Intranasal insulin: the effects of three dose regimens on postprandial glycaemic profiles in type II diabetic subjects

Central regulation of glucose metabolism in an insulin-dependent and -independent manner

The central nervous system (CNS) contributes significantly to glucose homeostasis. The available evidence indicates that insulin directly acts on the CNS, in particular the hypothalamus, to regulate hepatic glucose production, thereby controlling whole-body glucose metabolism. Additionally, insulin also acts on the brain to regulate food intake and fat metabolism, which may indirectly regulate glucose metabolism. Studies conducted over the last decade have found that the CNS can regulate glucose metabolism in an insulin-independent manner. Enhancement of central leptin signalling reverses hyperglycaemia in insulin-deficient rodents. Here, I review the mechanisms by which central insulin and leptin actions regulate glucose metabolism. Although clinical studies have shown that insulin treatment is currently indispensable for managing diabetes, unravelling the neuronal mechanisms underlying the central regulation of glucose metabolism will pave the way for the design of novel therapeutic drugs for diabetes.

Inhibitory Effects of Intranasal Administration of Insulin on Fat Oxidation during Exercise Are Diminished in Young Overweight Individuals

It remains unknown whether the high insulin (INS) levels in the brain affect fat oxidation during exercise. We examined the effects of the intranasal administration of INS, which increases the INS concentration in the cerebrospinal fluid when peripheral effects are lacking, on the maximum fat oxidation rate (maxFOR) and its intensity (FATmax) during exercise in 15 young normal-weight (N group) and eight young overweight (O group) individuals. On two separate days, either INS or placebo (PL) was randomly administered intranasally before a graded exercise test. Indirect calorimetry was used to assess maxFOR and FATmax during exercise. Blood INS and glucose levels did not change after INS administration. In the N group, maxFOR and FATmax were significantly smaller in the INS trial than in the PL trial. MaxFOR was significantly smaller in the O group than in the N group and was not influenced by INS administration. Exercise-induced elevation in blood epinephrine levels tended to be reduced by INS administration only in the N group. Intranasal INS administration reduces fat oxidation during exercise without any peripheral effects, possibly by suppressing sympathetic nerve activity. This inhibitory effect is diminished in overweight subjects, suggesting that cerebral insulin effects are attenuated in this population.

Insulin in the nervous system and the mind: Functions in metabolism, memory, and mood

BACKGROUND

Insulin, a pleotrophic hormone, has diverse effects in the body. Recent work has highlighted the important role of insulin's action in the nervous system on glucose and energy homeostasis, memory, and mood.

SCOPE OF REVIEW

Here we review experimental and clinical work that has broadened the understanding of insulin's diverse functions in the central and peripheral nervous systems, including glucose and body weight homeostasis, memory and mood, with particular emphasis on intranasal insulin.

MAJOR CONCLUSIONS

Implications for the treatment of obesity, type 2 diabetes, dementia, and mood disorders are discussed in the context of brain insulin action. Intranasal insulin may have potential in the treatment of central nervous system-related metabolic disorders.

Gut-brain mechanisms controlling glucose homeostasis

Our current understanding of glucose homeostasis is centered on glucose-induced secretion of insulin from pancreatic islets and insulin action on glucose metabolism in peripheral tissues. In addition, however, recent evidence suggests that neurocircuits located within a brain-centered glucoregulatory system work cooperatively with pancreatic islets to promote glucose homeostasis. Among key observations is evidence that, in addition to insulin-dependent mechanisms, the brain has the capacity to potently lower blood glucose levels via mechanisms that are insulin-independent, some of which are activated by signals emanating from the gastrointestinal tract. This review highlights evidence supporting a key role for a “gut-brain-liver axis” in control of glucose homeostasis by the brain-centered glucoregulatory system and the implications of this regulatory system for diabetes pathogenesis and treatment.

