Phase transitions in the classical simulability of open quantum systems

We introduce a Langevin unravelling of the density matrix evolution of an open quantum system over matrix product states, which we term the time-dependent variational principle-Langevin equation. This allows the study of entanglement dynamics as a function of both temperature and coupling to the environment. As the strength of coupling to and temperature of the environment is increased, we find a transition where the entanglement of the individual trajectories saturates, permitting a classical simulation of the system for all times. This is the Hamiltonian open system counterpart of the saturation in entanglement found in random circuits with projective or weak measurements. If a system is open, there is a limit to the advantage in simulating its behaviour on a quantum computer, even when that evolution harbours important quantum effects. Moreover, if a quantum simulator is in this phase, it cannot simulate with quantum advantage.

Persistence and compliance with osteoporosis therapies among postmenopausal women in the UK Clinical Practice Research Datalink

Gaining full benefits from osteoporosis medications requires long-term treatment. Investigating the real-world persistence of women receiving osteoporosis medications in the UK, we found that most patients stop treatment within a year. To prevent osteoporotic fragility fractures, long-term treatment persistence must be improved.

INTRODUCTION

Persistence with osteoporosis therapies has historically been poor. To treat this chronic and progressive disease, it is essential that patients receive the full benefit of these medications. We estimated persistence and compliance with osteoporosis therapies in a large sample of postmenopausal women in the UK.

METHODS

Data were obtained from the Clinical Practice Research Datalink for all women aged 50 years and over or women with early menopause, who received at least one prescription in primary care for any licensed osteoporosis therapy between January 1, 2010 and December 31, 2015. Persistence and compliance at 24 months (primary objective) and at 5 years (exploratory objective) were estimated in three patient cohorts: "All Patients," "Naïve Patients," and "Drug-Specific."

RESULTS

The All Patients cohort included 72,256 women. Persistence with any therapy was 56.1%, 43.6%, 36.4%, and 31.0% at 6, 12, 18, and 24 months, respectively, and 23.2% and 13.1% at 3 years and 5 years, respectively. Patients were generally more persistent and compliant if evaluated from their first exposure to osteoporosis therapy (Naïve Patients cohort). In the drug-specific analysis, 64% of patients receiving denosumab (administered subcutaneously every 6 months) were persistent at 24 months compared with 28% and 23% of those taking oral bisphosphonates and intravenous bisphosphonates, respectively.

CONCLUSIONS

Only about one in three patients who received osteoporosis therapy continued to be on treatment after 2 years. There is a need to improve persistence with osteoporosis therapy, especially for high-risk patients.

Designing Drug Trials for Frailty: ICFSR Task Force 2018

To reduce disability and dependence in older adults, frailty may represent an appropriate target for intervention. While preventing frailty through lifestyle interventions may be the optimal public health approach for many population groups, pharmacological approaches will likely be needed for individuals who meet frailty criteria or who have comorbid conditions that contribute to and complicate the frailty syndrome, and for those who are not compliant with lifestyle interventions. Barriers to successful development of drug treatments for frailty include variability in how the frailty syndrome is defined, lack of agreement on the best diagnostic tools and outcome measures, and the paucity of sensitive, reliable, and validated biomarkers. The International Conference on Frailty and Sarcopenia Research Task Force met in Miami, Florida, on February 28, 2018, to consider the status of treatments under development for frailty and discuss potential strategies for advancing the field. They concluded that at the present time, there may be a more productive regulatory pathway for adjuvant treatments or trials targeting specific functional outcomes such as gait speed. They also expressed optimism that several studies currently underway may provide the insight needed to advance drug development for frailty.

Inhibition by Heparin of Platelet Accumulation In Vivo

In vivo platelet aggregation has been studied using a novel, minimally invasive technique. No aggregatory effects of heparin were observed on normal circulating platelets nor was there enhancement of aggregation of platelets during activation by fhtravenous injection of ADP, collagen, PAF acether or thrombin. On the contrary, high doses of heparin were found to inhibit platelet accumulation induced by ADP, collagen or PAF-acether. Inhibition of these responses necessitated doses of heparin in excess of those required for anti-coagulant effects. The present experiments do not establish a mechanism for such inhibition. Extension to other species, including man, is needed before attributing clinical relevance to the present observations.

