Metolazone
Medication Facts
- Performance enhancing
- Yes
- Total hours to clear
- Not Published
- Frequently used
- N/A
- ESC ID
- METOLA-0577
- Trade names
- N/A
- Drug type
- Diuretic
- Plasma half-life · hours
- Not Published
- Equine dosing
- Consult veterinarian
- Cmax · peak plasma concentration
- N/A
- Tmax · time to peak plasma concentration
- N/A
- ESC concentration guidance
- May not exceed (LDL) Lowest Detectable Level of .05 ng/mL or 50 picograms per mL
- Primary withdrawal · hours
- 72
- Washout withdrawal · hours
- Not Applicable
- ESC control type
- B1 - Strictly Controlled - Conditionally PE
- Medication report required
- MED REPORT REQUIRED
Uses & side effects
Product-specific side effects await source review.
Drug interactions
In horses, the most critical drug interactions for diuretics (primarily loop diuretics like furosemide) involve NSAIDs, aminoglycoside antibiotics, corticosteroids, and cardiac glycosides, all of which can severely increase the risk of kidney damage or dangerous electrolyte imbalances.Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)Reduced Efficacy: Combining loop diuretics with common NSAIDs like phenylbutazone (Bute) or flunixin meglumine (Banamine) decreases the diuretic effect by roughly 25%.Blunted Hemodynamics: NSAIDs inhibit prostaglandins, which blocks the immediate, beneficial blood-vessel-widening effects that furosemide normally provides.Kidney Strain: Concurrent administration drastically spikes the risk of renal papillary necrosis and acute kidney injury due to restricted renal blood flow.COX-2 Selectives: Newer COX-2 selective NSAIDs like firocoxib (Equioxx) still cause a similar reduction in diuresis and present comparable kidney risks.Nephrotoxic AntibioticsAminoglycosides: Medications like gentamicin or amikacin are inherently tough on equine kidneys.Synergistic Toxicity: Because diuretics cause mild dehydration and lower blood volume, they slow down how fast the kidneys clear these antibiotics. This significantly amplifies the risk of severe kidney failure and ear toxicity.CorticosteroidsSevere Potassium Depletion: Both corticosteroids (such as dexamethasone or prednisolone) and loop diuretics flush potassium out of the body.Hypokalemia: Stacking these drugs can result in profound potassium deficits, leading to muscle weakness, lethargy, and heart arrhythmias.Cardiac MedicationsDigoxin: If a horse is being treated with digoxin for heart failure, furosemide-induced potassium loss makes the heart much more sensitive to the drug. This routinely triggers severe digitalis toxicity.ACE Inhibitors: Combining diuretics with blood pressure medications (like enalapril) can cause a sudden drop in blood pressure and drastically reduced blood flow to the kidneys, potentially causing permanent organ damage.Diagnostic and Regulatory NotesDoping Screen Interference: Furosemide heavily dilutes urine, which can lower the concentration of other drugs (like Bute) up to 18-fold. This makes routine pre-race urinalysis testing highly unreliable for regulatory bodies.