Article Text

Download PDFPDF
Research paper
Dantrolene for cerebral vasospasm after subarachnoid haemorrhage: a randomised double blind placebo-controlled safety trial
  1. Susanne Muehlschlegel1,2,3,
  2. Raphael Carandang1,3,
  3. Wiley Hall1,3,
  4. Nisha Kini4,
  5. Saef Izzy1,
  6. Bridget Garland1,
  7. Cynthia Ouillette1,
  8. Imramsjah M J van der Bom5,
  9. Thomas F Flood5,
  10. Matthew J Gounis5,
  11. John P Weaver6,
  12. Bruce Barton4,
  13. Ajay K Wakhloo1,5,6
  1. 1Departments of Neurology (Neurocritical Care), University of Massachusetts Medical School, Worcester, Massachusetts, USA
  2. 2Department of Anesthesia/Critical Care, University of Massachusetts Medical School, Worcester, Massachusetts, USA
  3. 3Department of Surgery, University of Massachusetts Medical School, Worcester, Massachusetts, USA
  4. 4Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, Massachusetts, USA
  5. 5Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
  6. 6Department of Neurosurgery, University of Massachusetts Medical School, Worcester, Massachusetts, USA
  1. Correspondence to Dr Susanne Muehlschlegel, Departments of Neurology (Neurocritical Care), Anesthesia/Critical Care and Surgery, University of Massachusetts Medical School, 55 Lake Ave. North, S5, Worcester, MA 01655, USA; susanne.muehlschlegel{at}


Background Dantrolene is neuroprotective in animal models and may attenuate cerebral vasospasm (cVSP) in human aneurysmal subarachnoid haemorrhage (aSAH). We evaluated safety, feasibility and tolerability of intravenous dantrolene (IV-D) in patients with aSAH.

Methods In this single-centre, randomised, double blind, placebo-controlled trial, 31 patients with aSAH were randomised to IV-D 1.25 mg every 6 h for 7 days (n=16) or equiosmolar free water/5% mannitol (placebo; n=15). Primary safety end points were incidence of hyponatraemia (sNa≤132 mmol/L) and liver toxicity (proportion of patients alanine transaminase, aspartate aminotransferase and AlkPhos >5× upper-limit-of-normal). Secondary end points included tolerability, systemic hypotension and intracranial hypertension. Efficacy was explored for clinical/radiological cVSP, delayed cerebral ischaemia (DCI), and 3-month functional outcomes. Quantitative analyses of angiograms and daily transcranial Doppler (TCD) were performed.

Results Between IV-D versus placebo, no differences were observed in the primary outcomes (hyponatremia 44% vs 67% (p=0.29); liver toxicity 6% vs 0% (p=1.0)). Three patients in the IV-D versus two in the placebo group had severe adverse events possibly attributable to infusion and reached stop criteria: one IV-D patient developed liver toxicity; two patients in each group developed brain oedema requiring osmotherapy. The majority of adverse events were not related to infusion (17 vs 5 (RR 2.2; 95% CI 0.7 to 6.7; p=0.16) in IV-D vs placebo). No differences in any categorical cVSP outcomes, DCI, 3-month outcomes or quantitative angiogram and TCD analyses were seen in this small safety trial not powered to detect efficacy.

Conclusions In this small trial, IV-D after aSAH was feasible, tolerable and safe.

Trial registration number NCT01024972.


Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


Cerebral vasospasm (cVSP) after aneurysmal subarachnoid haemorrhage (aSAH) has been associated with delayed cerebral ischaemia (DCI) and to date is thought to be largest contributor of morbidity and mortality after aSAH.1 Treatments ameliorating not only cVSP but also improving neurological outcomes after aSAH are lacking.1

Dantrolene, an already US Food and Drug Administration (FDA) approved ryanodine-receptor (RyR) blocker, is a promising pharmacological agent for improving outcomes after aSAH given its dual mechanism; it is neuroprotective,2 ,3 and in animal models inhibits cerebral vasoconstriction alone and exponentially more in combination with nimodipine.4 In fact, the common pathway for cVSP and neurotoxicity is the continuous elevation of intracellular Ca2+, resulting from the influx of extracellular Ca2+ and, to a much higher degree, release from the largest intracellular Ca2+-store, the endo/sarcoplasmatic reticulum, mediated by the RyR.5 ,6 Thus, the combined blockage of L-type specific Ca2+-channels (by nimodipine) and RyRs (by dantrolene) may be a key downstream mechanism in ameliorating cVSP and neurotoxicity. Two small human studies have suggested that a single dose of intravenous dantrolene (IV-D) may attenuate cVSP after aSAH,7 ,8 but the feasibility and safety profile of IV-D in critically-ill patients with aSAH over several days is unknown, and effects on outcome have never been explored.

The temporal pattern of cVSP and IV-D's pharmacology calls for repeated IV-D infusions during the cVSP period. IV-D's chemical structure requires reconstitution in free water with 5% mannitol.9 Hence, safety concerns of IV-D in critically ill aSAH include exacerbation of hyponatraemia and brain oedema. Other potential concerns include systemic hypotension (combined with nimodipine), and liver toxicity, as enteric dantrolene (but not IV-D) carries a ‘black-box warning’ for liver toxicity9 and patients with aSAH commonly receive other liver-metabolised medications concurrently (paracetamol, phenytoin/fosphenytoin, statin).

We conducted a single-centre, randomised, double blind, placebo-controlled phase-II trial to evaluate the feasibility, safety and tolerability of repeated IV-D doses in critically ill patients with aSAH. We tested the null-hypothesis that IV-D, compared to placebo, increases the incidence and degree of hyponatraemia, liver toxicity, brain oedema and systemic hypotension.

Materials and methods

The University of Massachusetts Medical School (UMMS) institutional review board (IRB) approved this investigator-initiated trial ( NCT01024972). Written, informed consent was obtained from all patients or the healthcare proxies prior to the occurrence of cVSP in order to increase the likelihood of patients self-consenting to the study, as required by our IRB. We followed the 2010 CONSORT guidelines for reporting parallel group trials.10 All patients presenting with aSAH to our institution were screened for study eligibility between October 2009 and October 2012. The main inclusion criteria were aSAH ≥18 years, aneurysm fully secured by coiling or clipping, Hunt & Hess grade <5, modified Fisher Scale >1, alanine transaminase (ALT), aspartate aminotransferase (AST) and AlkPhos <3× upper limit of normal, serum sodium (sNa) ≥135 mmol/L and no mannitol or hypertonic saline administered prior to study drug infusion (details in online supplement).

During the infusion period we measured sNa, ALT, AST, AlkPhos and osmolarity daily, and the research study nurse visited participants daily, reviewing flow sheets and speaking to the clinical team to assess for primary and secondary outcomes.

To standardise hyponatremia treatment, we instituted a step-wise protocol (online supplement), based on pretrial consensus by our neurointensivists and vascular neurosurgeon. To study the possible effects of IV-D on cVSP, but without increasing risks for patients, all study patients received baseline (before study drug) and daily transcranial Doppler (TCD) for 7 days during the study drug infusion period. One of three trained study TCD examiners performed these TCD, with the same examiner performing all TCD in a participant, when possible (details in online supplement and supplementary figure SI). Owing to safety concerns regarding radiation and contrast-dye exposure, repeat angiography was performed only when indicated clinically for suspicion of clinical cVSP (online supplement).

Routine patient management

All patients with aSAH were treated according to our institutional protocol following published aSAH critical care guidelines,11 ,12 including admission to our closed neuroscience intensive care unit with board-certified neurointensivsts as the primary attending. Details are listed in the online supplement.

