Lung deposition and protective effect of terbutaline delivered from pressurized metered-dose inhalers and the Turbuhaler in asthmatic individuals

Repurposing drugs as inhaled therapies in asthma

For the first 40 years of the 20th century treatment for asthma occurred in response to an asthma attack. The treatments were given by injection or orally and included the adrenergic agonists adrenalin/epinephrine and ephedrine and a phosphodiesterase inhibitor theophylline. Epinephrine became available as an aerosol in 1930. After 1945, isoprenaline, a non-selective beta agonist, became available for oral use but it was most widely used by inhalation. Isoprenaline was short-acting with unwanted cardiac effects. More selective beta agonists, with a longer duration of action and fewer side-effects became available, including orciprenaline in 1967, salbutamol in 1969 and terbutaline in 1970. The inhaled steroid beclomethasone was available by 1972 and budesonide by 1982. Spirometry alone and in response to exercise was used to assess efficacy and duration of action of these drugs for the acute benefits of beta₂ agonists and the chronic benefits of corticosteroids. Early studies comparing oral and aerosol beta₂ agonists found equivalence in bronchodilator effect but the aerosol treatment was superior in preventing exercise-induced bronchoconstriction. Inhaled drugs are now widely used including the long-acting beta₂ agonists, salmeterol and formoterol, and the corticosteroids, fluticasone, ciclesonide, mometasone and triamcinolone, that act locally and have low systemic bio-availability. Repurposing drugs as inhaled therapies permitted direct delivery of low doses of drug to the site of action reducing the incidence of unwanted side-effects and permitting the prophylactic treatment of asthma.

Methacholine challenge testing: comparative pharmacology

Standardization of the methacholine inhalation challenge, the most common direct bronchoprovocation test, is important. One aspect of standardization is the appropriate washout period for pharmacologic agents which affect the response. This review summarizes the available data on pharmacologic inhibition of the methacholine response. Specific (anti-muscarinic) agents demonstrate marked bronchoprotection (up to 7 days for the long-acting drugs) which lasts longer than the duration of bronchodilation. The functional antagonist (beta 2 agonist class of medications) shows marked, but less, bronchoprotection which is relatively short lived and is similar to the duration of bronchodilator efficacy. Tolerance develops quickly, especially to the long-acting agents. Single doses of controller medications, such as inhaled corticosteroids (ICS) and leukotriene receptor antagonists, have no effect on the methacholine test, while regular use, at least for ICS, has a modest protective effect whose duration is uncertain and likely variable. Theophylline has a small effect and H1 blockers (all generations) have a negligible effect.

Fast-dissolving sublingual films of terbutaline sulfate: formulation and in vitro/in vivo evaluation

Terbutaline sulfate fast dissolving sublingual films were prepared using seven drug compatible film formers in different combinations and proportions. The film polymers are maltodextrin, Na alginate, Carpabol 430, xanthan gum, HPMC E5, PVP K-25, and Na CMC. Propylene glycol and sorbitol were used as plasticizers and mannitol as filler. The optimum polymer concentrations and the plasticizer amount were selected on the basis of flexibility, tensile strength, and stickiness of the films. The prepared films were evaluated for their tensile strength, thickness uniformity, disintegration time (in vitro and in vivo), in vitro dissolution, and moisture content. Polymer type rather than total polymer concentration or plasticizer amount showed a significant effect on the tested film properties. A randomized, single dose, crossover study was conducted in four healthy volunteers to compare the pharmacokinetic profile of terbutaline sulfate from the prepared films and the conventional oral tablets. The film formula of choice gave a significantly faster drug absorption rate and recorded a relative bioavailability of 204.08%. Sublingual films could be promising as a convenient delivery system for terbutaline sulfate in patients with swallowing problems. The improved extent of absorption (higher AUC(0-24)) indicates success in improving drug bioavailability, and the faster absorption rate could be promising for the management of acute episodes of asthma.

