Pulmonary insulin administration using the AERx system: physiological and physicochemical factors influencing insulin effectiveness in healthy fasting subjects

Quality by Design in Pulmonary Drug Delivery: A Review on Dry Powder Inhaler Development, Nanotherapy Approaches, and Regulatory Considerations

Dry powder inhalers (DPIs) are state-of-the-art pulmonary drug delivery systems. This article explores the transformative impact of nanotechnology on DPIs, emphasizing the Quality Target Product Profile (QTPP) with a focus on aerodynamic performance and particle characteristics. It navigates global regulatory frameworks, underscoring the need for safety and efficacy standards. Additionally, it highlights the emerging field of nanoparticulate dry powder inhalers, showcasing their potential to enhance targeted drug delivery in respiratory medicine. This concise overview is a valuable resource for researchers, physicians, and pharmaceutical developers, providing insights into the development and commercialization of advanced inhalation systems.

The Pharmacokinetics of Inhaled Drugs

The pharmacokinetic (PK) profile of a drug after inhalation may differ quite markedly from that seen after dosing by other routes of administration. Drugs may be administered to the lung to elicit a local action or as a portal for systemic delivery of the drug to its site of action elsewhere in the body. Some knowledge of PK is important for both locally- and systemically-acting drugs. For a systemically-acting drug, the plasma concentration-time profile shares some similarities with drug given by the oral or intravenous routes, since the plasma concentrations (after the distribution phase) will be in equilibrium with concentrations at the site of action. For a locally-acting drug, however, the plasma concentrations reflect its fate after it has been absorbed and removed from the airways, and not what is available to its site of action in the lung. Consequently, those typical PK parameters which are determined from plasma concentration measurements, e.g., area under the curve (AUC), Cmax, tmax and post-peak t1/2 may provide information on the deposition and absorption of drugs from the lung; however, the information from these parameters becomes more complicated to decipher for those drugs which are locally-acting in the lung. Additionally, the plasma concentration profile for both locally- and systemically-acting drugs will not only reflect drug absorbed from the lung but also that absorbed from the gastrointestinal (GI) tract from the portion of the dose which is swallowed. This absorption from the GI tract adds a further complication to the interpretation of plasma concentrations, particularly for locally-acting drugs. The influence of physiological and pathological factors needs to be considered in the absorption of some inhaled drugs. The absorption of some hydrophilic drugs is influenced by the inspiratory maneuver used during initial inhalation of the drug, and at later times after deposition. Similarly, the effects of smoking have been shown to increase lung permeability and increase the absorption of certain hydrophilic drugs. The effects of different disease states of the lung have less defined influences on absorption into the systemic circulation.

Devices for Improved Delivery of Nebulized Pharmaceutical Aerosols to the Lungs

Nebulizers have a number of advantages for the delivery of inhaled pharmaceutical aerosols, including the use of aqueous formulations and the ability to deliver process-sensitive proteins, peptides, and biological medications. A frequent disadvantage of nebulized aerosols is poor lung delivery efficiency, which wastes valuable medications, increases delivery times, and may increase side effects of the medication. A focus of previous development efforts and previous nebulizer reviews, has been an improvement of the underlying nebulization technology controlling the breakup of a liquid into droplets. However, for a given nebulization technology, a wide range of secondary devices and strategies can be implemented to significantly improve lung delivery efficiency of the aerosol. This review focuses on secondary devices and technologies that can be implemented to improve the lung delivery efficiency of nebulized aerosols and potentially target the region of drug delivery within the lungs. These secondary devices may (1) modify the aerosol size distribution, (2) synchronize aerosol delivery with inhalation, (3) reduce system depositional losses at connection points, (4) improve the patient interface, or (5) guide patient inhalation. The development of these devices and technologies is also discussed, which often includes the use of computational fluid dynamic simulations, three-dimensional printing and rapid prototype device and airway model construction, realistic in vitro experiments, and in vivo analysis. Of the devices reviewed, the implementation of streamlined components may be the most direct and lowest cost approach to enhance aerosol delivery efficiency within nonambulatory nebulizer systems. For applications involving high-dose medications or precise dose administration, the inclusion of active devices to control aerosol size, guide inhalation, and synchronize delivery with inhalation hold considerable promise.

Understanding concentrated insulins: a systematic review of randomized controlled trials

OBJECTIVE

To compile, analyze, and summarize the literature on concentrated insulins (i.e. concentrations >100 units/mL) from randomized controlled trials and derive guidance on appropriate use of these agents.

METHODS

Searches were conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, Trialtrove (through April 2016) and ClinicalTrials.gov (through April 2017) for phase 1-4 clinical studies using concentrated insulins. Selected studies included multiple-arm, randomized controlled trials evaluating subcutaneously administered concentrated insulins. Trial registration numbers (selected studies) were searched in Medline, Embase and Google Scholar (through April 2017). Late-phase studies were graded using guidance from the Agency for Healthcare Research and Quality.

RESULTS

Thirty-eight completed trials (7900 participants) and 34 qualifying publications were identified. Four marketed concentrated insulins were evaluated: two long-acting basal (insulin glargine 300 units/mL and insulin degludec 200 units/mL [IDeg200]), one rapid-acting prandial (insulin lispro 200 units/mL [ILis200]), and one prandial/basal (human regular insulin 500 units/mL). Early-phase trials established bioequivalence for IDeg200 and ILis200 with the corresponding 100 units/mL formulations. Efficacy studies showed noninferior glycemic control between comparators for long-acting basal and prandial/basal products with generally low severe hypoglycemia. Six additional concentrated insulins with completed early-phase development were also identified.

CONCLUSION

Concentrated-insulin products demonstrated efficacious and safe outcomes in appropriate patients. Clinical findings (HbA1c and hypoglycemia) and methodology (initiation and titration), patient factors (insulin experience and dosing requirements) and treatment characteristics (bioequivalence, potency and device features) are important considerations. This overview of these and other factors provides essential information and guidance for using concentrated insulins in clinical practice.

Protein stability in pulmonary drug delivery via nebulization

Protein inhalation is a delivery route which offers high potential for direct local lung application of proteins. Liquid formulations are usually available in early stages of biopharmaceutical development and nebulizers are the device of choice for atomization avoiding additional process steps like drying and enabling fast progression to clinical trials. While some proteins were proven to remain stable throughout aerosolization e.g. DNase, many biopharmaceuticals are more susceptible towards the stresses encountered during nebulization. The main reason for protein instability is unfolding and aggregation at the air-liquid interface, a problem which is of particular challenge in the case of ultrasound and jet nebulizers due to recirculation of much of the generated droplets. Surfactants are an important formulation component to protect the sensitive biomolecules. A second important challenge is warming of ultrasound and vibrating mesh devices, which can be overcome by overfilling, precooled solutions or cooling of the reservoir. Ultimately, formulation development has to go hand in hand with device evaluation.

Systemic delivery of biotherapeutics through the lung: opportunities and challenges for improved lung absorption

The development of Exubera(®) (inhaled insulin) has paved the way for consideration of future inhaled biotherapeutic products for systemic delivery. This route of drug delivery favors highly potent small peptides without self-association and large proteins resistant to enzymatic degradation for high bioavailability, while likely resulting in transient therapeutic effects. Improved therapeutic benefits with a needle-free delivery, such as inhaled insulin, are also rational pursuits. Molecules and their formulations must be carefully chosen and designed to optimize the rates of lung absorption and nonabsorptive loss. Novel molecular or formulation approaches, for example, Technosphere(®), Fc-/scFv-fusion protein, PEGylation, polymeric or lipid-based micro/nanoparticles and liposomes, offer opportunities to improve lung absorption and therapeutic duration of some biotherapeutics. Critical assessments are now essential as to their therapeutic benefits, safety, patient acceptance and market competition, as carried out for Exubera.