An In Vivo Model for Studying Platelet Aggregation and Disaggregation

A simple minimally invasive technique has been developed for the continuous monitoring of 111-Indium labelled homologous platelets in the thoracic (C1) and abdominal (C2) regions of experimental animals. The effects of the aggregatory agents adenosine diphosphate (ADP), collagen and platelet activating factor (PAF) and the anti-aggregatory agent, prostacyclin (PGI2) have been studied in the guinea-pig. Administration of ADP, collagen or PAF produces an increase in counts in C1, a decrease in counts in C2, and hence an increase in the ratio C1/C2. The rise in C1/C2 is more protracted after collagen administration than after ADP or PAF. PGI2 (50-500 ng/kg) reduces the response to ADP. The present technique is both simple, reproducible and although the present experiments are in the presence of heparin, the technique remains functional in the presence of minimal heparin, thus making it a suitable method for studies of platelet function and the evaluation of anti-aggregatory agents in vivo.

Implications of ICD-10 for Sarcopenia Clinical Practice and Clinical Trials: Report by the International Conference on Frailty and Sarcopenia Research Task Force

Establishment of an ICD-10-CM code for sarcopenia in 2016 was an important step towards reaching international consensus on the need for a nosological framework of age-related skeletal muscle decline. The International Conference on Frailty and Sarcopenia Research Task Force met in April 2017 to discuss the meaning, significance, and barriers to the implementation of the new code as well as strategies to accelerate development of new therapies. Analyses by the Sarcopenia Definitions and Outcomes Consortium are underway to develop quantitative definitions of sarcopenia. A consensus conference is planned to evaluate this analysis. The Task Force also discussed lessons learned from sarcopenia trials that could be applied to future trials, as well as lessons from the osteoporosis field, a clinical condition with many constructs similar to sarcopenia and for which ad hoc treatments have been developed and approved by regulatory agencies.

Implications of ICD-10 for Sarcopenia Clinical Practice and Clinical Trials: Report by the International Conference on Frailty and Sarcopenia Research Task Force

Establishment of an ICD-10-CM code for sarcopenia in 2016 was an important step towards reaching international consensus on the need for a nosological framework of age-related skeletal muscle decline. The International Conference on Frailty and Sarcopenia Research Task Force met in April 2017 to discuss the meaning, significance, and barriers to the implementation of the new code as well as strategies to accelerate development of new therapies. Analyses by the Sarcopenia Definitions and Outcomes Consortium are underway to develop quantitative definitions of sarcopenia. A consensus conference is planned to evaluate this analysis. The Task Force also discussed lessons learned from sarcopenia trials that could be applied to future trials, as well as lessons from the osteoporosis field, a clinical condition with many constructs similar to sarcopenia and for which ad hoc treatments have been developed and approved by regulatory agencies.

Designing pharmaceutical trials for sarcopenia in frail older adults: EU/US Task Force recommendations

An international task force of academic and industry leaders in sarcopenia research met on December 5, 2012 in Orlando, Florida to develop guidelines for designing and executing randomized clinical trials of sarcopenia treatments. The Task Force reviewed results from previous trials in related disease areas to extract lessons relevant to future sarcopenia trials, including practical issues regarding the design and conduct of trials in elderly populations, the definition of appropriate target populations, and the selection of screening tools, outcome measures, and biomarkers. They discussed regulatory issues, the challenges posed by trials of different types of interventions, and the need for standardization and harmonization. The Task Force concluded with recommendations for advancing the field toward better clinical trials.

Vitamin D supplementation in older adults: searching for specific guidelines in nursing homes

BACKGROUND

The prevalence of vitamin D insufficiency is very high in the nursing home (NH) population. Paradoxically, vitamin D insufficiency is rarely treated despite of strong clinical evidence and recommendations for supplementation. This review aims at reporting the current knowledge of vitamin D supplementation in NH and proposing recommendations adapted to the specificities of this institutional setting.

DESIGN

Current literature on vitamin D supplementation for NH residents was narratively presented and discussed by the French Group of Geriatrics and Nutrition.

RESULT

Vitamin D supplementation is a safe and well-tolerated treatment. Most residents in NH have vitamin D insufficiency, and would benefit from vitamin D supplement. However, only few residents are actually treated. Current specific and personalized protocols for vitamin D supplementation may not be practical for use in NH settings (e.g., assessment of serum vitamin D concentrations before and after supplementation). Therefore, our group proposes a model of intervention based on the systematic supplementation of vitamin D (1,000 IU/day) since the patient's admission to the NH and throughout his/her stay without the need of a preliminary evaluation of the baseline levels. Calcium should be prescribed only in case of poor dietary calcium intake.