Equivalence considerations for orally inhaled products for local action-ISAM/IPAC-RS European Workshop report

The purpose of this article is to document the discussions at the 2010 European Workshop on Equivalence Determinations for Orally Inhaled Drugs for Local Action, cohosted by the International Society for Aerosols in Medicine (ISAM) and the International Pharmaceutical Consortium on Regulation and Science (IPAC-RS). The article summarizes current regulatory approaches in Europe, the United States, and Canada, and presents points of consensus as well as ongoing debate in the four major areas: in vitro testing, pharmacokinetic and pharmacodynamic studies, and device similarity. Specific issues in need of further research and discussion are also identified.

Lung deposition and efficacy of inhaled formoterol in patients with moderate to severe COPD

BACKGROUND

Little is known about the impact of COPD on lung deposition of inhaled drugs and the relationship between lung-dose and response of pulmonary function measurements.

METHODS

Nineteen patients with varying degrees of COPD were randomized to inhale single doses of formoterol (Oxis) Turbuhaler 4.5, 9, 18, and 36 microg in a double blind, placebo-controlled, crossover design. Urinary excreted formoterol during 32 h was used to determine absolute lung deposition. Peak inspiratory flow (PIF) and inhaled volume (IV) were recorded to assess the patients' ability to use Turbuhaler. Efficacy was measured by spirometry, inspiratory capacity (IC), airway conductance (sG(AW)), and absolute lung volumes.

RESULTS

Mean pulmonary bioavailability of formoterol was about 24% of the nominal delivered dose after inhalation for the different treatments. No significant correlations between lung deposition and baseline FEV(1), PIF or IV were shown. All formoterol doses produced statistically significant increases in FEV(1), FVC, IC, and sG(AW) relative to placebo. Linear dose/response relationships were observed for these variables, with more narrow limits of the slopes for the lung-dose/response relationships than for the nominal-dose/response relationships. Moreover, 36 and 18 microg formoterol statistically significantly decreased functional residual capacity (FRC) and residual volume (RV) relative to placebo.

CONCLUSIONS

This study could not show any difference in lung deposition of formoterol inhaled via Turbuhaler between patients with moderate and severe COPD. Moreover, the effect of formoterol on various pulmonary function measurements were more closely related to lung deposition than the inhaled nominal dose.

Inspiratory Muscle Training May Increase Peak Inspiratory Flow in Chronic Obstructive Pulmonary Disease

BACKGROUND

When choosing a specific inhalation device for a chronic obstructive pulmonary disease (COPD) patient, the internal airflow resistance and the ability of the patient to overcome it and to create an optimal inspiratory flow are essential.

OBJECTIVES

The purpose of the present study was to investigate: (1) the peak inspiratory flow (PIF) that a patient with COPD can generate while breathing through two dry powder inhalers and (2) whether in patients with low PIF specific inspiratory muscle training (SIMT) will increase the PIF and exceed the minimal PIF that is considered necessary to guarantee optimal lung deposition of the drug.

METHODS

Inspiratory muscle strength and PIFs were measured in 60 patients with COPD. Then 28 patients with severe COPD and low PIF were randomized to receive SIMT or to a control group.

RESULTS

With the Turbuhaler, 12 patients (20%) could not generate the optimal flow of 60 l/min. PIF correlated very well with maximal inspiratory mouth pressure (PI(max)) for the Diskus and the Turbuhaler, as well as for both males and females (p < 0.001). Following the training period, there was a statistically significant increase in the PI(max) in the training group. This increase was associated with a significant increase in the PIF. All patients overcame the minimal threshold PIF following the training.

CONCLUSIONS

Some patients with severe COPD are not able to generate adequate flow to secure optimal lung deposition of the inhalation with the Turbuhaler. SIMT improves inspiratory muscle strength as well as PIF. Following 8 weeks of training, the optimal PIF enabling adequate lung deposition of the drug was attained in all the trained patients.

