Relative bioavailability of terbutaline to the lungs following inhalation using different methods.

The primary aim was to validate and implement a urinary pharmacokinetic method for terbutaline to determine the relative lung and systemic bioavailability following inhalation and to measure the in-vitro characteristics of the emitted dose by these inhalation methods. Two new robust, accurate and sensitive high performance liquid chromatography methods for the determination of terbutaline in aqueous and urine samples were validated in accordance with the FDA and ICH guidelines. Terbutaline was extracted using solid phase extraction with salbutamol and bamethane as internal standards. The accuracy, precision, lower limit of detection and recovery for both methods were within recognized limits. The in-vitro characteristics of terbutaline sulphate inhalers were measured according to standard compendial methodology as well as adaptation of this methodology to simulate routine patient use. The dose emission of terbutaline sulphate from a Bricanyl Turbuhaler was determined using an inhalation volume of 4 L at inhalation flows of 10-60 L min-1. The particle size distribution was measured using an Anderson Cascade Impactor (ACI) with a mixing inlet valve to allow measurement at different flows. A steady increase in total emitted dose (TED) and the fine particle dose (FPD) was observed as the inhalation flow increased thereby highlighting the flow dependent dose emission characteristics of the Turbuhaler. The in-vitro dose emission characteristics of terbutaline sulphate from Bricanyl MDIs were measured according to the standard compendial methodology at a flow of 28.3 L min-1 using a 4 L inhalation volume. The TED and particle size distribution of terbutaline sulphate from the Bricanyl MDI were determined alone and with different spacers [AeroChamber Max (AMAX), AeroChamber Plus (APLUS), Fisonair and Nebuhaler]. The TED from the MDI alone was significantly higher than all MDI+spacers (p<0.001). The MDI with APLUS resulted in the smallest mass median aerodynamic diameter (MMAD) and the highest fine particle fraction (FPF). The MDI with AMAX resulted in the highest FPD. The in-vitro characteristics of terbutaline sulphate from Bricanyl respules using the Aeroneb Pro (vibrating mesh) and Sidestream jet nebulisers were determined by the CEN methodology and the Next Generation Impactor (NGI) methodology. The Aeroneb Pro was found to have significantly better aerodynamic properties than the Sidestream. The results from the NGI method were significantly different from the CEN method suggesting further evaluation of both methods. Cooling the NGI decreased the evaporation effect. Twelve healthy volunteers (6 females) completed in-vivo urinary terbutaline pharmacokinetic studies to determine the relative bioavailability following inhalation. The differences between the amounts excreted 0.5, 1, 2, 4, 6 and 24 hour post inhalation from a Bricanyl MDI (I) and oral (O) dosing of 500 µg terbutaline sulphate and with the co-administration of oral charcoal (IC and OC, respectively) were studied. No terbutaline was found in OC samples. The amount of terbutaline excreted 30 minutes post I and IC were significantly (p<0.001) higher than post O suggesting that the amount of terbutaline excreted 30 minutes post dosing can be used as an index of the lung deposition. The amount of terbutaline excreted 24 hour post I was significantly (p<0.01) higher than post O suggesting that the amount of terbutaline excreted 24 hour post dosing can be used as an index of the relative systemic bioavailability. The dose response relationships and the low inter and intra-subject variability studies confirm the feasibility of this method. To demonstrate the application of the method the effect of inhalation technique on the lung and systemic bioavailability following inhalation from a dry powder inhaler was evaluated. The effect of different spacers on the dose emitted from the Bricanyl MDI and the effect of different nebulisers on the dose emitted were also studied using twelve healthy volunteers (6 females) for each study. A fast inhalation flow using the Bricanyl Turbuhaler resulted in significantly higher amounts of terbutaline excreted 0.5 and 24 hour post dosing (2 doses of 500µg terbutaline sulphate from Bricanyl Turbuhaler) than slow inhalation flow (p<0.001). The Bricanyl MDI alone resulted in a significantly higher amount of terbutaline excreted 24 hour post dosing (2 doses of 250µg terbutaline sulphate from Bricanyl MDI) and significantly lower amounts excreted 30 minutes post dosing than the MDI+Spacers. The AMAX provided a greater amount of urinary terbutaline excreted 30 minutes post dosing than the APLUS and Nebuhaler. The Aeroneb Pro resulted in significantly higher amounts of terbutaline excreted 0.5 and 24 hour post dosing (1 dose of 5mg/2ml terbutaline sulphate from Bricanyl respule) than a Sidestream Jet nebuliser (p<0.001). Further application of the method was demonstrated by 12 (6 female) COPD non-invasive mechanically ventilated patients. One dose of 2mg in 0.8ml terbutaline sulphate respiratory solution from Aeroneb Pro and one dose of 5mg in 2ml terbutaline sulphate respiratory solution from Sidestream jet nebuliser resulted in a similar amounts of urinary terbutaline excreted 0.5 and 24 hour post dosing. The results were consistent with the results of the ex-vivo study performed on the same patients. The thesis highlights extension of the urinary pharmacokinetic method following inhalation to terbutaline and its application in volunteer and patient studies.Egyptian Culture Office in UK, Missions Department in Egyp

