Human Insulin + Insulin Isophane

Human insulin plus insulin isophane is a premixed human insulin preparation containing short-acting soluble human insulin and intermediate-acting human insulin isophane, also known as NPH insulin. A commonly used 30/70 formulation contains 30% soluble human insulin and 70% insulin isophane, providing both an earlier mealtime glucose-lowering effect and a longer-lasting effect between meals. Human insulin is structurally identical to endogenous insulin and lowers blood glucose by promoting glucose uptake into muscle and fat while reducing hepatic glucose production. Insulin isophane contains insulin complexed with protamine, which slows absorption after subcutaneous administration and prolongs its action. The combination is administered by subcutaneous injection, with available presentations including vials, cartridges and prefilled pens depending on the product. It is clinically important because it provides a fixed combination of prandial and intermediate-acting insulin in a single injection regimen, which can simplify treatment for selected patients who require insulin. Premixed preparations are not interchangeable with other insulin products without appropriate medical supervision because their concentration, insulin components, timing of administration and pharmacokinetic profiles may differ. The commonly used 30/70 formulation is generally administered before meals and is typically given once or twice daily according to the individual's glucose-control needs.

Human insulin was developed using recombinant DNA technology and produced using microorganisms such as Saccharomyces cerevisiae, allowing production of insulin with the same amino-acid sequence as human pancreatic insulin. Premixed formulations combine soluble human insulin with insulin isophane to provide complementary durations of action. In the United States, the FDA-approved prescribing information for NOVOLIN 70/30 records an initial U.S. approval in 1991 for a preparation containing 30% regular human insulin and 70% NPH human insulin isophane. In Europe, the EMA has authorised Actraphane formulations containing human insulin in different soluble-to-isophane ratios, including Actraphane 30 with a 30/70 ratio; the European public assessment report was first published in 2006. In India, CDSCO records regulatory approvals for biphasic isophane insulin preparations, including a 30/70 human insulin formulation. CDSCO records also document approval activity for biphasic isophane insulin 30/70 formulations in subsequent years, including clinical and post-marketing evaluation programs.

Human insulin plus insulin isophane is indicated for treatment and glycemic control in diabetes mellitus when insulin therapy is required. The combination may be used in adults and, depending on the specific product and regulatory approval, pediatric patients with diabetes. The soluble insulin component provides relatively rapid glucose lowering around meals, while the isophane component provides intermediate-duration insulin coverage. Premixed insulin may be used as part of a twice-daily regimen or another individualized regimen when the patient's meal pattern and glucose requirements are compatible with a fixed insulin ratio. It may be used alone as the principal insulin regimen or alongside selected non-insulin diabetes medicines when clinically appropriate, although the suitability of combination treatment depends on the patient's diabetes type, glucose profile and risk of hypoglycemia. The exact approved population and indications vary between products and jurisdictions.

Human insulin plus insulin isophane is administered by subcutaneous injection into areas such as the abdomen, thigh, upper arm or buttocks, with injection sites rotated to reduce the risk of lipodystrophy and localized cutaneous amyloidosis. For commonly used 30/70 preparations, administration is generally approximately 30 minutes before a meal, and treatment is typically given once or twice daily depending on the product and individual requirements. EMA information for Actraphane describes a usual total daily insulin requirement in the range of 0.3–1.0 IU/kg/day, with the dose individualized according to blood glucose results and clinical response. U.S. labeling emphasizes that dosing must be individualized according to metabolic needs, glucose monitoring and glycemic targets rather than applying a fixed dose to all patients. Dose adjustments may be required with changes in meals, physical activity, renal or hepatic function, acute illness, or when changing from another insulin. Human insulin plus insulin isophane should not be administered intravenously or used in an insulin infusion pump.

The most common adverse effect of human insulin plus insulin isophane is hypoglycemia, particularly when the insulin dose exceeds the patient's current requirements. Other possible effects include injection-site reactions, redness, itching, swelling or discomfort, weight gain, peripheral edema and changes in the distribution of subcutaneous fat at injection sites. Temporary visual changes can occur when glucose control changes rapidly. Localized skin reactions are generally manageable, but repeated injections into the same area can contribute to lipodystrophy or localized cutaneous amyloidosis and may affect insulin absorption. The frequency and severity of adverse effects vary with the dose, meal pattern, physical activity, kidney and liver function, and individual response to insulin therapy.

The principal serious risk is severe or prolonged hypoglycemia, which can cause confusion, seizures, loss of consciousness or, if untreated, death. Hypokalemia can occur with insulin treatment and may become clinically significant in susceptible patients. Severe systemic hypersensitivity reactions, including anaphylaxis, are uncommon but require immediate medical management. Rapid changes in insulin therapy can also result in hyperglycemia or diabetic ketoacidosis if inadequate insulin is administered. Patients should not change insulin type, strength, dose or administration schedule without medical supervision. Repeated injections into areas of lipodystrophy or localized cutaneous amyloidosis should be avoided because altered absorption can lead to unexpected glucose control. The product should not be administered intravenously or used in an insulin pump when the formulation is intended for subcutaneous use.

Before treatment, clinicians should assess diabetes type, current insulin regimen, meal pattern, blood glucose or continuous glucose monitoring results, renal and hepatic function, and the patient's ability to recognize and manage hypoglycemia. Increased glucose monitoring is particularly important when changing insulin products or doses. Beta-blockers may mask some symptoms of hypoglycemia, while corticosteroids, sympathomimetics, diuretics and other medicines can alter insulin requirements or glycemic control. Thiazolidinediones used with insulin may increase the risk of fluid retention and heart failure in susceptible patients. Alcohol can increase or decrease the glucose-lowering effect of insulin and may increase the risk of delayed hypoglycemia. Classic metabolic interactions are not the primary issue with insulin; however, many medicines can alter glucose regulation and therefore require dose adjustment. Pregnancy and breastfeeding require individualized insulin management because glycemic targets and insulin requirements may change.

Confirm the exact insulin formulation, concentration and insulin ratio before dispensing or administering treatment because different premixed insulins are not automatically interchangeable. Patients should be taught the correct injection technique, timing in relation to meals, blood glucose monitoring and recognition and treatment of hypoglycemia. For suspensions such as 30/70 human insulin plus insulin isophane, the product should be gently resuspended according to its instructions before injection and should appear uniformly mixed; abnormal clumping or persistent clear appearance should prompt product rejection. Injection sites should be rotated and areas affected by lipodystrophy or localized cutaneous amyloidosis avoided. During dose changes, illness, changes in diet or physical activity, or switching between insulin preparations, closer glucose monitoring is appropriate. Pharmacists should reinforce correct storage, insulin-strength verification and avoidance of accidental substitution between products with different concentrations or ratios.