Paromomycin Sulfate — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	10-20 mg/kg	q12h	Duration: 5-7 days Notes: For giardiasis, often used in combination with metronidazole or fenbendazole.
Cat	PO	10-20 mg/kg	q12h	Duration: 5-7 days Notes: For giardiasis, often used in combination with metronidazole or fenbendazole.
Horse (foal)	PO	25-50 mg/kg	q24h	Duration: 5-7 days Notes: For Lawsonia intracellularis, may be used for 7 days or longer.
Cattle (calf)	PO	50-100 mg/kg	q24h	Duration: 3-5 days Notes: For cryptosporidiosis, may be used at higher doses; not FDA-approved for this use.
Small Ruminants (lamb/kid)	PO	50-100 mg/kg	q24h	Duration: 3-5 days Notes: For cryptosporidiosis, may be used at higher doses; not FDA-approved for this use.
Rabbit	PO	20-50 mg/kg	q12h	Duration: 5-7 days Notes: Use with caution due to risk of GI dysbiosis.
Poultry	PO (in water)	50-100 mg/kg body weight	q24h	Duration: 3-5 days Notes: Administer in drinking water; ensure adequate water intake.

Clinical Indications & Species Uses

General Indications

Treatment of intestinal infections caused by susceptible organisms
Treatment of protozoal infections such as giardiasis, cryptosporidiosis, and amebiasis

Dog (Canine)

Treatment of intestinal infections caused by susceptible bacteria (e.g., Salmonella, E. coli)
Treatment of giardiasis (in combination with other drugs)
Adjunct in treatment of cryptosporidiosis

Cat (Feline)

Treatment of intestinal infections caused by susceptible bacteria
Treatment of giardiasis (in combination with other drugs)
Adjunct in treatment of cryptosporidiosis

Horse (Equine)

Treatment of intestinal infections (e.g., Salmonella, Clostridium) in foals
Treatment of proliferative enteropathy (Lawsonia intracellularis) in foals

Cattle (Bovine)

Treatment of bacterial enteritis in calves (e.g., E. coli, Salmonella)
Treatment of cryptosporidiosis in calves (off-label)

Small Ruminants (Sheep / Goat)

Treatment of bacterial enteritis in lambs and kids
Treatment of cryptosporidiosis (off-label)

Rabbit & Small Mammals

Treatment of intestinal infections (e.g., Clostridium, E. coli)
Treatment of coccidiosis (off-label)

Avian & Poultry

Treatment of bacterial enteritis in poultry (e.g., Salmonella, E. coli)
Treatment of histomoniasis (blackhead) in turkeys (off-label)

Exotic & Other Species

Treatment of intestinal infections in reptiles (e.g., Salmonella)
Treatment of giardiasis in small mammals (off-label)

Pharmacology & Mechanism of Action

Drug Class: Aminoglycoside antibiotic | Pharmacological Group: Antibacterial, antiprotozoal

Mechanism of Action: Paromomycin is an aminoglycoside antibiotic that binds to the 30S ribosomal subunit of susceptible bacteria, causing misreading of the genetic code and inhibition of protein synthesis. It is bactericidal and also has antiprotozoal activity against certain parasites such as Entamoeba histolytica, Giardia lamblia, and Cryptosporidium parvum. Its action is primarily in the gastrointestinal tract when given orally, as it is poorly absorbed.

Pharmacodynamics: Paromomycin exerts its antibacterial effect by interfering with protein synthesis, leading to cell death. It is active against many gram-negative and some gram-positive bacteria, as well as certain protozoa. Its efficacy is pH-dependent, with optimal activity in alkaline environments. In veterinary medicine, it is used mainly for its local effects in the gut, as systemic absorption is minimal after oral administration.

⚡ Pharmacokinetics Summary

Absorption: Paromomycin is poorly absorbed from the gastrointestinal tract after oral administration. In ruminants, it may be partially degraded by ruminal microflora. Systemic absorption is minimal, making it suitable for local treatment of intestinal infections.

Distribution: Due to poor absorption, distribution is mainly limited to the gastrointestinal tract. If absorbed (e.g., after parenteral administration, which is not recommended), it distributes into extracellular fluids and may accumulate in the renal cortex.

Metabolism: Paromomycin is not significantly metabolized. It is excreted largely unchanged in the feces after oral administration.

Excretion: After oral administration, the majority of the drug is excreted unchanged in the feces. Any absorbed fraction is excreted renally by glomerular filtration.