Randomisation and intervention

Eligible patients were randomised 1:1 to IV-D 1.25 mg/kg every 6 h for 7 days or equi-osmolar placebo, consisting of the same solution (free water with 5% mannitol) as IV-D, without active drug, using block randomisation in blocks of four (kept in sealed envelopes in the research pharmacy until patient consent; generated by SAS V.9.2 (PROC PLAN), SAS Institute Inc, Cary, North Carolina, USA; figure 1). We chose this placebo over normal saline as we wanted to specifically explore the safety of dantrolene, and differentiate the effects of dantrolene from those of its solution. The dose was determined by our previous single-dose study in which we explored two doses (1.25 mg/kg and 2.5 mg/kg, both within the maximum FDA approved dose) and found that there was no further vasodilatatory effect with the higher dose.8 To maintain rigorous double blinding, the research pharmacy covered the entire length of the tubing and infusion bag with a brown plastic bag because of IV-D's bright yellow colour. We administered study drug over a 7-day period, initiated within the first week after the sentinel headache indicating aSAH onset. While funding did not permit a longer administration period, we were confident that IV-D would be administered during the most critical time period for cVSP development.

Figure 1

Study design. The baseline TCD and screening labs were performed prior to randomisation to ensure that eligibility criteria were still met. ALT, alanine transaminase; AST, aspartate aminotransferase; AlkPhos, alkaline phosphatase; BP, blood pressure; DCI, delayed cerebral ischaemia; GOS, Glasgow Outcome Scale; ICP, intracranial pressure; IV, intravenous; mRS, modified Rankin Scale; Na, sodium; aSAH, (aneurysmal) subarachnoid hemorrhaege; TCD, transcranial Doppler.

Outcome measures

The primary safety outcomes were hyponatremia, liver toxicity, and number of severe adverse events (SAEs) and adverse events (AE); secondary safety outcomes were systemic hypotension, intracranial hypertension, brain oedema and overall tolerability. Detailed outcome definitions and stop rules are listed in online supplementary table SI and the online supplement. Efficacy outcomes explored were TCD, angiographic and clinical cVSP, mortality and delayed ischaemic deficits, assessed at discharge. Modified Rankin Scale (mRS), Glasgow Outcome Scale (GOS) and Barthel Index (BI) were assessed at 3 months post-aSAH. Additionally, changes in daily TCD peak systolic (PSV) and mean flow velocities (MVF) for each vessel at prespecified depths, as well as angiographic vessel diameters were quantitatively analysed to explore the effect of IV-D on vessel diameters (online supplement).

Safety monitoring

The FDA granted an IND exemption (IND 106340). All SAEs were reported to our IRB within 24 h. Additionally, a data safety monitoring board (DSMB) reviewed the results of a planned interim analysis after 50% of patients were enrolled, and ruled that the study be continued without need for study protocol modifications. The DSMB additionally asked to analyse daily white cell count, haematocrit and platelets, which were part of clinical routine laboratory measurements, as aplastic anaemia and leukopoenia are rare IV-D side effects.9

Sample size calculation

Based on detecting a clinically important difference in the change in mean sNa from baseline (≥5 mmol/L; details in the online supplement), one planned interim analysis, assuming a two-sided α=0.05, and allowing for attrition, we planned to enrol a total n=30 (n=15 per arm) over a 3-year period, providing a power of 93%. After the interim analysis, we increased the sample size to n=32 because two patients withdrew consent from the study for subjective reasons (‘nervous about research’). Sample size calculation was performed using EAST (V.5, Cytel Inc, Cambridge, Massachusetts, USA).