Young and Elderly Type 2 Diabetic Patients Inhaling Insulin with the AERx® Insulin Diabetes Management System: A Pharmacokinetic and Pharmacodynamic Comparison

The objective of this study was to compare the pharmacokinetics (PK), pharmacodynamics (PD), and safety of inhaled insulin delivered by the AERx iDMS in young and elderly patients with type 2 diabetes. Twenty-seven young (18-45 years, inclusive) and 28 elderly (>/= 65 years) type 2 diabetic patients were enrolled in this study. A single inhalation of 1.57 mg (45 IU, effect comparable to 6 s.c. units) of regular human insulin was administered to each patient on each of 2 dosing days, and blood samples were drawn up to 360 minutes postdosing to generate the PK/PD curves. AUC(0-360 min) and Cmax values of inhaled insulin were comparable between young and elderly subjects (p = 0.476 for AUC(0-360 min) and p = 0.414 for Cmax). However, the elderly group had significantly less glucose reduction, as indicated by plasma glucose AOC(0-360) (area over the curve) values (p = 0.011). The intrasubject variability of inhaled insulin using the AERx iDMS was similar for young and elderly subjects and was similar to what has previously been reported for soluble insulin administered subcutaneously. Inhaled insulin was well tolerated in these patients, and no changes in pulmonary function tests were observed. A single inhalation of insulin using the AERx iDMS demonstrated comparable insulin PK profiles between the elderly and young type 2 patients but less glucose reduction in the elderly. Based on these results, elderly diabetic patients may need to inhale more insulin than young patients to achieve similar glycemic control. Long-term clinical trials using the AERx device will be useful to study age-related differences.

Intestinal receptor targeting for peptide delivery: an expert's personal perspective on reasons for failure and new opportunities

The technology has been available more than 25 years that would enable the oral delivery of vaccines, proteins and peptides, thus avoiding the need for injection. To this day, injection is still the mode of delivery, yet not the main mode of choice. This review focuses on several of the potential modes for oral delivery of peptides, proteins and vaccines. Additionally, the review will provide the reader with an insight into the problems and potential solutions for several of these modes of oral delivery of peptides and proteins.

The effect of terbutaline on the absorption of pulmonary administered insulin in subjects with asthma

AIM

To investigate the effect of prior administration of a bronchodilator on the absorption of inhaled insulin in people with asthma treated with inhaled corticosteroids.

METHODS

A single-centre, randomized, open-label, two-period cross-over trial was carried out in 41 nondiabetic subjects with asthma treated with inhaled steroids, with reversible bronchoconstriction (Rev+; n= 25) or without reversible bronchoconstriction (Rev-; n= 16). A dose of 0.10 U kg(-1) inhaled human insulin was administered on each dosing day with or without prior administration of the bronchodilator terbutaline (in random order).

RESULTS

Prior administration of terbutaline led to a 44% increase in absorption of insulin over 6 h for the Rev+ group compared with no prior administration of bronchodilator [ratio (95% confidence interval) 1.44 (1.13, 1.82), P= 0.004], whereas no effect was seen for the Rev- or the whole group. The maximum insulin concentration (C(max)) increased by 34% for the Rev+ group (P = 0.018) and 17% for the whole group (P= 0.046), whereas no significant effect of prior terbutaline administration was seen for Rev-. The time to C(max) was not significantly different for the Rev+ group, whereas it was approximately 30% longer after bronchodilator administration for the Rev- group (P= 0.044) and the whole group (P= 0.032).

CONCLUSIONS

In people with asthma and reversible bronchoconstriction, the administration of a bronchodilator prior to administration of inhaled insulin led to increased absorption of insulin, whereas no effect on insulin absorption in subjects without significant reversibility could be detected.

Inhaled insulin: overview of a novel route of insulin administration

Diabetes is a chronic disease characterized by inadequate insulin secretion with resulting hyperglycemia. Diabetes complications include both microvascular and macrovascular disease, both of which are affected by optimal diabetes control. Many individuals with diabetes rely on subcutaneous insulin administration by injection or continuous infusion to control glucose levels. Novel routes of insulin administration are an area of interest in the diabetes field, given that insulin injection therapy is burdensome for many patients. This review will discuss pulmonary delivery of insulin via inhalation. The safety of inhaled insulin as well as the efficacy in comparison to subcutaneous insulin in the various populations with diabetes are covered. In addition, the experience and pitfalls that face the development and marketing of inhaled insulin are discussed.

Safety and efficacy of inhaled insulin (AERx iDMS) compared with subcutaneous insulin therapy in patients with Type 1 diabetes: 1-year data from a randomized, parallel group trial

AIMS

Assessment of the long-term safety and efficacy of liquid inhaled insulin via AERx insulin Diabetes Management System (iDMS) in a basal/bolus treatment regimen of adults with Type 1 diabetes.

METHODS

Patients were randomized 2 : 1 to prandial inhaled (n = 205) or subcutaneous (s.c.) (n = 99) insulin, plus one/two daily injections of neutral protamine Hagedorn (NPH) insulin for 12 months. The primary endpoints were pulmonary function tests (PFT) and baseline changes in chest X-rays at 12 months. Safety and efficacy assessments were measured at regular intervals.

RESULTS

PFTs after 12 months were comparable between the groups, except for reduced per cent of predicted carbon monoxide lung diffusing capacity with inhaled insulin (difference: -2.03%, P = 0.04) occurring after the first 3 months and then stabilizing. There were no apparent treatment differences in chest X-rays. Overall risk of hypoglycaemia [risk ratio (RR) 1.02, P = 0.83] and adverse events were comparable between groups. Risk of nocturnal hypoglycaemia was higher in the inhaled group (RR 1.58, P = 0.001). Cough [10% (inhaled); 3% (s.c.)] tended to be mild in nature. Inhaled insulin was non-inferior to s.c. insulin for change in glycated haemoglobin (HbA(1c)) after 12 months [difference 0.18% (CI 95%-0.04; 0.39)]. At trial end, mean laboratory measured fasting plasma glucose was lower in the inhaled group (inhaled 9.2 mmol/l; s.c. 11.7 mmol/l; difference: -2.53 mmol/l, P < 0.001).

CONCLUSIONS

The safety and efficacy results in this trial were similar to those reported with other inhaled insulins; however, inhaled insulin using AERx iDMS requires further optimization to reduce nocturnal hypoglycaemia before it has comparable safety and efficacy to s.c. insulin aspart.

Current therapies and technological advances in aqueous aerosol drug delivery

Recent advances in aerosolization technology have led to renewed interest in pulmonary delivery of a variety of drugs. Pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) have experienced success in recent years; however, many limitations are presented by formulation difficulties, inefficient delivery, and complex device designs. Simplification of the formulation process as well as adaptability of new devices has led many in the pharmaceutical industry to reconsider aerosolization in an aqueous carrier. In the acute care setting, breath-enhanced air-jet nebulizers are controlling and minimizing the amount of wasted medication, while producing a high percentage of respirable droplets. Vibrating mesh nebulizers offer advantages in higher respirable fractions (RFs) and slower velocity aerosols when compared with air-jet nebulizers. Vibrating mesh nebulizers incorporating formulation and patient adaptive components provide improvements to continuous nebulization technology by generating aerosol only when it is most likely to reach the deep lung. Novel innovations in generation of liquid aerosols are now being adapted for propellant-free pulmonary drug delivery to achieve unprecedented control over dose delivered and are leading the way for the adaptation of systemic drugs for delivery via the pulmonary route. Devices designed for the metered dose delivery of insulin, morphine, sildenafil, triptans, and various peptides are all currently under investigation for pulmonary delivery to treat nonrespiratory diseases. Although these devices are currently still in clinical testing (with the exception of the Respimat), metered dose liquid inhalers (MDLIs) have already shown superior outcomes to current pulmonary and systemic delivery methods.

Inhaled insulin: take a deep breath, but how?

