9 A

It is appropriate because it meets most of the requirements for initiation of insulin therapy in Type 1 DM. Calculating at 1 unit per kg body weight, he will need 50 units of insulin per day. Half of this - 25 units - should be prandial insulin and a similar amount should be basal insulin. The prandial insulin is spread out over three main meals: 8 units before breakfast, lunch and dinner. The basal insulin (25 units) is given two-thirds in the morning and one-third in the evening/night. This means that he should receive about 16 units in the morning and 9 units in the evening of basal insulin.

To provide these insulin requirements, the boy is being given a biphasic insulin (Humulin 30/70) which contains a pre-mixed combination of 30 percent short acting and 70 percent long acting insulin in the morning and evening. This makes it easier to administer because it avoids the need to mix two different types of insulin for the injections in the morning and evening. In the afternoon, before lunch, he is given short acting insulin alone in the form of Actrapid Insulin.

You will notice that the boy gets prandial insulin 8 units before breakfast, 8 units before lunch and 4 units before dinner. He gets basal insulin 16 units in the morning and 8 units in the evening. He is receiving less than the expected amount of prandial insulin before dinner. This cannot be avoided because biphasic insulins come in fixed dose combinations.

Note: 24 units of Humulin 30/70 contains 8 units short acting and 16 units long acting insulin. And, 12 units of Humulin 30/70 contains approximately 4 units of short acting insulin and 8 units of long acting insulin.

You will notice here that the patient is given Actrapid insulin and not Humulin 30/70 insulin before lunch. This is important. A long acting insulin (or a biphasic insulin) should not be prescribed before lunch because its peak action will be at midnight and that increases the risk of nocturnal hypoglycemia. Similarly, short acting insulin (or a biphasic insulin) must not be prescribed at bedtime if there is no bedtime snack.



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