Model-free treatment of the dehydration kinetics of nedocromil sodium trihydrate.

The conventional model-fitting approach to kinetic analysis assumes a fixed mechanism throughout the reaction and therefore may be too simplistic for many solid-state reactions. Even for a reaction with a fixed mechanism, model fitting sometimes cannot identify the reaction model uniquely. The alternative model-free approach is sufficiently flexible to allow for a change of mechanism during the course of a reaction and therefore provides a more realistic treatment of solid-state reactions kinetics. The application of model-free analysis to solid-state dehydrations was investigated using the two consecutive dehydration reactions of nedocromil sodium trihydrate. The complexity of such reactions is illustrated by the variation of the activation energy as each dehydration proceeds. The 1st-step dehydration follows one-dimensional phase boundary kinetics until the fraction dehydrated reaches 0.75, and deviates from this model thereafter. The 2nd-step dehydration follows a mechanism intermediate between two- and three-dimensional diffusion that cannot be described by any of the common models. The model-free approach is clearly better than the model-fitting approach for understanding the details of these solid-state dehydration reactions.

Allergen challenge and deposition of nedocromil sodium in asthma.

We examined whether the acute protective effect of nedocromil sodium aerosol could be enhanced by increasing the deposition uniformity of the drug in the lungs of adult patients with allergic asthma. Ten patients with mild-to-moderate asthma were challenged with the same doses of allergen on two occasions in a randomized manner. Thirty minutes before these challenges, patients inhaled 4 mg nedocromil sodium, admixed with the radioisotope (99m)technetium. Radiolabeled drug was inhaled during slow (25.4 +/- 4.6 L/min) and faster (58.0 +/- 7.3 L/min) inhalations from a 700 ml holding chamber. Percent changes in FEV(1) at the same top dose of allergen on the two treatment visits were compared. Lung deposition fraction (LDF) and indices of distribution uniformity, quantified from gamma camera images, were also compared. Acute protection against allergen challenge was similar and complete after slow or faster inspiration of nedocromil sodium. Mean (+/- SD) allergen-induced changes in FEV(1) were -1.05 +/- 2.78% and -0.39 +/- 2.80%, respectively, compared to -26.30 +/- 8.49% on a screening challenge (no drug). Mean LDF was also similar on the two visits, averaging 16.4 +/- 4.6% and 16.1 +/- 7.2% of administered drug, respectively. Distribution of nedocromil sodium was most uniform after slow inspiration, but increased uniformity was not related to enhanced protection. Complete protection against acute bronchoconstriction induced by inhaled allergen can be obtained with 4 mg of nedocromil sodium aerosol, inhaled from a large volume holding chamber, 30 min before the exposure, and at inspiratory flow rates between approximately 20-60 L/min. Protection does not appear to be enhanced by increased uniformity of drug distribution within the lungs.

Corticosteroides inhalados en pediatría / Inhaled corticoteroids in pediatrics

Los corticosteroides inhalados (CEI), con sus actuales formulaciones, son los agentes antinflamatorios más eficaces a largo plazo para el tratamiento del asma leve, moderada, persistente grave y la rinitis alérgica. Su utilización precoz mejora los síntomas, la calidad de vida, normaliza la función pulmonar, previene la recurrencia de ataques asmáticos, mejora la inflamación de las vías aéreas y puede prevenir sus posibles lesiones irreversibles de remodelado. Estos fármacos disminuyen la mortalidad, los costes terapéuticos, el uso de otros medicamentos y las hospitalizaciones; por tanto, la relación riesgo-beneficio de estos tratamientos es claramente favorable a su aplicación y son sustancias de primera elección en el tratamiento del asma. El nuevo compuesto propionato de fluticasona (PF) constituye un importante avance en el tratamiento del asma y la rinitis alérgica del niño, y aporta importantes ventajas respecto a otros corticosteroides inhalados, como lo han demostrado numerosos ensayos clínicos con más de 1.600 niños. El propionato de fluticasona tiene una gran actividad antinflamatoria, con una baja disponibilidad sistémica oral, y, administrado con dispositivos Accuhaler y Diskhaler o aerosoles presurizados, resulta muy eficaz para el tratamiento del asma con dosis de 50-100 ug bid (2 por día) en función de la gravedad. La dosis de dipropionato de beclometasona (DPB) es de 100-400 y la de budesonida (Bu), 200-800. PF consigue una mejoría más rápida del flujo espiratorio máximo (FEM), a los 4-7 días, que DPB y Bu, por lo que su índice eficacia/seguridad es superior, y, a mitad de las dosis de Bu y DPB, es equivalente. Por tanto, su eficacia es al menos el doble que la de budesonida, y con dosis mayores produce menor supresión del cortisol sérico. Dosis altas de PF permiten suspender los tratamientos con corticosteroides (CE) orales, y en agudizaciones, resulta tan eficaz como tratamientos cortos con dosis decrecientes de CE orales. PF mejora más la función pulmonar que cromoglicato y nedocromilo sódicos. Y, asimismo, a mitad de dosis de DPB, junto con salbutamol y Babyhaler, mejora la función pulmonar de los lactantes con sibilancias. El mayor riesgo sanitario en los asmáticos es la interrupción, infrautilización o no utilización de los CEI (AU)