Inhalation of insulin is the first alternative route of insulin administration, which has been developed to such a mature status that the first product (Exubera, Pfizer) was made available to the market and subsequently withdrawn as of early 2008. In view of the relatively low bioavailability of inhaled insulin and the intraindividual variability of the metabolic effect induced (which is in the range of that of subcutaneously applied regular insulin), one wonders how to improve both aspects. Unfortunately, it appears as if the impact of the inhalation maneuver on insulin deposition in the deep lung has not been studied extensively. We present some thoughts and data from an alveolar model and propose an experimental procedure that might be helpful in the quantitative evaluation of the impact of the insulin inhalation maneuver.

The effect of exercise on the absorption of inhaled human insulin in healthy volunteers

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Exercise is known to affect absorption of other inhaled substances, but so far there are no reports on the effect of exercise on the absorption of inhaled insulin in humans.

WHAT THIS PAPER ADDS

This report is the first to investigate the effect of exercise on the absorption of inhaled insulin. In this study in healthy volunteers we found that exercise early after dosing increased absorption (15-20%) of inhaled insulin over the first 2 h after start of exercise, with an approximately 30% increase in maximal insulin concentration, and unchanged overall absorption.

AIMS

To investigate the effect of moderate exercise on the absorption of inhaled insulin.

METHODS

A single-centre, randomized, open-label, three-period cross-over trial was carried out in 12 nonsmoking healthy subjects. A dose of 3.5 mg inhaled human insulin was administered via a nebulizer and followed in random order by either 1) no exercise (NOEX), 2) 30 min exercise starting immediately after dosing (EX0), or 3) 30 min exercise starting 30 min after dosing (EX30). The study was carried out as a 10 h euglycaemic glucose clamp (90 mg dl(-1) (5.0 mmol l(-1))).

RESULTS

The absorption of insulin over the first 2 h after start of exercise was 16% increased for EX0 (ratio (95%CI) 1.16 (1.04, 1.30), P = 0.01) and 20% increased for EX30 (1.20 (1.05, 1.36), P < 0.01), both compared with NOEX; the overall insulin absorption during 6 h and 10 h after dosing was not influenced by exercise. The maximum insulin concentration (C(max)) increased by 32% for EX0 and 35% for EX30 (both P < 0.01) compared with NOEX, while the time to C(max) was 31 min faster for EX0 (P < 0.01), but not significantly different after EX30, compared with NOEX.

CONCLUSIONS

A significant and clinically relevant increase of insulin absorption over the first 2 h after the beginning of exercise was observed. Until data from studies using the specific insulin inhalers exists, patients using inhaled insulin should be made aware of a potential increased absorption and higher concentration of insulin in connection with exercise.

Inhaled insulin using AERx insulin Diabetes Management System (AERx iDMS)

Diabetes is a chronic, debilitating disease that afflicts millions of people worldwide and poor glycemic control in this disease leads to numerous microvascular and macrovascular complications. There is growing evidence that tight glycemic control prevents the development, and delays the progression, of microvascular complications and possibly macrovascular disease in patients with diabetes. All patients with Type 1 diabetes and many patients with Type 2 diabetes require intensive insulin therapy to achieve optimal glucose control. Although subcutaneous insulin therapy is the mainstay of insulin therapy, there are patients who fear needles and often refuse to start insulin therapy despite suboptimal glucose control. In these patients, inhaled insulin represents a non-invasive, painless method to administer intensive insulin treatment. The Novo Nordisk AS AERx iDMS (insulin Diabetes Management System) for inhaled insulin is a novel device that administers an aerosol of liquid insulin into the deep lung with dose adjustments as precise as one subcutaneous unit. Initial pharmacokinetic and pharmacodynamic studies demonstrate that the device delivers liquid insulin in a clear dose-response manner and with a rapid onset of action similar to the fast-acting analog insulins. At present, large, long-term Phase III studies are in progress to document not only the efficacy, but also the safety and feasibility of this device in the treatment of patients with diabetes.

The effect of exercise on the absorption of inhaled human insulin via the AERx insulin diabetes management system in people with type 1 diabetes

OBJECTIVE

This study investigated the effect of moderate exercise on the absorption of inhaled insulin via the AERx insulin diabetes management system (iDMS).

RESEARCH DESIGN AND METHODS

In this randomized, open-label, four-period, crossover, glucose clamp study 23 nonsmoking subjects with type 1 diabetes received a dose of 0.19 units/kg inhaled human insulin followed in random order by either 1) no exercise (NOEX group) or 30 min exercise starting, 2) 30 min after dosing (EX30), 3) 120 min after dosing (EX120), or 4) 240 min after dosing (EX240).

RESULTS

Exercise changed the shape of the free plasma insulin curves, but compared with the NOEX group the area under the curve for free plasma insulin (AUC(ins)) for the first 2 h after the start of exercise was unchanged for EX30 and EX240, while it was 15% decreased for EX120 (P < 0.01). The overall insulin absorption during 6 and 10 h after dosing was 13% decreased for EX30 (P < 0.005), 11% decreased for EX120 (P < 0.01), and unchanged for EX240. Exercise did not influence the maximum insulin concentration (Cmax), while the time to Cmax was 22 min earlier for EX30 (P = 0.04). The AUC for the glucose infusion rate (AUC(GIR)) for 2 h after the start of exercise increased by 58% for EX30, 45% for EX120, and 71% for EX240 (all P < 0.02) compared with the NOEX group.

CONCLUSIONS

Thirty minutes of moderate exercise led to unchanged or decreased absorption of inhaled insulin via AERx iDMS and faster Cmax for early exercise. Thus, patients using AERx iDMS can adjust insulin dose as usual independent of time of exercise, but they should be aware of the faster effect if exercising early after dosing.

Inhaled insulin in patients with asthma and chronic obstructive pulmonary disease

The effect of inhaled insulin in subjects with diabetes and chronic lung disease, such as asthma or chronic obstructive pulmonary disease (COPD), is of particular interest because these diseases are quite common, and it is likely that patients with asthma or COPD who are poorly controlled on oral agents and are reluctant to start subcutaneous insulin would benefit from inhaled insulin to improve their glucose control. Since patients with asthma or COPD have varied pulmonary symptoms and abnormal pulmonary function, it is important to establish the pulmonary safety and efficacy of inhaled insulin in subjects with diabetes and asthma or COPD. Pharmacokinetic and pharmacodynamic studies in non-diabetic subjects with asthma consistently show lower absorption of inhaled insulin and lesser glucose lowering effects by approximately 30-40%, as compared to subjects without asthma. Thus, it would be expected that the dose of insulin required to obtain equivalent glycemic control would be higher by approximately 30-40% in subjects with asthma and diabetes (as compared to subjects without asthma but with diabetes). However, prior administration of a bronchodilator inhaler in individuals with asthma and diabetes reverses airway obstruction and thus may obviate the need for increased insulin requirements. In contrast to patients with asthma, in patients with COPD and diabetes, the absorption of inhaled insulin appears to be variable (higher or lower than in non-COPD subjects). Whether this variability is secondary to differences in inhalation devices or different study populations is not clear at present. Overall, data from the clinical studies indicate that inhaled insulin is effective and well tolerated in subjects with diabetes and chronic lung disease. However, preliminary, limited data from the longer-term clinical studies suggest that there is a marginally greater decline in pulmonary function tests in subjects with asthma/COPD and diabetes compared to subjects with diabetes and no chronic lung disease. Thus, there is a clear need for longer-term studies in subjects with diabetes and chronic lung disease in order to further clarify the safety and efficacy of inhaled insulin in this population.

First approved inhaled insulin therapy for diabetes mellitus

The long-term benefits of tight glycemic control in preventing microvascular and macrovascular complications are well established in both Type 1 diabetes mellitus (Type 1 DM) and Type 2 diabetes mellitus (Type 2 DM). Nonetheless, achievement of recommended haemoglobin A1c (HbA(1c)) goals (< or = 6.5 - 7.0%) has remained elusive, especially in patients with diabetes who require insulin therapy. Delayed/suboptimal titration of insulin is partly related to poor acceptance of multiple injection regimen by both physicians and patients. EXUBERA (human insulin [rDNA origin]; Pfizer), the first approved inhaled insulin for the treatment of diabetic patients, has been shown to be safe and as effective as regular/rapidly acting insulin in improving glycemic control. In addition to controlling postprandial glucose excursions, EXUBERA exerts a major action to reduce fasting plasma glucose (FPG) concentration. Thus, it has the potential to be used as a monotherapy in Type 2 DM, as well as in combination with an insulin sensitizer in Type 2 DM or in combination with long-acting insulin in both Type 2 DM and Type 1 DM.

