Humulin I (Isophane) (Insulin Human (Rdna))

Humulin I (Isophane) is indicated for the management of blood glucose in adults and children with diabetes mellitus.

• Type 1 diabetes mellitus as part of basal insulin therapy.
• Type 2 diabetes mellitus when combined with oral agents or other insulins.
• Adjunct to meal‑time rapid‑acting insulin to provide basal coverage.
• Use during pregnancy only when benefits outweigh risks, under specialist supervision.
• May be employed in insulin‑pump therapy where intermediate‑acting insulin is required.
• For patients who have difficulty adhering to multiple daily injections, Humulin I can reduce injection frequency by providing a once‑or twice‑daily basal dose.

• Humulin I contains recombinant human insulin that binds to insulin receptors on muscle, adipose and hepatic cells. Receptor activation triggers autophosphorylation and downstream signaling through the PI3‑K/Akt pathway, promoting translocation of GLUT‑4 transporters to the cell membrane and enhancing glucose uptake. In the liver, it suppresses gluconeogenesis and glycogenolysis, thereby lowering circulating glucose concentrations. The intermediate‑acting formulation creates a delayed onset and prolonged duration, providing basal insulin coverage over 12 to 18 hours.

Adverse reactions to Humulin I may vary in frequency and severity, ranging from mild injection‑site symptoms to rare systemic events.

Common

• Mild hypoglycemia, especially if meals are delayed or carbohydrate intake is insufficient.
• Redness, swelling, or itching at the injection site.
• Lipodystrophy presenting as localized thickening or loss of subcutaneous fat.
• Transient weight gain due to fluid retention.

Serious

• Severe hypoglycemia with neuroglycopenic symptoms such as confusion, seizures, or loss of consciousness.
• Allergic reactions including urticaria, angioedema, or anaphylaxis.
• Persistent hyperglycemia indicating possible insulin resistance or dosing error.

When prescribing Humulin I, clinicians should evaluate patient‑specific factors and monitor for conditions that may alter insulin requirements or increase risk of adverse events.

• Assess renal and hepatic function, as impairment can prolong insulin action.
• Review history of hypoglycemia unawareness and adjust dosing accordingly.
• Counsel patients on proper injection technique and rotation of sites to prevent lipodystrophy.
• Advise regular blood glucose monitoring, especially during illness, stress, or changes in physical activity.
• Consider pregnancy status; insulin is the preferred agent but dosing may need adjustment.
• Evaluate concomitant use of beta‑blockers, which may mask hypoglycemia symptoms.

Humulin I can interact with other medications that affect glucose metabolism or insulin pharmacodynamics, requiring dose adjustments or heightened monitoring.

Avoid

• Concurrent use of other rapid‑acting insulins without appropriate dose reduction, which may cause severe hypoglycemia.
• Combination with meglitinides (e.g., repaglinide, nateglinide) that also stimulate insulin release, increasing hypoglycemia risk.

Use with caution

• Beta‑blockers may blunt adrenergic warning signs of hypoglycemia.
• Corticosteroids can raise blood glucose, potentially necessitating higher insulin doses.
• Diuretics, especially thiazides, may impair glucose tolerance.
• Oral antidiabetic agents such as sulfonylureas may have additive hypoglycemic effects.