Can a diabetic patient on furosemide (Lasix) for one month with recent normal labs and previously resolved macrocytosis receive a refill now, and which labs should be repeated before the refill?

Can Furosemide Be Refilled Now and Which Labs Are Needed?

Yes, provide the furosemide refill now for this diabetic patient who has been on it for one month with recent normal labs, but order comprehensive metabolic panel (CMP) and complete blood count (CBC) to be drawn within the next 1-2 weeks before the next refill.

Rationale for Immediate Refill

• The patient should not be without diuretic therapy, as interruption can lead to acute decompensation in heart failure or worsening fluid retention 1
• The FDA label for furosemide emphasizes that patients require careful monitoring but does not mandate lab checks before every refill in stable patients 2
• Recent normal labs (within 3 months) provide reasonable safety assurance for a short-term bridge refill 2

Required Laboratory Monitoring Before Next Refill

Order the following labs within 1-2 weeks:

Essential Tests (CMP Components):

• Serum electrolytes (particularly potassium, sodium, chloride) - furosemide causes hypokalemia, hyponatremia, and hypochloremic alkalosis 2
• Renal function (creatinine, BUN) - to assess for deterioration, especially critical in diabetic patients who are at higher risk for diabetic kidney disease 3, 2
• Glucose - furosemide can precipitate or worsen diabetes mellitus 2
• Calcium and magnesium - furosemide lowers both, with rare cases of tetany reported 2
• Uric acid - asymptomatic hyperuricemia is common and gout may be precipitated 2

Additional Required Test:

• Complete blood count (CBC) - to monitor the macrocytosis (MCV 101) that was previously noted, as patients should be observed for blood dyscrasias 2

Monitoring Frequency Guidelines

The FDA label is explicit about monitoring requirements 2:

• Serum electrolytes, CO2, creatinine, and BUN should be determined frequently during the first few months of furosemide therapy
• Determinations are particularly important when the patient is vomiting profusely or receiving parenteral fluids
• Urine and blood glucose should be checked periodically in diabetics receiving furosemide 2

Special Considerations for Diabetic Patients

Diabetic patients require more intensive diuretic management:

• Diabetic heart failure patients need 26% higher odds of requiring at least 80mg furosemide compared to non-diabetics and are independently associated with higher furosemide doses 4
• Furosemide may increase blood glucose levels and affect urine glucose tests, requiring closer diabetes monitoring 2
• Diabetic patients are at higher risk for diabetic kidney disease, making renal function monitoring even more critical 3
• The American Diabetes Association recommends monitoring for diabetic kidney disease with annual urine albumin excretion testing in type 2 diabetics starting at diagnosis 3

Critical Safety Monitoring

Watch for signs of fluid/electrolyte imbalance 2:

• Hypokalemia symptoms: muscle cramps, weakness, fatigue, arrhythmias
• Hyponatremia symptoms: lethargy, drowsiness, confusion
• Volume depletion: dryness of mouth, thirst, hypotension, oliguria, tachycardia
• GI disturbances: nausea, vomiting

Common Pitfalls to Avoid

• Do not withhold necessary diuretic therapy due to excessive concern about azotemia, as this leads to refractory edema and persistent symptoms 1
• Do not ignore the macrocytosis - while B12 was normal, continue monitoring CBC as the FDA label requires observation for blood dyscrasias 2
• Do not assume once-monthly lab checks are sufficient during the first few months of therapy - the FDA label specifically states "frequently during the first few months" 2
• Ensure potassium supplementation or monitoring is adequate, as digitalis therapy (if used) may exaggerate metabolic effects of hypokalemia 2

Foot Care Education Reinforcement

The documented foot care education is appropriate given that:

• Good glucose control is essential as diabetes damages blood vessels and nerves, worsening neuropathy 3
• The American Diabetes Association emphasizes optimizing glycemic control to reduce risk of nephropathy and neuropathy progression 3
• Daily foot inspection and proper care are standard recommendations for diabetic patients 3