What are the recommended adult dose, administration protocol, monitoring requirements, contraindications, side effects, and reversal agent for Lexiscan (regadenoson) used in pharmacologic myocardial perfusion stress testing?

Lexiscan (Regadenoson) for Pharmacologic Myocardial Perfusion Stress Testing

Administer Lexiscan as a single fixed dose of 0.4 mg (5 mL) via rapid intravenous injection over 10 seconds, followed immediately by a 5 mL saline flush, with the radionuclide tracer injected 10-20 seconds after the flush. 1

Adult Dosing and Administration Protocol

Standard Dose

• Fixed dose of 0.4 mg (5 mL) for all patients - no weight-based adjustment required, making administration simpler than other vasodilators 2, 1
• Inject through a 22-gauge or larger peripheral catheter or needle 1
• Critical timing: Complete injection within 10 seconds (longer injection times may increase duration and magnitude of coronary blood flow, potentially increasing adverse effects) 1

Sequential Administration Steps

1. Administer regadenoson 0.4 mg IV over 10 seconds 1
2. Immediately follow with 5 mL saline flush 1
3. Inject radionuclide tracer (typically 99mTc-sestamibi) 10-20 seconds after saline flush 2, 1
4. Perform SPECT imaging 60-90 minutes after regadenoson administration 2

Pre-Procedure Requirements

• Patients must avoid all methylxanthine products for at least 12 hours before testing, including caffeinated coffee, tea, other caffeinated beverages, caffeine-containing drugs, aminophylline, and theophylline 1
• Inspect solution for particulate matter or discoloration before administration 1

Absolute Contraindications

Do not administer regadenoson to patients with: 1

• Second- or third-degree AV block without a functioning pacemaker 1
• Sinus node dysfunction without a functioning pacemaker 1
• Acute coronary syndrome or unstable angina 2
• Symptoms or signs of acute myocardial ischemia or cardiovascular instability 1

Relative Contraindications

• Uncontrolled hypertension or hypotension 3
• Severe bronchospastic disease (though regadenoson may be used in mild-to-moderate reactive airway disease, unlike adenosine) 4

Monitoring Requirements

Essential Pre-Administration Preparation

• Cardiac resuscitation equipment and trained staff must be available before administering regadenoson 1
• Establish adequate IV access with 22-gauge or larger catheter 1

During and Post-Administration Monitoring

• Continuous ECG monitoring for arrhythmias, AV blocks, and bradycardia 1, 3
• Blood pressure monitoring (expect slight decreases in both systolic and diastolic pressures) 5
• Heart rate monitoring (expect rapid and greater peak increase compared to adenosine, with slower return to baseline) 5
• Observe for adverse effects, which typically begin soon after administration and resolve within approximately 15 minutes 5

Common Side Effects and Their Management

Expected Adverse Effects (Generally Mild and Self-Limited)

• Dyspnea (most frequent complaint) 6
• Flushing 6
• Chest pain or discomfort 5, 6
• Headache 5
• Minimal tachycardia 6
• Minimal blood pressure changes 6

Comparative Safety Profile

• Regadenoson produces no atrioventricular block (0% vs. 10% with adenosine) 6
• Fewer patients experience severe complaints with regadenoson compared to adenosine (17% vs. 32%) 6
• Overall symptom score significantly lower than adenosine (6.7±6.3 vs. 10.0±7.9) 6
• Side effects are milder and shorter in duration than with adenosine 6

Serious Adverse Events (Rare but Critical)

Life-threatening complications have been reported and include: 1, 7

• Fatal and nonfatal myocardial infarction 1
• Ventricular arrhythmias 1
• Cardiac arrest 1
• Asystole with hemodynamic collapse (even in stable outpatients) 7, 3
• Second-degree type II heart block progressing to pulseless electrical activity 3

Critical caveat: The prevalence of potentially life-threatening bradycardia and asystole may be greater than previously expected, occurring even in stable outpatients without obvious risk factors 7

Reversal Agent

Aminophylline is the reversal agent for regadenoson - it acts as an adenosine antagonist to shorten the duration of increased coronary blood flow induced by regadenoson 1

When to Consider Reversal

• If serious reactions to regadenoson occur 1
• For persistent or severe adverse effects beyond the typical 15-minute resolution period 5

Clinical Indications and Patient Selection

Preferred Patient Populations

• Patients unable to undergo adequate exercise stress testing 8, 2, 1
• Patients with physical limitations preventing exercise 2
• Patients with left bundle-branch block or electronically paced ventricular rhythm (regadenoson preferred over exercise MPI due to higher specificity) 8, 2
• Patients with abnormalities on resting ECG that impair diagnostic interpretation (LV hypertrophy with "strain" pattern, digitalis effect) 2

Diagnostic Performance

• Normal or mildly abnormal results indicate annual risk for cardiac death and acute MI less than 1% 2
• Moderate to severe abnormalities (multivessel perfusion defects) predict annual risk for cardiovascular death or MI of 5% or higher 2
• Negative predictive value is high, typically 90-100% 2