What is the appropriate dosage and administration schedule of Mixtard (biphasic isophane insulin) for a patient with diabetes?

Mixtard Dosing and Administration for Diabetes Management

For a patient requiring Mixtard (biphasic isophane insulin), start with 0.3-0.5 units/kg/day divided into two doses given 30 minutes before breakfast and dinner, with two-thirds of the total daily dose given in the morning and one-third in the evening. 1

Initial Dosing Strategy

Type 2 Diabetes Patients

• Begin with 0.3 units/kg/day as augmentation therapy if the patient has some residual insulin secretion and is on oral medications 1
• For more severe hyperglycemia (HbA1c ≥10%), use replacement therapy starting at 0.6-1.0 units/kg/day 1
• Divide the total daily dose with approximately two-thirds given before breakfast and one-third before dinner 2

Type 1 Diabetes Patients

• Total daily insulin requirements typically range from 0.4-1.0 units/kg/day 3
• For metabolically stable patients, 0.5 units/kg/day is the typical starting point 3
• Mixtard can be given as two or three injections per day, though basal-bolus regimens with separate insulins are generally preferred 4

Administration Timing

• Administer Mixtard 30 minutes before meals to allow the short-acting component to begin working when food is consumed 2
• The morning dose should be given 30 minutes before breakfast 2
• The evening dose should be given 30 minutes before dinner 2

Dose Titration Protocol

• Increase the dose by 2-4 units every 3 days based on fasting and pre-dinner glucose readings 3
• Target fasting plasma glucose of 80-130 mg/dL (4.4-7.2 mmol/L) 3
• If hypoglycemia occurs without clear cause, reduce the corresponding dose by 10-20% immediately 3

Critical Monitoring Requirements

• Check fasting blood glucose daily during titration 3
• Monitor pre-dinner glucose to assess morning dose adequacy 3
• Assess HbA1c every 3 months during intensive titration 3

Foundation Therapy Considerations

• Continue metformin at maximum tolerated dose (up to 2000-2550 mg daily) when using Mixtard, as this combination reduces insulin requirements and weight gain 1, 4
• Do not abruptly discontinue oral medications when starting insulin due to risk of rebound hyperglycemia 4

Special Population Adjustments

Elderly or High-Risk Patients

• Start with lower doses of 0.1-0.25 units/kg/day for patients over 65 years, those with renal impairment, or poor oral intake 3
• Reduce total daily dose by 20% when transitioning from home insulin regimen to hospital setting if on high doses (≥0.6 units/kg/day) 3

Renal Impairment

• For CKD Stage 5 with type 2 diabetes, reduce total daily insulin dose by 50% 3
• For CKD Stage 5 with type 1 diabetes, reduce total daily insulin dose by 35-40% 3

Critical Pitfalls to Avoid

• Never use premixed insulin like Mixtard in hospitalized patients, as randomized trials show unacceptably high rates of hypoglycemia compared to basal-bolus regimens 3
• Do not rely on sliding scale insulin alone—always use scheduled insulin doses 5, 3
• Avoid giving any insulin at bedtime without the evening meal, as this significantly increases nocturnal hypoglycemia risk 3
• Do not continue escalating Mixtard doses beyond 1.0 units/kg/day without reassessing the regimen, as this may indicate need for transition to basal-bolus therapy 3

When to Transition Away from Mixtard

• Consider switching to separate basal and prandial insulins when total daily dose exceeds 0.5-1.0 units/kg/day without achieving glycemic targets, as this allows more flexible dosing and better glycemic control 3
• Basal-bolus therapy provides superior glycemic control with reduced hospital complications compared to premixed insulin regimens 3
• For patients with type 1 diabetes, multiple daily injections with separate basal and prandial insulins are generally preferred over premixed formulations 4