Influence of storage humidity on the in vitro inhalation properties of salbutamol sulfate dry powder with surface covered lactose carrier

The influence of storage humidity on the in vitro inhalation properties of salbutamol sulfate dry powder with surface covered lactose carrier was investigated. In the present study, drug/carrier powder mixtures were prepared consisting of micronized salbutamol sulfate and lactose carriers with different particle surface conditions prepared by surface covering. Lactose carrier surfaces were covered with vegetable magnesium stearate (Mg-St-V) by a high-speed elliptical-rotor-type powder mixer (Theta-Composer). These powder mixtures were aerosolized by a Jethaler), and the in vitro inhalation properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with uncovered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface covered lactose carrier were little decreased with increased in relative humidity (RH), showing that the in vitro inhalation properties of salbutamol sulfate were improved at high RH. Using this surface covering technique would thus be valuable for storage humidity of dry powder inhalation (DPI) with lactose carrier particles.

Design and characterization of mucoadhesive buccal patches of salbutamol sulphate

Mucoadhesive patches for delivery of salbutamol sulphate were prepared using polyvinyl alcohol, hydroxypropylmethyl cellulose and chitosan. Mechanical property, swelling and bioadhesive characteristics were detemined for both plain and medicated patches. Mechanical properties were determined in presence of carbopol and polyvinylpyrrolidone. The results showed an increase in swelling after addition of salbutamol sulphate to the plain formulation. This was attributed that the salbutamol sulphate modifies the way water is bound to or taken by the polymer. A decrease in residual time was observed for polyvinyl alcohol and citosan containing formula. High drug release was obtained from polyvinyl alcohol compared to the hydroxypropylmethylcellulose. Physical characteristics of the studied patches showed promising with good bioadhesion.

The Cohesive-Adhesive Balances in Dry Powder Inhaler Formulations I: Direct Quantification by Atomic Force Microscopy

PURPOSE

To obtain a quantitative assessment of the cohesive and adhesive force balance within dry powder inhaler formulations.

METHODS

The atomic force microscope (AFM) colloid probe technique was used to measure the adhesive and cohesive force characteristics of dry powder systems containing an active component (budesonide, salbutamol sulphate) and alpha-lactose monohydrate. To minimize the variations in contact area between colloid probe and substrates, nanometer smooth crystal surfaces of the drugs and the excipient were prepared.

RESULTS

The uniformity in contact area allowed accurate and reproducible force measurements. Cohesive-adhesive balance (CAB) graphs were developed to allow direct comparison of the interaction forces occurring in model carrier-based formulations. A salbutamol sulphate-lactose system revealed a significant tendency for the two materials to adhere, suggesting a propensity for the powder to form a homogenous blend. In contrast, the budesonide-lactose system exhibited strong cohesive properties suggesting that the formulation may exhibit poor blend homogeneity and potential for segregation upon processing and handling.

CONCLUSIONS

The novel approach provides a fundamental insight into the cohesive-adhesive balances in dry powder formulations and further understanding of powder behavior.

Single-enantiomer drugs: elegant science, disappointing effects

Most new drugs are marketed as single enantiomers but many older agents are still available in racemic form. As these drugs reach the end of their patent life manufacturers become interested in marketing single enantiomer equivalents. This is called 'chiral switching' and it has been claimed that it will bring clinical benefits in terms of improved efficacy, more predictable pharmacokinetics or reduced toxicity. We reviewed the clinical evidence and prices for three recently marketed single enantiomer versions of widely used racemic drugs: escitalopram, esomeprazole and levosalbutamol. Claims of increased efficacy were based on comparisons of non-equivalent doses and any advantages seemed small and clinically unimportant. Prices of esomeprazole and levosalbutamol were higher than their racemic alternatives and we predict that these prices will remain high despite the market presence of generic versions of the racemates. Patent protection and a perception of superiority based on promotion rather than evidence will maintain price premiums for single enantiomer drugs that are not justified on the basis of clinical performance.