The efficacy of a \u27spacer\u27 in the delivery of salbutamol for the prevention of exercise-induced asthma

Salbutamol is a Beta-2-agonist, commonly prescribed for the prevention and reversal of Exercise induced asthma (EIA). The purpose of this study was to compare the efficacy of a spacer device in the delivery of salbutamol for the prevention of EIA Thirteen confirmed asthmatic subjects (10 female and 3 male), completed 3 exercise test sessions consisting of three treatments a) Ventolin via MDI (metered dose inhaler) and placebo via spacer, b) Ventolin via spacer and placebo via MDI and c) Placebo via spacer and MDI, randomly administered utilising a single blind, cross--over design. Following treatment, subjects completed an asthmogenic physical challenge (8-minute, graded treadmill run at 75-85% predicted heart rate maximum). The lung function variables FEV, FVC, PEFR, FEF­­50, and FEF25-75 were recorded pre-treatment, pre exercise and 0, 3, 5, 7, 10, 20 and 30 minutes post-exercise. Of the 13 subjects, only 7 demonstrated sufficient decrement in FEV1 to be classified as ElA. In the subjects who demonstrated EIA, no significant differences were found for post-exercise lung function measures between the spacer and MDI mean scores. Administration of salbutamol via the spacer resulted in significant improvements over the- placebo scores in MEF50 and FEF25-75 and significant test/time interactions for FVC and FEV1, however the MDI scores were not significantly different to the placebo. The findings were congruent with previous findings which suggest that spacer delivery offers no significant advantage m preventing EIA in subjects who are skilled m MDI administration techniques. The inability to induce EIA in 6 of the 13 subjects may relate to the high lability scores recorded for several subjects suggesting that bronchoconstriction was evident prior to testing. This may have been due to the high pollen count recorded during testing. Secondly, the asthmogenic nature of the testing environment may have been hindered due to the high level of fluctuation in the relative humidity recorded for each test. Although conclusions have been made concerning spacer efficacy, this study should be replicated under more asthmogenic conditions to confirm the findings of this study

Generation of deeply inspirable clouds from dry powder mixtures.

SIGLEAvailable from British Library Document Supply Centre- DSC:DX187842 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Safety aspect of β2-agonists in chronic obstructive pulmonary diesease

