Erythromycin

Macrolide antibiotic; historically used for Rhodococcus equi in foals; GI prokinetic at sub-antimicrobial doses. Macrolide antibiotic. Mechanism: binds 50S ribosomal subunit (23S rRNA) → inhibits bacterial translocation and protein synthesis (bacteriostatic). At sub-antimicrobial doses: motilin receptor agonist → gastric prokinetic effects. Prototype macrolide; largely replaced by azithromycin/clarithromycin in foals due to adverse effects (hyperthermia, diarrhea). Key information Do NOT use in adult horses — fatal GI dysmotility/dysbiosis. Can be used in foals (with monitoring). Foals: may cause hyperthermia — monitor temperature. Administer on empty stomach. Drug interactions: inhibits CYP3A4 — raises theophylline, cyclosporine levels.

Oral: Administer orally. May be given with food to improve compliance and reduce GI upset. Administer with food to reduce GI adverse effects. to reduce severe GI effects. Suspension: Shake well before each use. Store refrigerated (2–8°C); do not freeze. IV (extra-label): dilute in D5W; infuse over 60 min — do not rapid infuse (pain, phlebitis). Foals: monitor body temperature every 6 hrs during therapy. Store at room temperature; protect from light. (tablets). If a dose is missed Administer as soon as you remember. If it is almost time for the next scheduled dose, skip the missed dose and resume the normal schedule. Never double up doses to make up for a missed one.

GI: nausea, vomiting, diarrhea, abdominal cramping (common — motilin receptor stimulation). Foals: hyperthermia, tachypnea, enterocolitis; mares nursing treated foals may develop severe diarrhea — management precautions required. Hepatotoxicity (cholestatic). QT prolongation. CYP3A4 inhibitor (drug interactions).

For animals Foals: hyperthermia, enterocolitis, and severe diarrhea risk — NOT recommended as first-line therapy; monitor closely if used. Nursing mares: keep separate from treated foals (macrolide exposure via mammary secretions causes diarrhea). CONTRAINDICATED in horses at high risk for heat stress. Drug interactions: CYP3A4 inhibitor; QT prolongation. Use with caution in hepatic impairment. For people handling this medication Wash hands thoroughly with soap and water after handling. Avoid contact with eyes; if contact occurs, flush with water for 15 minutes and seek medical attention. Keep out of reach of children. If accidental ingestion occurs, contact Poison Control (1-800-222-1222). Macrolide — Wash hands thoroughly with soap and water after handling. after handling. Foal diarrhea can be spread to mares — hygiene precautions for handlers.

Contact your veterinarian. Overdose causes severe GI upset. In horses, any erythromycin use is dangerous — contact your vet immediately if used in adult horses.