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

Humulin I (Isophane) is used to improve glycemic control in adults and children with diabetes.

• Type 1 diabetes mellitus as part of a basal insulin regimen.
• Type 2 diabetes mellitus when basal insulin is required.
• Combination therapy with rapid‑acting insulin analogues in a basal‑bolus schedule.
• Situations where intermediate‑acting insulin provides smoother glucose coverage between meals and overnight.
• Adjunct to oral antidiabetic agents when those agents alone do not achieve target glucose levels.

• Humulin I (Isophane) consists of recombinant human insulin molecules that form micro‑precipitates after subcutaneous injection. These precipitates release insulin slowly, allowing prolonged activation of insulin receptors on muscle, adipose, and hepatic cells. Receptor binding stimulates the tyrosine kinase pathway, enhancing glucose transporter (GLUT4) translocation and increasing glucose uptake, while simultaneously suppressing hepatic gluconeogenesis. The net effect is a gradual reduction in blood glucose concentrations over several hours.

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

Common

• Mild to moderate hypoglycemia (low blood glucose).
• Redness, swelling, or itching at the injection site.
• Lipohypertrophy or lipoatrophy at injection sites.
• Transient weight gain.
• Edema, especially in the lower extremities.
• Localized rash or urticaria.

Serious

• Severe hypoglycemia with loss of consciousness or seizures.
• Anaphylactic reaction, including difficulty breathing or throat swelling.
• Acute allergic dermatitis or serum‑sickness‑like reaction.
• Hypokalemia associated with prolonged insulin action.
• Insulin antibody‑mediated resistance or hyperglycemia.
• Acute pancreatitis (rare).

Before initiating Humulin I (Isophane), clinicians should consider several safety considerations.

• Assess renal and hepatic function, as impairment may prolong insulin action.
• Review history of hypoglycemia unawareness or frequent low glucose episodes.
• Adjust doses when patients are pregnant, lactating, or planning pregnancy (category unknown).
• Monitor for signs of allergic reactions, especially with prior insulin sensitivities.
• Use caution in patients with cardiovascular disease or edema.
• Consider potential for weight gain and fluid retention during therapy.
• Educate patients on proper injection technique and rotation of sites.

Humulin I (Isophane) can interact with other medicines, affecting glucose control or insulin activity.

Avoid

• Concurrent use of other insulin products without dose adjustment.
• Beta‑blockers that may mask hypoglycemia symptoms.
• MAO‑inhibitors or certain antidepressants that can potentiate insulin effects.
• High‑dose corticosteroids that may cause hyperglycemia requiring dose changes.
• Oral sulfonylureas or meglitinides that increase risk of hypoglycemia.

Use with caution

• Thiazide diuretics, which may raise blood glucose levels.
• ACE inhibitors or ARBs, which can affect renal function and insulin clearance.
• Antipsychotics (e.g., olanzapine) that may exacerbate hyperglycemia.
• Alcohol, which can cause delayed hypoglycemia.
• Exercise, requiring possible insulin dose reduction.