Statistical analysis

We applied intention-to-treat analysis throughout. Categorical data were analysed using Fisher Exact test, while continuous and ordinal data were analysed with Student's t test or Wilcoxon signed-rank test, as appropriate. The odds of AE/SAE were calculated with Generalised Estimation Equation with the patient as the clustering unit. Quantitative TCD and angiogram measurements were analysed using hierarchical linear models, allowing nesting of multiple observations per patient. We calculated the difference between each specific vessel at prespecified locations and each patient's baseline, per previously published methods13 (details in online supplement), and adjusted this difference to each patient's baseline value. Unlike the daily per-protocol TCD assessments, angiograms were only performed when clinically indicated for suspected cVSP, with a small proportion undergoing follow-up angiogram during the infusion period. Therefore, we differentiated angiogram assessments as ‘during’ the infusion period, from ‘after’. Some patients received additional TCD examinations per clinical routine after the 7-day infusion period for suspicion of cVSP. Post hoc we assessed these TCD for ‘delayed TCD cVSP’, without quantitative analysis, as different examiners, but not our trained study TCD examiners, performed these studies. p Values <0.05 were considered significant. Analyses were performed using SAS V.9.3 (SAS Institute Inc, Cary, North Carolina, USA). Graphs were created using Prism 6.0 (GraphPad Software Inc, La Jolla, California, USA).


Of 134 patients screened, 32 patients were consented (24%), and 31 (23%) randomised (IV-D: n=16, placebo: n=15; figure 2). One patient withdrew consent prior to randomisation, as we were unable to comply with the request to receive active study drug only. Two patients in the placebo group withdrew consent during the infusion period for any subsequent blood draws or follow-up (‘nervous about research’), resulting in 13 patients analysed in the placebo group. Baseline characteristics all enrolled participants are presented in table 1 and see online supplementary table II, and revealed grossly balanced groups.

Table 1

Baseline characteristics

Figure 2

CONSORT diagram. The number of participants screened, enrolled, completed infusions and analysed is shown. Patients were not enrolled for various reasons listed.

Laboratory and physiological data

The proportion of participants who developed hyponatraemia (sNa ≤132 mmol/L) was similar between groups: seven (43.8%) in the IV-D, and 10 (66.7%) in the placebo group (p=0.29). At the same time, there was no difference in the number of participants on the step-wise sNa treatment protocol receiving fludrocortisone, and the total mEq hypertonic saline given (table 1). No differences were seen in the adjusted mean, nadir and difference between baseline and nadir sNa, as well as any of the other laboratory values, including liver function tests (see online supplementary table III). One IV-D participant experienced liver toxicity and required the drug to be stopped on the last infusion day (6.25% in IV-D group vs 0% in placebo group; p=1). This patient was on the lower dose of simvastatin (40 mg daily), received only two enteral phenytoin doses (300 mg daily) preinfusion, and no acetaminophen, phenytoin or fosphenytoin during the infusion period.

AE and tolerability

The most common AE was venous infiltration/irritation in four IV-D participants (none among placebo), which exclusively occurred in patients without central access, and were self-limited without the need for medical intervention (table 2). The total number of AE/SAEs in the IV-D versus placebo group was 17 versus 5 (OR 2.2, 95% CI 0.73 to 6.65, p=0.16), and SAE occurred in 5 vs 3, respectively. Of these SAEs, study drug was stopped in 4 versus 2 participants in the IV-D versus placebo group (tolerability rates 75% vs 87%, respectively).

Table 2

Adverse events

Vasospasm outcomes

All patients underwent daily TCD examinations during the infusion period; 6/16 (37.5%) in the IV-D and 8/13 (61.5%) required a follow-up cerebral angiogram for suspected cVSP (p=0.27), with 5 (31.3%) during and 4 (25%) after the infusion period in the IV-D group versus 5 (38.5%; p=0.71) during and 6 (46.2%; p=0.27) after the infusion in the placebo group. No statistically significant differences or trends between IV-D and placebo groups were seen in any categorical cVSP end points (figure 3). Quantitative TCD analyses showed higher mean velocities from baseline in the IV-D group in one vessel (PSV and MFV), and lower mean velocities in another vessel (PSV only; see online supplementary table IV and figure II) when compared to placebo. The quantitative angiogram analyses revealed no clinically meaningful efficacious or deleterious effects of IV-D on vessel diameters (see online supplementary table IV) during or after the infusion period. On postinfusion angiograms, compared to placebo, IV-D participants had a significantly larger mean diameter in one vessel, and a smaller mean diameter in another vessel (see online supplementary figure II).

