Humulin R (Insulin Human (Rdna))

Humulin R is indicated for the treatment of diabetes mellitus when rapid‑acting insulin is required to manage post‑prandial glucose excursions.

• Type 1 diabetes mellitus in adults, adolescents, and children.
• Type 2 diabetes mellitus as part of a basal‑bolus regimen.
• Gestational diabetes when rapid glucose control is needed and other options are unsuitable.
• Situations requiring correction of hyperglycemia, such as pre‑meal dosing or acute illness.
• Use in insulin pump therapy where a short‑acting insulin is required for bolus delivery.

• Humulin R contains recombinant human insulin that binds to insulin receptors on muscle, adipose and hepatic cells. Receptor activation triggers autophosphorylation of the insulin receptor substrate, initiating the phosphatidylinositol‑3‑kinase (PI3K)/Akt signaling cascade. This cascade promotes translocation of GLUT‑4 transporters to the cell surface, increasing glucose uptake, while simultaneously suppressing hepatic gluconeogenesis and glycogenolysis, thereby lowering circulating glucose concentrations. The rapid onset of action reflects the formulation’s lack of protamine or other delaying agents.

Adverse reactions to Humulin R are reported in clinical practice and can be grouped by frequency.

Common

• Mild hypoglycemia, typically presenting as shakiness, sweating, or dizziness when meals are delayed or carbohydrate intake is insufficient.
• Injection‑site reactions such as localized redness, swelling, itching, or a transient lump at the puncture site.
• Lipodystrophy, which may appear as localized thickening (lipohypertrophy) or loss of subcutaneous fat (lipoatrophy) after repeated injections.
• Transient weight gain that can accompany improved glycemic control and fluid balance.

Serious

• Severe hypoglycemia with neuroglycopenic symptoms such as confusion, seizures, or loss of consciousness requiring immediate assistance.
• Allergic reactions ranging from urticaria and angio‑edema to anaphylaxis, which may manifest as difficulty breathing or throat swelling.
• Edema or fluid retention leading to peripheral swelling, particularly in the lower extremities.
• Rare cases of insulin‑induced hypokalemia, characterized by low serum potassium levels and muscle weakness.

When prescribing or using Humulin R, clinicians and patients should consider several safety precautions to minimize risks.

• Verify blood glucose levels before each dose to avoid inadvertent hypoglycemia.
• Adjust the dose in patients with renal or hepatic impairment, as insulin clearance may be reduced.
• Use caution in pregnant or breastfeeding women; insulin requirements may change and close monitoring is advised.
• Store the product according to label instructions; discard any solution that appears cloudy, discolored, or contains particles.
• Educate patients on proper injection technique and rotation of sites to prevent lipodystrophy.
• Monitor for signs of allergic reaction, especially after the first administration.

Humulin R may interact with other medicines, altering its glucose‑lowering effect or increasing the risk of adverse events.

Avoid

• Concurrent use of other rapid‑acting insulins or insulin analogues without dose adjustment, which can cause severe hypoglycemia.
• Beta‑blockers that mask hypoglycemia symptoms, making detection more difficult.

Use with caution

• Oral antidiabetic agents (e.g., sulfonylureas, meglitinides) that also lower blood glucose; dose titration may be required.
• Corticosteroids, which raise blood glucose and may necessitate higher insulin doses.
• Diuretics, especially thiazides, that can affect electrolyte balance and insulin sensitivity.
• Alcohol, which can cause delayed hypoglycemia after insulin administration.