Ryanodex Side Effects Center

Last updated on RxList: 5/24/2022
Ryanodex Side Effects Center

What Is Ryanodex?

Ryanodex (dantrolene sodium) is a skeletal muscle relaxant used to treat malignant hyperthermia in conjunction with appropriate supportive measures, and to prevent malignant hyperthermia in patients at high risk.

What Are Side Effects of Ryanodex?

Common side effects of Ryanodex include:

  • loss of grip strength
  • weakness in the legs
  • muscle weakness
  • drowsiness
  • dizziness
  • nausea
  • vomiting
  • blood clots
  • hives
  • flushing
  • difficulty speaking or swallowing
  • headache
  • blurred vision
  • pain in the extremities
  • fast heart rate, and
  • injection site reactions (pain, redness, swelling)

Dosage for Ryanodex?

Ryanodex is administered by intravenous push at a minimum dose of 1 mg/kg.

What Drugs, Substances, or Supplements Interact with Ryanodex?

Ryanodex may interact with calcium channel blockers, muscle relaxants, and antipsychotic and antianxiety drugs. Tell your doctor all medications and supplements you use.

Ryanodex During Pregnancy and Breastfeeding

During pregnancy, Ryanodex should be administered only if prescribed. It may harm a fetus. Ryanodex passes into breast milk. This drug is not recommended for use while breastfeeding.

Additional Information

Our Ryanodex (dantrolene sodium) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Ryanodex Consumer Information

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor right away if you have signs of liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, or jaundice (yellowing of the skin or eyes). These side effects may be most likely to occur between 3 and 12 months of your treatment with dantrolene.

Also call your doctor right away if you have:

  • severe drowsiness;
  • severe muscle weakness;
  • weak or shallow breathing;
  • severe or ongoing vomiting or diarrhea;
  • problems with vision or speech;
  • painful or difficult urination;
  • a seizure; or
  • a light-headed feeling, like you might pass out.

Common side effects may include:

  • dizziness, drowsiness;
  • diarrhea;
  • weakness; or
  • feeling tired.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Read the entire detailed patient monograph for Ryanodex (Dantrolene Sodium Injectable Suspension)


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Ryanodex Professional Information


Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In a study designed to evaluate the safety and tolerability of RYANODEX, healthy volunteers were randomly assigned to receive treatment with RYANODEX or an active comparator at doses ranging from 1 mg/kg to 2.5 mg/kg.

  • The RYANODEX dose was infused over the course of 1 minute for each of the doses evaluated.
  • The active comparator was an injectable formulation of dantrolene sodium that differed from RYANODEX in that it contained dantrolene sodium and mannitol at concentrations of 0.33 mg/mL and 50 mg/mL, respectively, when reconstituted according to the product's prescribing information. The active comparator was infused at a rate that administered 20 mg of dantrolene per minute for each of the doses evaluated.

Table 1 displays the most common adverse events in this study. These data are not an adequate basis for comparison of the types or frequencies of adverse event types between RYANODEX and the dantrolene sodium comparator.

Adverse events increased in frequency with increasing doses in the trial, but did not differ in frequency between the two treatment groups. RYANODEX-treated subjects were more likely to report immediate adverse events of flushing, dystonia, and dysphagia than those receiving the active comparator.

In all dose groups, hand grip strength declined after dosing. In general, the decline in hand grip strength was more pronounced and occurred more rapidly in the RYANODEX-treated subjects in the 1.0, 1.75, 2.0 and 2.25 mg/kg treatment groups. In the 2.5 mg/kg treatment group, the decline in hand grip strength both in amount and duration was similar between the two treatment groups.

Table 1: Adverse Events in Healthy Volunteers

Number of subjects (%)
[N=30] n (%)
Dantrolene Sodium Comparator
[N=31] n (%)
Flushing8 (27)1 (3)
Somnolence5 (17)4 (13)
Dysphonia4 (13)1 (3)
Dysphagia3 (10)4 (13)
Nausea3 (10)3 (10)
Feeling abnormal3 (10)3 (10)
Headache1 (3)4 (13)
Vomiting1 (3)2 (6)
Vision blurred1 (3)1 (3)
Pain in extremity1 (3)1 (3)
Muscular weakness/Asthenia1 (3)1 (3)
Atrioventricular block1 (3)0
Tachycardia1 (3)0
Infusion site pain1 (3)0
Dizziness1 (3)0

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of another formulation of dantrolene sodium for injection. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Pulmonary Edema

There have been reports of pulmonary edema developing during the treatment of malignant hyperthermia crises with another dantrolene sodium dosage form. The contributory effect of the diluent volume and mannitol in these cases is not known.

Thrombophlebitis And Tissue Necrosis

There have been reports of thrombophlebitis following administration of intravenous dantrolene. Tissue necrosis secondary to extravasation has been reported [see WARNINGS AND PRECAUTIONS].

Hypersensitivity/Anaphylactic Reactions

There have been reports of urticaria and erythema possibly associated with the administration of dantrolene sodium for injection. Anaphylaxis has been reported.

Injection Site Reactions

Injection site reactions including pain, erythema, and swelling, commonly due to extravasation, have been reported.

Read the entire FDA prescribing information for Ryanodex (Dantrolene Sodium Injectable Suspension)

© Ryanodex Patient Information is supplied by Cerner Multum, Inc. and Ryanodex Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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