ESRD REDUCES INSULIN CLEARANCE
In healthy nondiabetic people, the pancreatic beta cells secrete half of the daily insulin requirement (about 0.5 units/kg/day) at a steady basal rate independent of glucose levels. The other half is secreted in response to prandial glucose stimulation.
Secreted into the portal system, insulin passes through the liver, where about 75% is metabolized, with the remaining 25% metabolized by the kidneys. About 60% of the insulin in the arterial bed is filtered by the glomerulus, and 40% is actively secreted into the nephric tubules.34 Most of the insulin in the tubules is metabolized into amino acids, and only 1% of insulin is secreted intact.
For diabetic patients receiving exogenous insulin, renal metabolism plays a more significant role since there is no first-pass metabolism in the liver. As renal function starts to decline, insulin clearance does not change appreciably, due to compensatory peritubular insulin uptake.35 But once the GFR drops below 20 mL/min, the kidneys clear markedly less insulin, an effect compounded by a decrease in the hepatic metabolism of insulin that occurs in uremia.36 Thus, despite the increase in insulin resistance caused by renal failure, the net effect is a reduced requirement for exogenous insulin in ESRD.37
A variety of insulin preparations are available, including rapid-acting, intermediate-acting, and long-acting forms and premixed combinations, each with its specific onset, peak, and duration of action (Table 2). To our knowledge, no study of neutral protamine Hagedorn (NPH) insulin or other long-acting insulins has been done in patients with ESRD, and very few studies have described the use of insulin analogues in ESRD.Aisenpreis et al38 showed that the pharmacokinetic profile of insulin lispro (Humalog), which has a short onset of action and a short duration of action, may not only facilitate the correction of hyperglycemia but may also decrease the risk of late hypoglycemic episodes, which is of increased relevance in hemodialysis patients.
On the basis of the available evidence,39,40 we recommend a long-acting insulin such as insulin glargine (Lantus) or NPH insulin for basal requirements, along with a rapid-acting insulin analogue such as lispro or insulin aspart (NovoLog) before meals two or three times daily.
When the GFR drops to between 10 and 50 mL/min, the total insulin dose should be reduced by 25%; once the filtration rate is below 10 mL/min, as in ESRD, the insulin dose should be decreased by 50% from the previous amount.41,42
The newer insulins such as glargine and lispro are more favorable than NPH and regular insulin, but they cost more, which can be an obstacle for some patients.
OBSERVATIONS AND RECOMMENDATIONS
After reviewing the available evidence for the use of diabetic therapy in ESRD, we offer the following observations and recommendations:
- Glycemic control and monitoring in ESRD are complex.
- Patients with ESRD are especially susceptible to hypoglycemia, so diabetic drug therapy requires special caution.
- ESRD patients need ongoing diabetes education, with an emphasis on how to recognize and treat hypoglycemia.
- Diabetic pharmacotherapy in ESRD should be individualized. The targets of therapy are a hemoglobin A1c value between 6% and 7%, a fasting blood glucose level less than 140 mg/dL, and a postprandial glucose level less than 200 mg/dL.
- Of the oral antidiabetic drugs available, glipizide, sitagliptin, and saxagliptin may be used in ESRD. Glipizide, starting with 2.5 mg daily, should be reserved for ESRD patients with a hemoglobin A1c value less than 8.5%.
- Thiazolidinediones may cause fluid overload and thus should be avoided in ESRD.
- We recommend a long-acting insulin (glargine or NPH) for basal requirements, along with rapid-acting insulin before meals two or three times daily.
- The newer basal insulin (glargine) and rapid-acting insulin analogues (lispro or aspart insulin) are more favorable than NPH and regular insulin, but their higher cost could be an issue.
- Some patients may prefer a premixed insulin combination for convenience of dosing. In that case, NPH plus lispro insulin may be better than NPH plus regular insulin.
- For ESRD patients with type 1 diabetes, insulin therapy should be started at 0.5 IU/kg, which is half the calculated dose in patients without renal failure.
- For ESRD patients with type 2 diabetes, insulin therapy should be started at a total daily dose of 0.25 IU/kg.
- Further adjustments to the regimen should be individualized based on self-monitored blood glucose patterns.
- We recommend consulting an endocrinologist with expertise in managing diabetes in ESRD.