Site of deposition and absorption of an inhaled hydrophilic solute

AIMS

To characterize the absorption kinetics and bioavailability of an inhaled hydrophilic solute deposited at various sites within the airways.

METHODS

Nine healthy nonsmokers received one intravenous, one oropharyngeal and two pulmonary doses of technetium-99 m-labelled diethylene triamine pentaacetic acid ((99m)Tc-DTPA) in an open and crossover fashion. Pulmonary doses were administered as nebulized large and fine droplet-sized aerosols by Pari and UltraVent nebulizers at fairly rapid and slow inhalation flows, respectively. Plasma concentration-time profiles and 24 h urinary excretion of radioactivity were determined. One dose of (99m)Tc-labelled Nanocoll, as a marker of mucociliary clearance (MCC), was also administered by Pari for similar lung deposition as the (99m)Tc-DTPA and followed by repeated chest gamma-imaging.

RESULTS

Intrapulmonary deposition patterns of (99m)Tc-DTPA differed significantly (the mean ratio of penetration index (Pari : UltraVent) was 76% with 95% CI 63%, 91%). However, no differences in rate or extent of (99m)Tc-DTPA absorption were detected. Mean absorption time was 1.8 h (mean difference (Pari-UltraVent): -0.1 h with 95% CI -0.6 h, 0.3 h) and the bioavailability was 70% (mean ratio (Pari : UltraVent): 101% with 95% CI 90%, 115%). The pulmonary elimination half-life of (99m)Tc-Nanocoll (8 h and 45 min) was significantly longer than that of (99m)Tc-DTPA (less than 2 h). The oral bioavailability of (99m)Tc-DTPA was estimated to be 3.1%.

CONCLUSIONS

The main elimination pathway of the inhaled hydrophilic solute (99m)Tc-DTPA from the lungs is trans-epithelial absorption. Despite different intrapulmonary radioaerosol deposition patterns, as verified by gamma scintigraphy, no differences in (99m)Tc-DTPA absorption kinetics or bioavailability were detected.

The impact of large tidal volume ventilation on the absorption of inhaled insulin in rabbits

Previous studies have shown that ventilation patterns affect absorption of inhaled compounds. Thus, the aim of this study was to investigate the effect of large tidal volume ventilation (LTVV) on the absorption of inhaled insulin in rabbits. Mechanically ventilated rabbits were given human insulin via a nebuliser system, and plasma insulin was measured for the following 120min. Ventilation was adjusted to (1) normal tidal volume ventilation (NTVV) for the entire period after dosing (NTVV group), to (2) LTVV for the entire period after dosing (LTVV group), to (3) NTVV except for 15min LTVV immediately after dosing (Early LTVV group), or to (4) NTVV except for 15min LTVV starting at 60min after dosing (late LTVV group). Insulin absorption (AUC(ins(0-120min))) was increased by 149% for the LTVV group compared to NTVV group (p<0.01) with increased maximal insulin concentration (106%, p=0.03). The Early LTVV group showed a changed absorption profile. For the late LTVV group an increase in insulin levels was observed after the LTVV period (not significant compared to the NTVV group). These data could potentially have implications for patients using inhaled insulin in situations where a change in breathing pattern is seen, such as exercise.

Alternatives routes of insulin delivery

Optimal glycaemic control is necessary to prevent diabetes-related complications. An intensive treatment, which could mimic physiological insulin secretion, would be the best one. However subcutaneous insulin treatment is not physiologic and represents a heavy burden for patients with type 1 and type 2 diabetes mellitus. Consequently, more acceptable, at least as effective, alternative routes of insulin delivery have been developed over the past years. Up to now, only pulmonary administration of insulin (inhaled insulin) has become a feasible alternative to cover mealtime insulin requirements and one of the various administration systems was recently approved for clinical use in Europe and the United States. But, due to advances in technology, other routes, such as transdermal or oral (buccal and intestinal) insulin administration, could become feasible in a near future, and they could be combined together to offer non-invasive, efficacious and more physiological way of insulin administration to patients with diabetes.

Inhaled insulin delivery--where are we now?

Since 1925, when the concept of treating diabetes with inhaled insulin (INH) was originally published, a number of clinical challenges have been resolved through technological advancements. Efforts by pharmaceutical partnerships or individual companies have resulted in the development of both injection-free devices and novel insulin formulations. Four different INH systems are now in phase 3 of clinical development, and several other INH systems are in earlier stages of clinical study. Clinical data consistently demonstrate that INH therapy is comparable to subcutaneous (SC) therapy in improving glycaemic control in patients with either type 1 or type 2 diabetes, generally without greater risk of overall hypoglycaemia. INH is generally well tolerated and appears to be safe. Adverse-event profiles for INH therapies are similar to SC insulin therapy, with the majority of events being reported as being mild to moderate. Long-term safety studies are ongoing, with emphasis on evaluating the impact of INH therapy on pulmonary function and immune responses. Although small, reversible decreases in pulmonary diffusion capacity (DL(co)) and FEV1 have been reported in response to INH, pulmonary function and structure do not appear to be affected in any clinically significant way. While insulin antibodies are increased in INH therapy, these antibodies have not been correlated with haemoglobin A1c (HbA1c), insulin dosage, hypoglycaemia, pulmonary function or adverse events. Nevertheless, properly controlled, long-term studies will best answer any remaining concerns. From the patient's perspective, INH therapy is preferred by the majority of patients over conventional SC insulin therapy. Studies have shown that patients prefer INH therapy, because it provides greater lifestyle flexibility and social acceptability while at the same time avoiding the pain associated with injection. Thus, after more than 80 years during which the injection route has been the only means of administering insulin, patients and physicians may soon avail themselves of another valuable tool in management of diabetes.

Clinical evaluation of inhaled insulin

Diabetes affects over 18.2 million individuals in the United States alone. Current therapy to treat type 1 diabetes relies on subcutaneous insulin administration either by injection or continuous infusion. In addition, patients with type 2 diabetes who fail lifestyle intervention and oral therapy require subcutaneous insulin. Optimal injection protocols to achieve tight metabolic control often prove burdensome to patients. Thus, development of pulmonary insulin delivery to supplement and/or replace subcutaneous insulin injections may be an effective alternative, allowing patients to achieve intensive diabetes management. This review will discuss the devices in development for the delivery of inhaled insulin. In addition, the efficacy of inhaled insulin in both type 1 and type 2 diabetic populations will be discussed. Finally, the available safety data with respect to the unique pulmonary effects of inhaled insulin will be covered.

Advances in asthma and COPD management: delivering CFC-free inhaled therapy using Modulite technology

Inhaled corticosteroids (ICS) and long-acting beta-agonists (LABA) are currently used in the management of asthma and chronic obstructive pulmonary disease (COPD). Localized targeted delivery of these drugs into the lungs is achieved by means of two types of inhalation devices; pressurized metered-dose inhalers (pMDIs) and dry powder-inhalers (DPIs). For environmental reasons, the chlorofluorocarbon (CFC) propellants used in pMDIs are now being replaced by ozone friendly hydrofluoroalkanes (HFAs). These new generation HFA-based pMDIs, developed to provide effective lung deposition of the active moiety, have a favorable safety and tolerability profile. However, HFA-based re-formulation of LABAs and ICS for pMDIs presents particular technical difficulties, especially in terms of ensuring dose content uniformity. This review focuses on the technology and clinical efficacy of the HFA solution pMDIs using Modulite platform technology (Chiesi Farmaceutici S.p.A). Modulite technology allows the development of HFA solution formulations that can mimic the established CFC-based drug formulations on a microgram to microgram basis and provides formulations with novel particle size distributions that improve on existing delivery systems; by manipulation of aerosol clouds and particle size, the delivery of HFA-formulated drugs can be optimized to either achieve fine particle fractions and deposition patterns similar to established CFC-based drug formulations, thus facilitating the transition to new environment-friendly pMDIs in the clinical setting, or achieve finer drug particles able to penetrate deeper into the bronchi for targeted drug delivery as medical need may dictate. Long-term, multiple-dose clinical studies of Modulite formulations of beclomethasone dipropionate (BDP), budesonide and formoterol have been demonstrated to be therapeutically equivalent to their respective previously established CFC or DPI formulations. As a result, a number of Modulite pMDIs have either recently gained regulatory approval in several European countries, or have completed clinical trials and are in the regulatory submission phase. Availability, in pMDI form, of drugs like formoterol, ICSs, and ICS/LABA combinations, all central to the effective management of asthma and COPD, is therefore expected to impact positively in assuring the continued availability of vital treatment options to patients and physicians.

