In type 2 patients the effect of inhaled insulin before meals on HbA1c did not seem to differ from that of fast-acting human insulin. Adding three times inhaled insulin to existing oral therapy is generally more effective than adding another oral hypoglycaemic agent. In the trials, subjects have been more satisfied with inhaled insulin than with subcutaneous insulin treatment. Whether this outcome will be borne out in clinical practice remains to be determined. Inhaled insulin seems to be most suitable in patients with controlled fasting blood glucose using a basal insulin.
Smoking is a contraindication for inhaled insulin and inhaled insulin is not recommended in patients with asthma or chronic obstructive pulmonary disease. All candidates for inhaled insulin should have their lung function checked before and after 6 months and then every year. If lung function has declined more than 20% or by more than 500 ml from baseline, inhaled insulin should be discontinued. The long-term effect of inhaled insulin in the human lung and on neoplastic lung tissue is unknown. Pulmonary insulin is much more expensive than human insulin and still needs to be compared with the rapid-acting insulin analogues. In the UK, the NICE institute recommends that inhaled insulin should be only prescribed by diabetes specialists for patients with needle phobia or severe problems at injection sites.
Insulin Monotherapy versus Combinations of Insulin with Oral Hypoglycaemic Agents in Patients with Type 2 Diabetes
A Cochrane meta-analysis from 2004 of 20 studies including 1,811 patients with type 2 diabetes concluded that the quality of the studies was low, with no assessment of morbidity or mortality . Insulin plus OH A combination therapy statistically had benefits on glycaemic control compared with insulin alone, but only when the latter was applied as once-daily injections of NPH insulin . Conversely twice-daily bipha-sic premix or NPH insulin were superior to insulin plus OHA therapy regimens where insulin was administered as once-daily injection. Insulin plus OHA combination therapy was associated with a 43% relative reduction in total daily insulin requirement . No significant differences in hypoglycaemia between insulin plus OHA and insulin alone were reported. Combination therapy with metformin and bedtime NPH insulin reported significantly less weight gain compared with insulin monotherapy. Insulin plus OHA combination therapy should be considered a suitable simple starting regimen for most insulin requiring type 2 diabetic patients . Another comprehensive meta-analysis has reached similar conclusions .
Type 2 diabetes mellitus is a progressive disease, where both fasting and postprandial blood glucose concentrations are elevated. Owing to the progressive nature of the disease, an evolving treatment strategy is necessary to maintain glycaemic control. A main problem in the treatment of subjects with type 2 diabetes is that physicians do not initiate and increase pharmacologic treatment in a timely fashion, but often wait until HbAlc has increased to above 8% . Therefore, better definitions of the goals and method for initiating insulin therapy are needed.
The insulin regimen recommended for the individual patient will often depend on the state of the disease. If insulin treatment is started early, when the patient is treated with one or two OADs and HbAlc is about 7%, most patients can be treated with NPH insulin or one of the long-acting insulin analogues at bedtime. Later, when the endogenous insulin secretion has diminished treatment with a twice-daily biphasic premix insulin may be reliable to control glucose. Later treatment with multiple injections can be necessary in a subgroup of type 2 patients to control hyperglycaemia.
The regimen based on premixed insulin achieves good glycaemic control but with unwanted effects of more hypoglycaemia than the long-acting analogues. The place of inhaled insulin in the treatment of type 2 diabetes is at present unknown. Inhaled insulin can be an option in a few patients with needle phobia, but the degree of control obtained is comparable to that observed using fast-acting human insulin before main meals. The practical burdens imposed by the frequency of injections and glucose testing may be taken into consideration when choosing the insulin regimen.
It can be recommended that insulin treatment is combined with metformin. The combination improves glycaemic control and reduces the weight increase after starting up insulin when compared with treatment with insulin alone. The combination with metformin reduces the insulin dose.
An increasing number of type 2 diabetic subjects are treated with insulin, including insulin analogues. At present, there is no hard end point on mortality, morbidity or late diabetic complication, indicating the superiority of analogue insulins compared with conventional insulin treatment. HbAlc, fasting plasma glucose, postprandial glucose regulation, day-to-day variation in blood glucose control, risk of hypoglycaemia and change in weight have been the main outcome in the clinical randomised studies comparing the new and old insulin preparations. No major difference in HbAlc has been demonstrated between the analogue and human insulin-based regimens. The benefit of the long-acting analogues has been seen in relation to the reduction of risk of hypo-glycaemia and in less weight gain with insulin detemir. It is still unknown whether it is essential to address the postprandial hyperglycemia by use of rapid-acting insulin or a biphasic premix insulin analogue before the meals to reduce the risk of cardiovascular events and late diabetic complications.
Lastly, the profile of adverse events and benefits, the relative costs of the different insulin preparations, and the complexity of insulin regimens together with the wishes of the individual patients should be considered when the treatment strategy is decided.
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