Impact of dose frequency on compliance and health outcomes: a literature review (1966-2006)

In order for treatments to be effective, patients must be compliant with their medication regimens. Currently, patient compliance is seen as one of the most challenging issues in treating patients with chronic diseases. Studies in which dose frequency has been changed have been reviewed across several different diseases to examine the impact of a change in dose frequency on compliance and health outcomes, as well as efficacy and tolerability. In general, reducing dose frequency may improve medication compliance and effectiveness, and reduce adverse events, while possibly reducing healthcare costs. Suggestions for future research have been presented, including a need to measure compliance with injectable formulations and a standardized definition of compliance.

Coverage of prandial insulin requirements by means of an ultra-rapid-acting inhaled insulin

Barriers to the use of prandial insulin regimens include inadequate synchronization of insulin action to postprandial plasma glucose excursions as well as a significant risk of hypoglycemia and weight gain. Technosphere® insulin (TI) is an inhaled ultra-rapid-acting human insulin that is quickly absorbed in the alveoli. With a time to maximum plasma drug concentration of approximately 14 min and a time to maximum effect of 35 to 40 min, TI more closely matches the postprandial insulin concentrations seen in nondiabetic individuals. Studies have shown that long-term administration of prandial TI in combination with long-acting basal insulin results in reductions in hemoglobin A1c comparable to conventional subcutaneously injected prandial insulins but with improved control of early postprandial BG. Furthermore, TI has been associated with less weight gain and a lower incidence of hypoglycemia, which may enhance patient satisfaction and acceptability of insulin therapy. This review discusses the clinical properties of TI and proposes strategies for optimal use.

Ultrafast-acting insulins: state of the art

Optimal coverage of prandial insulin requirements remains an elusive goal. The invention of rapid-acting insulin analogs (RAIAs) was a big step forward in reducing postprandial glycemic excursions in patients with diabetes in comparison with using regular human insulin; however, even with these, the physiological situation cannot be adequately mimicked. Developing ultrafast-acting insulins (UFIs)-showing an even more rapid onset of action and a shorter duration of action after subcutaneous (SC) administration-is another step forward in achieving this goal. The need for UFIs has been gradually recognized over the years, and subsequently, a number of different approaches to cover this need are in clinical development. A rapid increase in circulating insulin levels can be achieved by different measures: modification of the primary structure of insulin molecule (as we know from RAIAs), addition of excipients that enhance the appearance in the monomeric state post-injection, or addition of enzymes that enable more free spreading of the insulin molecules in the SC tissue. Other measures to increase the insulin absorption rate increase the local blood flow nearby the insulin depot in the SC tissue, injecting the insulin intradermally or applying via another route, e.g., the lung. The development of these approaches is in different stages, from quite early stages to nearing market authorization. In time, daily practice will show if the introduction of UFIs will fulfill their clinical promise. In this review, the basic idea for UFIs will be presented and the different approaches will be briefly characterized.

Insulin's 85th anniversary--An enduring medical miracle

In 1922, the discovery of insulin led to a revolution in diabetes management. Since then, many improvements have been made to insulin preparations: early preparations of bovine and porcine insulins were purified and their duration of action prolonged, giving rise to the introduction of Neutral Protamine Hagedorn (NPH) insulin and monocomponent insulins. Then, with the advances in genetic engineering in the 1980s, it became possible to produce recombinant human insulin. Nowadays, modern molecular biology techniques enable the production of insulin analogues, which have several advantages over human insulin preparations including a reduced risk of hypoglycaemia. Insulin delivery is still predominantly via subcutaneous injections, but alternative routes of insulin administration are being investigated. Pulmonary delivery has emerged as the most feasible option thus far but oral delivery is an ultimate goal, although basic problems of insulin stability in the gut and absorption from the gastrointestinal tract still need to be resolved. The availability of a true artificial pancreas by means of a closed-loop system, linking continuous glucose monitoring with insulin-pump technology, would also constitute a significant advance, but major technological problems still need to be overcome.