Effect of surface covering of lactose carrier particles on dry powder inhalation properties of salbutamol sulfate

The effect of the surface covering of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate was investigated. Lactose carrier surfaces were covered with sucrose tristearate (J-1803F) by a high-speed elliptical-rotor-type powder mixer (Theta-Composer). In the present study, drug/carrier powder mixtures were prepared consisting of micronized salbutamol sulfate and lactose carriers with various particle surface conditions prepared by surface covering. These powder mixtures were aerosolized by a Jethaler), and the in vitro inhalation properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with uncovered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface covering lactose carrier were significantly different, showing that the in vitro inhalation properties of salbutamol sulfate were improved. In vitro inhalation properties increased with the percentage of J-1803F added. Using this surface covering system would thus be valuable for increasing the inhalation properties of dry powder inhalation with lactose carrier particles.

Levalbuterol in the treatment of patients with asthma and chronic obstructive lung disease

Effective asthma control requires long-term (anti-inflammatory) controller medications for patients with mild-persistent to severe-persistent disease, and quick-relief bronchodilator medication for all patients with asthma to control intermittent symptoms of cough, wheeze, and bronchoconstriction, as well as acute exacerbations. For patients with chronic obstructive pulmonary disease, quick-relief and long-acting bronchodilators are primarily used in the maintenance and treatment of associated symptoms, including shortness of breath. For many years, the most widely used bronchodilator has been racemic (R, S)-albuterol, a short-acting beta2-adrenergic agonist, commonly dispensed as an inhaled aerosol or solution. Until the introduction of levalbuterol inhalation solution (Xopenex) in 1999, all marketed forms of albuterol (including Ventolin and Proventil brands) were racemic mixtures composed of a 1:1 ratio of (R)- and (S)-stereoisomers. Administered as a proportionally equivalent nebulized dose, levalbuterol [(R)-albuterol] provides greater bronchodilation than racemic albuterol and, in the appropriate clinical setting, offers the possibility for improving clinical outcomes in patients with asthma and other obstructive airway diseases. Additionally, levalbuterol can be given at lower doses than racemic albuterol to provide comparable bronchodilation, with the potential for reduced beta-mediated adverse effects in adults and children. Only since the past decade has the technology to separate stereoisomers become available, and thus the biologic activities of the albuterol stereoisomers had not been established. Binding studies have demonstrated that (R)-albuterol binds to the beta2-adrenergic receptor with a high affinity, whereas (S)-albuterol binds with 100-fold less affinity than (R)-albuterol. Other evaluations have suggested that (R)-albuterol possesses the bronchodilatory, bronchoprotective, and ciliary-stimulatory properties of racemic albuterol, while (S)-albuterol does not contribute beneficially to the therapeutic effects of the racemate and was originally assumed to be inert. However, preclinical evaluations have shown that (S)-albuterol has effects that work in opposition to (R)-albuterol and may diminish the therapeutic effects of (R)-albuterol.

The influence of humidity on the aerosolisation of micronised and SEDS produced salbutamol sulphate

The influence of storage humidity on the aerosolisation efficiency of micronised and supercritical fluid salbutamol sulphate formulations (containing a lactose carrier) were investigated using the twin stage impinger (TSI). Storage humidity had a significant effect on the aerosolisation efficiency of both micronised and solution enhanced dispersion by supercritical fluids (SEDS) salbutamol sulphate (ANOVA P <0.05), suggesting capillary interactions to be an important factor when considering formulation performance. Furthermore, significant differences between the aerosolisation performance of micronised and SEDS salbutamol sulphate were observed at elevated humidities (>63% RH) (Fishers pairwise P <0.05). It is suggested that such variations may be due to differences in physical stability of the micronised and SEDS produced material. Dynamic vapor sorption, and atomic force microscopy (AFM) phase imaging suggested the micronised material to contain amorphous content that was most likely present on the micronised particulate surfaces. Thus, at high humidity, surface amorphous regions may have the ability to re-crystallize and effectively 'fuse' to the lactose carrier surface. This would potentially reduce the ability for the micronised material to be aerosolized and thus result in a greater decrease in FPF when compared to SEDS produced material at equivalent RH.