Figure 3

Categorical vasospasm outcomes. Different predefined categories of vasospasm were analysed and shown. ‘Delayed’ transcranial Doppler (TCD) and angiogram vasospasm represents occurrence after the 7-day infusion period. This was analysed to determine presence of rebound vasospasm after the completion of study drug infusion. ‘TCD vasospasm’ refers to only the 7-day infusion period. Clinical vasospasm and delayed cerebral ischaemia (DCI) refer to the entire hospital course. p Values <0.05 were considered significant.

Clinical outcomes

In-hospital mortality was 2/16 (12.5%) in the IV-D, and 1/13 (7.7%) in the placebo group (p=1). Mean follow-up was 91±4 days post-aSAH in the IV-D group and 102±19 days in the placebo group, which had follow-up outliers at 152 and 129 days. One patient in the placebo group was lost to follow-up, with survival status derived from the medical record. Thirteen participants (81.3%) in the IV-D, and 12 (92.3%) in the placebo group survived to follow-up (p=0.61). Statistically, there were no differences in the 90-day functional outcomes, although more patients in the IV-D group were at the extremes of the mRS (0 or 6; figure 4).

Figure 4

Functional outcomes. Depicted are functional neurological outcomes at 3 months postaneurysmal subarachnoid haemorrhage. In the placebo group, two patients withdrew consent during the infusion period, and one patient was lost to follow-up. Figure legends indicate the number of participants for each scale category. Barthel Index is shown as median with IQR, and individual data points. p Values <0.05 were considered significant.


This randomised placebo-controlled trial in patients with aSAH at risk for cVSP demonstrates feasibility of repeated IV-D infusions in critically ill patients with aSAH over a 7-day period, and suggests safety. The number of AE/SAE was numerically higher in the IV-D group, not reaching statistical significance; yet more participants were treated with IV-D than placebo. We identified certain AE/SAE likely/possibly related to IV-D (venous infiltration, liver toxicity), which have to be regarded with great caution given the small sample size and require further evaluation in a larger trial. There were no differences, even trend-wise, in the categorical or quantitative cVSP analyses, but the trial was not powered to detect outcome efficacy. Proportionally fewer patients required angiography for suspected cVSP in the IV-D compared to placebo group, but this was not statistically significant.

Important clinical observations, confirmed by preclinical studies, and a plausible biological mechanism mediated by blockade of intracellular calcium release led to this trial. Our first observations on TCD were made during the administration of IV-D for shiver control associated with induced normothermia in patients with aSAH with cVSP. We incidentally observed improvement in TCD velocities in one patient shortly after a dose, and systematically studied this phenomenon in two additional patients before and after a dose of IV-D.7 Subsequently, in an ex vivo rat vasoconstriction model,4 and then in patients with aSAH receiving a single dose of IV-D, vasorelaxation was noted.8 Most recently, intra-arterially administered dantrolene induced a sustained improvement of severe, refractory cVSP in a single patient with aSAH.14

Dantrolene's additional advantageous effect, neuroprotection, should be specifically highlighted.2 ,3 ,15 ,16 Two recent large trials testing the endothelin-1 antagonist clazosentan for cVSP after aSAH17 ,18 dampened the enthusiasm for drugs only targeting vasoconstriction after aSAH. Both studies showed improvements in cVSP without gains in functional neurological outcome. Therefore, pharmacological interventions providing additional neuroprotective effects and not merely treating cVSP may offer more hope of improving outcome.

