Formulary
Insulin (Regular/Soluble): Uses, Dosing, Side Effects and Indian Brand Names
Regular (soluble) insulin is a short-acting insulin and the only insulin that can be given IV. It is the drug of choice for diabetic ketoacidosis and hyperglycaemic emergencies, and is used for perioperative glucose control and hyperkalaemia management.
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Insulin (Regular/Soluble): Uses, Dosing, Side Effects and Indian Brand Names
Regular (soluble) insulin is a short-acting insulin and the only insulin that can be given IV. It is the drug of choice for diabetic ketoacidosis and hyperglycaemic emergencies, and is used for perioperative glucose control and hyperkalaemia management.
NEET PG High-Yield: Regular insulin is the ONLY insulin given IV and is the drug of choice for DKA. Key exam point: do NOT give insulin if potassium <3.3 mEq/L in DKA. Insulin drives potassium intracellularly -- this is why it is used in hyperkalaemia management. Somogyi effect (rebound hyperglycaemia after nocturnal hypoglycaemia) vs Dawn phenomenon (early morning hyperglycaemia due to growth hormone surge) is a classic NEET PG differentiator.
Clinical overview
Regular insulin (soluble insulin) is a short-acting insulin preparation that has been in clinical use since Banting and Best's discovery in 1921. It is the only insulin that can be administered intravenously and is therefore the insulin of choice in diabetic ketoacidosis (DKA) and hyperglycaemic hyperosmolar state (HHS). When given subcutaneously, it has an onset of 30-60 minutes, peaks at 2-4 hours, and lasts 6-8 hours. Regular insulin is also used in insulin sliding scales, perioperative glucose management, and as a component of basal-bolus regimens (administered before meals). In India, regular insulin is available from multiple manufacturers and is affordable, listed in the NLEM 2022 and available free of cost in many government hospitals. A critical clinical consideration is that regular insulin must be given 30 minutes before meals (unlike rapid-acting analogues like lispro and aspart which can be given immediately before or with meals). In DKA management, continuous IV regular insulin infusion at 0.1 units/kg/hour is the standard protocol. Regular insulin is also used therapeutically for emergency management of hyperkalaemia (drives potassium intracellularly via Na-K-ATPase stimulation, co-administered with dextrose to prevent hypoglycaemia). The most dangerous side effect of insulin is hypoglycaemia, which can be fatal if untreated.
Pharmacological class
Insulin (Regular/Soluble) belongs to the Rapid-acting endogenous hormone (antidiabetic, short-acting insulin) class. Regular insulin binds to the insulin receptor (a tyrosine kinase receptor) on cell surfaces, activating the IRS-PI3K-Akt signalling cascade. This promotes GLUT4 transporter translocation to the cell membrane in skeletal muscle and adipose tissue, increasing glucose uptake. It also suppresses hepatic gluconeogenesis and glycogenolysis, promotes glycogen synthesis, lipogenesis, and protein synthesis, and inhibits lipolysis and proteolysis.
Indian brand names and formulations
Available as: Actrapid (Novo Nordisk), Huminsulin R (Eli Lilly India), Insuman Rapid (Sanofi India), Wosulin R (Wockhardt).
Injection: 40 IU/mL vials (10 mL), 100 IU/mL vials (10 mL), 100 IU/mL penfill cartridges (3 mL). Clear, colourless solution (unlike NPH which is cloudy). Can be mixed with NPH in the same syringe (draw regular insulin FIRST to avoid contamination).
Regulatory status
Insulin (Regular/Soluble) is classified under Schedule H in India under the Drugs and Cosmetics Act, 1940. Schedule H prescription drug. Must be stored at 2-8 degrees C (cold chain); can be kept at room temperature (<25 degrees C) for 4-6 weeks once opened. NLEM 2022 listed. Available in 40 IU/mL (common in India) and 100 IU/mL vials.
Indications
- Diabetic ketoacidosis (DKA) -- drug of choice (IV infusion)
- Hyperglycaemic hyperosmolar state (HHS)
- Type 1 diabetes mellitus (as part of basal-bolus regimen)
- Type 2 diabetes mellitus (when oral agents fail, perioperative management)
- Gestational diabetes mellitus (insulin is first-line; regular + NPH)
- Emergency management of hyperkalaemia (with dextrose)
- Perioperative blood glucose management
- Total parenteral nutrition (insulin added to TPN bags)
Dosing
DKA: 0.1 units/kg IV bolus followed by 0.1 units/kg/hour continuous infusion (OR 0.14 units/kg/hour without bolus). Titrate to reduce blood glucose by 50-75 mg/dL/hour. Subcutaneous (premeal): 4-10 units 30 minutes before meals, adjusted based on blood glucose. Hyperkalaemia: 10 units regular insulin IV with 25 g dextrose (50 mL of 50% dextrose). Sliding scale: per institutional protocol. Note: India uses both 40 IU/mL and 100 IU/mL concentrations -- syringe must match the vial concentration to avoid dosing errors.
