NAPLEX Practice Question # 55

NAPLEX Examination.

Practice Question # 55.



Initial dosage of insulin

T1DM, without concomitant infection or physiologic stress condition.

Insulin should be dosed based on weight and requires a calculation of the total daily dose (TDD). Th e total daily dose for an adult with T1DM is estimated as 0.6 units/kg/day, which can then be applied to determine an initial starting dose of insulin.

(1) 50/50 rule:

50% of the TDD is given as a basal (e.g., NPH, glargine, detemir) dose and the remaining 50% is given as the bolus (e.g., regular, lispro, aspart, glulisine) dose, divided between the meals. For example, if a person who weighs 120 lb is to start insulin, the estimated TDD would be approximately 32 units. Half of the TDD (16 units) would be initiated as the basal insulin and the remaining 16 units would be divided into an approximate bolus dose as follows:

(a) Glargine or detemir as a basal with short- or rapid-acting insulin as bolus: 16 units once daily of basal insulin; 5 units t.i.d. of bolus insulin with meals.

(b) NPH as a basal requires twice daily dosing in persons with T1DM. Also, when using NPH, the total bolus dose should be decreased by 20% and given twice daily to prevent hypoglycemia. Th us, the regimen for this example would be 8 units of NPH and 6 units of bolus, each given b.i.d.

(2) Premixed insulin should be initiated as two-third of the TDD in the morning and the remaining one-third of the TDD in the evening, prior to meals. Th is means for the same example used earlier with a TDD of 32 units, the insulin regimen would be 21 units in the morning prior to breakfast and 11 units in the evening prior to the evening meal. It should be noted that this type of dosing is not preferred for the individual with T1DM because it cannot be easily adjusted for changes in diet, exercise, or health (e.g., sick days), nor does it allow the titration of one insulin type to target the specifi c phase of insulin release that is primarily contributing to the impaired glycemic control.

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