What is the initial dose of nicardipine (calcium channel blocker) for a patient with severe hypertension (blood pressure 200/150 mmHg)?

Nicardipine Dosing for Severe Hypertension (BP 200/150 mmHg)

Start nicardipine at 5 mg/hr IV infusion and titrate by increasing 2.5 mg/hr every 5-15 minutes to a maximum of 15 mg/hr until desired blood pressure reduction is achieved. 1, 2, 3

Initial Dosing Protocol

• Starting dose: 5 mg/hr IV continuous infusion 1, 2, 3
• Titration increments: Increase by 2.5 mg/hr every 5-15 minutes 1, 2, 3
• Maximum dose: 15 mg/hr 1, 2, 3
• Target BP reduction: Aim for 10-15% reduction in mean arterial pressure within the first hour, not exceeding 25% reduction in the first 24 hours 1, 2

Expected Time Course

• Onset of action: 5-15 minutes after starting infusion 2
• Time to therapeutic response: Approximately 77 minutes on average for severe hypertension (defined as achieving diastolic BP ≤95 mmHg or ≥25 mmHg decrease, and systolic BP ≤160 mmHg) 4
• Offset after discontinuation: 30-40 minutes 2

Titration Strategy Based on Response

At higher infusion rates (15 mg/hr), therapeutic response occurs more rapidly (approximately 18 minutes) compared to lower doses (4 mg/hr requires approximately 66 minutes). 5, 6

• If BP remains severely elevated after reaching 7.5 mg/hr, continue increasing by 2.5 mg/hr increments every 5 minutes until reaching the 15 mg/hr maximum 2, 5
• The average maintenance dose in severe hypertension is typically 8 mg/hr 4
• Once target BP is achieved, reduce to 3 mg/hr as maintenance dose 2

Monitoring Requirements

• During titration: Check BP every 15 minutes 2, 3
• After achieving target: Monitor every 30 minutes for 6 hours, then hourly 2, 3
• Continuous monitoring: Heart rate should be monitored continuously during titration 3

Clinical Context and Efficacy

Two trials have demonstrated that nicardipine may be superior to labetalol in achieving short-term BP targets in hypertensive emergencies. 1

• In severe hypertension studies, nicardipine (5-15 mg/hr) produced dose-dependent decreases in BP with 98% of patients achieving therapeutic response 4, 7
• Nicardipine requires fewer dose adjustments per hour (0.5 adjustments/hour) compared to sodium nitroprusside (1.5 adjustments/hour), making it easier to manage 7
• The drug demonstrates excellent correlation between plasma levels and BP reduction 5, 6

Important Safety Considerations

• Avoid excessive BP reduction: In patients with chronic severe hypertension, autoregulation of tissue perfusion is disturbed, making precipitous BP drops dangerous 1
• Phlebitis risk: Local phlebitis can develop after 14+ hours of infusion at a single IV site; rotate sites to minimize this risk 5
• Common side effects: Flushing and headache are common but generally mild 1, 5
• Heart rate increase: Expect an increase of approximately 10 beats/minute, which is less than with other dihydropyridines like nifedipine 5, 7

Drug Interactions to Monitor

• Immunosuppressants: Nicardipine inhibits CYP3A4, significantly elevating cyclosporine and tacrolimus levels; monitor trough levels closely 3
• Cimetidine: Increases nicardipine levels; use caution if co-administered 3

Alternative Considerations

If nicardipine is unavailable or contraindicated, labetalol is the recommended alternative, starting at 0.3-1.0 mg/kg (maximum 20 mg) IV bolus every 10 minutes or as continuous infusion at 0.4-1.0 mg/kg/hour. 1, 3