Chronic Obstructive Pulmonary Disease (COPD) presents an enormous public health challenge. Cigarette smoking remains the most important aetiological factor and although legislation to reduce smoking has been introduced in parts of the more developed world, consumption is increasing in many of the poorest parts of the world. With the predicted rise in disease prevalence, COPD is expected to become the worlds third largest cause of death by 2020. COPD is a disease state characterised by airflow limitation that is not fully reversible. Inhaled bronchodilators can only produce a small improvement in the airflow obstruction, but despite this, patients with COPD frequently use high doses of beta-2-agonists as the disease progresses and they develop breathlessness and exercise limitation. Short-acting beta-2-agonists are generally used as required to reduce breathlessness and reduce airflow obstruction whereas long-acting beta-2-agonists are prescribed on a regular twice-daily basis to reduce symptoms and rescue medication use and because of a potential beneficial effect on quality of life and exacerbation rates. Although generally well tolerated, the safety of inhaled beta-2-agonists has been a source of some concern since the late 1960s, when an epidemic of asthma deaths was associated with the use of a high dose formulation of isoprenaline. Further controversy has followed and questions have extended to long-acting beta-2-agonists, most notably after a recent large-scale post marketing surveillance study identified an association between the regular use of inhaled salmeterol and asthma-related deaths. The safety of inhaled beta-2-agonists is also an important consideration for patients with COPD. Being older and likely to have a history of cigarette consumption means that they are at risk of having symptomatic, or subclinical, ischaemic heart disease. Beta-2-agonists cause a number of systemic effects including an increase in heart rate, transient hypoxaemia and hypokalaemia. Since many patients with COPD are already hypoxaemic and may be taking other drugs that stimulate the myocardium and cause hypokalaemia, the additional systemic effects from beta-2-agonists may be more likely to produce adverse cardiac events including dysrhythmia and ischaemia. This thesis is concerned with the safety of inhaled beta-2-agonists in the management of COPD. The introduction consists of an overview of the epidemiology, natural history and pathology of COPD (Chapter 1) and a review of human beta-2-adrenoceptor function and inhaled beta-2-agonist pharmacology (Chapter 2). This is followed by a systematic literature review of the results from long-term clinical studies of inhaled beta-2-agonists in subjects with COPD (Chapter 3). The original work consists of three clinical studies that have examined aspects of the effect of high dose inhaled beta-2-agonists in subjects with COPD and a discussion to place these findings in context. Most published studies of inhaled beta-2-agonists in subjects with COPD have focused on their efficacy, rather than safety. We were concerned that some individuals with COPD and limited bronchodilator reversibility may experience an increase in adverse systemic effects after inhaling high doses of beta-2-agonists, which could lead to detrimental outcomes in certain clinical situations. Apart from the cardiac effects mentioned above, beta-2-agonists increase tremor, which causes CO2 production, and cardiac output and tissue perfuson, which increases the transport of CO2 to the lungs. The increase in CO2 flux to the lungs will normally increase ventilation. We were concerned however that some subjects with severe COPD would not be able to increase ventilation appropriately in response to the beta-2-agonist and this would lead to an increase in PaCO2. Our hypothesis was that high dose inhaled beta-2-agonists could worsen respiratory failure in some subjects with severe COPD. The first two studies in the thesis examined the effect of high dose inhaled salbutamol on the partial pressure of arterial oxygen and carbon dioxide in subjects with severe COPD. We initially conducted a double blind, randomised study on subjects within 48 hours of being admitted to hospital with an acute exacerbation of COPD (Chapter 4). The study was designed to determine whether high dose salbutamol caused an increase in the partial pressure of arterial carbon dioxide. We randomised subjects at a ratio of 3:1 to receive either salbutamol or ipratropium bromide and studied the pharmacodynamic effect on heart rate, PaO2 and PaCO2 over five hours. Over eighteen months and despite extensive efforts I was only able to recruit ten subjects, of whom five completed the study. I found that subjects who required hospital admission with an acute exacerbation of COPD were either too unwell for the study, had co-morbidities that precluded participation or the individuals were unwilling to participate. Although the study was terminated prematurely and we were unable to perform statistical analysis, I have presented the findings from the five subjects who completed the study, of whom four were randomised to receive salbutamol. We used ascending doses of salbutamol (1.25mg, 1.25mg, 25mg, 5mg, 5mg) and found no consistent effect on PaCO2 or PaO2 and no dose response relationship. The subject with the highest baseline PaCO2 did however have a rise in PaCO2 with the highest 5mg doses of salbutamol. To test the hypothesis further we conducted a randomised, double blind, crossover study and examined the effect of salbutamol on the arterial blood gas tensions of fourteen patients with stable severe COPD and a history of chronic or intermittent hypercapnia. The study was designed to determine whether high dose salbutamol causes a rise in PaCO2 when inhaled by subjects with severe COPD and a history of alveolar hypoventilation. We compared the effect of two 5mg doses with two 200 microgram doses of salbutamol on PaO2 and PaCO2 and heart rate. The subjects had severe COPD with a mean FEV1 of 0.71 L (27% predicted) and a mean smoking history of 53 pack years. The mean baseline PaO2 was 7.9 kPa and the mean baseline PaCO2 was 7.0 kPa. The high dose of salbutamol caused a mean fall in both PaO2 and PaCO2 and a small increase in heart rate. There was some support for our hypothesis however as three subjects had a small rise in PaCO2 after high dose nebulised salbutamol (Chapter 5). The third study was a double blind, crossover, dose-response examination of the bronchodilator and systemic effects of inhaled formoterol in subjects with COPD (Chapter 6). The rapid onset and prolonged duration of action of formoterol offers potential for the drug to be used as rescue medication in addition to twice daily maintenance therapy, as is the case in the management of asthma. Our hypothesis was that high doses of formoterol would produce adverse systemic effects that would outweigh the beneficial bronchodilator effects in subjects with COPD and limited bronchodilator response to salbutamol. We studied 20 subjects, with a mean FEV1 of 1.32 L (47% predicted) and a mean smoking history of 42 pack years. Each subject was studied on five days and after receiving placebo, formoterol 6, 12, 24 and 48 mg in a random sequence, we examined the effect of each dose on FEV1, tremor, dyspnoea, heart rate, blood pressure, SpO2, walk distance, potassium and satisfaction. We found that all doses were well tolerated and although there was a small dose related increase in FEV1 and the mean satisfaction scores were higher with each dose of formoterol than placebo, there was no dose related improvement in measures that are important to the patient, including breathlessness and walk distance. Apart from a dose related increase in tremor, other systemic effects were limited. All three studies found that high dose inhaled beta-2-agonists produced relatively modest systemic effects in subjects with COPD. This probably reflects the fact that almost all subjects were taking beta-2-agonists on a regular basis and had developed tolerance to the systemic effects of an inhaled beta-2-agonist. Although the results from the three studies were generally reassuring, questions still remain about the balance between beneficial and adverse effects with high dose inhaled beta-2-agonists in subjects with COPD. The results may have been different if subjects had more severe disease, were exposed to higher doses of beta-2-agonists, had certain beta-2-adrenoceptor polymorphisms or were beta-2-agonist naive