Inhaled insulin: recent advances in the therapy of Type 1 and 2 diabetes

There are promising data in the field of inhaled insulin. This article describes the current devices being developed for insulin delivery via inhalation. Encouraging advanced clinical data are available in Type 1 diabetes, where inhaled insulin is used in conjunction with basal insulin. Moreover, patients with Type 2 diabetes who have failed oral therapy show improved control when inhaled insulin therapy is initiated. Safety data show that cough is the most common side effect. Pulmonary function tests have shown some changes in carbon monoxide diffusion in the lung. Further studies are needed to clarify the significance of this finding. Inhaled insulin appears to be a non-invasive, well-tolerated and -liked modality of treatment, with potential in both Type 1 and 2 diabetes.

Influence of acute upper respiratory tract infection on the absorption of inhaled insulin using the AERx insulin Diabetes Management System

AIMS

To assess the effects due to an uncomplicated acute upper respiratory tract infection (URTI) on the pharmacokinetics and glucose response of insulin when delivered by oral pulmonary absorption.

METHODS

Normally healthy adult men (n = 11) and women (n = 9) received a single dose of inhaled human insulin, equivalent to approximately 6 IU subcutaneous, using the AERx insulin Diabetes Management System (iDMS), during and following recovery from an URTI. The first dose was administered with ongoing symptoms of < 3 days' duration, the second dose following recovery, and within 3 weeks of the first. Blood sampling for determination of insulin pharmacokinetics (serum AUC(0-6 h), AUC(0-8), C(max),t(max), t(1/2), MRT) and glucose response (plasma AOC(0-6 h)) was performed from 15 min predose to 6 h postdose.

RESULTS

Insulin pharmacokinetics were not different for subjects during and following recovery from URTI [e.g. URTI: no URTI ratio in serum AUC(0-6 h) = 0.92 (95% confidence interval 0.81, 1.05)]; this was reflected by a similar glucose response. Inhaled insulin delivered by AERx iDMS was well tolerated by all subjects; no significant changes were observed in pulmonary function tests. No safety concerns arising from the mode of insulin administration were raised by either dose.

CONCLUSIONS

The results suggest that insulin can be administered via AERx iDMS to nondiabetic subjects experiencing a URTI without any statistically significant changes in insulin pharmacokinetics or pharmacodynamics, and that the necessity for dose adjustments will not differ from subjects with an acute URTI who are receiving subcutaneous insulin.

Inhaled Insulins

The inhalation of insulin was conceptualized by the mid-1920s, but the first successful testing of inhaled insulin occurred in the mid-1990s. The lung has proven to be an organ well capable of absorbing insulin in a reproducible and dose-dependent manner. At present, two concepts of pulmonary insulin delivery at relatively advanced stages of development have been investigated in several published studies. The first involves the Exubera device, a system consisting of a formulation of insulin in a dry and amorphous powder, which is then packaged into blisters. A special delivery system generates a pulse of compressed air, which causes the insulin to form a white fog in a transparent reservoir that can be inhaled by deep breathing. The second approach is the AERx insulin Diabetes Management System, which uses an aqueous formulation of insulin, delivered as an aerosol generated by a special, microprocessor-controlled, inhalation device. This device is capable of monitoring the patient's inspiratory flow and guiding the inhalation by a microelectronic feedback system. The therapeutic efficacy and safety of these inhaled insulins seem comparable to those of subcutaneous insulin regimens; however, inhaled insulins do not appear to achieve significantly better glycemic control. Several other concepts for the pulmonary delivery of insulin are also being developed. With the incidence of diabetes mellitus, especially type 2 diabetes, dramatically increasing worldwide, patients with type 2 diabetes appear to be an important target group for new modalities of insulin delivery. In this group, the onset of insulin treatment is frequently delayed due to the fear of self-injection, preventing effective glycemic control. Patient acceptance of inhaled insulins is excellent and no serious adverse effects have been observed to date. Further advantages of inhaled insulins are the more rapid onset of insulin action and a mitigation of postprandial glucose excursions. However, there are some open questions. The most important concerns the possible long-term effects of insulin inhalation on the lung, as insulin is known to have growth-promoting properties. Thus far, there are no observations of the effects of inhaled insulin on lung structure and function that extend beyond 10 years. In patients with pulmonary disease, the smaller cumulative alveolar surface may cause problems in absorption, and in smokers the action of inhaled insulin has been shown to be stronger and with a faster onset. Furthermore, treatment with inhaled insulin requires larger doses of insulin compared with the subcutaneous route of insulin administration to achieve the same systemic effect, and the costs of this therapy could therefore be significantly higher than the costs of present insulin therapies.

Respirable Microspheres for Inhalation

Several particle engineering technologies have recently emerged, which have enabled inhaled microspheres to seek to manipulate pulmonary biopharmaceuticals, and to improve therapeutic efficacy for both local and systemic treatments. These microspheres may be designed to sustain drug release, to prolong lung retention, to achieve drug targeting and/or to enhance drug absorption and thereby, to seek the potentials of reducing dosing frequency and/or drug dose, while maintaining therapeutic efficacy and/or reducing adverse effects. While product development is still in process, in many cases, considerable therapeutic benefits and/or new therapeutic opportunities can be envisaged. 'Proof-of-concept' results are now available for various drug classes including beta(2)-adrenoceptor agonists, corticosteroids, antimycobacterial antibacterials, estradiol and therapeutic macromolecules such as insulin. Nevertheless, their development success must overcome several critical and unique challenges including toxicological evaluations of microsphere materials, and, clearly, successful products should meet the needs of the patient and the market place. Unfortunately, such issues have not always been addressed or examined adequately in the current studies, and thus we may anticipate paradigm shifts in the research of several groups seeking to develop products with improved therapeutic profiles. Nevertheless, it seems likely that improved inhalation products, with greater therapeutic efficacy and reduced adverse effects, will result from next-generation respirable microspheres. These may be expected to contain drugs intended for both local and systemic activity.

Future therapy of diabetes mellitus

For reaching near normal glycemic control, multiple daily insulin injections are necessary, although subcutaneous insulin therapy cannot get the physiological profile, results in hypoglycemia, weight gain, peripheral hyperinsulinemia, and may not be accepted for painful injections. Glucagon-like peptide 1(GLP-1) analogs and alternative routes of insulin, especially oral (enteric-gastrointestinal, inhaled) route, are most promising and attractive now. Biotechnology and biochemistry will make it possible to overcome several disadvantages of low absorption, short half-life, low bioavailability, and many clinical trials are now in progress. We will show the review of these drugs and another candidate for the treatment of diabetic complications, protein kinase C inhibitor.

Compliance with inhaled insulin treatment using the AERx iDMS Insulin Diabetes Management System

OBJECTIVE

The AERx Insulin Diabetes Management System [AERx iDMS, jointly developed by Novo Nordisk (Bagsvaerd, Denmark) and Aradigm Corp. (Hayward, CA)] provides insulin by pulmonary administration. This investigation was designed as a pilot trial to demonstrate the ability of patients to use the electronic device to deliver mealtime inhaled insulin doses and explore the impact on compliance.

