How to administer nimodipine (oral or intravenous) to a patient with a subarachnoid hemorrhage?

How to Administer Nimodipine in Subarachnoid Hemorrhage

Administer nimodipine 60 mg orally every 4 hours for 21 consecutive days, starting within 96 hours of hemorrhage onset, and never give it intravenously as this can cause fatal hypotension. 1, 2

Route of Administration

• Oral administration only - nimodipine capsules must never be administered intravenously or by any other parenteral route, as inadvertent IV administration causes clinically significant hypotension requiring cardiovascular support with pressor agents 2
• The FDA label explicitly warns against IV administration due to life-threatening complications 2

Standard Dosing Protocol

• 60 mg (two 30 mg capsules) every 4 hours for 21 consecutive days is the evidence-based regimen recommended by the American Heart Association 1, 3
• Begin therapy within 96 hours of subarachnoid hemorrhage onset 1, 3, 2
• This dosing reduces cerebral infarction by 34% and poor outcomes by 40% 3, 4
• Capsules should be swallowed whole with liquid, preferably at least one hour before or two hours after meals 2
• Avoid grapefruit juice as it interferes with CYP3A4 metabolism 2

Alternative Administration for Patients Unable to Swallow

• If the patient cannot swallow (e.g., unconscious, intubated, or perioperative), extract the capsule contents using this specific technique 2:
  • Make holes in both ends of the capsule with an 18-gauge needle 2
  • Extract contents with a parenteral syringe, then transfer to a syringe that cannot accept a needle and is designed for oral/enteral use only 2
  • Label the administration syringe "Not for IV Use" to prevent fatal administration errors 2
  • Empty contents into nasogastric tube or PEG tube 2
  • Flush with 30 mL of normal saline (0.9%) 2

Managing Hypotension While Maintaining Nimodipine

• Continue nimodipine at standard dose even in patients requiring vasopressor support - the American College of Cardiology recommends attempting standard medical interventions to maintain blood pressure before considering dose reduction 5
• Concurrent vasopressor use is not a contraindication to nimodipine 5
• Maintain euvolemia (not hypervolemia) and titrate vasopressors to support blood pressure 1, 5, 3
• Once the aneurysm is secured, blood pressure can be safely augmented with vasopressors without rebleeding risk 5

When Dose Reduction Is Necessary

• Only reduce dose if recurrent hypotension occurs despite standard interventions 2, 6
• In patients with severe liver cirrhosis, reduce to 30 mg every 4 hours with close blood pressure and heart rate monitoring due to increased bioavailability 2
• Patients on moderate/weak CYP3A4 inhibitors may require dose reduction if hypotension develops 2
• Research shows that dose reduction occurs in approximately 28-39% of patients due to hypotension, and is associated with worse outcomes 7, 6

Critical Importance of Uninterrupted Therapy

• Disruption of nimodipine therapy is directly associated with greater incidence of delayed cerebral ischemia (ρ=0.431, P<0.001) 5
• Only 33-44% of patients in real-world practice complete the full 21-day course at full dose, often due to hypotension or early hospital discharge 7, 6
• Application of full nimodipine dosage decreases risk of unfavorable outcome (OR 0.895, p=0.029) 6

Drug Interactions Requiring Dose Adjustment

• Strong CYP3A4 inhibitors are contraindicated with nimodipine 2
• Strong CYP3A4 inducers should generally not be administered with nimodipine 2
• Patients on moderate/weak CYP3A4 inducers should be monitored for lack of effectiveness and may require dose increase 2

Common Pitfalls to Avoid

• Do not discontinue nimodipine simply because vasopressors are needed - this is manageable, not a contraindication 5
• Do not use hypervolemia to manage blood pressure, as it increases complications; euvolemia with vasopressor support is the correct approach 1, 5, 3
• Do not forget to prescribe nimodipine at discharge if the patient leaves before completing 21 days - 47% of patients in one study were discharged without continuation orders 7
• Do not administer oral solution formulation if tablet is available - oral solutions cause blood pressure drops three times more frequently than tablets, though plasma levels are equivalent 8