Generic Name

Humulin R

Mechanism

• Insulin architecture: Humulin R is a recombinant human insulin that binds the insulin receptor (INSR) on target cells (muscle, liver, adipose).
• Signal transduction: Receptor binding triggers autophosphorylation, activating the PI3K/Akt pathway for glucose uptake and glycogen synthesis, and the MAPK pathway for lipogenesis.
• Glucose lowering: Reduces hepatic gluconeogenesis and increases peripheral glucose uptake, resulting in decreased plasma glucose.
• Time course: Onset 30–60 min, peak 2–4 h, duration 6–10 h—requires multiple daily injections.

Pharmacokinetics

> Key takeaway: Humulin R’s short action necessitates careful timing around meals; hypoglycemia is most common if meals are delayed.

Indications

• Type 1 diabetes mellitus (T1DM) – as basal + prandial insulin.
• Type 2 diabetes mellitus (T2DM) – when oral agents or basal insulin insufficient.
• Gestational diabetes mellitus (GDM) – for glycemic control when diet/exercise alone fails.
• Diabetic ketoacidosis (DKA) – in acute IV insulin therapy, followed by subcutaneous transition.
• Hypoglycemia treatment – when rapid glucose replenishment is needed.

##indications and Warnings

Contraindications
• Hypersensitivity to human insulin or components (polysorbate 80).
• Severe insulin allergy (rare due to recombinant nature).

Warnings
• Hypoglycemia – especially in elderly, renal/hepatic impairment, or if meals are skipped.
• Edema – due to fluid retention; monitor in heart failure patients.
• Insulin antibodies – may develop resistance or allergic reactions; monitor clinical response.
• Diffuse skin involvement – inflammed injection sites (e.g., cellulitis) impair absorption.

Dosing

• Starting dose: 0.5–1.0 U/kg/day, split 2–3 times daily.
• Basal‑bolus approach: 30 % basal (pre‑meal) + 70 % prandial.
• Adjustment: Titrate every 2–3 days based on capillary glucose logs.
• Mixing: Use insulin syringe; do not mix with other insulins or additives unless manufacturer‑approved.
• Injection sites: Abdomen, thighs, upper arms, buttocks – rotate to prevent lipohypertrophy.
• Pumps: Humulin R can be used in insulin pumps but ensure accurate dose calibration due to its swift absorption.
• Storage: 2–8 °C in possession; maintain expiry; do not freeze.

Adverse Effects

Monitoring

• Self‑monitoring of blood glucose (SMBG): 6× daily (fasting, pre‑meal, 2 h post‑meal, bedtime).
• HbA1c: Every 3 months (or sooner if unstable).
• Ketones (urine/blood) in T1DM or early DKA treatment.
• Serum electrolytes: Particularly K⁺, Na⁺ if on diuretics.
• Renal function: BUN/creatinine clearance; adjust dose for eGFR <30 mL/min.
• Weight & BMI: Monitor for excessive weight gain.
• Injection site integrity: Check for lipohypertrophy or necrosis.

Clinical Pearls

• Meal timing is critical: Administer pre‑meal or 15 min after eating to align peak action with glucose load.
• Divide basal insulin into 2–3 daily injections: Achieves smoother basal coverage; avoid a single large dose that spikes and falls sharply.
• Avoid trailing at the syringe: Always use a new vial or properly purged syringe to prevent protein contamination and unpredictable absorption.
• Use a “pre‑treatment” protocol: If a patient skips a dose, give a shorter‑acting bolus (e.g., 20 U) 30 min prior to the next meal.
• Monitor antibody titers only if loss of efficacy or unexplained hypoglycemia: Routine titers are unnecessary.
• Check for lipohypertrophy: Rotate sites to avoid subcutaneous fibrosis that delays absorption.
• In pregnancy, titrate cautiously: Many clinicians prefer insulin glulisine or aspart; still, Humulin R can be used relying on close glucose monitoring.

Bottom line: Humulin R remains a cornerstone in diabetes management, offering predictable, rapid‑acting insulin action when used with meticulous timing, dose adjustments, and regular monitoring.