Muco-adhesive multivesicular liposomes as an effective carrier for transmucosal insulin delivery

Considering limitations of conventional insulin therapies, the present study characterizes usefulness of novel mucoadhesive multivesicular liposomes as a mucoadhesive sustained release carrier of insulin via nasal and ocular routes, thus attempts to develop non-invasive carrier system for the controlled release of bioactives. Multivesicular liposomes (MVLs) of 26-34 microm were prepared with a high protein loading (58-62%) and were coated with chitosan and carbopol. These mucoadhesive carriers were characterized by zeta potential studies, in vitro mucoadhesion test and insulin protective ability against nasal aminopeptidase. In vitro, mucoadhesive carriers released insulin for a period of 7-9 days compared to 24 h of conventional liposomes. After intranasal administration to STZ induced diabetic rats, the mucoadhesive MVLs (chitosan coated MVLs) effectively reduced plasma glucose level up to 2 days (35% reduction), compared to non-coated MVLs (32% at 12 h) and conventional liposomes (34% at 8 h). Although the differences are statistically insignificant, chitosan coated formulation has shown a better hypoglycemic profile as the effects were prolonged compared to carbopol coated formulation. When compared to ocular route, chitosan formulation after nasal administration has shown better therapeutic profile as the hypoglycemic effects were prolonged until 72 h. The effectiveness of this chitosan coated MVLs was further demonstrated by the significant quantities of ELISA detectable insulin levels after nasal (334.6 microIu/ml) and ocular (186.3 microIu/ml) administration. These results demonstrate that mucoadhesive carrier is a viable option for a sustained release transmucosal insulin carrier, and open an avenue to develop a non-invasive carrier platform for the controlled release of bioactives.

Intranasal delivery: physicochemical and therapeutic aspects

Interest in intranasal (IN) administration as a non-invasive route for drug delivery continues to grow rapidly. The nasal mucosa offers numerous benefits as a target issue for drug delivery, such as a large surface area for delivery, rapid drug onset, potential for central nervous system delivery, and no first-pass metabolism. A wide variety of therapeutic compounds can be delivered IN, including relatively large molecules such as peptides and proteins, particularly in the presence of permeation enhancers. The current review provides an in-depth discussion of therapeutic aspects of IN delivery including consideration of the intended indication, regimen, and patient population, as well as physicochemical properties of the drug itself. Case examples are provided to illustrate the utility of IN dosing. It is anticipated that the present review will prove useful for formulation scientists considering IN delivery as a delivery route.

In vitro formulation optimization of intranasal galantamine leading to enhanced bioavailability and reduced emetic response in vivo

The purpose of the current investigation was to optimize an intranasal (IN) galantamine (an acetylcholinesterase inhibitor used for treatment of Alzheimer's disease) formulation using an in vitro tissue model, to correlate those results to in vivo bioavailability, and to compare emetic response to oral dosing. A design-of-experiments (DOE) based formulation screening employing an in vitro tissue model of human nasal epithelium was used to assess drug permeability, tight junction modulation, and cellular toxicity. In vivo studies in rats compared pharmacokinetic (PK) profiles of different formulations dosed intranasally. Finally, studies in ferrets evaluated PK and gastrointestinal (GI) related side effects of oral compared to nasal dosage forms. Galantamine permeation was enhanced without increasing cytotoxicity. Pharmacokinetic testing in rats confirmed the improved drug bioavailability and demonstrated an in vitro-in vivo correlation. Compared to oral dosing, IN galantamine resulted in a dramatically lowered incidence of GI-related side effects, e.g., retching and emesis. These findings illustrate that IN delivery represents an attractive alternative to oral dosing for this important Alzheimer's disease therapeutic. To our knowledge, the data herein represent the first direct confirmation of reducing GI-related side effects for IN galantamine compared to oral dosing.

Therapeutic utility of a novel tight junction modulating peptide for enhancing intranasal drug delivery

