Switching from Rizodec to Lantus: Unit-for-Unit Conversion
Yes, you can switch a patient from Rizodec (insulin glargine) to Lantus (insulin glargine) on a unit-for-unit basis, as both are U-100 insulin glargine formulations with identical pharmacokinetic and pharmacodynamic profiles. 1
Direct Unit-for-Unit Conversion Protocol
- Administer the exact same daily dose of Lantus that the patient was receiving with Rizodec, as both products contain 100 units/mL of insulin glargine and have equivalent glucose-lowering effects 1, 2.
- Maintain the same injection time (once daily at the same time each day) to preserve stable basal insulin coverage 1, 3.
- Continue all concurrent medications (metformin, other oral agents, or prandial insulin) without adjustment during the switch 4.
Administration Guidelines
- Inject subcutaneously into the abdominal area, thigh, or deltoid, rotating injection sites within the same region to reduce lipodystrophy risk 1.
- Visually inspect the solution before each injection; it must be clear and colorless with no visible particles 1.
- Do not dilute or mix Lantus with any other insulin or solution due to its acidic pH 1, 5.
- Administer at the same time daily—typically at bedtime (20:00 h), though morning or any consistent time is acceptable 1, 6, 7.
Monitoring Requirements During Transition
- Check fasting blood glucose daily for the first 1–2 weeks after switching to confirm stable glycemic control 1, 3.
- Measure pre-meal glucose if the patient is on a basal-bolus regimen to ensure prandial insulin doses remain appropriate 4.
- Reassess HbA1c at 3 months to verify sustained glycemic control 4, 8.
When to Adjust the Dose
- Increase by 2 units every 3 days if fasting glucose is 140–179 mg/dL 4, 8.
- Increase by 4 units every 3 days if fasting glucose is ≥180 mg/dL 4, 8.
- Reduce by 10–20% immediately if unexplained hypoglycemia (glucose <70 mg/dL) occurs 4, 8.
- Target fasting glucose: 80–130 mg/dL 4, 8.
Critical Threshold for Basal Insulin Escalation
- When Lantus dose approaches 0.5–1.0 units/kg/day without achieving glycemic targets, add prandial insulin or a GLP-1 receptor agonist rather than continuing to escalate basal insulin alone 4, 8, 5.
- Signs of "overbasalization" include basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL, hypoglycemia, and high glucose variability 4, 8.
Common Pitfalls to Avoid
- Do not reduce the dose prophylactically when switching from Rizodec to Lantus, as both are bioequivalent U-100 formulations 1, 2.
- Do not switch to Toujeo (U-300 glargine) on a unit-for-unit basis, as U-300 requires a 10–18% dose increase due to lower per-unit efficacy 5.
- Do not administer intravenously or via an insulin pump, as Lantus is formulated exclusively for subcutaneous injection 1.
- Do not delay dose adjustments if glucose patterns change; 75% of patients with hypoglycemia receive no insulin adjustment before the next dose 8.
Expected Clinical Outcomes
- Equivalent glycemic control to the prior Rizodec regimen, with similar HbA1c reductions and fasting glucose levels 2, 7, 9.
- Lower nocturnal hypoglycemia risk compared to NPH insulin, though this advantage applies to both Rizodec and Lantus equally 6, 2, 7.
- 24-hour peakless basal coverage with once-daily dosing in most patients 6, 2, 7.
Special Considerations
- Twice-daily dosing may be required in type 1 diabetes patients with high glycemic variability or when once-daily administration fails to provide 24-hour coverage 5, 6.
- Reduce dose by 25% the evening before surgery to lower perioperative hypoglycemia risk 8.
- Lower starting doses (0.1–0.25 units/kg/day) are recommended for elderly patients (>65 years), those with renal impairment, or poor oral intake 8.