Humulin I (Isophane) (Insulin Human)

Humulin I is indicated for the management of hyperglycemia in adults and children with diabetes.

• As basal insulin in type 1 diabetes mellitus to provide long‑duration coverage between meals and overnight.
• As part of a basal‑bolus regimen in type 2 diabetes mellitus when oral agents are insufficient.
• In combination with rapid‑acting insulin analogues to achieve tighter post‑prandial control.
• For patients requiring a predictable intermediate‑acting insulin profile with a peak effect 4–12 hours after injection.
• To simplify dosing schedules in patients who prefer fewer daily injections.

• Humulin I contains 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 and increasing glucose uptake. In the liver, insulin suppresses gluconeogenesis and glycogenolysis, reducing endogenous glucose production. The protamine component slows absorption, creating an intermediate‑acting pharmacokinetic profile that provides steady glycemic control.

Adverse reactions to Humulin I may vary in frequency and severity; they are typically related to its insulin activity or formulation components.

Common

• Mild hypoglycemia characterized by sweating, tremor, or hunger.
• Injection‑site reactions such as redness, swelling, or itching.
• Lipodystrophy presenting as localized thickening or thinning of subcutaneous fat.
• Weight gain due to increased caloric storage.
• Edema or fluid retention, especially in patients with cardiac or renal disease.

Serious

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

When prescribing Humulin I, clinicians should consider several precautionary measures to minimize risk and ensure appropriate use.

• Assess renal and hepatic function before initiating therapy, as impairment may alter insulin clearance.
• Monitor blood glucose closely during periods of illness, stress, or changes in physical activity.
• Adjust doses in pregnant or lactating patients only under medical supervision.
• Educate patients on recognizing and treating hypoglycemia promptly.
• Review concomitant medications that can potentiate insulin effects, such as sulfonylureas or meglitinides.
• Avoid use in patients with known hypersensitivity to human insulin or protamine.

Humulin I can interact with other medicines, affecting glucose control or increasing the risk of adverse events.

Avoid

• Concurrent use of other insulin products or insulin secretagogues without dose adjustment, which may cause severe hypoglycemia.
• Beta‑blockers that mask hypoglycemia symptoms, making detection difficult.

Use with caution

• Oral antidiabetic agents such as sulfonylureas, meglitinides, or thiazolidinediones, which may enhance insulin effect.
• Corticosteroids, thyroid hormones, or growth hormone therapy that can raise blood glucose and require dose changes.
• Alcohol consumption, which can cause delayed hypoglycemia, especially after a dose of insulin.