METHODS

AERx iDMS was evaluated in a substudy of a 12-week, multicenter open trial by adult patients with type 2 diabetes previously on any insulin regimen. The device was used for dosing fast-acting human insulin immediately before main meals, in combination with bedtime NPH insulin. The AERx iDMS device recorded the date and time of each insulin inhalation, insulin units used, and inhalation technique during aerosol delivery. Compliance was defined as the percentage of prescribed doses taken during the treatment period, dose timing, and the efficiency of dosing technique.

RESULTS

Insulin dosing for 49 patients (age 59.1 +/- 7.7 years) using AERx iDMS was monitored for 78.9 +/- 10 days (range, 41-94 days) with 226 +/- 35 doses (range, 122-272 doses). Patients inhaled on average 2.9 +/- 0.3 doses of insulin daily, taking an average of 11.8 +/- 5.6 units per dose. Compliance with the prescribed regimen was 94.3 +/- 9.1% (range, 45-100%). Overall, 4.2 +/- 9.5% of prescribed doses were omitted. Hemoglobin A1c decreased 0.77 +/- 0.96% from baseline to the end of the study. Inhalation technique was excellent, with 97% of patients experiencing fewer than five inadequate doses.

CONCLUSIONS

Excellent compliance with AERx iDMS dosing, timing, and inhalation technique showed that the device was well accepted by patients. The electronic monitoring feature could be used as an educational tool to help patients and clinicians manage insulin dosing.

Waiting to inhale: noninjectable insulin, are we there yet?

Subcutaneous injection has been the only route of insulin administration for patients with type 1 or type 2 diabetes for the past 80 years. Although research and development in this time has improved the insulin treatments themselves, it is only now that alternative routes of insulin administration are becoming viable. Many avenues of insulin administration have been explored, including oral, buccal, and pulmonary routes. However, these methods of noninvasive insulin delivery are not free from difficulties and only preliminary data are available for oral insulin pills and buccal insulin sprays. The most promising alternative route of delivery appears to be inhaled insulin and two devices are already in phase III testing. Nevertheless, inhaled insulin devices will still have to overcome some problems and recent studies show that these challenges are currently being confronted. It appears that years of research into noninvasive methods of insulin administration are close to fruition and this review outlines the most recent findings in this area.

Insulin disposition in the lung following oral inhalation in humans : a meta-analysis of its pharmacokinetics

BACKGROUND

Oral inhalation of insulin potentially offers non-invasive treatment and better glycaemic control in diabetes by virtue of its apparently faster absorption into the systemic circulation compared with subcutaneous injection. Nevertheless, the lung kinetics of inhaled insulin in humans have yet to be fully clarified because of the complexity of insulin-glucose (patho)physiology and the difficulty in approximating the inhaled dose. As a result, there remains considerable debate on the mechanisms of absorption and metabolism of insulin in the lung.

OBJECTIVES

To develop and apply a physiologically realistic insulin-glucose kinetic model to a meta-analysis of insulin-glucose profiles from well-controlled clinical studies of inhaled insulin published in the literature, and thereby, to derive the kinetic descriptors of insulin in the lung following inhalation through curve fitting.

MODEL DEVELOPMENT

The model assumed first-order absorption (k(a,L)) and parallel non-absorptive loss (k(mm,L)), the latter primarily occurring via metabolism and mucociliary clearance in the lung, alongside two systemic compartments. Where necessary, glucose-dependent endogenous pancreatic insulin secretion was also taken into account by using blood glucose data as the second independent variable.

RESULTS

Despite the model's simplicity and the use of mean data, 16 insulin-glucose profiles from ten clinical studies were successfully fitted to the model, yielding values for the rate constants k(a,L) and k(mm,L). Whole serum insulin profiles were rate-determined by k(a,L) and k(mm,L) combined, representing 'flip-flop' pharmacokinetics. The best estimate for k(a,L) was found to be 0.020-0.032 h(-1), effectively unchanged across doses (0.3-1.8 IU/kg), formulations (powder vs liquid) and subjects (healthy vs diabetic), suggesting passive diffusive absorption of insulin from the lung. In contrast, the values for k(mm,L) were much larger (0.5-1.6 h(-1)) and decreased with increasing inhaled dose. Therefore, it is likely that dose-dependent saturable lung metabolism controls the value of k(mm,L), alongside mucociliary clearance. As a result, the absolute bioavailability ranged from 1.5% to 4.8%. The modelling analysis also enabled derivation of increased values for both k(a,L) and k(mm,L) as a possible cause of faster absorption for deep inspiratory manoeuvres and increased absorption in smokers, and faster and increased absorption for insulin lispro.

CONCLUSIONS

Although some of these results need to be substantiated experimentally, it appears that this modelling analysis has enabled unification of the literature information associated with the kinetics and mechanisms of insulin disposition in the lung following inhalation in humans.

Inhaled micronized crystalline human insulin using a dry powder inhaler: dose-response and time-action profiles

AIM

The aim of this euglycaemic glucose clamp study was to investigate the pharmacokinetics, glucodynamics, safety and tolerability of micronized crystalline human insulin inhalation powder delivered by a Spiros dry powder inhaler system in healthy volunteers.

METHODS

Thirteen healthy, non-smoking, male and female volunteers [age 30 +/- 7 years; BMI 23.5 +/- 2.7 kg/m(2); (mean +/- sd)] with normal pulmonary function participated in an open-label, randomised, 6-period crossover trial. Each volunteer received four single doses of inhaled insulin (60, 90, 120, 150 U) on separate occasions. For comparison, each volunteer also received two of three possible doses of subcutaneous (s.c.) injected regular human insulin (8, 14, or 20 U).

RESULTS

Serum immunoreactive insulin following inhalation of insulin peaked an average of 60 min earlier compared with s.c. injected insulin (P < 0.0001). Following inhalation, the time to maximum glucose infusion rate occurred an average of 70 min earlier than with s.c. insulin: 187, 129, 161 and 162 min vs. 227, 241 and 241 min (P < 0.0001). The dose-response relationships for serum insulin pharmacokinetics and glucodynamics were linear for both inhaled and s.c. insulin. Relative bioavailability (based on serum insulin levels) ranged from 11.5 to 12.2% for the four doses of inhaled insulin and relative biopotency (based on glucose infusion rates) was 10.0 to 16.5%, respectively. Dosing was well tolerated by all volunteers.

CONCLUSION

This study demonstrates that inhalation of human insulin via a dry powder inhaler system provides a promising alternative route for administration of insulin.

Impact of particle size and aerosolization time on the metabolic effect of an inhaled insulin aerosol