The cost effectiveness of levalbuterol versus racemic albuterol

Albuterol is a selective beta2-agonist that is widely used in the prevention and treatment of reactive airway disease. It is formulated as a racemic mixture containing equal parts of the R- and S-isomers. The therapeutic activity of albuterol is due entirely to the R-isomer, whereas the S-isomer may actually have detrimental effects. Because the slowly metabolized S-isomer tends to accumulate in the body, there has been concern that chronic use of racemic albuterol might lead to loss of effectiveness and clinical deterioration, with potentially serious health and cost consequences. Levalbuterol is a formulation containing only the R-isomer of albuterol, and clinical trials have demonstrated that it offers therapeutic advantages over racemic albuterol. The cost effectiveness of levalbuterol derives mainly from reduced need for acute medical care and hospitalization.

An Atomic Force Microscopy Study of the Effect of Nanoscale Contact Geometry and Surface Chemistry on the Adhesion of Pharmaceutical Particles

PURPOSE

To understand differences in particle adhesion observed with increasing humidity between samples of salbutamol sulfate prepared by two different methods.

METHODS

Atomic force microscopy (AFM) force measurements were performed as a function of humidity (<10% to 65% RH) using two systems. The first system used clean AFM tips against compressed disks of micronized and solution enhanced dispersion by supercritical fluid (SEDS) salbutamol. The second system involved particles of both salbutamol samples mounted onto the apexes of AFM cantilevers, and force measurements being performed against a highly orientated pyrolytic graphite (HOPG) substrate. Following these measurements, the contact asperities of the tips were characterized.

RESULTS

The first system showed a maximum in the observed adhesion at 22% relative humidity (RH) for the SEDS salbutamol compared to 44% RH for the micronized salbutamol. The second system showed a mix of peaks and continual increases in adhesion with humidity. The predicted Johnson-Kendall-Roberts forces were calculated and divided by the actual forces in order to produce a ratio.

CONCLUSIONS

By relating the nature of the asperities to the force measurements, we propose a model in which adhesion scenarios range from single asperity nanometer-scale contact in which peaks in the adhesion were observed, to multiasperity contact where a continuous increase in adhesion was seen with humidity.

(S)-Albuterol activates pro-constrictory and pro-inflammatory pathways in human bronchial smooth muscle cells

BACKGROUND

Pro-constrictory and proinflammatory properties of (S)-albuterol have been widely reported both under in vivo and in vitro conditions. However, underlying mechanisms are unclear.

OBJECTIVE

We examined and compared the cellular effects of albuterol enantiomers on key intracellular molecules involved in constrictory and inflammatory pathways in human bronchial smooth muscle cells (hBSMCs).

METHODS

Primary hBSMCs were grown in culture and treated with various concentrations of albuterol enantiomers for various periods. Methacholine was used to stimulate cells. The expression and activity of Gs and Gi proteins, the intracellular free calcium concentration ([Ca2+]i), the activity of phosphatidylinositol 3'-OH-kinase (PI3) kinase, and the transcriptional nuclear factor kappaB (NF-kappaB) level were examined.

RESULTS

There was a significant increase in the expression and activity of Gialpha-1 protein and a decrease in the expression of Gs protein in hBSMCs after 8 hours of treatment with (S)-albuterol. These effects of (S)-albuterol were observed in a dose-dependent manner. Nonreceptor-mediated activation of adenylate cyclase by forskolin was attenuated with (S)-albuterol. Treatment of the cells for 24 hours with (S)-albuterol significantly increased [Ca2+]i on stimulation with methacholine. Interestingly, the effect of (R)-albuterol was opposite to that of (S)-albuterol. The effect of the racemic albuterol in some cases was similar to that of (S)-albuterol. (S)-Albuterol significantly activated both PI3 kinase and NF-kappaB in hBSMCs.

CONCLUSION

These studies demonstrated an (S)-albuterol-induced increase in the expression and activity of pro-constrictory pathways involving Gialpha-1 protein and [Ca2+]i and a decrease in the activity of the bronchodilatory pathway involving Gs proteins in hBSNMCs. Additionally, (S)-albuterol activated proinflammatory pathways involving PI3 kinase and NF-kappaB. Because (S)-albuterol metabolizes at least 10-fold slower than (R)-albuterol and has a longer elimination half-life, these cellular effects of (S)-albuterol might explain the detrimental effect seen with chronic administration of racemic albuterol in the treatment of airway diseases, such as bronchial asthma.

