# Dantrolene: veterinary dose and monograph

> Dantrolene is a veterinary drug. A direct-acting skeletal-muscle relaxant and the specific ANTIDOTE for MALIGNANT HYPERTHERMIA (MH) — the life-threatening hypermetabolic crisis triggered by volatile anaesthetics/succinylcholine (notably in susceptible PIGS, and rarely… Indications include malignant hyperthermia crisis — specific antidote (IV); prevention of MH in known-susceptible patients (pigs) before triggering anaesthesia; equine exertional rhabdomyolysis ("tying-up") — prevention/management (oral). This monograph lists 7 reference doses for dogs, cats, horses and pigs, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/dantrolene · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Dantrium, Revonto, Ryanodex
- **Species with doses:** Dogs, Cats, Horses and Pigs
- **General dose range:** 1–5 mg/kg IV as needed (MH crisis) / q8–12h (oral) — check the species tables for the indication
- **Routes:** IV, PO
- **Last reviewed:** 1 October 2026

## Indications

- Malignant hyperthermia crisis — specific antidote (IV)
- Prevention of MH in known-susceptible patients (pigs) before triggering anaesthesia
- Equine exertional rhabdomyolysis ("tying-up") — prevention/management (oral)
- Functional (reflex dyssynergia) urethral obstruction — external urethral sphincter relaxation

## Dantrolene dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Dantrolene doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Malignant hyperthermia (IV) | 2–3 mg/kg | IV | repeat to effect (up to ~10 mg/kg total) | — |
| Functional urethral obstruction (oral) | 1–5 mg/kg | PO | q8–12h | — |

- Malignant hyperthermia (IV): Papich 5e: prevention 2–3 mg/kg IV; crisis 2.5–3 mg/kg rapid IV bolus (up to 5–10 mg/kg) — canine doses are anecdotal/extrapolated. Plumb’s p.347: acute attack 0.2–3 mg/kg IV (Axlund); hops toxicosis 2–3 mg/kg IV or 3.5 mg/kg PO ASAP (Wismer). Also stop the trigger, cool actively, give 100% oxygen and treat hyperkalaemia/acidosis.
- Functional urethral obstruction (oral): Papich 5e: 1–5 mg/kg PO q8h (or 0.5–1 mg/kg IV). Plumb’s p.347: 1–5 mg/kg PO q8–12h (Lane; Coates); 1 mg/kg PO q8h (Lulich). Relaxes the striated external urethral sphincter — combine with an alpha-blocker (prazosin) for the smooth-muscle component. Hepatotoxic with chronic use.

### Cats

*Dantrolene doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Functional urethral obstruction / muscle relaxation | 0.5–2 mg/kg | PO | q8–12h | — |

- Functional urethral obstruction / muscle relaxation: Papich 5e: muscle relaxation 0.5–2 mg/kg PO q12h; urethral relaxation 1–2 mg/kg PO q8h. Plumb’s p.347: 0.5–2 mg/kg PO q12h or 0.5–1 mg/kg IV (Gunn-Moore); 0.5–2 mg/kg three times daily (Coates); 2–10 mg per cat three times daily with prazosin or phenoxybenzamine (Sparkes). Monitor for weakness and hepatotoxicity.

### Horses

*Dantrolene doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Exertional rhabdomyolysis ("tying-up") prevention | 2–4 mg/kg | PO | once daily (≈1 h before exercise, after a fast) | — |
| Post-anaesthetic myopathy prevention | 6–10 mg/kg | PO | once, 60–90 min before anaesthesia | — |

- Exertional rhabdomyolysis ("tying-up") prevention: Papich 5e: most commonly 500 mg per horse PO, or 4 mg/kg PO. Plumb’s p.347: 4 mg/kg PO to fasted horses (McKenzie 2003); 2 mg/kg PO once daily for 3–5 days then every 3rd day for a month, or 300 mg per horse daily (MacLeay — efficacy uncertain); 800 mg per horse 1 h before exercise (Edwards). Monitor liver function.
- Post-anaesthetic myopathy prevention: Plumb’s p.347: 6 mg/kg via nasogastric tube 60 min before anaesthesia (McKenzie & Mosley 2009); 10 mg/kg intragastric 1.5 h before surgery, with 2.5 mg/kg q60min if more is needed (Court 1987).

### Pigs

*Dantrolene doses for pigs*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Malignant hyperthermia (treatment) | 1–3.5 mg/kg | IV | once IV | — | Withdrawal NOT established — treat as extra-label |
| Malignant hyperthermia prophylaxis | 5 mg/kg | PO | once before anaesthesia | — | Withdrawal NOT established — treat as extra-label |

- Malignant hyperthermia (treatment): Papich 5e: 1–3 mg/kg IV once. Plumb’s p.347 (Booth 1988): 3.5 mg/kg IV. Obtain a FARAD withdrawal before slaughter.
- Malignant hyperthermia prophylaxis: Papich 5e: 5 mg/kg PO for prophylaxis in susceptible (RYR1) pigs. Obtain a FARAD withdrawal.

## Contraindications

Significant hepatic impairment (oral dantrolene is hepatotoxic with chronic use). Known hypersensitivity. (For tying-up prevention, give on an empty stomach for absorption.) Use the IV form promptly in an MH crisis. Avoid extravasation (irritant).

## Species-specific warnings

> **Caution:** Pigs: Pigs (RYR1/halothane-sensitive) are the classic malignant-hyperthermia species — pre-treat known-susceptible pigs and have IV dantrolene ready for triggered crises.