Adrenergic Control of Potassium and Magnesium: Interaction with Drug Therapy

Hypokalaemia is potentially fatal (Chapter 2). The internal regulation of potassium, i. e. the movement of potassium between body compartments, has not been extensively investigated (Chapter 1). Rapid movements of potassium can occur across cell membranes, e. g. in diabetic ketoacidosis the hyperkalaemia can be rapidly reversed by insulin administration, and the existence of a specific membrane enzyme controlling movement of potassium and sodium between the intracellular and extracellular compartments, Na+/K+ ATPase, has been known for 30 years (Chapter 1. 5). Some acutely ill patients have hypokalaemia on admission to hospital which resolves without treatment. This observation led to the hypothesis that increased sympathetic activity, raising circulating adrenaline levels, stimulates a Na+/K+ ATPase linked to a beta2-adrenoreceptor on cell membranes pumping potassium into cells. Animal work by Clausen supported this theory and several studies in humans, some carried out in the Department of Materia Medica, were also supportive, demonstrating that infusing adrenaline resulted in hypokalaemia (Chapter 1). In the studies presented in this thesis both the mechanism and the clinical relevance of adrenaline induced hypokalaemia, with particular emphasis on the effects of a number of widely used drugs, have been studied. Many drugs have been designed to specifically act on receptors in the sympathetic nervous system, either as agonists or antagonists, e. g. beta-blockers and beta2-agonists, and they are frequently administered to patients with cardiovascular disease who are at increased risk of dysrhythmias should hypokalaemia occur. Such patients are at increased risk of suffering acute stress, such as myocardial infarction, which increases circulating adrenaline levels. An infusion regimen of (-)-adrenaline which would safely raise circulating adrenaline to concentrations similar to those seen in acute severe illness was developed (Chapter 3). This regimen consistently raised adrenaline levels seen in normal subjects during supine rest by 10 fold or more. During the infusions adrenaline levels did fluctuate, but they remained in the pathophysiological range. The regimen involved stepwise increases in the rate of adrenaline infusion and proved safe despite the adrenaline infusion being combined with other drugs with sympathomimetic activity. The mechanism of adrenaline induced hypokalaemia in man is unproven. However, the possibility that adrenaline induced hypokalaemia could be the result of B-agonist induced changes in plamsa insulin was excluded (Chapter 4.2). Both plasma insulin and potassium concentrations fell during the adrenaline infusion. Attenuation of adrenaline induced hypokalaemia by beta-adrenoceptor antagonists with varying degrees of cardioselectivity (B1) was studied and demonstrated that adrenaline induced hypokalaemia was mediated via the B2 adrenoceptor (Chapter 4.3 & 4.4). Whether the fact that cardioselective beta-antagonists will be less effective in protecting patients from adrenaline induced hypokalaemia during the acute stress of severe illness is of any clinical significance remains unknown. Salbutamol, a selective beta2-agonist, was also shown to cause hypokalaemia when given intravenously (Chapter 4.2). It is administered in high doses in acute attacks of asthma, where it might be expected that circulating adrenaline levels are raised. An additive hypokalaemic effect of exogenous adrenaline and salbutamol was demonstrated (Chapter 4.2) . Hypokalaemia is a relatively common adverse effect of many diuretics and such hypokalaemia could increase the severity of hypokalaemia during acute stress. No synergistic action on potassium levels was demonstrated (Chapter 5) between adrenaline and any diuretic. However, both frusemide and bendrofulazide lowered plasma potassium and, therefore, during the adrenaline infusion more profound hypokalaemia was observed because baseline potassium was lower. Theophylline, widely used as a bronchodilator, has been reported to increase circulating catecholamine levels and to interact with sympathomimetics (Chapter 6.1 & 6.2). Hypomagnesaemia can occur in situations in which circulating adrenaline levels are known to be raised, such as acute myocardial infarction (Chapter 7.1). The control of internal regulation of magnesium is not understood. The role of adrenaline in the control of magnesium levels was studied, using the same adrenaline infusion regimen, and a small but significant fall in plasma magnesium was observed (Chapter 7.2). This was unaltered by pretreatment with diuretics (Chapter 7.3). The mechanisms and clinical relevance of adrenaline induced hypomagnesaemia require further study but these have not yet been attempted

