Medication Update


South Med J. 2002;95(1) 

In This Article


Mode of Action

Insulin is produced by beta cells of the pancreas, and it lowers blood glucose by increasing peripheral glucose uptake (mostly into fat and skeletal muscle) and inhibiting hepatic gluconeogenesis.


Known hypersensitivity to the particular insulin, or components of the preparation.


Pregnancy Category: B. (Insulin glargine and insulin aspart are Pregnancy Category C.)

Adverse Effects

Hypoglycemia, hypokalemia, lipodystrophy (which can be avoided by rotating the injection sites), reactions at the injection site.

Injection site pain has been more frequently reported with insulin glargine (2.7%) than with NPH insulin (0.7%).

Drug-Drug Interactions

The following drugs may decrease the effectiveness of insulin, resulting in hyperglycemia: acetazolamide, albuterol, asparaginase, calcitonin, corticosteroids, cyclophosphamide, danazol, dextrothyroxine, diazoxide, diltiazem, diuretics, dobutamine, epinephrine, estrogens, ethacrynic acid, HIV antivirals, isoniazid, lithium, morphine, niacin, oral contraceptives, phenothiazines, phenytoin, somatropin, terbutaline, thiazide diuretics, and thyroid supplements. The following drugs may increase the effectiveness of insulin, resulting in hypoglycemia: ACE inhibitors, alcohol, anabolic steroids, beta blockers, calcium, chloroquine, clofibrate, clonidine, disopyramide, fluoxetine, guanethidine, lithium, mebendazole, monoamine oxidase inhibitors, octreotide, pentamidine, phenylbutazone, propoxyphene, pyridoxine, salicylates, sulfinpyrazone, sulfonamides, and tetracyclines.

Commonly Used Human and Human Analog Insulin Products

  • Regular (Humulin R, Novolin R): Onset, 0.5 - 1 hours. Peak, 2.5 - 5 hours. Duration, 8-12 hours. Give 30-60 minutes prior to meal.

  • Semilente (Iletin): Onset, 1-1.5 hours. Peak, 5 - 10 hours. Duration, 12 - 16 hours.

  • Lispro (Humalog): Onset, 0.25 hours. Peak, 0.5-1.5 hours. Duration, 6 - 8 hours. Give 15 minutes prior to or immediately after meal.

  • Aspart (NovoLog): Onset, 0.25 hours. Peak, 1 - 3 hours. Duration, 3-5 hours. Give 5-10 minutes prior to meal.

  • NPH (Humulin N, Novolin N): Onset, 1 - 1.5 hours. Peak, 4 - 12 hours. Duration, 24 hours.

  • Lente (Humulin L, Novolin L): Onset, 1 - 2.5 hours. Peak, 7 - 15 hours. Duration, 22 - 24 hours.

  • Glargine (Lantus): Onset, 1.1 hours. Peak, 5 hours. Duration, 24 hours. Give dose once a day at bedtime. Should not be mixed with any other insulin or given IV. Average starting dose is 10 units/day.

  • PZI (Protamine Zinc Iletin I): Onset, 4-8 hours. Peak, 14-24 hours. Duration, 36 hours.

  • Ultralente (Humulin U, Ultralente): Onset, 4-8 hours. Peak, 10-30 hours. Duration, >36 hours.

Human and Human Analog Combination Insulin Products

  • 70% NPH and 30% regular: Humulin 70/30, Novolin 70/30.

  • 50% NPH and 50% regular: Humulin 50/50.

  • 75% NPH and 25% lispro: Humalog Mix 75/25.

  • 50% NPH and 50% lispro: Humalog Mix 50/50.

Recommended Doses

Most patients require 0.5-1 unit/kg/day of insulin. Dosing is highly individualized based upon patient response.

Other Points of Interest

When mixing insulins, such as regular and NPH, the regular insulin should be drawn into the syringe first.


  1. Hutchison TA, Shahan DR, Anderson ML (eds): DRUGDEX System. MICROMEDEX, Inc, Englewood, Colo. (Edition expires 12/2000)

  2. Hebel SK, Katstrup EK (eds): Drug Facts and Comparisons. St. Louis, Mo. 2001


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