Previously, a novel tight junction modulating (TJM) peptide was described affording a transient, reversible lowering of transepithelial electrical resistance (TER) in an in vitro model of nasal epithelial tissue. In the current report, this peptide has been further evaluated for utility as an excipient in transepithelial drug formulations. Chemical stability was optimal at neutral to acidic pH when stored at or below room temperature, conditions relevant to therapeutic formulations. The TJM peptide was tested in the in vitro tissue model for potential to enhance permeation of a low-molecular-weight (LMW) drug, namely the acetylcholinesterase inhibitor galantamine, as well as three peptides, salmon calcitonin, parathyroid hormone 1-34 (PTH(1-34)), and peptide YY 3-36 (PYY(3-36)). In all cases, the TJM peptide afforded a dramatic improvement in drug permeation across epithelial tissue. In addition, a formulation containing PYY(3-36) and TJM peptide was dosed intranasally in rabbits, resulting in a dramatic increase in bioavailability. The TJM peptide was as or more effective in enhancing PYY(3-36) permeation in vivo at a 1000-fold lower molar concentration compared to using LMW enhancers. Based on these in vitro and in vivo data, the novel TJM peptide represents a promising advancement in intranasal formulation development.

Future alternative therapies in a quest to halt aberrations in diabetes mellitus

Under normal physiological conditions, euglycaemia is maintained principally by the homeostatic balance of insulin and glucagon which are secreted from the pancreas. In both type 1 and type 2 diabetes mellitus there is a substantial and chronic increase in the circulating glucose concentration. This elevation in glucose levels is accompanied by a plethora of other biochemical disturbances, including disruption of carbohydrate, fat and protein metabolism. Clinical manifestations of diabetes, which arise from the metabolic disturbances vary between individuals but are often a serious threat to quality and length of life. Pancreas transplantation (Tx) and islet modifications are methods used to restore endogenous insulin secretion in insulin-dependent diabetic patients. In order for this to be achieved successfully, however, some of the problems such as hyperglycemia states (> 150 mg/dl), which may harm pancreatic graft beta cells, immunorejection, the effects of immunosuppression, for example, must be overcome. Considering these problems, therefore, it seems logical that the replacement of the islet tissue itself, either by transplanting a vascularised pancreatic allograft or by transplanting modified pancreatic islet cells, provides a better alternative therapeutic approach than simply replacing insulin that has been lost. This review will show the recent development in the use of pancreatic islets and their modification in a quest to halt the aberrations seen in diabetes mellitus.

Insulin Therapy: Current Alternatives

In normal humans, blood glucose and insulin are maintained within a narrow range despite wide variations in physical activity and dietary intake. At present, reproducing this pattern is an impossible task in type 1 diabetes and extremely difficult in type 2 DM. New approaches using novel insulin analogs and routes of administration, attempting to replicate physiological insulin secretion in diabetic patients, are improving the profiles of glucose levels and, thus, the quality of life. Ultra-short-acting insulin analogues and ultra-long-acting analogues are being used for prandial and basal effects with better results, lower prevalence of hypoglycemia, and, hopefully, fewer chronic complications. Non-invasive routes of administration are being developed. The most promising appears to be inhaled insulin according to studies demonstrating excellent control, apparently without significant side effects, although in relatively short-term trials. Longer-term studies to assure the safety are still necessary before recommending its extended use. This is an extensive, up-to-date review of recent advances in insulin therapy.

Pharmacokinetics and pharmacodynamics of intranasal insulin administered to healthy subjects in escalating doses

BACKGROUND

This exploratory study examined the pharmacokinetics and pharmacodynamics of a Bentley Pharmaceuticals, Inc. (North Hampton, NH) proprietary insulin formulation utilizing CPE-215 technology designed for intranasal administration.

METHODS

Eight fasting healthy volunteers (four men, four women; body mass index, 23.6 +/- 1.7 kg/m2) received up to four doses of intranasal insulin at least 1 week apart. Serum insulin, C-peptide, and plasma glucose were measured in the 4-h period following administration.

RESULTS

At doses of 18.75 IU and above, a rise in serum insulin levels accompanied by a decrease in plasma glucose and serum C-peptide levels was seen. Insulin levels peaked in 10-20 min and remained elevated for approximately 1 h, and the resultant hypoglycaemic effect peaked at 40 min and returned to normal 1.5-2 h post-dosing. At 25 IU (n = 11 doses; eight subjects with three replicates), there was a mean fall in plasma glucose of 20.49%; a greater fall in plasma glucose was seen with higher insulin doses. In addition, mean peak insulin levels increased with dose escalation. For the 25 IU dose (a single 90-microL spray), the maximum measured insulin concentration was 19.52 +/- 9.28 mIU/L, and the area under the concentration-time curve from 0 to 4 h was 19.06 +/- 5.56 mIU/L/h. Three subjects with repeated 25 IU doses demonstrated similarly reproducible peaks for maximum measured insulin concentration and for plasma glucose reductions. As seen with other insulin studies, the inter-individual responsiveness to insulin was variable.