Use of an impinging jet for dispersion of dry powder inhalation aerosols

The dispersion of Ventodisk (salbutamol sulphate with lactose) from different drug reservoirs by an air jet at normal impingement is examined experimentally. The effect on dispersion efficiency of jet velocity, nozzle location, reservoir size and shape, and the loaded dose is investigated for possible design of new dosing methods or inhalers. Results show that higher jet velocity (as high as feasible), lower drug loading (2 mg or smaller), a cylindrical hole reservoir (6 mm in diameter and 3 mm in depth) and a medium distance (approximately 5 jet diameters) from the nozzle to the reservoir yield optimum dispersion. The dispersed fine particle dose improves by a factor of 2-3 times between optimized conditions and poor conditions.

Predicting the physical state of spray dried composites: salbutamol sulphate/lactose and salbutamol sulphate/polyethylene glycol co-spray dried systems

The effect of spray drying salbutamol sulphate, salbutamol sulphate/lactose and salbutamol sulphate/polyethylene glycol (PEG) solutions was investigated. Co-spray drying salbutamol sulphate with lactose, which is amorphous when spray dried alone, resulted in amorphous composites. Co-spray drying salbutamol sulphate with PEG 4000 and PEG 20,000, which do not form amorphous systems when spray dried alone, resulted in systems of varying crystallinity, the crystallinity depending on the weight ratio of polymer to drug. Examination of the physical properties of these salbutamol sulphate co-spray dried systems and those of bendroflumethiazide/PEG and lactose/PEG composites suggested that the formation and physical stability of amorphous composites prepared by spray drying is dependent on whether the glass transition temperature, Tg, of one of the two components is high enough to result in a Tg of the composite sufficiently high that the Kauzmann temperature of the mix is greater than the temperature of storage. The modified Gordon-Taylor equation proved to be useful in predicting the likelihood that a two-component composite will be amorphous on spray drying. Furthermore, the Gordon-Taylor equation was also useful in predicting the likely physical stability of amorphous two component composites and predicted that even polymers with apparently low Tgs, such as PEGs, may be stabilised in an amorphous composite by a suitable additive having a sufficiently high Tg.

Effect of carrier size on the dispersion of salmeterol xinafoate from interactive mixtures

The objective of this study was to determine the influence of lactose carrier size on drug dispersion of salmeterol xinafoate (SX) from interactive mixtures. SX dispersion was measured by using the fine particle fractions determined by a twin stage impinger attached to a Rotahaler. The particle size of the lactose carrier in the SX interactive mixtures was varied using a range of commercial inhalation-grade lactoses. In addition, differing size fractions of individual lactose samples were achieved by dry sieving. The dispersion of SX appeared to increase as the particle size of the lactose carrier decreased for the mixtures prepared from different particle size commercial samples of lactose and from different sieve fractions of the same lactose. Fine particles of lactose (<5 microm) associated with the lactose carrier were removed from the carrier surface by a wet decantation process to produce lactose samples with low but similar concentrations of fine lactose particles. The fine particle fractions of SX in mixtures prepared with the decanted lactose decreased significantly (analysis of variance, p < 0.001) and the degree of dispersion became independent of the volume mean diameter of the carriers (analysis of variance, p < 0.05). The dispersion behavior is therefore associated with the presence of fine adhered particles associated with the carriers and the inherent size of the carrier itself has little influence on dispersion.

[Diffusion behaviors of drugs in thermosensitive in situ gels]

AIM

To study the diffusion behaviors of drugs in thermosensitive in situ gels, and provide valuable information for designing such delivery systems.

METHODS

A free diffusion model was used to evaluate the effects of concentration, the property of drugs, as well as the gel compositions on the diffusivity of drugs.

RESULTS

Drug transport through the aqueous channels of the gel followed Fickian mechanism, and no significant influence on the diffusivity was observed when the drug concentration was lowered from 5% to 0.25%. The diffusion coefficients of propranolol, timolol maleate, and salbutamol sulfate were 0.91, 1.32, and 3.30 x 10(-6) cm2 x s(-1), respectively. The flux of hydrophilic drug was 3.6 fold faster than that of the lipophilic one implied the latter partitioned into the hydrophobic micellar core, and consequently the diffusion was retarded. The diffusivity was decreased with increased poloxamer and sodium hyaluronate concentration, due to the distorted aqueous channels and higher microviscosity.