Pharmacokinetic and pharmacodynamic properties of inhaled beclometasone dipropionate delivered via hydrofluoroalkane-containing devices

Inhaled corticosteroids have a key role in the treatment of asthma and chronic obstructive pulmonary disease. In recent times, beclometasone dipropionate has been reformulated in pressurised metered dose inhalers (pMDIs), using hydrofluoroalkanes (HFAs) as a propellant. Extensive toxicological testing has shown that HFA-propellants are well tolerated. Among the reformulated beclometasone dipropionate-containing pMDIs, only the characteristics of the two Qvar formulations have been thoroughly explored. Compared to the reference beclometasone dipropionate formulation, the mass median aerodynamic diameter of the Qvar formulations are substantially smaller (1.1 vs 4.0 microm), whereas that of Modulite averages 2.6 microm. Scintigraphic and pharmacokinetic studies indicate a higher lung deposition for both the Qvar and the Beclazone formulations, compared with reference beclometasone dipropionate formulation. Since the 2- to 3-fold increase in pulmonary deposition results in a 2.6- to 3-fold difference in relative efficacy for Qvar, half the dose of the reference beclometasone dipropionate formulation has been currently recommended in adult patients with asthma, a recommendation that is supported by a large number of clinical trials. Conversely, the design of the studies conducted to compare the efficacy of Qvar with fluticasone propionate and budesonide does not allow establishing their equivalence on a milligram per milligram basis. Good studies on the bioequivalence between the reference beclometasone dipropionate formulation and the Modulite or Beclazone formulations are not available.

Bronchial challenge, assessed with forced expiratory manoeuvres and airway impedance

OBJECTIVE

The Methacholine concentration at which a 20% decrease of the forced expiratory volume in 1s (PC20_FEV1) or a 40% increase in airway resistance (PC40_Rrs6) occur are accepted indicators for airway hyperresponsiveness. We hypothesised that the level of detection of bronchial hyperresponsiveness will differ between the two methods.

METHODS

The response to Methacholine was assessed by forced oscillation technique (FOT) and spirometry in 20 stable hyperresponsive asthmatics. The effects of repeated lung function measurements on respiratory muscle fatigue were measured from maximal inspiratory mouth pressure (MIP). After each dose, patients scored their perception of dyspnoea on a BORG scale. Differences in patient's burden were measured by comparing the BORG-score at PC40_Rrs6 (BORG-PC40_Rrs6) and at PC20_FEV1 (BORG-PC20_FEV1). Reproducibility was also evaluated.

RESULTS

The PC20_FEV1-values were 2.2 (0.4) doubling dose higher as compared to the PC40_Rrs6 (P<0.001). The mean BORG-score at PC40_Rrs6 was 1.7 points lower as compared to the BORG-score at PC20_FEV1 (P<0.001). The difference (mean(sd)) between the PC20_FEV1 of measurement 1 and 2 was -0.1 (1.4) doubling dose, and -0.3 (2.7) doubling dose for PC40_Rrs6. The MIP after Methacholine provocation was 1.0(0.2) kPa lower as compared to the MIP before the challenge test (P<0.001), suggesting respiratory muscle fatigue.

CONCLUSION

Measuring PC40_Rrs6 shortens the challenge test and lowers the concentrations of bronchoconstrictor agents as compared to measurements of PC20_FEV1. The FOT-method was less strenuous for patients. In spite of the fact that the reproducibility is two-fold worse than measuring PC20_FEV1, it still remains quite acceptable at a mean of 0.3 doubling dose. The respiratory muscle strength was deteriorated after the challenge test.

Salbutamol pMDI gives less protection to methacholine induced airway obstruction than salbutamol via spacer or DPI

BACKGROUND

Inhalation device and inhalation technique influence the deposition of drug in the lung. This study evaluated the efficacy of salbutamol as a bronchoprotective agent administered via Diskus, Turbuhaler, pMDI or pMDI + Volumatic against methacholine-induced bronchoconstriction.

METHODS

Twenty stable asthmatics participated in this open randomised comparison of the protective effects of 200 microg salbutamol, administered via the various inhalation devices on methacholine-induced airway obstruction, with respect to pulmonary function and dyspnoea sensation. The inhalation technique was controlled by measuring the peak inspiratory flow (and actuation time, in the case of pMDI and Volumatic) through the device, during inhalation.

RESULTS

Inhalation of salbutamol increased the provocative dose of methacholine by 1.2 doubling doses (dd) for pMDI, 1.9 dd for Diskus, 2.3 dd for Turbuhaler and 2.5 dd for Volumatic. Salbutamol via pMDI provided less protection from methacholine-induced airway obstruction than did salbutamol administered via Diskus, Turbuhaler or Volumatic (P<0.05). The inadequate pMDI use of 70% of our patients might contribute to a lower deposition of drug in the central airways, resulting in the lower protective effect. However, the PC20_FEV1 of the adequate- and inadequate pMDI users showed no significant difference.