Half-Life: Oral: not well defined due to poor absorption; systemic half-life if absorbed is approximately 2-3 hours in humans, but in animals it is not commonly measured.

Bioavailability: Oral bioavailability is very low (<1-3%) due to poor absorption.

Protein Binding: Low protein binding (less than 10%).

Available Formulations & Strengths

Oral Solution Various concentrations (e.g., 100 mg/mL) (PO)

Oral Powder Various concentrations (e.g., 100 g/kg) (PO)

Capsule 250 mg (PO)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to paromomycin or other aminoglycosides
Intestinal obstruction or severe ulcerative bowel lesions (risk of systemic absorption)
Renal impairment (if systemic absorption occurs)
Concurrent use with other nephrotoxic or ototoxic drugs (e.g., other aminoglycosides, loop diuretics)

Warnings & Clinical Precautions:

Use with caution in animals with renal disease, as systemic absorption may occur if GI mucosa is compromised.
In ruminants, oral administration may disrupt ruminal flora; monitor for digestive disturbances.
In poultry, ensure proper mixing in water to achieve accurate dosing.
Avoid use in animals with known hypersensitivity to aminoglycosides.
Prolonged use may result in overgrowth of non-susceptible organisms (superinfection).
In food animals, observe withdrawal times; extra-label use requires veterinary oversight.

Adverse Effects & Reactions

Common:

Gastrointestinal upset (nausea, vomiting, diarrhea)
Soft stools or diarrhea due to alteration of intestinal flora

Serious / Severe:

Nephrotoxicity (if absorbed systemically)
Ototoxicity (if absorbed systemically)
Neuromuscular blockade (rare, if absorbed)

Rare:

Allergic reactions (rash, anaphylaxis)
Superinfection with resistant organisms

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other aminoglycosides (e.g., gentamicin, neomycin)	Additive nephrotoxicity and ototoxicity if systemic absorption occurs.	High
Loop diuretics (e.g., furosemide)	Increased risk of ototoxicity and nephrotoxicity if systemic absorption occurs.	High
Neuromuscular blocking agents	Potential enhancement of neuromuscular blockade, leading to respiratory depression.	Moderate
Nonsteroidal anti-inflammatory drugs (NSAIDs)	Increased risk of nephrotoxicity if systemic absorption occurs.	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Gastrointestinal distress (vomiting, diarrhea)
Nephrotoxicity (if absorbed)
Ototoxicity (if absorbed)
Neuromuscular blockade (respiratory depression)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Discontinue the drug, provide fluid therapy to maintain renal perfusion, and monitor renal function. In severe cases of neuromuscular blockade, calcium salts or neostigmine may be considered, but this is rarely needed due to poor absorption.

Food Animal Withdrawal Times

🥩 Meat: 14 days🥛 Milk: 7 days🥚 Eggs: 7 days

Withdrawal times are estimates; consult regulatory guidelines for specific products and countries. Extra-label use may require extended withdrawal periods.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature (20-25°C, excursions permitted to 15-30°C).

Handling & Special Conditions: Protect from moisture. Keep container tightly closed. Follow manufacturer's storage instructions for specific formulations.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Paromomycin is not FDA-approved for veterinary use in the US; it is used extra-label. It is approved for human use (Humatin) and may be used in animals under veterinary discretion.

Extra-Label (Off-Label) Use: In the US, extra-label use in food animals is permitted under AMDUCA with veterinary oversight, but requires extended withdrawal times and a valid VCPR. In non-food animals, extra-label use is allowed.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Paromomycin sulfate is an aminoglycoside antibiotic used primarily for its local effects in the gastrointestinal tract. It is poorly absorbed, making it effective for treating intestinal infections and protozoal diseases such as giardiasis, cryptosporidiosis, and amebiasis. In veterinary medicine, it is commonly used in dogs, cats, horses (foals), cattle (calves), and poultry. Dosing varies by species and indication; for example, foals with Lawsonia intracellularis may require higher doses. Adverse effects are generally limited to GI upset, but systemic toxicity can occur if the intestinal mucosa is compromised, leading to absorption. It is contraindicated in animals with renal impairment or hypersensitivity to aminoglycosides. Withdrawal times must be observed in food animals. Due to lack of FDA approval, use is extra-label and requires veterinary oversight. Always consult current veterinary pharmacology references for the most up-to-date dosing and safety information.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)