The impact of acute and chronic administration of short-acting β2-agonists on urinary pharmacokinetics and athletic performance

Exercise Induced Bronchoconstriction (EIB) is common amongst elite athletes. Short-acting β2-agonists represent the first-line treatment of EIB, however; limited data currently exists examining the ergogenic and pharmacokinetic impact of chronic short-acting β2-agonist administration. Furthermore, the ergogenic impact of acute and chronic administration of short-acting β2-agonists in asthmatic individuals is unknown. Whilst the short-acting β2-agonist salbutamol is permitted in and out of competition due to a known pharmacokinetic response, no urinary threshold has been established for the use of the alternative short-acting β2-agonist terbutaline. The purpose of study 1 was to investigate the ergogenic potential of the WADA upper daily limit of 1600 μg·day-1 salbutamol every day for 6 weeks versus placebo, alongside combined resistance and endurance training. Findings highlighted improvements in; 1 repetition maximum (1RM) bench press (Baseline: 65.6 ± 5.4 kg vs. 64.3 ± 4.9 kg – 6 weeks: 70.3 ± 4.9 vs. 72.5 ± 5.4 kg) and leg press (Baseline: 250 ± 26.9 vs. 217.9 ± 19 kg – 6 weeks: 282.5 ± 22.5 vs. 282.8 ± 18.3 kg); vertical jump test (Baseline: 53.5 ± 4.1 vs. 50.4 ± 2.1 cm – 6 weeks: 55 ± 3.5 vs. 52.4 ± 1.7 cm); 3 km running time-trial performance (Baseline: 988.7 ± 68.7 vs. 1040.5 ± 66.3 s – 6 weeks: 947.5 ± 54.9 vs. 1004.3 ± 70.5 s); isokinetic dynamometry (Baseline: 196.1 ± 47.3 vs. 184.6 ± 35.0 n.m. – 6 weeks: 179.5 ± 48.9 vs. 195.2 ± 28.9 n.m.); and body composition (Baseline: 32.1 ± 13.9 vs. 34.9 ± 10.4 mm – 6 weeks: 32.4 ± 14.5 vs. 34.5 ± 10 mm) for both the salbutamol group and the placebo group, respectively, over the 6 week period, with no difference observed between groups, indicating long-term therapeutic use of salbutamol at the WADA upper daily limit has no ergogenic effect. Of note, one participant exceeded the urinary threshold, presenting with an adverse analytical finding (AAF) showing that the upper daily limit can lead to AAF’s in susceptible individuals. Athletes who respond poorly to salbutamol treatment are able to apply for the use of the short-acting β2-agonist terbutaline via a therapeutic use exemption (TUE) certificate. Urinary upper limits are unknown for terbutaline and as such it is prohibited at all times without the presentation of a TUE. The purpose of study 2 was to investigate the urinary excretion of terbutaline following single and repeated use of inhaled or oral terbutaline. The aim of the study was to establish a differential distinction between routes of administration which could assist the WADA with regard to anti-doping policy and procedure. Results demonstrated a significant difference in urine concentration of terbutaline between inhaled and oral administration for female Caucasian (670.1 ± 128.3 vs. 361.8 ± 43.8 ng·ml-1; P=0.019; 680.8 ± 91 vs. 369.9 ± 41.9 ng·ml-1; P=0.006), male Afro-Caribbean (343.18 ± 45 vs. 231.3 ± 32.95 ng·ml-1; P=0.044; 389.73 ± 67.4 vs. 212.4 ± 50.3 ng·ml-1; P=0.008) and male Asian (266.4 ± 23.7 vs. 143.3 ± 22 ng·ml-1; P=0.004; 379.5 ± 50.4 vs. 197.5 ± 38.6 ng·ml-1; P=0.000) groups for single (5 mg oral vs. 2 mg inhaled) and repeated (4 x 5 mg oral vs. 8 x 1 mg inhaled) administration trials, respectively. No difference was observed in male Caucasians. High intra- and inter-individual variability between samples meant that a clear distinction between routes of administration could not be established. The study was able to identify an upper urinary threshold following inhaled administration of 1284.3 ng·ml-1 and an upper urinary threshold following oral use of 2376.3 ng·ml-1 which may inform the process of distinguishing between inhaled and oral use. Athletes are permitted to use inhaled terbutaline therapeutically through the TUE process. The purpose of study 3 was to investigate the ergogenic effect of terbutaline at high (2 mg and 4 mg) therapeutic inhaled doses on 3 km running time-trial performance in males and females. The study found that inhaled terbutaline, when used at the highest therapeutic dose, has no impact upon 3 km time-trial performance in males (956.3 s vs. 982 s) and females (1249 s vs. 1214.7 s) for placebo vs. 4 mg inhaled terbutaline, respectively. The majority of studies investigating the ergogenic potential of salbutamol have been in healthy individuals. It is not yet understood whether the exercise response differs in asthmatic individuals. The purpose of study 4 was to investigate the use of inhaled salbutamol (400 μg) during a 3 km running time-trial in eucapnic voluntary hyperpnoea positive (EVH+ve) and negative (EVH-ve) individuals, in a low humidity environment. Results demonstrated increased FEV1 in both groups following salbutamol inhalation, which did not translate to improved performance. No performance differences were found between salbutamol and placebo (Sal: 1012.7 ± 50 vs. 962.1 ± 37.5 s – Pla: 1002.4 ± 46.5 vs. 962 ± 28.8 s) in the EVH+ve group vs. the EVH-ve group, respectively. This thesis is the first to investigate the effects of long-term use of salbutamol at the WADA upper daily limit on exercise performance. It is also the first study to establish upper urinary thresholds for terbutaline use, and the effects of therapeutic inhaled terbutaline on exercise performance. The effect of salbutamol on exercise performance at low humidity in asthmatic individuals has also never previously been investigated. Overall, the findings from this thesis support previous research that inhaled β2-agonist use does not provide any ergogenic potential. With β2-agonists being an essential therapy for the treatment of EIB their current position on the WADA List of Prohibited Substances and Methods is appropriate. Further research is warranted to fully elucidate the upper urinary threshold for terbutaline to inform WADA and support the re-introduction of terbutaline as a therapeutic tool in the treatment of EIB in athletes