CONCLUSIONS

This intranasal formulation was generally well tolerated and demonstrated rapid onset of action and appropriate duration of action for the potential use in controlling postprandial hyperglycaemia.

Willingness to pay for inhaled insulin: a contingent valuation approach

PURPOSE

To determine the willingness to pay (WTP) of patients with diabetes mellitus for inhaled insulin.

METHODS

A contingent valuation survey was administered to 96 diabetic outpatients at St. Michael's Hospital, Toronto, Canada. Standardised information about inhaled insulin and subcutaneous rapid-acting insulin was provided via video. Participants' WTP for their preferred product was elicited in Canadian dollars (Can dollars) using a 'payment-scale' method.

RESULTS

The mean age of participants was 51.8 years (SD 13.4). Seventy-seven patients had type 2 and 19 had type 1 diabetes. Significantly more participants preferred inhaled insulin over subcutaneous insulin (85 vs 11; p < 0.01). Mean monthly WTP for inhaled insulin (153.70 Can dollars, SD 99.90) was significantly more than the typical 50 Can dollars per month for subcutaneous insulin (p < 0.01). Significantly more participants with type 2 diabetes using oral drugs than those with type 1 diabetes and using insulin preferred inhaled insulin (98.5% vs 69%, p < 0.001). Diabetic patients who did not use insulin were willing to pay significantly more than were insulin users (p < 0.001). Multiple regression analysis showed that income was significantly associated with WTP for inhaled insulin.

CONCLUSION

Diabetic patients, particularly those who are not using insulin, indicated that they would prefer inhaled insulin over insulin injection and would be willing to pay a substantial amount per month to use it. An economic evaluation of inhaled insulin would provide important information to healthcare policy decision makers and private payers about its economic value.

Evolving strategies for insulin delivery and therapy

It has now been conclusively proven that adequate control of blood glucose delays or prevents the progression of diabetic complications. In order to achieve the suggested targets for glycaemic control necessary to reduce the incidence of diabetic complications, it has been established that a more intensive insulin regimen requiring multiple insulin injections is required for patients with type 1 diabetes mellitus. For patients with type 2 diabetes, oral antidiabetic therapy is generally used initially, but given the natural history of type 2 diabetes and the need to achieve improved glycaemic control, earlier use of insulin has been promoted. However, the use of insulin in more intensive regimens for the patient with type 1 diabetes or for earlier treatment of the patient with type 2 diabetes is not routine. Many factors are responsible for this observation. Nevertheless, available device options such as insulin pens or insulin pumps are routinely available for implementation of intensive insulin therapy. However, a major limitation for advancing to intensive insulin therapy is that the only viable way to administer insulin is through injection. Delivery options that use dermal, nasal and oral approaches have been explored. The oral approach may include gastrointestinal, buccal or pulmonary uptake. Recent evidence shows that delivery of insulin via the oral cavity with uptake occurring in the pulmonary alveoli may be the most viable clinical option in the future.

Absorption enhancers for nasal drug delivery

This paper describes the basic concepts for the transmucosal delivery of drugs, and in particular the use of the nasal route for delivery of challenging drugs such as polar low-molecular-weight drugs and peptides and proteins. Strategies for the exploitation of absorption enhancers for the improvement of nasal delivery are discussed, including consideration of mechanisms of action and the correlation between toxic effect and absorption enhancement. Selected enhancer systems, such as cyclodextrins, phospholipids, bioadhesive powder systems and chitosan, are discussed in detail. Examples of the use of these enhancers in preclinical and clinical studies are given. Methods for assessing irritancy and damage to the nasal membrane from the use of absorption enhancers are also described. Finally, the mucosal use of absorption enhancers (chitosan) for the improved nasal delivery of vaccines is reported with reference to recent phase I/II clinical studies.