Determination of the relative bioavailability of nedocromil sodium to the lung following inhalation using urinary excretion.

OBJECTIVE: To determine the relative lung deposition of nedocromil sodium following inhalation by comparing the amounts of nedocromil sodium excreted in the urine after oral and inhaled dosing. METHODS: Ten healthy volunteers swallowed 8 mg of nedocromil and inhaled 4 x 2-mg doses on separate days. Urine was collected at 0.0, 0.5. 1.0, 2.0, 5.0, 24 h and 36 h after dosing. Urinary excretion of nedocromil was determined by high-performance liquid chromatography. RESULTS: A significantly greater amount of nedocromil was excreted following inhalation than after oral dosing. The mean with (SD) amount excreted at 0.5, 1.0 h and 24 h following inhalation of 4 x 2-mg doses was 41.0 (19.5), 93.0 (39.1) and 319.9 (138.1) microg. Corresponding values after oral administration of 8 mg of nedocromil were 2.1 (2.2), 6.3 (4.7) microg and 74.4 (58.8) microg, respectively. CONCLUSION: Nedocromil excreted in the urine at 0.5 h and 1.0 h after dosing is representative of the amount of drug delivered to the lungs. This method could be used to compare the relative bioavailability to the lungs following inhalation, and hence the performance of different inhaled products and inhalation techniques. The amount of nedocromil excreted in 24 h post-dose is representative of the emitted dose which was delivered to the body.

The pulmonary deposition of two aerosol preparations of nedocromil sodium delivered by MDI assessed by single photon emission computed tomography.

The pulmonary deposition and pharmacokinetics of fine and coarse radioactive aerosols of nedocromil sodium, of mass median aerodynamic diameters 16 microns and 24 microns respectively, delivered by metered dose inhaler (MDI) have been investigated. The corresponding geometric standard deviations of the particle size distributions were 5.32 and 3.93. Pulmonary deposition was assessed by both planar radionuclide scintigraphy and multi-modality three dimensional imaging using single photon emission computed tomography (SPECT) and x-ray computed tomography (CT). The three dimensional data were analysed by transformation to a hemispherical shape based on the fractional radial distance of each point in the lung from the centre to the corresponding extrapolated point on the periphery. This enabled parameters on the variation of both concentration of deposition and total amount deposited with penetration distance to be calculated. For both planar and SPECT data the central to peripheral concentration ratio (C/P ratio) was calculated. The three dimensional C/P ratio showed a median value (3.21) which was significantly higher than for the planar imaging (2.03) (p < 0.001). The parameter used to express the variation of total amount deposited was the median dose position. This showed that for both aerosols 50% of the dose was deposited at sites with a percentage central to peripheral distance of greater than 68%. There was a trend for total percentage of the fine aerosol in the lungs to be higher than for the coarse and for its deposition to be more peripheral. In addition the mean concentrations in blood were measured to be greater for the fine aerosol. However these differences were relatively small and none were individually statistically significant. The technique of combined SPECT and CT imaging was shown to be valuable in obtaining more accurate information on pulmonary distribution of inhaled aerosol deposition. The merits, limitations and potential applications of the technique are discussed.

Speed of onset of action of Tilarin.

