Dimethyl Sulfoxide (DMSO)
**Dimethyl Sulfoxide (DMSO)** is a highly versatile, dipolar, aprotic solvent with unique pharmacological properties. It is primarily utilized in veterinary medicine as a **free radical scavenger** and **topical anti-inflammatory** agent. * **Primary Approved Use:** FDA-approved as a topical application to reduce acute swelling due to trauma in dogs and horses. * **Off-Label Uses:** Adjunctive treatment for CNS trauma, cerebral edema, transient ischemic conditions, skin ulcers, burns, intestinal surgeries, amyloidosis, and limitation of tissue damage following chemotherapeutic extravasation (e.g., doxorubicin). * **Penetration Enhancer:** DMSO easily penetrates intact skin and biological membranes without causing irreversible damage. It acts as a powerful carrier agent, promoting the percutaneous absorption of other drugs (e.g., corticosteroids, antibiotics, analgesics) and potentially toxic compounds. * **Clinical Pearls:** Because it is extremely hygroscopic, it will self-dilute if left exposed to room air. Medical-grade DMSO must be used to avoid carrying industrial impurities into the systemic circulation.
Mechanism: DMSO exhibits a diverse array of pharmacological effects through multiple pathways: * **Free Radical Scavenging:** DMSO directly traps the **free radical hydroxide (OHโข)**, while its primary metabolite, **dimethyl sulfide (DMS)**, traps free radical oxygen. This mechanism underpins its anti-inflammatory, cryopreservative, anti-ischemic, and radioprotective qualities. * **Enzyme Inhibition:** Inhibits **alcohol dehydrogenase** โ slows the metabolism of alcohol and prevents the conversion of ethylene glycol into its toxic metabolites (making it a potential, though less common, antidote for antifreeze toxicity). * **Prostaglandin Modulation:** Enhances **Prostaglandin E (PGE)** but blocks the synthesis of **PGE2, PGF2-alpha, PGH2, and PGG2**, contributing to its analgesic and anti-inflammatory effects. * **Vascular Effects:** Provokes **histamine** release from mast cells โ local vasodilation. It also decreases platelet aggregation. * **Neuromuscular:** Exhibits weak **anticholinesterase** activity.
Dosing by species
- Acute swelling due to trauma ยท Liberal application should be administered topically to the skin over the affected area 2-3 times daily. Total daily dosage should not exceed 100 grams (or mL of liquid) ยท topical ยท q8-12h ยท Max 30 days
- Adjunctive treatment with surgical colics ยท 25 mg/kg IV intraoperatively and continued twice daily for the first 24-48 hours post-op. ยท IV ยท q12h ยท 24-48 hours ยท Administer slowly at 10% concentration.
- Acute rhabdomyolysis ยท 1 g/kg in a 10% solution of lactated Ringer's or Multisol IV or orally. ยท IV/PO ยท once ยท May be given in the acute stages once hydration status has been restored.
- Adjunctive treatment for laminitis ยท 0.1-1 g/kg IV, 2-3 times daily ยท IV ยท q8-12h ยท Administer slowly at 10% concentration.
- Acute swelling due to trauma ยท Liberal application should be administered topically to the skin over the affected area 3-4 times daily. Total daily dosage should not exceed 20 grams (or mL of liquid) ยท topical ยท q6-8h ยท Max 14 days
- Calcinosis cutis ยท Apply topically to a small area of the body initially (if extensive areas are involved) once daily; and as these areas improve, add new treatment areas. ยท topical ยท q24h ยท Dogs may 'feel bad' if large areas are treated initially, but do not become hypercalcemic.
- Persistent cases of hemorrhagic cystitis (secondary to cyclophosphamide tx) ยท 10 mL of DMSO medical grade 50% solution is diluted with 10 mL of water and instilled into bladder and removed after 20 minutes. ยท intravesical ยท once ยท 20 minutes
Routes of administration
Contraindications
- Mastocytomas (due to mast cell degranulation)
- Dehydration or shock (diuretic and vasodilatory effects may exacerbate)
- Pregnancy (teratogenic at high doses in some species; use with extreme caution)
Adverse effects
- Local 'burning', erythema, vesiculation, and dry skin (topical)
- Garlic or oyster-like breath odor
- Lenticular changes (myopia) with chronic high doses
- Hemolysis and hemoglobinuria (IV in horses, especially at >10% concentration or rapid administration)
- Diarrhea, muscle tremors, and colic (IV in horses)
- Rare hepatotoxicity and renal toxicity
Drug interactions
- Organophosphates / Cholinesterase Inhibitors ยท Avoid concurrent use due to DMSO's anticholinesterase activity.
- Mercury salts ยท Can cause fatal mercury intoxication if mixed and applied topically.
- Alcohol ยท DMSO inhibits alcohol dehydrogenase and may prolong the effects of alcohol.
- Insulin ยท May be potentiated by DMSO.
- Corticosteroids ยท May be potentiated by DMSO.
- Atropine ยท May be potentiated by DMSO.
- Topical toxins or other topical medications ยท Profound enhancement of systemic absorption of the co-administered substance, potentially leading to systemic toxicity. ยท major
- Dexrazoxane ยท DMSO may decrease the activity and efficacy of dexrazoxane; concurrent use should be discouraged. ยท moderate
Monitoring
- Clinical efficacy (reduction in swelling/inflammation)
- Hemoglobinuria and hematocrit (especially in horses receiving IV therapy)
- Ophthalmic exams (with high doses or chronic use in dogs to monitor for lenticular changes)
Overdose
The reported LD50 following IV dosage is approximately 4 g/kg in cats and 2.5 g/kg in dogs. **Clinical Signs of Toxicity:** * *Non-lethal doses:* Sedation and hematuria. * *Higher dosages:* Coma, seizures, opisthotonus, dyspnea, and pulmonary edema. **Treatment:** Should an acute overdosage be encountered, treat supportively.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.