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.

Novel drug delivery systems for insulin: clinical potential for use in the elderly

Diabetes mellitus is a very common disease in the elderly and its complications are responsible for excess morbidity/mortality, loss of independence and impaired quality of life. Recent studies, while not performed in the elderly, have outlined the importance of achieving tight glycaemic control in order to prevent complications. Eighty years after its discovery, subcutaneous insulin remains a major treatment for diabetes. It is used as a first-line agent in type 1 diabetes, and in type 2 diabetes when oral antihyperglycaemic agents combined with diet and exercise fail to achieve an appropriate metabolic control. To avoid injections, other routes of insulin administration have been studied, including oral, dermal and rectal routes but they were not found to be appropriate for clinical use. Buccal or nasal insulin combined with absorption enhancers proved to have interesting properties. Inhaled insulin appears to be suitable for use in patients with diabetes because of its better bioavailability and a pharmacokinetic profile that mimics the time kinetics of insulin secretion after a meal. Clinical studies were conducted among small numbers of patients with type 1 or type 2 diabetes who had been treated with subcutaneous insulin. Inhaled insulin was given three times daily, just before meals, and was combined with a bedtime subcutaneous injection of long-acting insulin. In patients with type 1 or type 2 diabetes the metabolic control achieved with inhaled insulin was similar to that obtained with a subcutaneous insulin regimen. Tolerance of inhaled insulin was good and treatment satisfaction was better than that with the subcutaneous regimen. Insulin inhalation appears to be an interesting way of insulin delivery for elderly patients with diabetes. However, no studies have been conducted in elderly patients with diabetes to assess this route's acceptability, convenience and ease of use in this particular population. In addition, it is necessary to conduct pharmacokinetic studies in the elderly because lung aging might reduce the bioavailability of inhaled insulin.

Inhaled insulin--a new therapeutic option in the treatment of diabetes mellitus

The beneficial effects of maintaining an optimal glucose control on chronic complications of diabetes have been firmly established in patients with both Type 1 and 2 diabetes mellitus. Effective glucose control usually requires multiple daily injections of subcutaneous insulin. Limitations of these intensive regimens include inconvenience and poor patient adherence and acceptability. As a consequence, several alternative methods for insulin delivery have been developed with the aim of eliminating the pain, inconvenience and disruption of lifestyle associated with the need for insulin injections. Recent evidence suggests that intrapulmonary insulin delivery may be an effective, non-invasive alternative to subcutaneous regular insulin. In fact, clinical trials in the last few years have shown that intrapulmonary insulin was as good as subcutaneous insulin in controlling glucose levels in patients with both Type 1 and 2 diabetes mellitus. It was well-tolerated and, so far, there is no evidence of an increased risk of hypoglycaemia or adverse bronchopulmonary effects. Although the bio-availability of inhaled insulin is lower than that of subcutaneous insulin, the former has a more physiological pharmacokinetic profile than the latter. Inhaled insulin currently represents the most viable alternative insulin delivery method to preprandial subcutaneous injection.

Evaluation of alternative strategies for optimizing glycemia: progress to date

Adequate control of blood sugar has been repeatedly shown to translate into reductions in diabetic complications. Although insulin therapy in patients with type 2 diabetes can achieve and maintain near-normal glycemic goals associated with reductions in microvascular and macrovascular end points, it is often reserved for the later stages of management of these patients because of real or perceived concerns; these include fear and anxiety about worsening diabetes, failure of self-management, loss of quality of life, the pain of self-injection, and the possibility of multiple daily injections. Risks of hypoglycemia, weight gain, and cardiovascular disease may be concerns of physicians, but these risks are either manageable or, in the case of cardiovascular disease, unfounded. Taken together, the barriers to insulin therapy frequently compel physicians to consider it a treatment of last resort. Some of the more common barriers have been addressed through device options such as insulin pens and jet injectors, which may improve convenience but do not alleviate pain and discomfort. Transdermal delivery options using iontophoresis or ultrasound are in early stages of development, but methods based on transmucosal delivery-including buccal, nasal, and pulmonary routes-are further advanced. In particular, recent evidence shows that pulmonary forms of insulin are as safe and effective as rapid-acting injected insulin, and are well accepted by patients even over long-term periods of use. These innovative delivery systems may help overcome the barriers to insulin use.