Contraindications
- Hypoglycaemia (blood glucose <70 mg/dL)
- Known hypersensitivity to the specific insulin preparation
- Hypokalaemia (insulin drives potassium intracellularly, worsening hypokalaemia -- correct K+ first in DKA)
Adverse effects
- Hypoglycaemia (most dangerous and most common; symptoms: tremor, sweating, palpitations, confusion, seizures, coma)
- Weight gain (anabolic effect of insulin)
- Lipodystrophy at injection sites (lipoatrophy or lipohypertrophy with repeated injections at same site)
- Local injection site reactions (pain, redness)
- Hypokalaemia (insulin shifts K+ intracellularly -- monitor in DKA)
- Insulin allergy (rare with human insulin preparations)
- Insulin oedema (transient, with initiation of insulin therapy in poorly controlled diabetes)
Drug interactions
- Sulphonylureas, meglitinides -- additive hypoglycaemia risk
- Beta-blockers (propranolol) -- mask hypoglycaemic symptoms (tachycardia, tremor) and impair glycogenolysis; cardioselective beta-blockers safer
- Corticosteroids -- antagonise insulin effect (increase blood glucose)
- Thiazide diuretics -- hyperglycaemic effect, may increase insulin requirement
- Alcohol -- potentiates hypoglycaemia by inhibiting hepatic gluconeogenesis
- ACE inhibitors -- may enhance insulin sensitivity and increase hypoglycaemia risk
Pregnancy and lactation
Category B. Insulin does not cross the placenta and is the drug of choice for diabetes in pregnancy (both pre-gestational and gestational). Regular insulin and NPH insulin have the longest safety record in pregnancy. Insulin requirements increase during the second and third trimesters due to placental hormones (human placental lactogen, cortisol, progesterone) causing insulin resistance, and drop sharply after delivery.
Exam-style clinical scenario
A 22-year-old Type 1 diabetic presents with vomiting, abdominal pain, deep rapid breathing (Kussmaul respiration), blood glucose 450 mg/dL, pH 7.1, serum bicarbonate 8 mEq/L, and serum potassium 5.8 mEq/L. What is the initial fluid and insulin management? Answer: This is diabetic ketoacidosis (DKA). Management: (1) Start normal saline 1-1.5 L/hour initially. (2) If K+ is >5.2 mEq/L, begin IV regular insulin at 0.14 units/kg/hour WITHOUT potassium supplementation initially. (3) When blood glucose falls to 200 mg/dL, switch fluids to 5% dextrose + 0.45% saline and reduce insulin to 0.05 units/kg/hour. (4) Transition to subcutaneous insulin when the patient can eat and the anion gap normalises. IMPORTANT: NEVER give insulin if K+ is <3.3 mEq/L -- correct potassium first to avoid fatal hypokalaemia.
Cost in India
INR 100-200 per 10 mL vial (40 IU/mL); INR 250-400 per 10 mL vial (100 IU/mL); penfill cartridges INR 200-350
Clinical governance
Author: MedNext Editorial Team. Clinical reviewer: Awaiting clinical review. Jurisdiction: India (Drugs and Cosmetics Act, 1940). Sources: CIMS India, Indian Pharmacopoeia. Publication state: Awaiting clinical review. Correction: Report errors at support@mednext.academy.
Frequently Asked Questions
Why is regular insulin the only insulin that can be given IV?
Regular insulin is a clear, soluble preparation of monomeric/dimeric insulin in solution that can be directly infused intravenously. Other insulin preparations (NPH, glargine, detemir) are either suspensions (cloudy -- would embolise if given IV) or have pH-dependent precipitation mechanisms designed for subcutaneous depots. Rapid-acting analogues (lispro, aspart) are also clear solutions and can technically be given IV, but regular insulin has the longest safety record for IV use.
What is the difference between Somogyi effect and Dawn phenomenon?
Somogyi effect: nocturnal hypoglycaemia (due to excessive evening insulin) triggers counter-regulatory hormones (glucagon, cortisol, growth hormone, adrenaline), causing rebound fasting hyperglycaemia. Diagnosed by 3 AM blood glucose (low). Treatment: reduce evening insulin dose. Dawn phenomenon: early morning hyperglycaemia due to the physiological pre-dawn surge of growth hormone. The 3 AM glucose is NORMAL. Treatment: increase evening insulin or shift timing.
Why must potassium be checked before starting insulin in DKA?
Insulin activates the Na-K-ATPase pump, driving potassium from the extracellular to the intracellular compartment. In DKA, total body potassium is severely depleted (renal losses from osmotic diuresis), but serum potassium may appear normal or high due to extracellular shift from acidosis and insulin deficiency. Starting insulin without adequate potassium replacement can cause life-threatening hypokalaemia, cardiac arrhythmias, and cardiac arrest. If K+ is <3.3 mEq/L, potassium must be repleted BEFORE starting insulin.
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