Safety aspect of β2-agonists in chronic obstructive pulmonary diesease

Chronic Obstructive Pulmonary Disease (COPD) presents an enormous public health challenge. Cigarette smoking remains the most important aetiological factor and although legislation to reduce smoking has been introduced in parts of the more developed world, consumption is increasing in many of the poorest parts of the world. With the predicted rise in disease prevalence, COPD is expected to become the worlds third largest cause of death by 2020. COPD is a disease state characterised by airflow limitation that is not fully reversible. Inhaled bronchodilators can only produce a small improvement in the airflow obstruction, but despite this, patients with COPD frequently use high doses of beta-2-agonists as the disease progresses and they develop breathlessness and exercise limitation. Short-acting beta-2-agonists are generally used as required to reduce breathlessness and reduce airflow obstruction whereas long-acting beta-2-agonists are prescribed on a regular twice-daily basis to reduce symptoms and rescue medication use and because of a potential beneficial effect on quality of life and exacerbation rates. Although generally well tolerated, the safety of inhaled beta-2-agonists has been a source of some concern since the late 1960s, when an epidemic of asthma deaths was associated with the use of a high dose formulation of isoprenaline. Further controversy has followed and questions have extended to long-acting beta-2-agonists, most notably after a recent large-scale post marketing surveillance study identified an association between the regular use of inhaled salmeterol and asthma-related deaths. The safety of inhaled beta-2-agonists is also an important consideration for patients with COPD. Being older and likely to have a history of cigarette consumption means that they are at risk of having symptomatic, or subclinical, ischaemic heart disease. Beta-2-agonists cause a number of systemic effects including an increase in heart rate, transient hypoxaemia and hypokalaemia. Since many patients with COPD are already hypoxaemic and may be taking other drugs that stimulate the myocardium and cause hypokalaemia, the additional systemic effects from beta-2-agonists may be more likely to produce adverse cardiac events including dysrhythmia and ischaemia. This thesis is concerned with the safety of inhaled beta-2-agonists in the management of COPD. The introduction consists of an overview of the epidemiology, natural history and pathology of COPD (Chapter 1) and a review of human beta-2-adrenoceptor function and inhaled beta-2-agonist pharmacology (Chapter 2). This is followed by a systematic literature review of the results from long-term clinical studies of inhaled beta-2-agonists in subjects with COPD (Chapter 3). The original work consists of three clinical studies that have examined aspects of the effect of high dose inhaled beta-2-agonists in subjects with COPD and a discussion to place these findings in context. Most published studies of inhaled beta-2-agonists in subjects with COPD have focused on their efficacy, rather than safety. We were concerned that some individuals with COPD and limited bronchodilator reversibility may experience an increase in adverse systemic effects after inhaling high doses of beta-2-agonists, which could lead to detrimental outcomes in certain clinical situations. Apart from the cardiac effects mentioned above, beta-2-agonists increase tremor, which causes CO2 production, and cardiac output and tissue perfuson, which increases the transport of CO2 to the lungs. The increase in CO2 flux to the lungs will normally increase ventilation. We were concerned however that some subjects with severe COPD would not be able to increase ventilation appropriately in response to the beta-2-agonist and this would lead to an increase in PaCO2. Our hypothesis was that high dose inhaled beta-2-agonists could worsen respiratory failure in some subjects with severe COPD. The first two studies in the thesis examined the effect of high dose inhaled salbutamol on the partial pressure of arterial oxygen and carbon dioxide in subjects with severe COPD. We initially conducted a double blind, randomised study on subjects within 48 hours of being admitted to hospital