CONCLUSION

A population-based rather than individual-based approach may probably improve the management of vitamin D insufficiency in the older population living in NH, without increasing the risks of adverse health problems. The clinical relevance and cost effectiveness of this proposal should be assessed under NH real-world conditions to establish its feasibility.

Vasodilatation in the submaxillary gland of the rabbit

1. In the rabbit, in contrast to the cat and dog, the vasodilatation and the secretion in the submaxillary gland which accompany parasympathetic nerve stimulation are correspondingly sensitive to atropine block. 2. It is concluded that true vasodilator nerve fibres to the submaxillary gland exist in the chorda tympani nerve of the rabbit. 3. The vasodilatation which follows sympathetic vasoconstriction in the submaxillary gland of the rabbit is small and variable. The possibility that this after-dilatation is due to an adrenergic neurotransmitter agent acting on beta-vascular receptors is discussed.

Identification, Preparation, and Characterization of Several Polymorphs and Solvates of Terazosin Hydrochloride

The phenomenon of polymorphism is prevalent in pharmaceuticals, yet it is unusual to identify more than three or four forms for any particular drug. Terazosin hydrochloride has been found to exist at room temperature in four solvent-free forms that can be isolated directly, one solvent-free form that can be prepared by desolvation of a methanolate, a methanol solvate, and a dihydrate. This study presents characterization and methods for preparation of each of these forms. Data are also presented demonstrating the relative stability of these forms.

The pursuit of precision pharmaceuticals: divergent effects of beta2 agonist isomers

Beta2 agonists are the most commonly used treatment for acute bronchoconstriction. However, during regular use there is a progressive decline of protective efficacy of bronchodilators. This progressive decline has long been considered anomalous because with short-acting beta agonists, there is no corresponding change in bronchodilator efficacy. Airway hyper-responsiveness is itself a feature of asthma and there maybe however, there may be an increase in airway hyper-responsiveness following regular use of beta2 agonist. Airway hyperresponsiveness could diminish the capacity of beta agonists to protect from or result in paradoxical bronchospasm and there effects of racemic salbutamol. There have been reports of increased morbidity and mortality associated with excessive use of beta(2) agonists. As all beta agonists used clinically are racemates composed of 1:1 mixtures of R and S isomers, conducted on the possible involvement of the isomers in hyper-responsiveness. Hyper-responsiveness cannot be attributed to the R isomer, whose capacity to activate beta adrenoceptors will nullify this effect. In contrast, extensive evidence indicated that the S isomer might cause hyper-responsiveness and potential airway inflammation. Further, the S isomer shows a propensity to activate human eosinophils and alter muscarinic M(2) receptor functions. The S isomer, which makes no contribution to therapeutic efficacy and may exacerbate asthma, might therefore be excluded from asthma therapy.

Levalbuterol hydrochloride

Racemic salbutamol (racemic albuterol) ameliorates symptoms of asthma by activating beta-adrenoceptors on nerve, smooth muscle and inflammatory cells within the airways. Racemic salbutamol comprises equal proportions of 2 isomers: (S)-salbutamol and (R)-salbutamol, with the latter being exclusively responsible for activation of beta-adrenoceptors. Accordingly, within racemic salbutamol it is (R)-salbutamol that efficiently relieves obstruction of asthmatic airways and affords highly effective protection from bronchoconstrictor stimuli, including allergens. During regular use of racemic salbutamol, there is a progressive decline of protective efficacy and a corresponding intensification of airway responsiveness. This decline is largely absent during regular use of (R)-salbutamol. Consequently, bronchodilator responses to sub-maximal doses of (R)-salbutamol exceed responses to the equivalent dose of (R)-salbutamol given as the racemate. For example, in asthmatics with baseline FEVs <or= 60%, 1.25 mg of nebulised (R)-salbutamol achieved a maximal 52% change in FEV while 2.5 mg of racemic salbutamol only achieved a 38% change in FEV. Since extrapulmonary effects (e.g., tremor, heart rate) of beta agonists are related to dose and limit the use of beta agonist therapy, (R)-salbutamol at 0.63 mg provides uncompromised efficacy with marked reduction of side-effects. In addition to quantitative differences, the constituent isomers of salbutamol also exhibit qualitative differences. Thus, (R)-salbutamol inhibits activation of human eosinophils in vitro whereas, under the same conditions and concentrations, (S)-salbutamol augments activation of these cells. This property of (S)-salbutamol may explain why eosinophilia in induced sputum from subjects with allergic asthma is increased by regular use of racemic salbutamol. Similarly, the capacity of (R)-salbutamol to suppress hyperresponsiveness of the airways can be contrasted with the capacity of (S)-salbutamol to intensify hyperresponsiveness. This action of (S)-salbutamol would explain why regular use of racemic salbutamol intensifies the bronchoconstrictor response to antigen in subjects with allergic asthma. Taken together, these findings imply that replacement of racemic salbutamol by (R)-salbutamol will diminish, or even eliminate, the anomalous actions that have curtailed the efficacy of racemic salbutamol. Pharmacokinetically, (R)-salbutamol exhibits near absolute conformational stability (i.e., no conversion to (S)-salbutamol). If in vitro anti-inflammatory actions of (R)-salbutamol are also manifest in asthmatic airways, (R)-salbutamol could provide a novel approach to asthma therapy which combines bronchodilation and bronchoprotection with anti-inflammatory efficacy.

