Incidence of and factors associated with manipulation of nimodipine dosage in patients with aneurysmal subarachnoid hemorrhage.

BACKGROUND Aneurysmal subarachnoid hemorrhage is a significant cause of death and disability. Nimodipine 60 mg administered enterally every 4 h improves neurologic outcomes in these patients. However, hypotension is an adverse effect of nimodipine and is believed to prompt clinicians to prescribe an unproven, nonstandard nimodipine dosing regimen. OBJECTIVES The primary objective was to determine the prescribing incidence of a nonstandard nimodipine dosing regimen (30 mg every 2 h) after initial prescription of the standard dose (60 mg every 4 h). The secondary objective was to determine factors associated with this dosage change. METHODS This retrospective cohort study evaluated participants receiving nimodipine for aneurysmal subarachnoid hemorrhage at a tertiary care teaching hospital between October 2005 and December 2011. Univariate and multivariate regression analyses were performed to identify factors associated with dosage manipulation. RESULTS A total of 166 eligible patients were identified. For all of these patients, nimodipine 60 mg every 4 h was prescribed initially. Subsequently, 81 (49%) of the patients were switched to nimodipine 30 mg every 2 h, whereas 85 (51%) continued on the original dosage (nimodipine 60 mg every 4 h) for the duration of their treatment. Multivariate analysis revealed that occurrence of vasospasm (odds ratio [OR] 5.30, 95% confidence interval [CI] 2.08-13.47; p < 0.001) and exposure to vasopressor therapy (OR 3.29, 95% CI 1.27-8.50; p = 0.014) were associated with increased odds of receiving the nonstandard nimodipine regimen. CONCLUSIONS Half of patients for whom nimodipine was prescribed for aneurysmal subarachnoid hemorrhage were exposed to an unproven regimen. Vasospasm and exposure to vasopressor therapy were associated with higher odds of receiving the nonstandard regimen. Further research is needed to evaluate whether nimodipine 30 mg every 2 h is efficacious and safe for patients in this population.