with an acute exacerbation of COPD (Chapter 4). The study was designed to determine whether high dose salbutamol caused an increase in the partial pressure of arterial carbon dioxide. We randomised subjects at a ratio of 3:1 to receive either salbutamol or ipratropium bromide and studied the pharmacodynamic effect on heart rate, PaO2 and PaCO2 over five hours. Over eighteen months and despite extensive efforts I was only able to recruit ten subjects, of whom five completed the study. I found that subjects who required hospital admission with an acute exacerbation of COPD were either too unwell for the study, had co-morbidities that precluded participation or the individuals were unwilling to participate. Although the study was terminated prematurely and we were unable to perform statistical analysis, I have presented the findings from the five subjects who completed the study, of whom four were randomised to receive salbutamol. We used ascending doses of salbutamol (1.25mg, 1.25mg, 25mg, 5mg, 5mg) and found no consistent effect on PaCO2 or PaO2 and no dose response relationship. The subject with the highest baseline PaCO2 did however have a rise in PaCO2 with the highest 5mg doses of salbutamol. To test the hypothesis further we conducted a randomised, double blind, crossover study and examined the effect of salbutamol on the arterial blood gas tensions of fourteen patients with stable severe COPD and a history of chronic or intermittent hypercapnia. The study was designed to determine whether high dose salbutamol causes a rise in PaCO2 when inhaled by subjects with severe COPD and a history of alveolar hypoventilation. We compared the effect of two 5mg doses with two 200 microgram doses of salbutamol on PaO2 and PaCO2 and heart rate. The subjects had severe COPD with a mean FEV1 of 0.71 L (27% predicted) and a mean smoking history of 53 pack years. The mean baseline PaO2 was 7.9 kPa and the mean baseline PaCO2 was 7.0 kPa. The high dose of salbutamol caused a mean fall in both PaO2 and PaCO2 and a small increase in heart rate. There was some support for our hypothesis however as three subjects had a small rise in PaCO2 after high dose nebulised salbutamol (Chapter 5). The third study was a double blind, crossover, dose-response examination of the bronchodilator and systemic effects of inhaled formoterol in subjects with COPD (Chapter 6). The rapid onset and prolonged duration of action of formoterol offers potential for the drug to be used as rescue medication in addition to twice daily maintenance therapy, as is the case in the management of asthma. Our hypothesis was that high doses of formoterol would produce adverse systemic effects that would outweigh the beneficial bronchodilator effects in subjects with COPD and limited bronchodilator response to salbutamol. We studied 20 subjects, with a mean FEV1 of 1.32 L (47% predicted) and a mean smoking history of 42 pack years. Each subject was studied on five days and after receiving placebo, formoterol 6, 12, 24 and 48 mg in a random sequence, we examined the effect of each dose on FEV1, tremor, dyspnoea, heart rate, blood pressure, SpO2, walk distance, potassium and satisfaction. We found that all doses were well tolerated and although there was a small dose related increase in FEV1 and the mean satisfaction scores were higher with each dose of formoterol than placebo, there was no dose related improvement in measures that are important to the patient, including breathlessness and walk distance. Apart from a dose related increase in tremor, other systemic effects were limited. All three studies found that high dose inhaled beta-2-agonists produced relatively modest systemic effects in subjects with COPD. This probably reflects the fact that almost all subjects were taking beta-2-agonists on a regular basis and had developed tolerance to the systemic effects of an inhaled beta-2-agonist. Although the results from the three studies were generally reassuring, questions still remain about the balance between beneficial and adverse effects with high dose inhaled beta-2-agonists in subjects with COPD. The results may have been different if subjects had more severe disease, were exposed to higher doses of beta-2-agonists, had certain beta-2-adrenoceptor polymorphisms or were beta-2-agonist naive