CONCLUSION

The result suggested that sustained release could be achieved for the thermosensitive in situ gel by incorporating lipophilic drug or increasing polymer concentration.

Lactose Surface Modification by Decantation: Are Drug-Fine Lactose Ratios the Key to Better Dispersion of Salmeterol Xinafoate from Lactose-Interactive Mixtures?

PURPOSE

The role of fine lactose in the dispersion of salmeterol xinafoate (SX) from lactose mixtures was studied by modifying the fine lactose concentration on the surface of the lactose carriers using wet decantation.

METHODS

Fine lactose was removed from lactose carriers by wet decantation using ethanol saturated with lactose. Particle sizing was achieved by laser diffraction. Fine particle fractions (FPFs) were determined by Twin Stage Impinger using a 2.5% SX mixture, and SX was analyzed by a validated high-performance liquid chromatography method. Adhesion forces between probes of SX and silica and the lactose surfaces were determined by atomic force microscopy.

RESULTS

FPFs of SX were related to fine lactose concentration in the mixture for inhalation grade lactose samples. Reductions in FPF (2-tp 4-fold) of Aeroflo 95 and 65 were observed after removing fine lactose by wet decantation; FPFs reverted to original values after addition of micronized lactose to decanted mixtures. FPFs of SX of sieved and decanted fractions of Aeroflo carriers were significantly different (p < 0.001). The relationship between FPF and fine lactose concentration was linear. Decanted lactose demonstrated surface modification through increased SX-lactose adhesion forces; however, any surface modification other than removal of fine lactose only slightly influenced FPF.

CONCLUSIONS

Fine lactose played a key and dominating role in controlling FPF. SX to fine lactose ratios influenced dispersion of SX with maximum dispersion occurring as the ratio approached unity.

Effect of inhaled racemic and (R)-albuterol on airway vascular smooth muscle tone in healthy and asthmatic subjects

Although the relative effect of racemic and (R)-albuterol on airway smooth muscle tone have been investigated in patients with airflow obstruction, the comparative effectiveness of these drugs in relaxing airway vascular smooth muscle is unknown. Therefore, we determined the actions of inhaled racemic and (R)-albuterol on airway mucosal blood flow (Qaw) normalized for anatomic dead space as an index of airway vascular smooth muscle tone in 11 healthy subjects and 10 subjects with mild asthma. We also monitored the forced expiratory volume in 1 second (FEV1) as an index of airway smooth muscle tone. Mean +/- SE baseline Qaw was 43.1 +/- 1.5 microl x min(-1) x ml(-1) in healthy subjects and 53.4 +/- 2.1 microl x min(-1) x ml(-1) in asthmatic subjects (p < 0.01). The corresponding values for FEV1 were 95.6 +/- 1.4 and 86.8 +/- 2.5% respectively, of predicted (p = 0.01). Racemic and (R)-albuterol caused a transient, dose-dependent increase of Qaw in healthy, but not in asthmatic subjects; the responses were not different between the two drugs. The FEV1 tended to increase more in asthmatics than in healthy subjects, again without a difference between the two drugs. These results show that racemic and (R)-albuterol have comparable effects on airway vascular smooth muscle and suggest that the blunted airway vascular smooth muscle response to albuterol in asthmatics is not related to (S)-albuterol.

Validation of a chiral HPLC assay for (R)-salbutamol sulfate

A fast, reliable and specific method for the screening, confirmation, determination and quantitation of salbutamol enantiomers was developed and validated. The described procedure includes a single robust chiral HPLC determination employing a Teicoplanin stationary phase. The method was evaluated for specificity, robustness, linearity, precision and accuracy. Under the chromatographic conditions of the method, known impurities were separated from the active principle.

Characterization of the generation of radiolabeled monodisperse albuterol particles using the spinning-top aerosol generator

Inhaled radiolabeled aerosols provide invaluable information about in vivo drug deposition. Here, we report our methodology for radiolabeling and imaging monodisperse pharmacologic aerosols in order to study basic aerosol science concepts of drug delivery within the human airways.

METHODS

We used a spinning-top aerosol generator to produce (99m)Tc-labeled monodisperse albuterol sulfate aerosols of 1.5-, 3-, and 6- micro m mass median aerodynamic diameter.