Two studies have been carried out specifically to examine the speed of onset of action of intranasal nedocromil sodium 1% (Tilarin) for the relief of symptoms due to ragweed allergic rhinitis. One, a multicentre placebo-controlled comparative study using a QID regimen, 1 spray per nostril, was designed to assess the speed of onset of action of nedocromil sodium during the first week of treatment in patients with rhinitis symptoms, and to evaluate the efficacy and safety of nedocromil sodium during 6 weeks of treatment (1). A 1-week baseline, the start of which was timed to coincide with the start of the ragweed season, was followed by 6 weeks double-blind trial treatment; only patients (n = 166) who were symptomatic at the end of baseline were included in the double-blind phase. Non-parametric analyses of all variables including a summary score (stuffy nose, runny nose, itchy nose and sneezing) showed that the onset of action of nedocromil sodium occurred on the first day of treatment. Further, patients using nedocromil sodium had less symptoms during the 10 days of peak pollen, at which time physician assessment showed reduced mucosal oedema and nasal discharge, and both patient and clinician opinions favoured nedocromil sodium. No significant adverse events were reported during this 6-week study. In the second study (2), 104 patients were randomly allocated to receive either nedocromil sodium or placebo, QID. They then spent 10 hours per day for 2 consecutive days in Iowa City Park during the peak of the ragweed season. Only patients showing significant symptoms of seasonal allergic rhinitis (SAR) during 3 hourly baseline assessments were included. Over the 2-day period, symptom scores for stuffy nose, runny nose, itchy nose and sneezing, and global symptom summary scores, were recorded at 19 hourly time points. At home in the evening, patients recorded symptom scores for the post-exposure period. In comparison with placebo, nedocromil sodium significantly improved rhinitis symptoms within 2 hours, and this reduction in SAR symptoms was maintained throughout the 2-day exposure period. Post exposure symptom summary scores were also significantly lower in patients treated with nedocromil sodium than in those patients treated with placebo. Overall, very few adverse events were reported, none of them serious. In conclusion, nedocromil sodium 1% nasal spray acts rapidly, within 2 hours on the first day of treatment, to reduce ongoing symptoms of SAR. Relief of rhinitis symptoms is maintained throughout the peak pollen period with nedocromil sodium QID, which appears to be a safe and well tolerated treatment for ragweed SAR.

Equivalence of pharmacokinetic characteristics and bronchodilating effect between two combined formulations of nedocromil sodium and salbutamol: MDI and nebulizer solution.

The aim of this study was to determine the equivalence of single doses of two nedocromil sodium/salbutamol combined formulations, namely (a) metered dose inhaler (MDI) (nedocromil sodium 4 mg + salbutamol 0.2 mg) and (b) nebulizer solution (nedocromil sodium 10 mg + salbutamol 1.5 mg), in a group of healthy volunteers. The plasma pharmacokinetic profiles of nedocromil sodium and the pharmacodynamic effect (bronchodilation) of salbutamol were evaluated. Twelve healthy volunteers entered this randomized, cross-over study. All subjects completed the pharmacokinetic section of the study. Nine of them completed also the pharmacodynamic part of the study. After preliminary controls, treatments were administered on separate days and in random order. Blood samples were collected 5, 10, 20, 30, 45 min, 1, 1.5, 2, 3 and 4h after test medication. Specific airways resistance (sRaw) was measured 5, 10, 20, 30, 40, 50 and 60 min following test treatment administration. The pharmacokinetic profiles of nedocromil sodium were evaluated using the maximum plasma concentration (Cmax), the time to peak plasma concentration (tmax) and the area under the curve from 0 to infinity (AUCzero-->infinity), derived from the plasma concentration/time curves. The bronchodilating effect of the two test treatments were evaluated as sRaw percentage change at each time point, maximum sRaw percentage change (sRawMAX) and area under the curve (AUC) of sRaw percentage change plotted against the time of recording. The mean pharmacokinetic results for MDI and nebulizer solution were, respectively: Cmax = 7.59 ng.ml-1 +/- 4.99 and 9.64 ng.ml-1 +/- 5.22 (p = 0.36), tmax = 0.21 hour +/- 0.08 and 0.28 hour +/- 0.14 (p = 0.19), AUCzero-->infinity = 6.28 ng.ml-1.h +/- 2.91 and 12.91 ng.ml-1.h +/- 4.12 (p = 0.008), while the mean pharmacodynamic results were: sRawMAX = -37.91% +/- 13.77 and -39.69% +/- 9.69 (p = 0.69), AUC = -1465.5 delta %.h +/- 799.3 and -1683.4 delta %.h +/- 496.3 (p = 0.45). No statistically significant differences between treatments were found also for sRaw percentage change at each time point. The absorption of nedocromil sodium was proportional to the two administered nominal doses and similar to values obtained after administration of nedocromil sodium alone. The two combined formulations of nedocromil sodium and salbutamol produce an equivalent bronchodilating effect. These results confirm the pharmacological equivalence of the two products, whichever may be used according to specific therapeutic needs.