Classification of type 2 diabetes by clinical response to metformin-troglitazone combination and C-Peptide criteria

OBJECTIVE

To assess the ability of basal and stimulated C-peptide levels and stimulated glucose values after oral administration of glucose to predict a successful response to metformin and troglitazone combination therapy after discontinuation of insulin therapy.

METHODS

At the onset of the study, plasma glucose and C-peptide levels were measured in a group of 64 obese patients with insulin-treated type 2 diabetes while they were fasting and 2 hours after a challenge of 100 g of glucose administered orally. Then combination metformin-troglitazone treatment was initiated while insulin therapy was gradually tapered over 8 to 12 weeks. Subjects who successfully tolerated insulin withdrawal after the metformin-troglitazone combination were categorized as non-insulin-requiring responders, whereas those who needed insulin to obtain glycemic control were categorized as insulin-requiring nonresponders. Basal and glucose-stimulated C-peptide levels as well as stimulated glucose values were contrasted in the responder versus nonresponder groups. In a second protocol, eight obese patients with insulin-treated type 2 diabetes who successfully stopped insulin therapy were reassessed for C-peptide and glucose variables during the 2-hour oral glucose tolerance test. This reassessment followed a 12-week period of therapy to determine whether treatment of insulin resistance with the combination of metformin and troglitazone could normalize the impaired glucose tolerance in type 2 diabetes.

RESULTS

After metformin-troglitazone therapy, 48 study subjects (75%) could later be managed without insulin, whereas 16 (25%) needed insulin to achieve acceptable glycemic control. In a comparison of the non-insulin-requiring responder and insulin-requiring nonresponder groups, the responder group had significantly higher glucose-stimulated C-peptide levels and much lower stimulated glucose levels. The mean basal plasma C-peptide level was higher in the responder than in the nonresponder group, but a small degree of overlap was found between the two groups. Combination treatment with metformin and troglitazone for 12 weeks resulted in a significant reduction in the C-peptide response and glucose variables after the glucose load.

CONCLUSION

The results of this study indicate that stimulated C-peptide and glucose levels may be useful criteria to identify whether combination metformin-troglitazone treatment can successfully replace insulin therapy in the management of obese patients with type 2 diabetes. Inability to normalize glucose intolerance after restoring insulin resistance with insulin sensitizers is supportive of the presence of both disturbed beta-cell function and insulin resistance in patients with type 2 diabetes.

Use of bio-resorbable implants for stabilisation of distal radius fractures: the United Kingdom patients' perspective

Bio-resorbable implants have been, recently, introduced in the United Kingdom. To our knowledge there have been no randomised studies to assess perception of today's well-informed patients about this new method of fracture stabilisation. In order to assess the patients' perception a prospective study was performed on 100 consecutive adult patients with distal radius fractures. Following detailed verbal and written information about both resorbable and metal implants, the patients were asked to complete a specifically designed questionnaire. Ninety-five percent of the patients appreciated the 'resorbable' feature and responded that they would prefer to have their fracture stabilised with a resorbable implant. Conversely, 91% of the participants considered removal as the most negative aspect of the metal implant (p<0.0001). While 56% of the patients felt that it was relatively a new and evolving technology, 29% of them had apprehension about the relative strength of the resorbable implant. Eighty percent of the patients stated that they would be happy to participate in clinical trials to compare the use of bio-resorbable implants versus metal ones (p=0.0001). This study sets the foundation for the implementation of prospective randomised trials to assess the efficacy of the new generation of bio-resorbable implants.