RESULTS

In vitro Andersen cascade validation data showed that technetium and albuterol were coassociated on each impactor stage for all 3 aerosols, and the radiolabeling process itself did not affect their particle size distributions. Good-quality gamma-camera scintigraphic images of lung and extrathoracic deposition were obtained within an asthmatic patient.

CONCLUSION

We have successfully radiolabeled and imaged monodisperse albuterol aerosols within the human lungs. This novel technique provides an important tool to relate fundamental concepts of aerosol particle behavior, in vivo deposition, and therapeutic clinical response.

Effect of Surface Layering Time of Lactose Carrier Particles on Dry Powder Inhalation Properties of Salbutamol Sulfate

The effect of the surface layering time of lactose carrier particles on the dry powder inhalation properties of salbutamol sulfate was investigated. Lactose carrier particles were layered with vegetable magnesium stearate by physical mixing. In the present study, drug/carrier powder mixtures were designed consisting of micronized salbutamol sulfate and lactose carriers with various particle surface conditions prepared by surface layering. These powder mixtures were aerosolized by a Jethaler, and the in vitro deposition properties of salbutamol sulfate were evaluated by a twin impinger. Compared with the powder mixed with unlayered lactose carrier, the in vitro inhalation properties of the powder mixture prepared using the surface layering lactose carrier were significantly different, showing that the in vitro inhalation properties of the drug/carrier powder mixtures were improved. In vitro deposition properties (RP) increased with surface layering time. Using this surface layering system would thus be valuable for increasing the inhalation properties of dry powder inhalation.

Design of salbutamol EOP tablets from pharmacokinetics parameters

Salbutamol elementary osmotic pump (EOP) tablets were developed, and fundamental variables affecting their release characteristics were evaluated. The effects of film thickness and compression force on drug release from the tablets containing fixed amount of sodium chloride used as osmogent were evaluated. The core tablets were directly compressed at four compression forces and coated with 3% wt/vol cellulose acetate in acetone to levels of 2%, 3%, and 4% wt/wt. Coated tablets were drilled with CO2 laser beam to form drug delivery orifice of approximately 400 microm in diameter. The drug release was found to follow zero order fashion. The release rate decreased with the increased film thickness and was not affected by the compression force or porosity. The tablets coated to 3% and 4% levels exhibited the release rates within the range calculated from pharmacokinetic data. To illustrate the effect of osmogent content, the tablets were prepared at four osmogent levels and compressed at a constant compression force. The core tablets were coated to a level of 3% wt/wt. The release rate was initially increased with osmogent content and then decreased. At higher osmogent contents, the drug fraction in soluble component was decreased and resulted in the reduction of drug release. In conclusion, film thickness and osmogents played important roles in drug release from EOP tablets.

Delivery of liposomes in dry powder form: aerodynamic dispersion properties

OBJECTIVE

In our previous study, we reported a novel approach of delivering liposomes in dry powder form that relies on spontaneous formation of liposomes upon dispersion of micronised phospholipid(s) based powders in an aqueous environment, thereby creating reservoirs for the encapsulation of drugs [J. Pharm. Sci. 91 (2002) 482]. In this paper, we demonstrate the in vitro generation of aerosols from these novel powders.

METHODOLOGY

Various formulations comprising different phospholipid(s) exhibiting different physico-chemical properties were prepared. Aerosol was generated using a deagglomeration rig wherein the powder was entrained at a flow rate of 60 l/min and high turbulence was generated using air-jets. Two antimicrobial agents (ciprofloxacin and CM3, a novel peptide) and a bronchodilator, salbutamol sulfate, were used as model drugs to examine the powder dispersion properties.

RESULTS

The deagglomeration rig used in this study was able to disperse 87-95% of the total loaded powder into the cascade impactor. Amongst the various formulations comprising different phospholipid(s), DMPG and (DMPC+DMPG) based formulations exhibited excellent aerodynamic dispersion properties. Fine particle fractions (FPF) of more than 50% were achieved for these formulations for three model drugs. Encapsulation of the model drugs in the FPF, obtained upon dispersion of these novel powders, is also discussed in this paper. An encapsulation of approximately 35, 40 and 25% was achieved in the FPF for ciprofloxacin, CM3 peptide and salbutamol sulfate, respectively.