## Adverse effects

- Muscle weakness
- Sedation, lethargy
- Hepatotoxicity (chronic oral use)
- GI upset; phlebitis/irritation (IV)

## Drug interactions

- Volatile anaesthetics/succinylcholine: the MH triggers (dantrolene is the antidote)
- Calcium-channel blockers (verapamil/diltiazem) with IV dantrolene: risk of hyperkalaemia/cardiovascular collapse — avoid the combination
- Other CNS depressants/muscle relaxants: additive weakness/sedation
- Hepatotoxic drugs: additive (chronic oral use)

## Pregnancy and lactation

Used when needed for an MH crisis (life-threatening); limited routine data otherwise.

## Monitoring

- In MH: temperature, EtCO2, ECG/heart rate, potassium and acid–base (treat the crisis comprehensively)
- Muscle strength / respiration (weakness)
- Liver enzymes with chronic oral use
- Response of tying-up/urethral function for those indications

## Toxicity and overdose

Overdose causes excessive muscle weakness, sedation, and (chronic oral use) hepatotoxicity. The acute injectable, used appropriately in MH, is lifesaving; the chief chronic concern is dose-related hepatotoxicity with oral therapy.

Management: No specific antidote. Supportive — support ventilation if weakness compromises breathing, monitor and protect the airway; for hepatotoxicity, discontinue and provide hepatoprotection/monitoring. Avoid IV dantrolene + calcium-channel-blocker combination.

## Clinical pearls

- THE antidote for malignant hyperthermia — give IV immediately (with stopping the trigger, cooling, 100 % O2, treating hyperkalaemia/acidosis); stock it where volatile anaesthesia/MH-susceptible pigs are involved
- Reconstitution is slow (poorly soluble) — know your product (Ryanodex is faster) and have it ready before a crisis
- Orally, it helps prevent equine "tying-up" (give on an empty stomach before exercise) and relaxes the external urethral sphincter in functional obstruction (pair with an alpha-blocker)
- Avoid IV dantrolene with calcium-channel blockers (hyperkalaemia/collapse); watch the liver on chronic oral use

## Mechanism of action

Binds the skeletal-muscle ryanodine receptor (RyR1) on the sarcoplasmic reticulum and inhibits calcium release into the cytoplasm, uncoupling excitation from contraction — directly relaxing skeletal muscle WITHOUT acting at the neuromuscular junction. In malignant hyperthermia, this halts the uncontrolled sarcoplasmic calcium release that drives the hypermetabolic crisis; the same action reduces the muscle hyperactivity of rhabdomyolysis and relaxes the striated urethral sphincter.

## Formulations and products

- Injection 20 mg vial (reconstitute) / 250 mg Ryanodex vial
- 25 / 50 / 100 mg capsule (oral)
- Dantrium / Revonto / Ryanodex — 20 mg / 250 mg vial; 25–100 mg capsule, Injection / capsule (human-label)

## Storage

IV vials: protect from light; reconstitute per label just before use (poorly soluble — Ryanodex reconstitutes faster). Capsules: 15–30 °C, dry. Have it readily available where MH risk exists.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

## Other hormones, emergency drugs, supplements and other drugs

- [Cyanocobalamin (Vitamin B12)](https://vetmasterji.com/drugs/cyanocobalamin)
- [Cyclophosphamide](https://vetmasterji.com/drugs/cyclophosphamide)
- [Cyclosporine](https://vetmasterji.com/drugs/cyclosporine)
- [Cyproheptadine](https://vetmasterji.com/drugs/cyproheptadine)
- [Deferoxamine (Desferrioxamine)](https://vetmasterji.com/drugs/deferoxamine)
- [Deslorelin](https://vetmasterji.com/drugs/deslorelin)
- [Desmopressin (DDAVP)](https://vetmasterji.com/drugs/desmopressin)
- [Desoxycorticosterone Pivalate (DOCP)](https://vetmasterji.com/drugs/desoxycorticosterone)

## Frequently asked questions

### What is the dose of Dantrolene for dogs?

Reference doses for Dantrolene in dogs: 2–3 mg/kg IV repeat to effect (up to ~10 mg/kg total) (Malignant hyperthermia (IV)); 1–5 mg/kg PO q8–12h (Functional urethral obstruction (oral)). Confirm against the label and the patient before use.

### What is the dose of Dantrolene for cats?

Reference doses for Dantrolene in cats: 0.5–2 mg/kg PO q8–12h (Functional urethral obstruction / muscle relaxation). Confirm against the label and the patient before use.

### What is the dose of Dantrolene for horses?

Reference doses for Dantrolene in horses: 2–4 mg/kg PO once daily (≈1 h before exercise, after a fast) (Exertional rhabdomyolysis ("tying-up") prevention); 6–10 mg/kg PO once, 60–90 min before anaesthesia (Post-anaesthetic myopathy prevention). Confirm against the label and the patient before use.

### What is the withdrawal period for Dantrolene?

Pigs, IV (Malignant hyperthermia (treatment)): Withdrawal NOT established — treat as extra-label; Pigs, PO (Malignant hyperthermia prophylaxis): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Dantrolene not be used?

Significant hepatic impairment (oral dantrolene is hepatotoxic with chronic use). Known hypersensitivity. (For tying-up prevention, give on an empty stomach for absorption.) Use the IV form promptly in an MH crisis. Avoid extravasation (irritant).

### What are the side effects of Dantrolene in animals?

Muscle weakness; Sedation, lethargy; Hepatotoxicity (chronic oral use); GI upset; phlebitis/irritation (IV).

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

---

VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.