GENERIC NAME: insulin

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GENERIC NAME: insulin
BRAND NAME: various
DRUG CLASS AND MECHANISM: Insulin is a naturally-occurring hormone secreted by the pancreas. Insulin is required by the cells of the body in order for them to remove and use glucose from the blood. From glucose the cells produce the energy that they need to carry out their functions. Researchers first gave an active extract of the pancreas containing insulin to a young diabetic patient in 1922, and the FDA first approved insulin in 1939. Currently, insulin used for treatment is derived from beef and pork pancreas as well as recombinant (human) technology. The first recombinant human insulin was approved by the FDA in 1982.

Patients with diabetes mellitus have an inability to take up and use glucose from the blood, and, as a result, the glucose level in the blood rises. In type 1 diabetes, the pancreas cannot produce enough insulin. Therefore, insulin therapy is needed. In type 2 diabetes, patients produce insulin, but cells throughout the body do not respond normally to the insulin. Nevertheless, insulin also may be used in type 2 diabetes to overcome the resistance of the cells to insulin. By increasing the uptake of glucose by cells and reducing the concentration of glucose in the blood, insulin prevents or reduces the long-term complications of diabetes, including damage to the blood vessels, eyes, kidneys, and nerves. Insulin is administered by injection under the skin (subcutaneously). The subcutaneous tissue of the abdomen is preferred because absorption of the insulin is more consistent from this location than subcutaneous tissues in other locations.
Regular (rapid onset of action, short duration of action) and NPH (slower onset of action, longer duration of action) human insulin are the most commonly-used preparations. Regular insulin has an onset of action (begins to reduce blood sugar) within 30 minutes of injection, reaches a peak effect at 1-3 hours, and has effects that last 6-8 hours.

NPH insulin is an insulin with an intermediate duration of action. It has an onset of action starting about 2 hours following injection. It has a peak effect 4-12 hours after injection, and a duration of action of 18-26 hours.

Lente insulin also is an insulin with an intermediate duration of action. It has an onset of action 2-4 hours after injection, a peak activity 6-12 hours after injection, and a duration of action of 18 to 26 hours. Ultralente insulin is a long-acting insulin with an onset of action 4-8 hours after injection, a peak effect 10-30 hours after injection, and a duration of action of more than 36 hours.
An ultra rapid-acting insulin, insulin lispro is a chemically-modified, natural insulin. It was approved by the FDA in June, 1996. As compared to regular insulin, insulin lispro has a more rapid onset of action, an earlier peak effect, and a shorter duration of action. It reaches peak activity 0.5-2.5 hours after injection. Therefore, insulin lispro should be injected 15 minutes before a meal as compared to regular insulin which is injected 30-60 minutes before a meal.

Insulin aspart and insulin glargine are both human insulin that have had their chemical composition slightly altered. The chemical changes provide insulin aspart with a faster onset of action (20 minutes) and a shorter duration of action (3-5 hours) than regular human insulin. It reaches peak activity 1-3 hours after injection. Insulin glargine has a slower onset of action (70 minutes) and a longer duration of action (24 hours) than regular human insulin. Its activity does not peak.
GENERIC: no

PRESCRIPTION: yes

PREPARATIONS: Insulin comes in three different forms-vials, prefilled syringes, and cartridges. The cartridges are to be used in a pen-like device that simplifies injection. Human recombinant insulin, insulin lispro, insulin aspart, and insulin glargine are the commonly-used insulins. Beef and pork insulin are infrequently used. Regular human insulin (Novolin R, Humulin R) is available in vials, cartridges, and prefilled syringes.

NPH human insulin (Novolin N, Humulin N) is available in vials, cartridges and prefilled syringes. A mixture of 70% NPH human insulin and 30% regular human insulin (Novolin 70/30, Humulin 70/30) is available in vials, cartridges and pre-filled syringes.
A mixture of 50% NPH human insulin and 50% regular human insulin (Humulin 50/50) is available in vials.

Lente human insulin (Novolin L, Humulin L) is available in vials.

Ultralente human insulin (Humulin U) is available in vials.
Insulin lispro (Humalog) is available in vials and cartridges.

Insulin aspart (Novolog) is available in vials and cartridges.
Insulin glargine (Lantus) is available in vials and cartridges.

STORAGE: Unopened insulin should be stored in a refrigerator between 2 and 8°C (36 and 46°F); it should not be placed in a freezer. Insulin vials that are being used can be kept at room temperature for up to a month. All vials should be protected from light and excessive heat. Unused insulin should be thrown away after the expiration date. The vials should never be shaken.

PRESCRIBED FOR: Insulin is prescribed for the treatment of type 1 and type 2 diabetes mellitus.

DOSING: The abdomen is the preferred site for insulin injection, but the sites of injection must be rotated in order to prevent erosion of the fat beneath the skin, a condition called lipodystrophy.

DRUG INTERACTIONS: Several drugs augment the action of insulin and may lower blood glucose to a dangerous level (hypoglycemia). To prevent hypoglycemia when these drugs are used, the dose of insulin may need to be reduced. Such drugs include alcohol, MAO inhibitors like phenelzine (Nardil), beta-blockers like propranolol (Inderal), salicylates like aspirin (Bayer) or salsalate (Disalcid), and anabolic steroids like methyltestosterone (Android).

There are other drugs that augment the blood glucose-lowering effect of insulin, but they are less likely to interact with insulin or have less of an effect. Such drugs include tetracycline antibiotics like doxycycline (Vibramycin), guanethidine (Ismelin), oral hypoglycemic drugs like glyburide (Diabeta), sulfa antibiotics like sulfadiazine, and ACE inhibitors like captopril (Capoten).

There also are drugs that decrease the effect of insulin. Interactions are less likely and/or less serious. These drugs include diltiazem (Cardizem), niacin, corticosteroids like prednisone, estrogens, oral contraceptives, thyroid hormones like levothyroxine (Synthroid), isoniazid, epinephrine, thiazide diuretics like hydrochlorothiazide, and furosemide (Lasix).

PREGNANCY: Insulin is the drug of choice for controlling diabetes mellitus during pregnancy, that is, it is preferred over oral drugs to reduce blood sugar. Regular human insulin is preferred over insulin aspart or insulin glargine during pregnancy since the latter two insulins have not been studied in pregnant women. NPH, lente, and ultralente insulins also may be used in pregnancy.

NURSING MOTHERS: It is not known if insulin aspart, insulin glargine or insulin lispro are secreted in breast milk. Regular human insulin is secreted in to breast milk. Therefore, when insulin is used during breastfeeding, blood glucose levels should be monitored in both the mother and child.

SIDE EFFECTS: Hypoglycemia is the most common side effect that may occur during insulin therapy. Symptoms of hypoglycemia include confusion, nausea, hunger, tiredness, perspiration, headache, heart palpitations, numbness around the mouth, tingling in the fingers, tremors, muscle weakness, blurred vision, cold temperature, excessive yawning, irritability, and loss of consciousness.

Patients may experience blurred vision if they have had elevated blood sugar levels for a prolonged period of time and then have the elevated levels rapidly brought to normal. This is due to a shift of fluid within the lens of the eye. Over time, vision returns to normal. Other possible side effects that may occur include skin reactions (redness, swelling, itching or rash at the site of injection), worsening of diabetic retinopathy, changes in the distribution of body fat (lipodystrophy), allergic reactions, sodium retention, and general body swelling.