OCTOBER 30, 2021
Native or regular insulin molecules self associate as hexamers in an aqueous solution at a neutral PH and this aggregation slows absorption following subcutaneous injection. The onset of action is slow 30-60 minutes, long duration of the peak of 2-4 hours so it can cause postprandial hyperglycemia and late hypoglycemia. There is a mismatch between the need and availability of insulin and does not mimic physiologic bolus secretion of insulin.
Limitations of Regular Insulin
- Inconvenience : has to be administered 30-60 minutes before meal.
- Late postprandial hypoglycemia (4-6 hours after meal)
- The dose can not be adjusted according to the size of a meal.
- Time of onset, peak, duration are dose-dependent.
- Absorption varies with the dose, site of injection and exercise. The variability of absorption is 25%.
Action Profile of Standard Insulin
|1O-20 min||30-90 min||2-3 hrs|
Regular (Humulin R)
|30-60 min||2-4 hrs||6-8 hrs|
|Velosulin (for use in|
|30-60 min||1-2 hrs||2-3 hrs|
(NPH; Humulin N)
|1-2 hrs||4-10 hrs||10-16 hrs|
|Novolin N||90 min||4-12 hrs||up to 24 hrs|
|2-4 hrs||4-12 hrs||12-20 hrs|
|6-10 hrs||10-16 hrs||18-24 hrs|
|15-30 min||varies||18-24 hrs|
|Humulin 50/50||15-30 min||varies||18-24 hrs|
|Novolin 70/30||15-30 min||varies||up to 24 hrs|
Action Profile of Analogs of Insulin
Fast aspart analog
|8-15 min||30 -90 min||3-5 hr|
|5-15 min||30-90 min||3-4 hr|
|Glulisine (Apidra)||15-30 min||30-90 min||2-4 hrs|
|Lispro (Humalog)||5-15 min||30-90 min||3-4hr|
|Lispro U-200||10-30 min||30 min-1 hr||8-10 hr|
|2-6 hr||None||up to 36 hr|
|1-4 hr||None||up to 42 hr|
|30-60 min||None||up to 42 hr|
Novolog Mix 70/30
|10-20 min||dual||14-24 hr|
|Humalog Mix75/25||10-15 min||dual||18-26 hr|
|Humalog Mix50/50||15-30 min||dual||18-26 hr|
(70% Degludec/ 30% Aspart)
|10-20 min||1 hr||up to 24 hr|
Limitations of NPH Insulin
- Does not mimic physiological basal insulin secretion.
- Peak action 5-7 hours after administration so increases the risk of hypoglycemia.
- Duration of action (4-12 hours) is not long enough to cover the whole day.
- Action Profile depends on the dose.
- Variability of absorption with the dose, site of injection, and exercise. Small doses have lower, earlier peaks and a shorter duration of action.
- Highly unpredictably action profile
There are six analogs of Insulin. Six of them are rapid- acting and six are long- acting analogs. insulin analogs are designed to overcome the limitations of conventional insulins. Different analogs are created by altering the sequence of amino acids of regular insulin molecules to modify their absorption and pharmacokinetics profile.
Rapid Acting Analogs
There are three rapid-acting insulin analogs ( insulin lispro, aspart, and glulisine). They have similar time-action profiles. They rapidly absorb from the injection site and start acting within 15 minutes. They can be taken before, during, or even after the meal. They have a lower rate of hypoglycemia and improved A1c levels compared to regular insulin.
Insulin lispro (Humalog) is the first commercially available analog. In insulin lispro amino acids at positions 28 and 29, lysines and proline are reversed in the C- terminus end of the beta chain. A U200 concentration is available in a disposable pre-filled pen.
Insulin aspart (Novolog) is formed by the replacement of proline at B 28 with aspartic acid which reduces self-association.
Insulin glulisine (apidra) is formed when glutamic acid replaces lysine at B29 and lysine replaces asparagine at B3.
Long Acting Analogs
Insulin glargine, detemir, and degludec are long-acting Analogs. In insulin glargine two arginine residues are added at position B 31 and 32 of the beta chain and asparagine amino acid in position A21 is replaced with glycine. Insulin glargine is a clear solution with a pH of 4.0 which stabilizes the insulin hexamers. When injected into neutral PH of subcutaneous space, aggregation occurs, resulting in prolonged, predictable absorption from the injection site. Insulin glargine has a sustained peakless absorption profile and provides more predictable 24 hours insulin coverage than NPH insulin, and it also has a lower risk of hypoglycemia particularly overnight compared to NPH insulin. Suitable for once-daily dosing.
Insulin detemir: In this insulin the terminal threonine amino acid at B30 position is removed and myristic acid (a C -14 fatty acid chain) is attached to B29 lysine.These modification prolong the self aggregation in subcutaneous tissue and reversible albumin binding. Binding to plasma proteins cause gradual release so it has a smoother action profile and causes less hypoglycemia than NPH insulin. Its duration of action is 17 hours and injected once or twice daily.
Insulin Degludec is a modified insulin with Threonine amino acid at position B30 is removed. and lysine at position B29 is conjugated to hexadecanoic acid via a gamma-L-glutamyl spacer. Degludec which is active at physiologic PH forms multihexamers after injections. It has less severe hypoglycemia than glargine. The half- life of degludec is 25 hours. It is given once or twice daily. It is available in two concentration U100 and U 200and dispensed in pre-filled disposable pen.
A stable combination of short-acting and long-acting insulin provides convenience by reducing the number of daily injections.
Advantages of Analogs of Insulin
- Rapid -acting insulin analogs have onset of action of 10-20 minutes, peak 1-2 hours and a short duration of action. So have better control of postprandial blood glucose level and decrease risk of late hypoglycemia.
- Greater flexibility. Can be taken before, during, or after a meal.
- The dose can be adjusted with the size of the meal.
- More predictable action. Onset, peak, and duration of action are independent of the site of injection, dose, and variability of absorption is 5 %.
- Improved A1c levels.
- Lesser risk of hypoglycemia.
- Better control of glucose during fasting.
- Premixed formulations have a lower risk of hypoglycemia than premixed human insulins
- Less weight gain.
Disadvantages of Insulin Analogs
- Carcinogenicity: Recently published studies investigating a possible relationship between insulin analogs, in particular, glargine are under review. Glargine is theoretically more likely to cause cancer because of its high affinity six to sevenfold for insulin-like growth factor 1 (IGF-1) receptor. Clinical significance of this is unclear. FDA considered it as a black triangle drug.
- Cost: More expensive than conventional insulin.
Analogs are preferred in
- Type – 1 diabetic patients
- Person with uncertain lifestyle, quantity of meals and timings of meals.
- Patients having highly unpredictable fasting blood sugar
- Risk of nocturnal hypoglycemia especially in elderly
- People who have unexpected exercise e. g. in policemen, sportsmen
- Critical patients like patients with hepatic and renal disease, ICU patients, perioperative
- Patients who have weight gain problems with standard insulin.