What are the potential interactions between intravenous (IV) diclofenac (Voltaren) and IV furosemide (Lasix) 20mg in a patient with Type 2 Diabetes Mellitus (T2DM) and Hypertension (HTN) presenting with rigors and elevated blood pressure?

Significant Drug Interaction: Avoid Concurrent Use of Diclofenac and Furosemide

The combination of injectable diclofenac and furosemide 20mg should be avoided or used with extreme caution in this patient, as NSAIDs like diclofenac significantly reduce the antihypertensive and diuretic efficacy of furosemide, potentially worsening blood pressure control and precipitating acute kidney injury in a patient with T2DM and hypertension. 1, 2

Critical Drug-Drug Interaction Mechanism

NSAIDs antagonize the effects of loop diuretics through multiple mechanisms:

• Diclofenac inhibits renal prostaglandin synthesis, which directly opposes furosemide's mechanism of action and reduces its diuretic and antihypertensive effects 1
• NSAIDs cause sodium and fluid retention, counteracting the volume reduction needed to control this patient's elevated blood pressure of 170/80 mmHg 1, 2
• The combination increases risk of acute kidney injury, particularly dangerous in diabetic patients who already have compromised renal autoregulation 1

Immediate Management Priorities for This Patient

This patient presents with stage 2 hypertension (170/80 mmHg) and rigors, requiring urgent assessment for hypertensive emergency:

• Assess for target organ damage immediately to differentiate hypertensive emergency from urgency: perform focused neurologic exam (altered mental status, visual changes, headache), cardiac assessment (chest pain, dyspnea), and fundoscopic examination (papilledema, hemorrhages) 3, 4, 5
• If target organ damage is present, this constitutes a hypertensive emergency requiring ICU admission with IV antihypertensive therapy (nicardipine or labetalol), targeting 20-25% reduction in mean arterial pressure within the first hour 3, 4, 5
• If no target organ damage, this is hypertensive urgency manageable with oral antihypertensives and outpatient follow-up within 1 week 5

Alternative Pain Management Strategy

For rigors and associated discomfort, use acetaminophen instead of diclofenac:

• Acetaminophen is less likely to worsen blood pressure control compared to NSAIDs, though it provides minimal anti-inflammatory benefit 1
• If anti-inflammatory effect is essential, use the lowest effective NSAID dose for the shortest duration with close BP monitoring, recognizing that antihypertensive regimen adjustments will likely be necessary 1
• Completely avoid NSAIDs if this patient has any evidence of volume depletion or acute kidney injury 1

Optimal Antihypertensive Regimen for This Patient Profile

For a 50-year-old with T2DM and hypertension, the evidence-based approach is:

• First-line therapy: SGLT2 inhibitor (if eGFR ≥20 mL/min/1.73 m²) plus RAS blockade (ACE inhibitor or ARB) for patients with diabetes and hypertension 1
• Target blood pressure <130/80 mmHg for diabetic patients to reduce cardiovascular risk 1
• Loop diuretics like furosemide are appropriate when thiazides are insufficient or when eGFR <30 mL/min/1.73 m², but require twice-daily dosing for effective 24-hour control 1
• If using furosemide, chlorthalidone provides superior 24-hour BP control compared to hydrochlorothiazide and should be considered as alternative thiazide-type diuretic 1

Critical Clinical Pitfalls to Avoid

Common errors that worsen outcomes in this scenario:

• Do not dismiss the rigors as unimportant - investigate for underlying infection, which frequently precipitates hypertensive crisis in diabetic patients and may require adjustment of diabetes medications 4
• Do not reduce BP to "normal" acutely - patients with chronic hypertension have altered cerebral and renal autoregulation; excessive drops >70 mmHg systolic can precipitate cerebral, renal, or coronary ischemia 3, 4, 5
• Do not use immediate-release nifedipine for acute BP management due to unpredictable precipitous drops and reflex tachycardia 4, 5
• Monitor renal function and electrolytes 2-4 weeks after initiating or adjusting diuretic therapy, especially critical in diabetic patients 1

Post-Stabilization Evaluation

After achieving BP control, screen for secondary hypertension causes:

• 20-40% of patients with severe hypertension have secondary causes including medication non-compliance (most common), renal artery stenosis, primary aldosteronism, or pheochromocytoma 3, 4, 5
• Evaluate for diabetic nephropathy with urinalysis for proteinuria and serum creatinine 1
• Consider 24-hour ambulatory BP monitoring to assess true BP control and guide therapy adjustments 1