Comparison of racemic albuterol and levalbuterol for treatment of acute asthma

OBJECTIVE

To determine whether levalbuterol resulted in fewer hospital admissions than racemic albuterol when used for treatment of acute asthma. Study design A randomized, double-blind, controlled trial was conducted in the emergency department (ED) and inpatient asthma care unit of an urban tertiary children's hospital. Children age 1 to 18 years (n=482) provided a total of 547 enrollments. Patients received a nebulized solution of either 2.5 mg racemic albuterol or 1.25 mg levalbuterol every 20 minutes (maximum six doses). Patients admitted to the asthma care unit were treated in a standardized fashion by using the same blinded drug assigned in the ED. Hospitalization rate was the primary outcome.

RESULTS

Hospitalization rate was significantly lower in the levalbuterol group (36%) than in the racemic albuterol group (45 %, P=.02). The adjusted relative risk of admission in the racemic group compared with the levalbuterol group was 1.25 (95% confidence interval, 1.01-1.57). Hospital length of stay was not significantly shorter in the levalbuterol group (levalbuterol, 44.9 hours; racemic albuterol, 50.3 hours; P=.63). No significant adverse events occurred in either group.

CONCLUSIONS

Substituting levalbuterol for racemic albuterol in the ED management of acute asthma significantly reduced the number of hospitalizations.

Influence of mechanical activation on the physical stability of salbutamol sulphate

In order to obtain the optimal particle size distribution for pharmaceutical powders in dry powder inhalers the particles have to be micronised. In most cases the process of micronisation is connected with a high input of energy which induces disorder and defects on the surface of the drug particles and as a result changes in the crystallinity. Consequently, changes in the physical stability of the powders may occur. To investigate changes on the physical stability of the powder, different analytical methods are used in the present investigation: laser diffraction, Differential Scanning Calorimetry (DSC), isothermal microcalorimetry and DVS-method.Air-jet-milling is one of the most frequently used techniques in the pharmaceutical industry, in order to obtain particles of respirable size. In the treatise described here the influence of the critical parameters of the process, i.e. feed pressure, grind pressure and feed rate is assessed for salbutamol sulphate. The grind pressure is of utmost importance with respect to particle size distribution and the physical powder stability. For salbutamol sulphate, ground with a MC Jetmill 50, a grind pressure of 6 bar has been found optimal. Pressures below 6 bar are not sufficient to produce the required reduction in particle size. The feed pressure and rate have negligible influence on the powder quality. Furthermore, the micronisation process is optimised to achieve respirable particles while minimising the amorphous content. A correlation between mechanical activation and the amount of the amorphous regions is showed clearly.Air-jet-milling has been compared to ball milling in this investigation. In pilot tests ball milling was not suitable to achieve the needed particle size distribution, however, it generates a specific quantity of amorphous material. With the help of specific amorphous regions in the powder, the sensitivity of the used methods for salbutamol sulphate can be examined.

Changes in heart rate associated with nebulized racemic albuterol and levalbuterol in intensive care patients

The effects of equipotent doses of racemic albuterol and levalbuterol on heart rate (HR) in intensive care patients with and without baseline tachycardia were studied. Patients were included if they were hemodynamically stable and required bronchodilator therapy every four hours; patients were excluded if they were maintained on a beta-blocker. Four hours after the most recent bronchodilator treatment, each patient was randomized to receive at least two consecutive doses of albuterol 2.5 mg or levalbuterol 1.25 mg four hours apart via nebulization. HR was recorded at the end of the second dose and 5, 10, 15, 30, 60, 90, 120, 180, and 240 minutes after treatment. Twenty intensive care patients, including 10 with baseline tachycardia and 10 without baseline tachycardia, were enrolled. In patients with baseline tachycardia, the mean largest HR increase was 1.4 beats/min (1.3%) with albuterol and 2.0 beats/min (2.1%) with levalbuterol (both increases were not significant). In patients without baseline tachycardia, the mean largest HR increase was 4.4 beats/min (6.7%) with albuterol (p = 0.04) and 3.6 beats/min (5.0%) with levalbuterol (p = 0.03). Short-term use of nebulized albuterol and levalbuterol was associated with similar changes in HR in intensive care patients with or without baseline tachycardia.