TYLOSIN

Chemistry - A macrolide antibiotic related structurally to erythromycin, tylosin is produced from
Streptomyces fradiae. It occurs as an almost white to buff-colored powder with a pKa of 7.1. It isslightly soluble in water and soluble in alcohol. Tylosin is considered to be highly lipid soluble.
The tartrate salt is soluble in water. The injectable form of the drug (as the base) is in a 50%propylene glycol solution.

Storage, Stability, Compatibility

Unless otherwise instructed by the manufacturer, injectabletylosin should be stored in well-closed containers at room temperature. Tylosin, like erythromycin, is unstable in acidic (pH <4) media. It is not recommended to mix the parenteral injection with otherdrugs.

Pharmacology - TYLOSIN

Tylosin is thought to have the same mechanism of action as erythromycin (bindsto 50S ribosome and inhibits protein synthesis) and exhibits a similar spectrum of activity. It is abacteriostatic antibiotic. For more specific information on organisms that tylosin is usually activeagainst, refer to the erythromycin monograph just prior to this one. Cross resistance witherythromycin occurs.
Uses, Indications - Although the injectable form of tylosin is approved for use in dogs and cats, itis rarely used parenterally in those species. Oral tylosin is sometimes recommended for thetreatment of chronic colitis in small animals (see Doses), but controlled studies documenting itsefficacy have not been performed.
Tylosin is also used in clinically in cattle and swine for infections caused by susceptible organisms.

Pharmacokinetics - TYLOSIN

Tylosin tartrate is well absorbed from the GI tract, primarily from the intestine. The phosphate salt is less well absorbed after oral administration. Tylosin base injected SQ or IM is reportedly rapidly absorbed.
Like erythromycin, tylosin is well distributed in the body after systemic absorption, with theexception of penetration into the CSF. The volume of distribution of tylosin is reportedly 1.7 L/kgin small animals. Tylosin enters milk in concentrations of approximately 20% of those found inserum.
Tylosin is eliminated in the urine and bile apparently as unchanged drug. The elimination half lifeof tylosin is reportedly 54 minutes in small animals, 139 minutes in newborn calves and 64 minutesin calves 2 months of age or older.

Contraindications, Precautions, Reproductive Safety

Tylosin is contraindicated in patientshypersensitive to it or other macrolide antibiotics (e.g., erythromycin). Most clinicians feel thattylosin is contraindicated in horses, as severe and sometimes fatal diarrheas may result from its usein that species.
No information was located with regards to the reproductive safety of tylosin, but it is unlikely tohave serious teratogenic potential.

Adverse Effects, Warnings

Most likely adverse effects with tylosin are pain and local reactionsat intramuscular injection sites, and mild GI upset (anorexia, and diarrhea). Tylosin may inducesevere diarrheas if administered orally to ruminants or by any route to horses. In swine, adverseeffects reported include edema of rectal mucosa and mild anal protrusion with pruritis, erythema, and diarrhea.

Overdosage, Acute Toxicity

Tylosin is relatively safe in most overdose situations. The LD50 inpigs is greater than 5 g/kg orally, and approximately 1 g/kg IM. Dogs are reported to tolerate oraldoses of 800 mg/kg. Long-term (2 year) oral administration of up to 400 mg/kg produced no organtoxicity in dogs. Shock and death have been reported in baby pigs overdosed with tylosin, however.

Drug Interactions

Drug interactions with tylosin have not been well documented. It has beensuggested that it may increase digitalis glycoside blood levels with resultant toxicity. It is suggested to refer to the erythromycin monograph for more information on potential interactions.
Drug/Laboratory Interactions - Macrolide antibiotics may cause falsely elevated values of AST(SGOT), and ALT (SGPT) when using colorimetric assays.
Fluorometric determinations of urinary catecholamines can be altered by concomitant macrolideadministration.