Impact of intramedullary instrumentation versus damage control for femoral fractures on immunoinflammatory parameters: prospective randomized analysis by the EPOFF Study Group

BACKGROUND

Damage control orthopedic surgery has recently been advocated for the management of femoral shaft fractures in severely injured patients because surgical procedures were found to represent a second-hit phenomenon regarding the operative burden. It has been attempted to determine the operative burden by means of proinflammatory cytokines. In this study in clinically stable patients with multiple injuries, the effects induced by different types of primary fracture stabilization on the systemic release of proinflammatory cytokines were evaluated.

METHODS

This was a prospective, randomized, multicenter intervention study. Inclusion criteria were long bone shaft fracture of the lower extremity; age 18 to 65 years; Injury Severity Score > 16 or more than three extremity injuries (Abbreviated Injury Scale [AIS] score of 2 or more) in association with another injury (AIS score of 2 or more); and thoracic AIS score < 4. After informed consent, randomization for the treatment of the femoral shaft fracture was performed at admission. Groups were as follows: group I degrees FN (primary, < 24 hours) intramedullary nailing, and group DCO (DCO, I degrees ex.fix.) damage control orthopedic surgery and external fixation. In DCO patients, measurements were also performed at the time of conversion to the intramedullary procedure (DCO II degrees FN). Parameters included clinical parameters and complications (acute respiratory distress syndrome, multiple organ failure, sepsis). From serially sampled central venous blood, the perioperative concentrations of interleukin IL-1, IL-6, and IL-8 were determined. RESULTS Thirty-five patients were included (I degrees FN, n = 17; DCO, n = 18). In I degrees FN-patients, a perioperative increase of IL-6 levels was measured (preoperatively, 55 +/- 33 pg/dL; 24 hours postoperatively, +254 +/- 55 pg/dL; p = 0.03), which was not found in subgroup DCO I degrees Ex.fix.: preoperatively, 71 +/- 42 pg/dL; 24 hours postoperatively, 68 +/- 34 pg/dL; not significant [NS] or in group DCO II degrees FN: preoperatively, 36 +/- 21 pg/dL; 24 hours postoperatively, +39 +/- 25 pg/dL; NS. Likewise, in I degrees FN patients, a perioperative increase of IL-8 levels was measured only at the 7-hour time point (preoperatively, 35 +/- 29 pg/dL; 7 hours postoperatively, 95 +/- 23 pg/dL; p < 0.05), which was not found in group DCO I degrees Ex.fix.: preoperatively, 43 +/- 38 pg/dL; 24 hours postoperatively, 69 +/- 39 pg/dL; NS or in group DCO II degrees FN: preoperatively, 25 +/- 20 pg/dL; 24 hours postoperatively, 36 +/- 29 pg/dL; NS. There were no differences in the complication rate in terms of acute respiratory distress syndrome, sepsis, or multiple organ failure.

CONCLUSION

In this prospective, randomized, multicenter study, a sustained inflammatory response was measured after primary (<24 hours) intramedullary femoral instrumentation, but not after initial external fixation or after secondary conversion to an intramedullary implant. These findings may become clinically relevant in patients at high risk of developing complications. It confirms previous studies in that damage control orthopedic surgery appears to minimize the additional surgical impact induced by acute stabilization of the femur.

A comparison of the findings of wrist arthroscopy and magnetic resonance imaging in the investigation of wrist pain

Between 1996 and 1999, 54 patients with wrist pain had magnetic resonance imaging performed using a 1.5 Tesla scanner without a wrist coil. Wrist arthroscopy was performed using a standard technique. The findings were then compared. Magnetic resonance imaging had a low sensitivity for the detection of triangular fibrocartilage complex injuries (0.44) and scapholunate ligament injuries (0.11) when wrist arthroscopy was used as the standard of reference. We conclude that when a magnetoresonance technique that does not employ a dedicated wrist coil is used, a negative magnetic resonance imaging scan does not exclude these two significant injuries.

A case study of misrepresentation of the scientific literature: recent reviews of chiropractic

Accurate use of published data and references is a cornerstone of the peer-review process. Statements, inferences, and conclusions based upon these references should logically ensue from the data they contain. When journal articles and textbook chapters summarizing the safety and efficacy of particular therapies or interventions use references inaccurately or with apparent intent to mislead, the integrity of scientific reporting is fundamentally compromised. Ernst et al.'s publication on chiropractic include repeated misuse of references, misleading statements, highly selective use of certain published papers, failure to refer to relevant literature, inaccurate reporting of the contents of published work, and errors in citation. Meticulous analysis of some influential negative reviews has been carried out to determine the objectivity of the data reported. The misrepresentation that became evident deserves full debate and raises serious questions about the integrity of the peer-review process and the nature of academic misconduct.