The effects were compared of varying aerosol particle size and aerosolization time within each breath on the metabolic effect elicited by inhalation of a liquid insulin aerosol in comparison with that after subcutaneous injection (s.c.) of regular insulin. In this single-center, open-label euglycemic glucose clamp study, 13 healthy non-smoking subjects received five administrations of insulin in randomized order on separate study days, once by s.c. (0.15 U/kg of regular insulin) and four times by inhalation. Subjects inhaled 1.5 U/kg of liquid insulin aerosol administered by the Aerodose Insulin Inhaler (Aerogen Inc., Mountain View, CA) configured to deliver two aerosol particle sizes--fine [F, 4.4 +/- 0.3 microm (mean +/- SD)] or very fine (VF, 3.5 +/- 0.2 microm)--and two aerosolization times (aerosol released for the first 2 or 4 s after the start of each 5-s inhalation). Glucose infusion rate (GIR) values necessary to keep blood glucose concentrations constant at 5.0 mmol/L were determined over a 6-h period following insulin administration. After inhalation of insulin, the onset of action was substantially more rapid on all four inhalation study days than after s.c. insulin, and the time to maximal action [t(GIRmax) (min)] was reached earlier: F/2 s, 127 +/- 54; F/4 s, 128 +/- 55; VF/2 s, 158 +/- 91; VF/4 s, 132 +/- 72; s.c., 175 +/- 69 (P < 0.0001). The longer aerosolization time (4 vs. 2 s) resulted in higher maximal metabolic action [GIR(max) (mg/kg/min), F/4 s 8.1 +/- 3.6, VF/4 s 8.4 +/- 2.7 vs. F/2 s 6.6 +/- 2.4, VF/2 s 7.2 +/- 2.4 (P = 0.01 for 4 s vs. 2 s, grouped data)], total metabolic activity [area under the curve of GIR 0-6 h (g/kg), F/4 s 1.97 +/- 0.92, VF/4 s 2.14 +/- 0.86 vs. F/2 s 1.56 +/- 0.68, VF/2 s 1.78 +/- 0.60 (P = 0.01)], and relative biopotency [F/4 s 10.6 +/- 4.0%, VF/4 s 11.7% +/- 4.1% vs. F/2 s 8.5 +/- 3.2%, VF/2 s 9.7 +/- 2.4% (P = 0.01)]. None of these summary measures was significantly affected by particle size. No drug- or device-related adverse events were observed. This study shows that aerosolization time, but not particle size, in the ranges studied, had an impact on the metabolic effect elicited by inhaled insulin, allowing rational selection of delivery parameters for further clinical testing. Based on the observed biopotency and the rapid onset of action, inhalation of a liquid insulin aerosol generated by the Aerodose Insulin Inhaler shows promise for covering prandial insulin requirements.

Clinical Pharmacokinetics and Pharmacodynamics of Inhaled Insulin

The benefits of intensive insulin therapy in the prevention of complications in patients with diabetes mellitus are now well established. However, the current methods of insulin administration fall well short of the ideal. Consequently, alternative routes of insulin administration have been investigated. The pulmonary route has received the most attention, helped by advances in inhaler devices and insulin formulation technology. As a result, several insulin inhalation systems are at varying stages of development, with one already filed for marketing approval in Europe. Knowledge of the pharmacokinetic and pharmacodynamic characteristics of the various inhaled insulin formulations will help to determine their positioning in current and evolving diabetes treatment strategies. For instance, a rapid onset and short duration of action would be desirable for use in postprandial glucose control. Pharmacokinetic studies with inhaled insulin reveal that serum insulin concentrations peak earlier and decay more rapidly following inhalation compared with subcutaneously administered regular insulin, and pharmacodynamic studies measuring glucose infusion rate under euglycaemic glucose clamp show corresponding rapid changes in glucose control. Furthermore, intrapatient variability in the pharmacokinetics and pharmacodynamics of inhaled insulin is low; variability is similar to (or perhaps less than) that seen when insulin is administered subcutaneously. Estimates of the bioavailability and bioefficacy achievable with the current inhalation systems are typically in the region of 10% of that experienced with subcutaneously administered insulin. Most of the losses are in the device, mouth and throat, with approximately 30-50% of the insulin deposited in the lungs being absorbed. Clinical experience to date indicates that inhaled insulin has the potential to be an effective treatment in patients with diabetes, and that it may have particular utility in the treatment of postprandial hyperglycaemia.

Intensive therapy with inhaled insulin via the AERx insulin diabetes management system: a 12-week proof-of-concept trial in patients with type 2 diabetes

OBJECTIVE

To compare the glycemic control of inhaled insulin via the AERx insulin diabetes management system (iDMS) with that of subcutaneous (SC) insulin, both combined with NPH insulin at bedtime, in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

The AERx iDMS uses a liquid insulin formulation to achieve flexible precise mealtime dosing (with increments corresponding to 1 IU administered subcutaneously) and ensures insulin delivery only when the breathing technique is optimal. This trial in patients with type 2 diabetes compared the glycemic control (HbA(1c)) achieved by inhaled insulin administered via AERx iDMS with that using SC insulin. This was a randomized, 12-week, open-label, parallel, multicenter, multinational trial in 107 nonsmoking patients with type 2 diabetes (mean age 59 years, mean duration of diabetes 11.9 years). Patients were randomized to receive either inhaled fast-acting human insulin via AERx iDMS immediately before meals or SC fast-acting human insulin administered 30 min before meals, both in combination with evening NPH insulin.

RESULTS

Baseline and demographic characteristics were similar between the two groups. There was no statistically significant difference in HbA(1c) between the AERx and SC groups after 12 weeks of treatment (7.84 +/- 0.77 vs. 7.76 +/- 0.77%, P = 0.60). Fasting serum glucose was significantly lower in the AERx group compared with the SC group by the end of the trial (8.9 +/- 3.8 vs. 10.8 +/- 3.7 mmol/l, P = 0.01) with a similar NPH dose in the two groups (0.23 vs. 0.23 IU/kg, P = 0.93). There were no statistically significant differences between the two groups in the intra-subject variability of fasting or prandial blood glucose increment. Adverse events were similar in the two groups. No major safety concerns were raised during the trial.

CONCLUSIONS

In patients with type 2 diabetes, preprandial inhaled insulin via AERx iDMS is as effective as preprandial SC insulin injection in achieving glycemic control with similar tolerability.

Concept, strategies, and feasibility of noninvasive insulin delivery

OBJECTIVE

To comprehensively review the progress to date on the development of alternative routes for insulin delivery.

RESEARCH DESIGN AND METHODS

Study data were collected through a Medline review.

RESULTS

Proof of principle has been established for many routes of administration including dermal, nasal, oral, buccal, and pulmonary insulin delivery.

CONCLUSIONS

Of all the approaches to date, pulmonary delivery appears to be most feasible. Ongoing phase III studies will ultimately determine safety, tolerability, and efficacy before approval for clinical use.

Alternative routes of insulin delivery

Attempts at replicating physiological insulin secretion, as a means of restoring the normal metabolic milieu and thereby minimizing the risk of diabetic complications, has become an essential feature of insulin treatment. However, despite advances in the production, purification, formulation and methods of delivery of insulin which have occurred in recent years, this has met with limited success. The current advocacy of intensive insulin therapy regimens involving multiple daily subcutaneous injection places a heavy burden of compliance on patients and has prompted interest in developing alternative, less invasive routes of delivery. To date, attempts to exploit the nasal, oral, gastrointestinal and transdermal routes have been mainly unsuccessful. The respiratory tree, with a large surface area, offers the greatest potential for the delivery of polypeptide drugs and there is renewed interest in administrating insulin by the intrapulmonary route. Current pulmonary drug delivery systems include a variety of pressurized metered dose inhalers, dry powder inhalers, nebulizers and aqueous mist inhalers. Recent clinical studies suggest a possible role for inhaled insulin in fulfilling meal-related insulin requirements in persons with Type 1 and Type 2 diabetes. Most experience with inhaled insulin has been obtained using either dry powder formulation in the Nektar Pulmonary Inhaler/Exubera device (Nektar Therapeutics Inc., San Carlos, CA, Aventis, Bridgewater, NJ, Pfizer, NY) or a liquid aerosol formulation in the AERx Insulin Diabetes Management System (Aradigm Corp., Hayward, CA, NovoNordisk A/S, Copenhagen, Denmark). If long-term safety and efficacy is confirmed, inhalation may become the first non-subcutaneous route of insulin administration for widespread clinical use. Despite overwhelming interest and investment in administering insulin via the oral route, success is not expected in the short term. Attempts at utilizing the buccal mucosa and skin are also continuing. Pancreatic transplantation will remain limited to those patients receiving a kidney transplant and immunotherapy. Islet cell transplantation is at an early though encouraging stage following the availability of new less toxic immunosuppressive agents. True insulin independence will require further advances in the combined fields of cell biology and genetics to ensure freedom from both the need for lifelong administration of insulin and the complications of diabetes.

