Dantrolene
Dantrolene is used in veterinary medicine for malignant hyperthermia.
Group
Direct skeletal muscle relaxant
Mechanism of Action
Inhibits sarcoplasmic-reticulum calcium release through ryanodine receptors.
Dose Rates
Dog
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Malignant hyperthermia prevention | 2–3 mg/kg | IV | Canine regimens are empirical; pharmacokinetic studies question whether these doses achieve effective muscle concentrations. Higher 5–10 mg/kg doses have been cited but are not routine escalation targets. | |
| Malignant hyperthermia crisis | 2.5–3 mg/kg | IV | Canine regimens are empirical; pharmacokinetic studies question whether these doses achieve effective muscle concentrations. Higher 5–10 mg/kg doses have been cited but are not routine escalation targets. | |
| Muscle relaxation | 1–5 mg/kg | PO | Every 8 h | Canine regimens are empirical; pharmacokinetic studies question whether these doses achieve effective muscle concentrations. Higher 5–10 mg/kg doses have been cited but are not routine escalation targets. |
| Urethral relaxation | 1–5 mg/kg | PO | Every 8 h | Canine regimens are empirical; pharmacokinetic studies question whether these doses achieve effective muscle concentrations. Higher 5–10 mg/kg doses have been cited but are not routine escalation targets. |
| Urethral relaxation | 0.5–1 mg/kg | IV | Canine regimens are empirical; pharmacokinetic studies question whether these doses achieve effective muscle concentrations. Higher 5–10 mg/kg doses have been cited but are not routine escalation targets. | |
| Hops-associated hyperthermia | 2–3 mg/kg | IV | As soon as possible after ingestion; intensive supportive treatment is also required. | |
| Hops-associated hyperthermia | 3.5 mg/kg | PO | Alternative route reported for hops-associated syndrome; not an additional dose on top of IV treatment. | |
| Rhabdomyolysis case report | Reference only | PO | A published case used 1.5 mg/kg every 8 hours alongside intensive multidrug and supportive care; not a general-purpose regimen. | |
| Urethral relaxation | 1–5 mg/kg | PO | Every 8–12 h | |
| Urethral relaxation | 1 mg/kg | PO | Every 8 h | |
| Malignant hyperthermia | 0.2–3 mg/kg | IV | ||
| Black widow envenomation | Reference only | IV | Adjunctive regimen: 1 mg/kg IV, then 1 mg/kg orally every 4 hours. |
Cat
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Muscle relaxation | 0.5–2 mg/kg | PO | Every 12 h | |
| Urethral relaxation | 1–2 mg/kg | PO | Every 8 h | |
| Urethral relaxation | 1 mg/kg | IV | ||
| Urethral relaxation | 0.5–2 mg/kg | PO | Every 12 h | |
| Urethral relaxation | 0.5–1 mg/kg | IV | ||
| Urethral relaxation | 0.5–2 mg/kg | PO | Every 8 h | |
| Urethral relaxation | 0.5–1 mg/kg | PO | Every 12 h | |
| Urethral relaxation with alpha blockade | Reference only | PO | Dantrolene 2–10 mg/cat every 8 hours combined with either prazosin 0.5 mg/cat every 12–24 hours or phenoxybenzamine 2.5–7.5 mg/cat every 12–24 hours. |
Horse
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Muscle relaxation | 500 mg/animal | PO | Common empirical fixed amount; optimum preanesthetic and rhabdomyolysis regimens are not established. | |
| Muscle relaxation | 4 mg/kg | PO | Alternative studied weight-based regimen; clinical efficacy evidence is limited. | |
| Acute rhabdomyolysis | 2–4 mg/kg | PO | Every 24 h | Administered through a nasogastric tube in the cited regimen. |
| Recurrent exertional rhabdomyolysis prevention | 4 mg/kg | PO | Studied in Thoroughbreds after a 12-hour fast; efficacy is condition dependent. | |
| Rhabdomyolysis prevention taper | Reference only | PO | One regimen uses 2 mg/kg daily for 3–5 days, then every third day for one month. Fixed-dose alternatives use 300 mg daily, or 500 mg daily for 3–5 days followed by 300 mg every third day; choose a regimen rather than combining them. | |
| Pre-exercise rhabdomyolysis prevention | 800 mg | PO | Give one hour before exercise; disperse in 9 mL water and administer within 30 minutes. | |
| Perianesthetic myopathy prevention | Reference only | PO | Reported alternatives: 6 mg/kg by nasogastric tube 60 minutes before anesthesia; or 10 mg/kg 90 minutes beforehand with further 2.5 mg/kg doses hourly. IV alternatives were 1.9 mg/kg for about 20 minutes of anesthesia or 4 mg/kg for about 2 hours. These distinct procedural regimens are not interchangeable. | |
| High-dose acute rhabdomyolysis protocol | Reference only | IV | The additional text reports 15–25 mg/kg slowly IV four times daily. This is markedly inconsistent with other supplied equine doses; the amount is not enabled for calculation pending resolution. |
Pig
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Malignant hyperthermia crisis | 1–3 mg/kg | IV | Once | |
| Malignant hyperthermia prevention | 5 mg/kg | PO | ||
| Malignant hyperthermia | 3.5 mg/kg | IV |
Indications
- Malignant hyperthermia
- Skeletal muscle relaxation
- Urethral relaxation
- Exertional rhabdomyolysis
Contraindications
- Hepatic disease; use cautiously with weakness or debilitation
Interactions
- Acidic solutions are incompatible with the IV preparation.
Adverse effects
- Weakness
- Hyperkalemia, bradycardia and arrhythmias
- Hepatic injury
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Dantrolene 100 mg capsule | Capsule | 100 mg / capsule | PO |
| Dantrolene conventional injection 0.33 mg/mL Conventional 20 mg vial after prescribed reconstitution. | Injection | 0.33 mg / mL | IV |
| Dantrolene concentrated injection 50 mg/mL 250 mg presentation after prescribed reconstitution; not interchangeable by volume with conventional injection. | Injection | 50 mg / mL | IV |
Monitoring and Administration
Monitor temperature, acid–base status, potassium, ECG and hepatic enzymes.
Oral administration is usually on an empty stomach. Equine capsules may be dispersed in water or made into a paste.
Reconstituted conventional injection has a short use period; reject cloudy or precipitated solution. Concentrated and conventional vials require different reconstitution instructions.
Monitor baseline and serial liver enzymes during chronic or high-dose treatment; assess urinary function when used for urethral relaxation.
Older high-dose equine IV and peri-anesthetic protocols differ substantially from routine regimens; they require separate clinical verification before use.