Macroesthetic elements of smile design

BACKGROUND

Clinicians' expanding use of cosmetic restorative procedures has generated greater interest in the determination of esthetic guidelines and standards. The overall esthetic impact of a smile can be divided into four specific areas: gingival esthetics, facial esthetics, microesthetics and macroesthetics. In this article, the authors focus on the principles of macroesthetics, which represents the relationships and ratios of relating multiple teeth to each other, to soft tissue and to facial characteristics.

CASE DESCRIPTION

The authors categorize macroesthetic criteria based on two reference points: the facial midline and the amount and position of tooth reveal. The facial midline is a critical reference position for determining multiple design criteria. The amount and position of tooth reveal in various views and lip configurations also provide valuable guidelines in determining esthetic tooth positions and relationships.

CLINICAL IMPLICATIONS

Esthetics is an inherently subjective discipline. By understanding and applying simple esthetic rules, tools and strategies, dentists have a basis for evaluating natural dentitions and the results of cosmetic restorative procedures. Macroesthetic components of teeth and their relationship to each other can be influenced to produce more natural and esthetically pleasing restorative care.

The role of cosmetic dentistry in restoring a youthful appearance

BACKGROUND

Dentistry is faced with a population that is getting older and keeping more of its natural teeth. Smiles show physical and esthetic signs of aging. Advances in the area of cosmetic dentistry now offer the dental profession new opportunities in conservative and esthetic restorative procedures that have the potential to reverse the signs of dental aging, thereby making patients appear younger.

CASE DESCRIPTION

The physical and esthetic attributes of an aged dentition are identifiable. Tooth wear over time alters the appearance of the teeth and smile in a way that is perceptible to dentists and laypeople. Bonding and adhesive ceramic restorative procedures have the potential of reversing the esthetic manifestations of the aging process for teeth. Specific diagnostic tools, including a composite resin mock-up and construction of an incisal putty matrix, allow for previsualization of possible treatment outcomes and allow clinicians to resolve occlusal as well as esthetic treatment concerns before initiating actual treatment.

CLINICAL IMPLICATIONS

The ability to make patients look younger through cosmetic enhancement of teeth and smiles has tremendous implications for the future practice of dentistry. Dentists who have the training and skills to meet the increasing demand for esthetic procedures by patients seeking to restore a youthful appearance may find an expanded role within their practices for this type of treatment.

Contrasting properties of albuterol stereoisomers

Racemic albuterol is composed of an equimolar mixture of stereoisomers. For asthma therapy, (R)-albuterol is the eutomer and (S)-albuterol is the distomer. By interacting with beta(2 )-adrenoceptors, (R)-albuterol has bronchodilator, bronchoprotective, anti-edematous properties and inhibits activation of mast cells and eosinophils. (S)-albuterol does not activate beta(2 )-adrenoceptors and does not modify activation of beta(2 )-adrenoceptors by (R)-albuterol so that for many years it was presumed to be biologically inert. Recently, it has been established that regular and excessive use of racemic albuterol induces paradoxical reactions in some subjects with asthma. Because such effects cannot be accounted for by activation of beta(2 )-adrenoceptors, the pharmacologic profile of (S)-albuterol has been more carefully defined. (S)-albuterol has distinctive pharmacologic properties that are unrelated to activation of beta(2 )-adrenoceptors. Thus, (S)-albuterol intensifies bronchoconstrictor responses of sensitized guinea pigs and induces hypersensitivity of asthmatic airways; it also promotes the activation of human eosinophils in vitro. These actions of (S)-albuterol may explain why racemic albuterol can intensify allergic bronchospasm and promote eosinophil activation in asthmatic airways. The capacity of (S)-albuterol to elevate intracellular Ca(2+) would account for the paradox because this action will oppose, or even nullify, the consequences of adenylyl cyclase activation by (R)-albuterol. Because (S)-albuterol is metabolized more slowly than (R)-albuterol and is retained preferentially within the airways, paradoxical effects become more prominent during regular and excessive use of racemic albuterol. Because (S)-albuterol has detrimental effects in asthmatic airways, levalbuterol [homochiral (R)-albuterol] should have advantages over racemic albuterol in therapy for asthma.