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

Humulin I (isophane) is indicated for the long‑acting insulin needs of adults with diabetes.

• Type 1 diabetes mellitus as part of a basal insulin regimen.
• Type 2 diabetes mellitus when basal insulin is required.
• Adjunct to rapid‑acting insulin analogues for basal‑bolus therapy.
• Use in patients who need a steady insulin level over 24 hours.
• May be employed when oral antidiabetic agents are insufficient.

• Humulin I contains recombinant human insulin (isophane) that binds to insulin receptors on muscle, adipose and hepatic cells. Receptor activation triggers autophosphorylation and downstream signaling through the PI3‑kinase/Akt pathway, promoting translocation of GLUT‑4 transporters to the cell membrane and increasing glucose uptake. In the liver, it suppresses gluconeogenesis and glycogenolysis, resulting in reduced plasma glucose concentrations. The prolonged suspension formulation releases insulin slowly, providing basal coverage for up to 24 hours.

Adverse reactions to Humulin I may vary in frequency and severity.

Common

• Mild hypoglycemia (low blood sugar).
• Injection site redness or swelling.
• Lipodystrophy at the injection site.
• Weight gain.
• Transient headache.

Serious

• Severe hypoglycemia with neuroglycopenic symptoms.
• Allergic reactions such as urticaria or angioedema.
• Anaphylactic hypersensitivity.
• Persistent edema or exacerbation of heart failure.

Before initiating Humulin I, clinicians should evaluate several safety considerations.

• Assess renal and hepatic function, as impairment can alter insulin clearance.
• Review history of hypoglycemia unawareness or severe episodes.
• Adjust doses when patients are pregnant, lactating, or planning pregnancy; data are limited.
• Monitor for signs of cardiovascular disease, especially in patients with edema.
• Caution in patients using beta‑blockers, which may mask hypoglycemia symptoms.
• Avoid use in individuals with known hypersensitivity to recombinant human insulin.

Humulin I can interact with other medicines that affect blood glucose or insulin action.

Avoid

• Concomitant use of other insulin products without dose adjustment.
• Co‑administration with sulfonylureas or meglitinides, which may increase hypoglycemia risk.

Use with caution

• Beta‑adrenergic blockers, which can mask hypoglycemia signs.
• Oral corticosteroids, which may raise glucose levels.
• Thiazide diuretics, which can reduce insulin sensitivity.
• Alcohol, which can cause delayed hypoglycemia.