What is the recommended dose of nimodipine (calcium channel blocker) for preventing cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage?

Nimodipine Dosing for Aneurysmal Subarachnoid Hemorrhage

The recommended dose of nimodipine for aneurysmal subarachnoid hemorrhage is 60 mg orally every 4 hours for 21 consecutive days, starting within 96 hours of hemorrhage onset. 1, 2

Standard Dosing Protocol

• Administer 60 mg (two 30 mg capsules) every 4 hours for exactly 21 consecutive days 1, 2
• Begin therapy within 96 hours of subarachnoid hemorrhage onset 1, 2
• Continue for the full 21-day course without interruption, as disruption of therapy is directly associated with increased delayed cerebral ischemia (ρ=0.431, P<0.001) 1, 3

Route of Administration

• Oral administration is the only FDA-approved route—never administer intravenously or by other parenteral routes, as this can cause life-threatening hypotension 2
• For patients unable to swallow (unconscious, intubated, or perioperative): puncture both ends of the capsule with an 18-gauge needle, extract contents into a syringe labeled "Not for IV Use," and administer via nasogastric tube or PEG, flushing with 30 mL normal saline 2
• Capsules should be swallowed whole with liquid, preferably 1 hour before or 2 hours after meals, avoiding grapefruit juice 2

Managing Hypotension While Maintaining Full Dose

The most critical pitfall is premature dose reduction or discontinuation due to hypotension—this occurs in 28-56% of patients in real-world practice and is associated with worse outcomes. 4, 5

• Attempt standard medical interventions to manage blood pressure before reducing nimodipine dose, including vasopressor support 3
• Concurrent vasopressor use is not a contraindication to full-dose nimodipine 3
• In post-aneurysm securing (clipped or coiled), you can safely augment blood pressure with vasopressors without rebleeding risk 3
• Only reduce dose to 30 mg every 4 hours if hypotension persists despite aggressive blood pressure management 2
• Temporary discontinuation may be necessary only if nimodipine causes significant blood pressure variability that cannot be managed 1

Dose Modifications for Specific Populations

Hepatic impairment (particularly cirrhosis):

• Reduce dose to 30 mg every 4 hours due to doubled bioavailability from decreased first-pass metabolism 2
• Monitor blood pressure and heart rate closely; consider discontinuation if adverse effects are pronounced 2

Drug interactions:

• Strong CYP3A4 inhibitors are contraindicated with nimodipine 2
• Strong CYP3A4 inducers should generally not be co-administered 2
• Patients on moderate/weak CYP3A4 inhibitors may require dose reduction if hypotension develops 2
• Patients on moderate/weak CYP3A4 inducers may require dose increase if therapy appears ineffective 2

Evidence Supporting This Dosing

The 60 mg every 4 hours dosing is supported by:

• Class I, Level of Evidence A recommendation from the 2023 American Heart Association/American Stroke Association guidelines 1
• Original 1983 clinical trial and meta-analysis of 16 trials involving 3,361 patients demonstrating prevention of delayed cerebral ischemia and improved functional outcomes 1
• FDA approval specifically for this dose and indication 2
• Multivariate analysis showing full dosage decreases risk of unfavorable outcome (OR 0.895, p=0.029) 5

Common Pitfalls to Avoid

• Do not discontinue at hospital discharge before 21 days are complete—47% of patients in one study were discharged without continuation orders 4
• Do not reduce dose simply because patient requires vasopressors—this is manageable, not a contraindication 3
• Do not use prophylactic hypervolemia while on nimodipine—maintain euvolemia instead, as hypervolemia is associated with harm 1, 3
• Do not substitute other calcium channel blockers—only oral nimodipine has proven benefit for this indication 1