Isoxsuprine
Isoxsuprine Hydrochloride
Also known as: Vasodilan · Voxsuprine · Caa-40 · isoxsuprini hydrochloridum · phenoxyisopropylnorsuprifen · Dilum · Duvadilan · Fadaespasmol · Fenam · Inibina · Isodilan · Isotenk · Uterine · Vadosilan · Vasolan · Vasosuprina Ilfi · Xuprin
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of 'Raynaud-like' disease | 1 mg/kg/day PO | PO | daily | — | 🌎 NA |
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Treatment of orthopedic conditions, such as navicular disease (For long break-over if therapeutic shoeing does not correct) | 1.2 mg/kg PO q8h for 3 weeks. The dose is decreased as soundness improves, to 1.2 mg/kg PO once daily for 6 weeks, then every other day until heel first landing occurs. | PO | q8h initially | 3 weeks initially, then tapered | 🌎 NA |
| Treatment of orthopedic conditions, such as navicular disease (To increase the circulation to the podotrochlea) | 0.6-1.2 mg/kg twice daily until sound, then decreased to once daily for 2 weeks then further decreased to every other day. | PO | twice daily initially | Until sound, then tapered | 🌎 NA |
| Treatment of orthopedic conditions | 0.6-2 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
| As a tocolytic agent | 0.4-0.6 mg/kg IM or PO twice daily | IM or PO | twice daily | — | 🌎 NA |
- Treatment of orthopedic conditions, such as navicular disease (For long break-over if therapeutic shoeing does not correct): Phenylbutazone is added if lameness is greater than grade II on a scale of I-V, or until recheck occurs. The drug is classified as a 'blocking' agent by the AHSA.
- As a tocolytic agent: Efficacy is unproven and oral bioavailability appears highly variable.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Isoxsuprine is a peripheral vasodilator primarily used in veterinary medicine for the management of navicular disease in horses, though its oral efficacy has been recently questioned due to poor bioavailability.
- Equine Use: Historically prescribed to improve blood flow to the hoof and podotrochlea. Also used anecdotally as a tocolytic agent.
- Canine Use: Anecdotally used for Raynaud's-like syndrome (periodic digital cyanosis, onychogryphosis).
- Avian Use: May improve microcirculation.
Clinical Pearl: Because of its significant first-pass metabolism, oral administration in horses often fails to achieve detectable plasma concentrations, leading many modern practitioners to question its clinical utility for navicular syndrome compared to other hemorrheologic agents like pentoxifylline.
Mechanism of action
Isoxsuprine acts as a beta-adrenergic agonist (specifically beta-2 receptors), though its vasodilatory effects may also stem from direct smooth muscle relaxation independent of beta-receptors.
- Vasodilation: Stimulates beta-2 receptors → increases intracellular cAMP → decreases intracellular calcium → vascular smooth muscle relaxation (primarily in skeletal muscle).
- Uterine Relaxation: Relaxes uterine smooth muscle, acting as a tocolytic agent.
- Hemorrheologic Effects: At high doses, it can decrease blood viscosity and reduce platelet aggregation.
- Cardiac Effects: May exhibit positive inotropic and chronotropic effects on the heart via beta-1 receptor stimulation.
- Analgesia: Does not appear to possess significant analgesic properties in horses.
Safety & warnings
Contraindications
- Immediately post-partum
- Presence of arterial bleeding
Adverse effects
- CNS stimulation (uneasiness, hyperexcitability, nose-rubbing)
- Sweating
- Hypotension
- Tachycardia
- Gastrointestinal disturbances
Precautions
Warning: Do not administer immediately post-partum or in the presence of active arterial bleeding due to its vasodilatory properties.
- Pregnancy: FDA Category C (animal studies show adverse fetal effects; use with caution).
- Lactation: Safety is unknown.
- Regulatory: Classified as an ARCI Class 4 drug and a 'blocking' agent by the AHSA.
Monitoring
- Clinical efficacy (improvement in lameness or digital circulation)
- Adverse effects (tachycardia, GI disturbances, CNS stimulation)
Pharmacokinetics
Half-life
Absorption
In humans, almost completely absorbed from the GI tract. In horses, bioavailability is low after oral administration, probably due to a high first-pass effect.
Metabolism
Undergoes significant first-pass metabolism in horses.
Overdose
Serious toxicity is unlikely in horses after an inadvertent oral overdose due to poor bioavailability.
- Clinical Signs: CNS stimulation (uneasiness, hyperexcitability, nose-rubbing), sweating, hypotension, tachycardia, and GI disturbances.
- Treatment: Provide supportive care. Treat CNS hyperexcitability with diazepam, and hypotension with intravenous fluids.
Available products
Formulations
- Tablets
Human-labeled
- Isoxsuprine HCl Tablets: 10 mg & 20 mg (Vasodilan, Voxsuprine, generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Tablets should be stored in tight containers at room temperature (15-30°C).
Client information
- Consistency is Key: To be maximally effective, doses must be given routinely exactly as directed by your veterinarian.
- Administration Tip: Tablets may be crushed and mixed into a slurry or paste using corn syrup or cherry syrup just before administration to make it more palatable for your animal.
- What to Watch For: Contact your veterinarian if you notice signs of restlessness, excessive sweating, rapid heart rate, or gastrointestinal upset.
- Storage: Keep tablets in a tightly sealed container at room temperature.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.