Regional deposition of nebulized hypodense nonisotonic solutions in the human respiratory tract.

Deposition of nonisotonic therapeutic and diagnosis aerosols can cause changes in airway fluid composition and bronchoconstriction in sensitive subjects. "Hypodense" aerosols containing a relatively low concentration of droplets in the carrier air were used in the studies of regional deposition of radiolabelled nebulized solutions of hypo- and hypertonic saline, in order to investigate whether the number of droplets per volume of carrier can affect deposition. Solutions with and without 0.5% nedocromil sodium were nebulized in order to examine the effects of a potential modifier of the rates of heat and mass transfer. The deposition was quantified using penetration index (PI) calculated from images obtained by single photon emission computerized tomography (SPECT) in 11 healthy volunteers per study. There was an increase in the penetration index (10.9%, for the saline only; 15.5%, for the nedocromil study) of the hypotonic compared to the hypertonic aerosol, although the initial size distribution of both types of aerosols was very similar (mass median aerodynamic diameter (MMAD) 3.7 and 3.8 microns; geometric standard deviation (GSD) 1.8 and 1.5 for the hypo- and hypertonic aerosols, respectively). The present results confirm the effects of tonicity on deposition of aerosols found in a parallel study reported in this issue of the Journal. They also give support to the theory that, in addition to the concentration of the nebulized solutions, the number of droplets per volume of the carrier air is a factor affecting deposition of aqueous aerosols. The presence of 0.5% nedocromil sodium in the solutions did not appear to interfere with the processes of heat and water transfer in the airways.

The effect of physiological manoeuvres on the absorption of inhaled nedocromil sodium.

In a previous study we showed, in both asthmatic patients and in healthy subjects, a marked increase in plasma concentration of nedocromil immediately following an exercise challenge with associated FEV1 measurements. To identify which component of the exercise challenge is responsible, we have now studied the effect of various manoeuvres on plasma nedocromil concentration in eight healthy subjects after inhalation of 1 ml nedocromil solution (1% w/v) via a Wright nebuliser. Each patient was dosed on six occasions, separated by at least 3 days. Between 15 and 23 min after dosing one of the following manoeuvres was performed: control (no manoeuvre); steady exercise for 8 min, a series of FEV1 measurements, exercise plus FEV1 measurements, three Valsalva manoeuvres and hyperventilation for 3 min. Mean plasma drug concentrations under control conditions were similar at 15 and 23 min after dosing. However, there were significant increases in plasma drug concentration following exercise, FEV1 manoeuvres and exercise plus FEV1 manoeuvre. There were no significant changes in plasma drug concentration following Valsalva manoeuvres and hyperventilation. The results suggest that certain manoeuvres increase the absorption of nedocromil sodium, probably as a consequence of an increase in lung volume.

A new method of quantification of the pulmonary regional distribution of aerosols using combined CT and SPECT and its application to nedocromil sodium administered by metered dose inhaler.

Aerosols of nedocromil sodium labelled with 99Tcm were delivered on 20 separate occasions to healthy male volunteers. Planar and single photon emission computerized tomography (SPECT) gamma scintigraphy were immediately performed to assess the pulmonary regional distribution of delivered aerosol. On a separate occasion volunteers were imaged using X-ray computed tomography (CT). Alignment of SPECT and CT images was performed using marked anatomical features and the anterior and lateral skin outlines. CT images provided data for attenuation correction and were used to define the anatomical lung volume. Central to peripheral (CP) ratios of deposited activity were calculated from volumes of interest in coronal and transverse sections of the right lung. These were compared with CP ratios obtained from planar images obtained immediately following aerosol inhalation. Volumetric CP ratio correlated significantly with immediate planar CP ratio (p < 0.001). Analysis of deposition in the whole right lung was performed by separating the SPECT lung data into a series of thin concentric shells centred on the entry of the right main bronchus. Measures were defined for describing the variation of deposition density and cumulative total deposition with distance from the lung centre. These showed significant correlation with planar CP ratio (p < 0.001). SPECT analysis using CT is consistent with planar measures of aerosol deposition but offers a more complete quantification of aerosol penetration and absolute deposited activity within the whole lung. It is a valuable new tool for aerosol analysis.