CONCLUSION

Salbutamol administered via pMDI gave less protection from methacholine-induced bronchoconstriction than did salbutamol via Diskus, Turbuhaler or Volumatic. This study suggests that the pMDI may be less suitable for protecting a patient against bronchoconstriction due to airway hyperresponsiveness.

Efeito do salbutamol liberado através de inalador de pó seco sobre o broncoespasmo induzido por metacolina

INTRODUÇÃO: Os beta2-agonistas de curta duração sob a forma de nebulímetro pressurizado são os fármacos utilizados rotineiramente na reversão do broncoespasmo induzido pela metacolina. A administração desses fármacos na forma de pó seco, liberados por inaladores de pó seco pode ser uma alternativa eficaz. OBJETIVO: Avaliar a efetividade e rapidez de ação do salbutamol liberado através de inalador de pó seco pulvinal (Butovent®) na reversão do broncoespasmo induzido por metacolina, comparando-o com o salbutamol liberado por nebulímetro pressurizado. MÉTODO: Foram avaliados prospectivamente 60 pacientes sucessivos com broncoespasmo induzido por metacolina, cuja queda do volume expiratório forçado no primeiro segundo (VEF1) foi de, no mínimo, 20%. Foram randomizados 30 pacientes para receber 200 mcg de salbutamol liberado por nebulímetro pressurizado e 30 pacientes para receber 200 mcg de salbutamol através de inalador de pó seco (pulvinal), na etapa final do teste de broncoprovocação, com o objetivo de reverter o broncoespasmo induzido pela metacolina. Foram avaliados os VEF1 obtidos 1 minuto e 5 minutos após a administração do broncodilatador. RESULTADOS: Os grupos foram pareados por sexo, idade, peso, altura, dose provocativa causadora de queda de 20% no VEF1 (primeiro grupo: 1,3 mg ; segundo grupo: 1,19 mg; p = 0,79) e VEF1 pós-metacolina (primeiro grupo: 2,03 l; segundo grupo: 1,99 l; p = 0,87), sem diferença significativa entre eles. O incremento médio do VEF1 foi de 16,2% (1 minuto) e 22,2% (5 minutos) no primeiro grupo e de 17% (1 minuto) e 23,6% (5 minutos) no segundo grupo, não havendo diferença estatística entre eles (p = 0,8). CONCLUSÕES: Os beta2-agonistas administrados através de inalador de pó seco (pulvinal) apresentam a mesma eficácia broncodilatadora e rapidez de ação que no tradicional método por nebulímetro pressurizado.

Lung deposition and systemic availability of fluticasone Diskus and budesonide Turbuhaler in children

Pharmacokinetic studies can be used to measure lung dose of inhaled drugs. The aim of this study was to compare the lung deposition of budesonide (BUD) inhaled from Turbuhaler (AstraZeneca, Lund, Sweden) and fluticasone propionate (FP) inhaled from Diskus (GlaxoSmithKline, London, UK) and to assess if the study design used for pharmacokinetic studies can be simplified. Plasma levels of BUD and FP were measured for 21 hours on five separate days in 15 patients aged 8 to 14 years: (1) Intravenous infusion of 200 microg BUD, (2) intravenous infusion of 200 microg fluticasone dipropionate, (3) inhalation of 800 microg BUD via Turbuhaler, (4) inhalation of 750 microg FP via Diskus, and (5) inhalation of BUD and FP on the same day. Charcoal was ingested to eliminate drug uptake from the gastrointestinal tract. The mean lung deposition of drug after Turbuhaler and Diskus inhalation was 30.8 and 8.0% when BUD and fluticasone were administered on separate days and 29.5% (BUD) and 7.6% (fluticasone) when the two drugs were inhaled on the same day. Lung deposition is four times higher in children after inhalation from Turbuhaler than after inhalation from Diskus. Pharmacokinetic studies with BUD and FP can be simplified because the two treatments can be administered on the same day.