New Dantrolene formulation
Last year (2024), SALG responded to a ‘Prevention of Future Deaths’ report that concerned a post-operative death, probably caused by serotonin syndrome and iatrogenic pulmonary oedema.
The use of Dantrium [Dantrolene Sodium] 20mg vials, used to treat the [misdiagnosed] condition of malignant hyperthermia, was thought to have contributed to the fluid overload that this patient suffered. Each vial requires 60ml of sterile water to reconstitute. The initial treatment dose is 2.5 mg/kg so a 72kg patient required 9 vials containing 540ml of water together with 27g (0.375 g/kg) of mannitol.
Since that time, Dantrium 20mg vials have been withdrawn from the UK market, and are being replaced by Dantrolene sodium hemiheptahydrate, produced by Agilus. This new formulation is presented in 120mg vials and does not contain mannitol. Each vial should be reconstituted with 20ml of sterile water, giving a volume of 22.6ml. The new formulation can be prepared more quickly as fewer drug vials with smaller volumes of water are required. The initial dose remains 2.5 mg/kg. Dose calculations can be made using the table from the Electronics Medicines Compendium, which should be kept along with the vials. It is reproduced below for information. The volume of drug required for a 72 kg patient is 33.9 ml.
SALG advises departments to replace Dantrium 20mg vials with this new formulation and due to the significant differences between the old and new, not to stock both formulations.
The following table provides examples of dosing based on the number of vials needed for the initial 2.5mg/kg dose, required immediately by rapid injection. Reproduced from: https://www.medicines.org.uk/emc/product/15912/smpc/print
Table 1. Dosing examples
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Dosing examples by body weight to achieve a loading dose of 2.5 mg/kg for both adults and children |
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Number of vials to be prepareda |
Body weight range |
Example dosing recommendation |
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Body weight |
Dose to be administered |
Volume to be administereda |
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1 |
Up to 48 kg |
3 kg |
7.5 mg |
1.4 mL |
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6 kg |
15 mg |
2.8 mL |
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12 kg |
30 mg |
5.6 mL |
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24 kg |
60 mg |
11.3 mL |
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48 kg |
120 mg |
22.6 mL |
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2 |
From 49 kg to 96 kg |
72 kg |
180 mg |
33.9 mL |
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96 kg |
240 mg |
45.2 mL |
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3 |
From 97 kg |
120 kg |
300 mg |
56.5 mL |
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144 kgb |
300 mgb |
56.5 mL |
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aTotal volume of one reconstituted vial is 22.6 mL.
bFor all bodyweights, the initial dose and any repeat doses should not exceed 300 mg, equivalent to 2.5 vials.
Date: 28/07/2025