Sustained release microparticles for pulmonary drug delivery.

In this study, several formulation approaches for generating sustained release (SR) microparticles suitable for pulmonary deposition are described. The model drug chosen for investigation was the hydrophilic β2-adrenoceptor agonist, Terbutaline Sulphate (TS), used in the treatment of asthma. A particular challenge to achieving suitable sustained release profiles arose from the high water solubility and ionised state of TS. Initial investigations focused on generating TS microcrystals, which would be subsequently coated with a SR excipient. A controlled crystallization method was developed in which TS was crystallized from an anti-solvent, which contained particle size restricting growth retardants. Significantly smaller crystals were obtained in the presence of growth retardants relative to crystallization without retardants. However, the smallest crystals obtained (3.6 μm) were too large for progression, as the application of a SR coat to such crystals would have increased particle size beyond that suitable for inhalation. The next investigation assessed TS release from a polysaccharide matrix particle containing molecularly dispersed active. Drug release was measured (HPLC) using a custom-built diffusion cell, designed to mimic release at the pulmonary epithelium. Release profiles showed that a degree of SR was possible from polysaccharide-based particles; although, SR was not sufficient for further development. Finally TS nanoparticles, obtained from an emulsion-template process, were encapsulated (spray-drying) within hydrophobic microparticles of respirable particle size. Several optimised formulations of this type provided promising in-vitro sustained release of the active at a variety of drug loadings and in a range of release media. The most useful SR excipient chosen for further development was hydrogenated palm oil, which was observed to coat the nanoparticles effectively. In-vitro deposition profiles were determined for a selection of formulations using an Andersen Cascade Impactor, and it was shown that deposition profiles were formulation-dependant and of size ranges suitable for pulmonary deposition

Increasing drug retention in lung tissue through conjugation with polyethylene-glycol

The pulmonary delivery of drugs is an attractive route of administration because of the large surface area and high permeability of the airway epithelium. The large majority of inhaled drugs are used to manage asthma and Chronic Obstructive Pulmonary Disorder (COPD), such as inhaled corticosteroids and β2-adrenergic receptor agonists. Local delivery of small molecules often results in sub-optimal pharmacokinetics characterised by short absorption times (tmax) and high systemic concentrations (Cmax). Numerous drug delivery strategies have been attempted to increase lung retention time, including drug encapsulation in microspheres, the use of polymeric excipients, or the formation of low solubility drugs. So far, drug conjugation strategies have been limited to decreasing the prodrug solubility. The non-permanent conjugation of small molecules to a large hydrophilic polymer has not been studied for pulmonary delivery. The rationale behind such a strategy is that small molecules are mainly absorbed through the epithelium by passive diffusion, the absorption rates being positively correlated to the drug lipophilicity and molecular weight. This project has therefore been looking at the production, characterisation, in vitro and ex vivo evaluation of polyethylene glycol (PEG)-ester conjugates for the sustained delivery of drugs to the lung. This thesis presents the successful oxidation and subsequent esterification of PEG of various molecular weights with prednisolone (a corticosteroid) and salbutamol (a β2-adrenergic receptor agonist). This study illustrated the feasibility of a polymeric drug conjugate strategy for sustained release of drugs to the lung. The conjugates exhibited good in vitro stability which was translated into improved pharmacokinetics and longer residence time ex vivo in the isolated and perfused rat lung. Further studies must be conducted to fully assess the role of esterases in the pulmonary hydrolysis of the conjugates and in vivo experiments would be necessary to verify the safety of the conjugates and efficacy of the drug