Our trial has several limitations. First, its single-centre design restricts generalisability. Next, instead of normal saline the placebo group consisted of free water with 5% mannitol to achieve the same equiosmolar solution as IV-D, which requires reconstitution in free water. Therefore, we could not differentiate whether the effects on hyponatraemia or brain oedema may have been due to IV-D or its solution. We chose this placebo over normal saline in this initial safety study to evaluate whether dantrolene itself, and not its solution, may have detrimental effects on patients with aSAH. Mannitol may have contributed to hyponatraemia; however, both groups received the same concentration of mannitol, and therefore a differential effect of mannitol on hyponatraemia on one of the treatment groups is unlikely. The small sample size warrants great caution when interpreting our outcomes, even when statistical significance lacked. Furthermore, 76% of patients screened were excluded. Looking closely at the screen failures, many patients were excluded because they were too sick and at extremely high risk for death, or were angio negative. The 7-day infusion time-period may not have covered the entire cVSP risk period, limiting full exploration of potential efficacy on cVSP and functional outcomes. We did observe, however, but did not systematically analyse, hesitancy of patients and surrogates to consent to the trial due to the never-previously-studied length of IV-D infusion. A 14-day infusion may have resulted in much lower consent rates, rendering the study protocol unfeasible. The method of block randomisation did not fully prevent group imbalances regarding baseline characteristics. However, we feel that the racial and minor imbalances in aneurysm location did not contribute to the primary outcome, and unlikely contributed to the secondary outcomes.19 Finally, difficulties with technique resulted in a very low number of TCD Lindegaard ratios. Therefore, we cannot confidently claim that elevated TCD velocities were due to cVSP.

To our knowledge, this is the first randomised trial of repeated IV-D infusions conducted in critically ill patients with aSAH. Its strengths include bias avoidance by randomisation, double blind design and treatment standardisation by protocols.


We have demonstrated that repeated IV-D infusions over 7 days are feasible, and likely safe and well tolerated in critically ill patients with aSAH. A larger multicentre study using normal saline as placebo is required to confirm safety and explore efficacy trends prior to moving to a phase-III trial.


The authors appreciate the tremendous support of the Lakeside2-ICU clinical staff for their support and adherence to study protocols. The authors thank the DSMB: Raul Nogueira, MD and Stephen Baker, MScPH, PhD (ABD).



  • Contributors SM designed the trial, obtained funding, implemented the trial, designed data collection tools, recruited patients, performed transcranial Doppler studies, monitored data collection for the whole trial, wrote the statistical analysis plan, cleaned and analysed the data, drafted and revised the paper. She is guarantor. RC recruited patients, performed transcranial Doppler studies and revised the paper. WH recruited patients and revised the paper. NK cleaned and analysed the data, drafted and revised parts of the paper. SI cleaned part of the data, performed quantitative angiogram measurements and monitored data collection for part of the trial. BG designed data collection tools, recruited patients, cleaned part of the data, performed quantitative angiogram measurements, performed transcranial Doppler studies, monitored data collection for part of the trial and revised the paper. CO recruited patients, cleaned part of the data, performed transcranial Doppler studies, monitored data collection for part of the trial and revised the paper. IMJV performed quantitative angiogram measurements and revised the paper. TFF performed quantitative angiogram measurements and revised the paper. MJG designed data collection tools, performed quantitative angiogram measurements, cleaned and analysed part of the data. JPW implemented the trial and revised the paper. BB wrote the statistical analysis plan, and analysed the data. He is guarantor. AKW implemented the trial and revised the paper.

  • Funding American Heart Association (09SDG2030022), Worcester Foundation for Biomedical Research, UMASS Medical School Faculty Scholar Award, UMASS Center for Clinical & Translational Science, funded by the National Center for Advancing Translational Sciences at the National Institutes of Health (NIH Grant #UL1TR000161). The study drug dantrolene (Dantrium IV) was donated by JHP Pharmaceuticals (Parsippany, New Jersey, USA).

  • Competing interests The study was entirely investigator-initiated.

  • Ethics approval UMASS Medical School Institutional Review Board.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.