Dose-response relationships of inhaled insulin delivered via the Aerodose insulin inhaler and subcutaneously injected insulin in patients with type 2 diabetes

OBJECTIVE

To compare the dose-response relationship following inhalation of regular insulin delivered via the Aerodose insulin inhaler with that following subcutaneously injected regular insulin in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Twenty-four patients with type 2 diabetes (21 nonsmoking men, aged 36-80 years) each received two of three doses of 80, 160, or 240 units inhaled regular insulin, delivered via a clinical Aerodose insulin inhaler, and two of three corresponding doses of 8, 16, or 24 units by subcutaneous injection under isoglycemic clamp conditions on 4 separate study days in an incomplete block design study. Glucose infusion rates (GIRs) and serum insulin concentrations were monitored over the following 8 h.

RESULTS

Inhaled insulin exhibited significantly shorter time-to-peak insulin levels (T(max) 77 +/- 66 vs. 193 +/- 104 min, P < 0.001) and time-to-peak metabolic effects (T(GIRmax) 240 +/- 94 vs. 353 +/- 60 min, P < 0.001) compared with subcutaneously injected insulin. Comparison of total insulin absorption (insulin area under the curve [AUC]) versus total metabolic effect (GIR-AUC) from 0 to 8 h (group means) revealed overlapping dose-response relationships for both inhaled and subcutaneous injection treatments. Comparison of slopes revealed no significant differences between the inhaled and subcutaneous injection treatment groups (P = 0.6). No significant differences in either relative bioavailability or relative biopotency were found among doses, indicating a consistent subcutaneous injection-to-inhaled dosing conversion ratio among doses. No serious adverse events or clinically relevant changes in lung function were observed.

CONCLUSIONS

The overlapping dose-response curves of inhaled and subcutaneous treatments together with a consistent relative bioavailability and relative biopotency for inhaled insulin across doses suggest that the Aerodose insulin inhaler will deliver a pharmacologically predictable insulin dose to patients with diabetes similar to that observed following subcutaneous injection.

Benefits of different drug formulations in psychopharmacology

Adequate dosage forms are essential for achieving successful pharmacotherapy. Innovative dosage forms or delivery systems may direct a drug to its specific site of action, optimize the timing of the drug release, or increase comfort or convenience for the patient. Thus, such innovations may improve efficacy and tolerability and lead to improvements in health-related quality of life. Specialized dosage forms (e.g., depot injections, extended-release formulations) of several psychiatric agents have been extensively used. The latest addition is an orally disintegrating formulation of the antidepressant mirtazapine. This dosage form dissolves rapidly in the mouth and is convenient for the large proportion of patients who have difficulty in swallowing tablets.

Effects of different durations of breath holding after inhalation of insulin using the AERx® insulin diabetes management system

BACKGROUND

The AERx insulin diabetes management system (iDMS) is a new technology for the administration of insulin by inhalation.

OBJECTIVE

This study assessed the effects of different durations of breath holding (0, 3, and 10 seconds after inhalation) on the pharmacokinetic (PK) and pharmacodynamic (PD) properties of insulin.

METHODS

This was an open-label, randomized, 3-period crossover study in which healthy subjects received a single inhalation of 45 IU regular human insulin followed by breath holding for 0, 3, and 10 seconds on 3 separate study days. Blood levels of insulin and glucose were assessed for 6 hours.

RESULTS

Twenty-one healthy subjects (8 men, 13 women; mean [SD] age, 32.1 [6.9] years; mean body mass index, 24.8 [3.2] kg/m(2)) took part in the study. No significant differences were observed in any PK or PD parameter with the 3 durations of breath holding. Values for mean serum insulin area under the curve from 0 to 360 minutes were 8218, 8244, and 8404 microU/mL x min for the 0-, 3-, and 10-second durations of breath holding, respectively. Mean maximum insulin concentrations were a respective 44.9, 44.2, and 45.5 microU/mL. Values for mean plasma glucose area over the curve and below baseline from 0 to 360 minutes were a respective 3512, 4033, and 3708 mg/dL x min. Pairwise comparisons of serum insulin and plasma glucose concentrations showed no significant changes with the different durations of breath holding. Few adverse events were observed.

CONCLUSIONS

The duration of breath holding after a single inhalation of insulin using the AERx iDMS had no significant effect on the PK or PD parameters of insulin. On the basis of the results in these healthy subjects, breath holding may not be necessary after inhalation of insulin using the AERx iDMS.

Inhaled insulin using the AERx Insulin Diabetes Management System in healthy and asthmatic subjects

OBJECTIVE

The AERx insulin Diabetes Management System (AERx iDMS) (Aradigm, Hayward, CA) delivers an aerosol of liquid human insulin to the deep lung for systemic absorption. This study examined the effects on pulmonary function, pharmacokinetics, and pharmacodynamics of inhaled insulin in asthmatic and nonasthmatic subjects without diabetes.

RESEARCH DESIGN AND METHODS

A total of 28 healthy and 17 asthmatic (forced expiratory volume during the first second [ FEV(1)] 50-80% of predicted value) subjects were enrolled in a two-part, open-label trial. To assess insulin pharmacokinetics and pharmacodynamics, a single inhalation dose of 1.57 mg (45 IU) was given on each of the 2 dosing days in part 1. A dose of 4.7 mg (135 IU) of insulin was inhaled in part 2 to assess effects on pulmonary function.

RESULTS

Inhaled insulin showed area under the curve (AUC)((0-360 min)) values that were significantly greater for healthy subjects than for asthmatic subjects (P = 0.013), whereas no difference was observed for maximum concentration (C(max)) in the two groups. A greater reduction of serum glucose as indicated by area over the curve (AOC)((0-360 min)) was observed in healthy subjects (P = 0.007). Asthmatic subjects had greater intrasubject variations in insulin AUC((0-360 min)) and C(max) values than healthy subjects, but similar variations in glucose AOC((0-360 min)). No significant changes in FEV(1), forced vital capacity (FVC), and FEV(1)/FVC were observed from pre- to postdose times, and there were no observed safety issues.

CONCLUSIONS

After inhaling insulin using the AERx iDMS, asthmatic subjects absorbed less insulin than healthy subjects, resulting in less reduction of serum glucose. No effects on airway reactivity were observed. Diabetic patients with asthma may need to inhale more insulin than patients with normal respiratory function in order to achieve similar glycemic control.

An effective absorption behavior of insulin for diabetic treatment following intranasal delivery using porous spherical calcium carbonate in monkeys and healthy human volunteers

Porous spherical calcium carbonate (PS-CaCO(3)), in contrast to regular calcium carbonate (CaCO(3)), which has a cuboidal particle shape, has a characteristic spherical particle shape with a large number of porous, sliver crystals. The effect of PS-CaCO(3) as a drug carrier on intranasal insulin absorption was investigated in cynomolgus monkeys and healthy human volunteers. Each insulin formulation (powder) containing PS-CaCO(3) or regular CaCO(3) was administered intranasally. Serum insulin and glucose levels after administration were evaluated. The insulin absorption after intranasal administration with each CaCO(3) was found to be much more rapid than that after subcutaneous administration. The serum insulin level after intranasal insulin delivery (16 U per monkey) with PS-CaCO(3) showed a higher C(max) (403.5 microU/mL) and shorter T(max) (0.167 h) when compared with regular CaCO(3). The serum glucose level reduction rate after intranasal delivery using PS-CaCO(3) was faster than that of regular CaCO(3), reflecting the difference in absorption rates. Following repeated intranasal administrations for 4 weeks in monkeys, no toxicity was observed even with a maximum insulin dose level of 25 U. Furthermore, the intranasal insulin absorption rate with PS-CaCO(3) in healthy humans was also observed to be considerably faster than that with regular CaCO(3). Effects of PS-CaCO(3) on a more effective absorption behavior of insulin were considered to be the result of a greater affinity between the nasal mucosa layer and PS-CaCO(3), which is closely related to its structural characteristics. Thus, intranasal insulin delivery using PS-CaCO(3) is thought to be a safe and highly available system enabling more effective insulin absorption behavior with the appearance of endogenous postprandial insulin secretion in healthy humans. We believe that our intranasal insulin delivery system enabling a rapid and short-acting pharmacological effect against postprandial hyperglycemia will be more beneficial than pulmonary insulin delivery systems in the treatment of diabetes.