Dantrolene

What is dantrolene?

Dantrolene is a muscle relaxant used to help relax the urinary tract and improve urine flow in cats and dogs. It has also been used to help prevent muscle contractions caused by certain toxicities (e.g., black widow spider bites) in dogs and malignant hyperthermia in miniature pigs and dogs.

It is used off label (extra label) in veterinary medicine. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet dantrolene?

• Dantrolene comes in oral capsule form and as a powder to be reconstituted for injection.
• Capsules are given orally (by mouth). Injectable forms are given intravenously (into a vein) by your veterinarian.
• This medication should be given on an empty stomach. 
• If your animal vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with a small amount of food or a small treat. If vomiting continues, contact your veterinarian.  
• Give this medication to your pet for the entire time prescribed by your veterinarian, even if it appears that your pet is feeling better.

This medication should take effect within 1 to 2 hours.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then wait the recommended time as prescribed by your veterinarian for the next dose. Do not give the pet two doses at once.

Are there any potential side effects from dantrolene?

Dantrolene may cause the following side effects:

• Vomiting, nausea
• Weakness, sleepiness
• Constipation
• Increased need to urinate

The following reactions are rare, but if they occur, contact your veterinarian immediately:

• An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face
• Collapse
• Signs of liver toxicity (e.g., severe vomiting, jaundice/yellowing of the skin, severe and/or bloody diarrhea, not eating, painful abdomen, seizures)

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses, but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment. Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

DO NOT USE dantrolene in pets who:

• Are allergic to any component of the medication 

USE WITH CAUTION in pets who:

• Have liver disease
• Have heart or lung disease

Are there any drug interactions I should be aware of?

Certain medications should be USED WITH CAUTION when given with dantrolene, including: 

• Benzodiazepines (e.g., diazepam)
• Calcium-channel blockers (e.g., amlodipine)
• CNS depressants (e.g., cannabidiol, methocarbamol, phenobarbital)
• Estrogens (e.g., diethylstilbestrol)
• Opioids and similar drugs (e.g., fentanyl, buprenorphine)

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Your veterinarian may assess baseline blood work (including liver values and potassium) prior to starting the medication and periodically throughout treatment.
• Your veterinarian may schedule follow-up visits for monitoring. In this case, follow your veterinarian’s directions.
• At home, monitor urine output for any abnormal changes. If any occur, discontinue the medication and contact your veterinarian.

How do I store dantrolene?

• Store at room temperature of 68°F-77°F (20°C-25°C) in a tightly closed container, protected from light.
• Follow storage and expiration recommendations for specially compounded formulas.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Adverse effects should be reported to the FDA or Health Canada.