STUDY DESIGN

Consensus process.

OBJECTIVES

Reexamining and redirecting the research agenda for low back pain in primary care.

SUMMARY OF BACKGROUND DATA

Most research, publications, and funding have traditionally been directed toward specialty and biologically oriented investigations of "spinal disorders" from biomedical and biomechanical perspectives. Beginning in the mid-1980s, primary care researchers began to investigate this field in earnest, focusing on lower back pain as a pain syndrome within an individual, family, and community context. Unfortunately, more progress has been made on what should not be done in diagnosing and treating lower back pain than on what should be done.

METHODS

This was a modified group process designed to reach consensus among an international group of primary care lower back pain researchers.

RESULTS

Nearly all of the research priorities from the initial 1995 forum are still thought to be important, although only modest progress has been made on most of them. The priorities perceived to be the most feasible to investigate and the ones in which the greatest strides have been achieved are in methodologic rather than substantive areas. Identifying subgroups of people with lower back pain is still given top ranking in 1997, but the priorities have changed dramatically. Greater emphasis is given to finding predictors and risk factors for lower back pain chronicity, improving self-care strategies, and stimulating self-reliance. New items now make up 50% of the top 10 priorities. In general, the additions reflect a greater emphasis on expanding methodologic avenues of inquiry.

CONCLUSIONS

Methodologic advances, the enlistment of new techniques and disciplines, and redirected research efforts may facilitate progress in the diagnosis and treatment of lower back pain.

General practice care and patients' priorities in Europe: an international comparison

Insight into patients' priorities with respect to health care should complement the views of professionals and policy makers on what is thought to be appropriate health care. To determine the strengths and weaknesses of general practice care from patients' perspectives written surveys were performed among patients in Denmark, Germany, Israel, Netherlands, Norway, Portugal, Sweden and United Kingdom (n = 3540). The potential quality problems identified were spread over the different countries: the low involvement of general practitioners in out-of-hours services in Portugal; the low provision of routine screening in Sweden, Norway and The Netherlands; the lack of a defined patient population in Germany; the lack of a formal gatekeeper role to secondary care in general practice in Germany and Sweden; and the low number of home visits in Sweden.

Telemedicine in primary care in Israel

A primary-care teleconsulting system was established between an academic family medicine centre and a clinic about 50 km away. The videoconferencing units were connected at 384 kbit/s. Seven patients were examined by a physician in the clinic and then examined by a consulting physician using the telemedicine system. Four other patients were examined through the telemedicine system first and by a local physician later. The telemedicine consultation solved five of the patients' medical problems. The waiting period before receiving expert medical consultation was reduced. There was full patient satisfaction regarding this method of consultation, patient 'run around' was avoided and patients felt at ease. The telemedicine consultation process improved the patient-physician bond and the attending physician's level of confidence.

Acid/base properties of beta-blockers and benzodiazepines in sodium dodecyl sulfate micelles. A spectrophotometric and potentiometric study

The effect of sodium dodecyl sulfate (SDS) micelles on the acid-base properties of two family of pharmaceutical drugs (beta-blockers and benzodiazepines) at 25 degrees C and I = 0.1 M NaCl have been studied. The characterization of the several solution equilibria for the system drug/SDS micelle solution was performed by potentiometry and spectrophotometry, below and above the critical micelle concentration (cmc). Two widely used models have been applied to quantify the effect of micelles on the pKa of the drugs, and the results obtained point to different interactions of each family of drugs with the micelles.

Copper(II) increases bile acid binding to asparagine

Interactions of two bile acids (cholic and glycocholic acids) with asparagine have been studied by potentiometry in aqueous solutions under conditions similar to those observed in biological fluids (37 degrees C and I = 0.15 M NaCl), and in the absence and presence of copper(II). To characterize the equilibria for the systems copper(II)/bile acid/asparagine, specifically to assess cooperative binding between bile acids and asparagine, the acidity constant of asparagine and formation constants for copper(II)/bile acid and copper(II)/asparagine were also obtained under the same conditions. The results obtained suggest cooperativity in the binding of bile acid to asparagine in the presence of copper(II).

[Integration of the community emergency center into medical services]

The first community emergency center (CEC) in Israel was established in 1988 in Jerusalem. It provided medical services after health fund clinic working hours, in a primary care facility, by primary care physicians. In the past 5 years Israel has witnessed growth in this method of health care delivery and more than 20 such centers have been established throughout the country. We describe a CEC in a small town, and its function and its integration within the regional medical services. 2 retrospective studies examined 3 aspects of the CEC: patient profiles including age, sex, and major diagnoses, use of specific services; and referrals to the emergency room.

[Guidelines for treating low back pain in primary care. The Israeli Low Back Pain Guideline Group]

Low back pain (LBP) is a common problem in primary care, the successful management of which poses special challenges for patients and practitioners alike. It has been estimated that all adults will suffer LBP sometime during their lifetimes. It is one of the most frequent reasons for visiting a primary care physician, yet practitioners often find it difficult and frustrating to treat. This medical protocol is concerned with the diagnosis, treatment, and follow-up of low back pain in adults. It was developed for community-based, primary care physicians (general practitioners, family physicians, and internists) to serve as a general outline, to be adjusted in accord with the individual's circumstances. The protocol provides a "Ten Commandments" for the care of LBP, outlines the background of the problem, presents an overall algorithm and deals with issues of diagnosis, imaging, and treatment. In general, LBP in primary care is conceived of as a benign ailment, and emphasis is placed on reducing pain, resuming functioning and returning to work. The main task of the physician is to distinguish the less than 10% of cases with serious, specific causes of LBP from the more than 90% with nonspecific etiologies. In the great majority of patients, imaging studies such as X-ray, CT, MRI, and bone scan, and also EEG are unnecessary.

Talking about the pain: a patient-centered study of low back pain in primary care

Despite considerable research, low back pain (LBP) often proves resistant to treatment. This study was designed to increase the understanding of low back pain through access to patients' perceptions, beliefs, illness behaviors and lived experiences. The findings are based on focus groups, individual interviews and participant observation conducted in primary care practices and community settings in three regions in Israel. Inclusion criteria for the interviews and groups include age greater than 18 years and a history of at least one episode of LBP. Seventy-six LBP subjects between the ages of 18 and 67 (mean 39.5) participated, 65% male and 35% female. The analytic method is content analysis, consisting of a formal, multi-step process designed to elucidate inherent patterns and meanings. This research finds that LBP subjects articulate a rich world of pain sensation, awareness and meanings. From subjects' own words and experiences we present a patient-centered classification system of backache symptoms based on typical pain intensity, dysfunction, duration and treatment. An elaborate system of explanatory models of LBP and a typology of dominant coping styles designed to either minimize pain or maximize function are also derived. Subjects choose multiple conventional and alternative treatments based on 'what works', and articulate ample criticisms of and suggestions for the medical system. In addition, we find that variations in the social construction of the back pain experience vary sharply, even between similar neighboring communities. Given the difficult state of diagnosis and treatment and the frustration of practitioners, attempts at greater understanding of patients' health beliefs, experiences, and behaviors are warranted.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiometric determination of formation constants of copper(II)/bile acid/peptide in aqueous solution

A potentiometric method was used to study the equilibria in aqueous solution for the systems copper(II)/bile acid salt/peptide [bile acid salt-sodium cholate or glycocholate; and peptide-glutamic acid (glutamate), glutamine or glutamylglutamic acid], specifically to assess cooperative binding between small peptides and bile acids in the presence of copper(II). The results obtained suggest large cooperativity in formation of ternary complexes with amino acids when they are coordinated to copper(II) as bidentate ligands.