New horizons--alternative routes for insulin therapy

Since the introduction of insulin therapy 80 years ago, the lives of millions of patients with diabetes have been saved, prolonged and immeasurably improved. However, restoring normal glucose levels in diabetic patients through administering insulin by subcutaneous injection has proved virtually impossible. The consequences for patients are serious complications, including diabetic retinopathy and nephropathy, which tend to result from persistent hyperglycaemia. Maximizing glucose control in diabetic patients requires several daily injections. In an effort to reduce this burden, alternative and less-intrusive routes for the administration of insulin are being explored.

Efficacy and tolerance of intranasal insulin administered during 4 months in severely hyperglycaemic Type 2 diabetic patients with oral drug failure: a cross-over study

AIMS

We have evaluated the local tolerance and the metabolic efficacy of a lyophilized nasal insulin preparation in 10 severely hyperglycaemic Type 2 diabetic patients.

METHODS

The study included two 4-month randomized periods: (A) three preprandial doses of nasal insulin secondarily combined with one evening subcutaneous NPH if the desired glycaemic control was not achieved; (B) two NPH injections daily. We assessed: (i) diabetes control on monthly HbA1c levels and occurrence of hypoglycaemic events; (ii) local tolerance on clinical symptoms, rhinoscopy, nasal muco-ciliary clearance and nasal biopsies; (iii) insulin absorption at months 0 and 4.

RESULTS

One patient was withdrawn because of cough and dizziness after each nasal application. HbA1c was not significantly different at month 4 (9.4 +/- 0.5% vs. 8.8 +/- 0.2%, A vs. B). Blood glucose control remained only fair in the majority of our patients. Nasal insulin was able to replace the daytime fraction of the subcutaneous insulin with a 18% efficacy. Side-effects included transient nasal hyperactivity (pruritus, sneezing and rhinorrhoea) and chronic persistence of nasal crusts. Plasma insulin profiles were not significantly different between months 0 and 4.

CONCLUSIONS

The utilization of nasal insulin (with or without NPH) was associated with similar diabetes control compared with NPH twice daily. Nasal insulin alone was able to achieve an adequate glycaemic control in three of the 10 patients.

Treatment of type 2 diabetes mellitus

Although most patients with type 2 diabetes mellitus can be initially managed with diet and exercise alone, most eventually require at least oral agents if not insulin to maintain glycemic control. Appropriate therapeutic regimens may be difficult to design, given the diversity of drugs available for clinical use. Physicians must consider not only glycemic control, but also patient preference, concomitant medical conditions, and cost when designing therapeutic regimens.

Peptide hormones: Review of current and emerging uses by nasal delivery

The family of clinically available peptide hormones (PHs) is expanding in an exponential way, and advancement of knowledge of the basic mechanisms of action of PHs has led to multiplication of the possible clinical indications of already known PHs, and appears even more promising for still unknown PHs. A common obstacle to a full routine use of PHs is represented by the fact that PHs cannot be administered by the oral route, since they undergo digestion and inactivation in the gastrointestinal tract and a significant first pass metabolism in the liver. One alternative is represented by intranasal administration of PHs. The intranasal route of administration of PHs is also very attractive because of its convenience, which should assure a good compliance by patients. Luteinizing hormone releasing hormone, the analogues, desmopressin, oxytocin and salmon calcitonin are already marketed for intranasal administration; for salmon calcitonin, studies about bioavailability have been scanty in the past, but should be re-considered in order to fully explore its clinical benefit.Intranasal peptide hormones not yet on the market are insulin, glucagon, growth hormone releasing hormone (GHRH) and GHRP, GH and somatostatin, but the scenario is likely to change in a short period of time. Hexarelin seems very effective and is at a promising stage of development; also, glucagon appears mature enough to undergo extensive clinical evaluation and possibly marketing. The concern is why other peptides have not been further evaluated, as is the case for somatostatin and its analogues.