Week of May 13, 2005

Use of Insulin in the Outpatient Treatment of Diabetes

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While insulin administration is required for the treatment of all patients with type 1 diabetes, type 2 diabetic patients can be treated with diet and exercise, oral agents, insulin or a combination of these interventions.  Approximately 30% of patients with type 2 diabetes receive insulin, however most projections estimate that 75% or more will require insulin over the course of time. Insulin is available in long acting (insulin glargine (Lantus) and ultralente), intermediate (NPH and lente) or ultrashort acting (lispro (Humalog), aspart (NovoLog), glulisine (Apidra) or short-acting (Regular insulin) preparations. 

 

Barriers to the prescription and or/acceptance of insulin therapy commonly exist, and include the following:

 

1.         Insulin injection is perceived to be painful.  In fact, insulin administered with 31 g needles is not usually painful. Patients who perform blood glucose monitoring generally find insulin administration to be less unpleasant than self blood glucose testing.

2.         The progression from oral agents to insulin suggests that diabetes has become more “severe”.  In fact, the “severity” of diabetes correlates with the presence of associated complications and/or poor glycemic control, both of which can be corrected, prevented or delayed with insulin use.

3.       Insulin may be presented by caregivers in a form that might be perceived as a threat (e.g. “If you don’t lose weight, I will have to give you insulin.”).

4.                  Physicians who do not prescribe insulin regularly may not be comfortable with its use.

5.                  There may be limited availability of staff to teach insulin administration techniques.

6.                  Fear of hypoglycemia and weight gain may inhibit insulin use.

 

 

The following information is intended to assist physicians in prescribing insulin for their patients.

 

When should insulin be initiated?

 

When blood glucose is inadequately controlled in patients with type 2 diabetes, lifestyle interventions, initiation or revision of oral agent therapy and/or insulin administration are available therapeutic options.  In patients who have failed on treatment with an oral agent, the provision of multiple oral agents administered together is an easily selected next step. However, this can be associated with side effects and substantial cost to patients and insurers (noting, for example, the additive cost of multiple insurance copays).  Generally, when HbA1c is > 9, the addition of a single oral agent alone will not lead to glycemic control (HbA1c < 7), while a single daily dose of insulin may be adequate.  Having said that, it should be remembered that lifestyle measures (dietary alteration and regular exercise) can promote a marked improvement in glycemic control independent of medication effect, at times providing greater benefit than any other single intervention.

 

 

What overall strategy should I employ as I administer insulin?

 

Pancreatic insulin secretion in a non-diabetic individual includes the secretion of basal insulin (secreted continuously irrespective of food intake), and prandial insulin (secreted for a short interval quickly after initiating a meal).  The treatment of type 1 diabetes requires both basal and prandial administration. A commonly used regimen includes insulin glargine (Lantus) once per day with pre-meal ultrashort-acting insulin (lispro, aspart, or glulisine), generally two to three times per day.  Patients with type 2 diabetes, on the other hand, generally produce endogenous pancreatic insulin, and basal plus prandial insulin may not be needed.  Type 2 diabetes can be treated with once per day glargine, NPH or lente, and pre-meal insulin is often not required.  If preprandial insulin is required to control glucose levels satisfactorily, Regular or ultrashort-acting preparations may be used. The latter is often found to be more convenient (especially for type 1 patients, who must administer pre-prandial doses two to four times each day), since it can be given immediately before eating.  In fact, ultra-short acting insulin should be given during or immediately after a meal when meal size may be not be certain (e.g. in the setting of nausea or anorexia).

 

 

How should insulin be initiated?

 

Patients who have type 2 diabetes and are thin can be treated with NPH, lente or insulin glargine with an initial dose of 10 units per day.  Those who are overweight generally require larger doses and a starting dose of up to 20 units may be appropriate.  Insulin glargine is generally given at bedtime.  NPH or lente can be given in the morning, before dinner, before bed, or twice per day (for example, before breakfast and at bedtime) A number of Partners diabetes experts prefer NPH or lente insulin particularly in type 2 diabetes, noting relatively low cost and the fact that either can be mixed with other insulins (insulin glargine cannot).

 

 

What dose of insulin is required and how should insulin be given?

 

Patients with type 1 diabetes generally require 10 – 30 units of basal insulin.  As a general rule, approximately one-half (40 – 60%) of the total insulin dose should be basal insulin (e.g. glargine).  The remainder should be prandial.  Obese patients with type 2 diabetes often require a substantially greater insulin dose, e.g. starting at 20 units per day and titrating up to as much as 150 units and more.  When insulin dose is substantial in type 2 diabetes, an insulin sensitizer (metformin or a thiazolidinedione) can promote insulin sensitivity and decrease insulin dose requirement – but often at greater expense

 

When NPH or lente insulin is given in the evening, h.s. dosing is generally preferred to pre-dinner to avoid hypoglycemia during sleep, although it is recognized that when given with pre-dinner prandial insulin, an additional nighttime injection is avoided. When pre-meal insulin is given, the short acting insulin dose can be adjusted by the patient based on meal size and pre-meal blood sugar.  A variety of techniques can be used to compensate for variation in meal size and composition, of which one commonly used method is carbohydrate counting. A common starting prandial insulin dose is one unit per 15 gm of ingested carbohydrate, plus 1 unit per 50 mg of measured blood glucose above that desired, generally 100 or 120; both measures may need to be adjusted among patients, based on their insulin sensitivity.  Carbohydrate counting and insulin dose determination require appropriate teaching from a diabetes educator and/or dietitian and can generally be undertaken without great difficulty, allowing a greater degree of dietary freedom.

 

What do I need to know about insulin administration and insulin delivery devices?

 

Insulin can be administered via syringes (30, 50 and 100 unit sizes are available, depending on the dose administered) as well as “pen” syringes, which are convenient items that allow the patient to dial in a specific dose with less to carry when away from home.  Devices are also available for patients who are visually impaired.  75/25 and 70/30 pre-mixed insulins are available (the former number represents the percentage of NPH, the latter that of short-acting or ultrashort acting insulin), providing greater ease of administration but less opportunity for individualization of dose.  In general, the need for frequent adjustments of short-acting or ultrashort doses precludes the use of these fixed ratio insulins by those with type 1 diabetes.  Insulin pumps have been used for more than 20 years and are prescribed for selected type 1 patients, allowing for even greater flexibility, including variation of basal insulin dose over a 24-hour interval.

 

Storage of insulin requires some care. Freezing and excessive heat must be avoided. Generally a currently used insulin bottle does not require refrigeration and insulin is less uncomfortable when administered at room temperature, but extra supplies should be refrigerated. Most forms of insulin should be discarded one month after a bottle has been accessed, although judicious flexibility can be used in this regard.  

 

 

In summary, insulin use has changed substantially over the past 10 years and insulin administration has become more acceptable to those who use it.  Injection no longer causes discomfort and we are better able to recommend variable meal timing and meal size/components with use of non-peaking basal insulin and variable dose ultra-short acting insulin.  As a result, we are able to more closely approximate usual pancreatic physiology and achieve desired glycemic control with better patient acceptance, compliance, and satisfaction.

 

 

 

 

 

 

This review was created by the Partners Diabetes Council, a multidisciplinary 35-member body created by Signature Initiative 3 (Uniform High Quality).  The PDC seeks to enhance diabetes care throughout the Partners community, focusing on clinical information systems and on provider and patient education and support.  To access the Diabetes Council, contact Alan Cole, M.D. or Lisa Gintner.