Chlortetracycline
Chlortetracycline is a broad-spectrum, first-generation **tetracycline antibiotic**. While it shares a nearly identical spectrum of activity with oxytetracycline and tetracycline, it is primarily utilized in veterinary medicine as a feed or water additive for food-producing animals (cattle, swine, poultry). Key clinical features include: * **Broad-spectrum activity:** Effective against many *Mycoplasma*, spirochetes (including *Borrelia*), *Chlamydia*, and *Rickettsia*. * **Increasing resistance:** Many gram-positive and gram-negative bacteria (e.g., *E. coli*, *Klebsiella*, *Pseudomonas*) have developed resistance over time. * **Exotic animal use:** Frequently used in avian medicine (especially for chlamydiosis) and in certain small mammals, though it is strictly contraindicated in guinea pigs due to fatal enterotoxemia. > **Clinical Pearl:** Because of its formulation as a feed/water additive, it is highly practical for herd or flock treatment, but individual dosing in companion animals is less common compared to newer tetracyclines like doxycycline.
Mecanismo: Chlortetracycline is a **bacteriostatic** antibiotic that inhibits bacterial protein synthesis. * **Primary Mechanism:** Reversibly binds to the **30S ribosomal subunit** of susceptible organisms → blocks the binding of aminoacyl transfer-RNA to the mRNA-ribosome complex → halts peptide chain elongation. * **Secondary Mechanism:** May also reversibly bind to **50S ribosomes** and alter cytoplasmic membrane permeability. * **Mammalian effects:** At very high concentrations, it can inhibit protein synthesis in mammalian cells, leading to antianabolic effects.
Dosificación por especie
- Susceptible infections · 25 mg/kg PO q6-8h · PO · q6-8h
- Bacterial conjunctivitis, keratitis, blepharitis, and spontaneous chronic corneal epithelial defects (SCCEDs) · 0.5-2 cm of ointment to affected eye · topical · q6h · 5 days · Used for immunomodulatory mechanism in SCCEDs.
- Chlamydiosis (Small birds) · 0.05% concentration in food · PO · Continuous
- Chlamydiosis (Larger psittacines) · 1% CTC concentration in food · PO · Continuous
- Susceptible infections (Ratites) · 15-20 mg/kg PO three times daily · PO · TID
- Susceptible infections (Pigeons) · 50 mg/kg PO q6-8h; or 1000-1500 mg/gallon drinking water · PO · q6-8h or continuous · In warm weather mix fresh every 12 hours. Calcium inhibits absorption; withhold grit and layer pellets during treatment.
- Susceptible infections · 25 mg/kg PO q6-8h · PO · q6-8h
- To prevent recurrence of mycoplasma or chlamydial conjunctivitis in large catteries · 50 mg per day per cat · PO · q24h · 1 month · Administer soluble chlortetracycline powder in food.
- Feline chlamydial conjunctivitis, mycoplasmal conjunctivitis, bacterial keratitis/blepharitis · 0.5-2 cm of ointment to affected eye · topical · q6h · 5 days · Oral doxycycline is the treatment of choice for feline chlamydial conjunctivitis.
Vías de administración
Contraindicaciones
- Known hypersensitivity to chlortetracycline or other tetracyclines
- Guinea pigs (causes fatal clostridial enterotoxemia)
Efectos adversos
- Gastrointestinal distress (nausea, vomiting, anorexia, diarrhea)
- Discoloration of developing teeth and bones (yellow, brown, or gray)
- Delayed bone growth and healing (at high doses)
- Hepatotoxicity
- Increased BUN (antianabolic effect)
- Ruminal microflora depression and stasis (in ruminants)
- Intravascular hemolysis and hemoglobinuria (with rapid IV injection of propylene glycol-based products)
- Colic, fever, and hair loss (in cats)
- Severe diarrhea (in stressed horses)
- Superinfections (bacterial or fungal overgrowth)
- Photosensitivity
Interacciones farmacológicas
- Beta-lactam Antibiotics · Bacteriostatic action of tetracyclines may interfere with the bactericidal activity of penicillins and cephalosporins.
- Aminoglycosides · May interfere with bactericidal activity.
- Digoxin · May increase the bioavailability of digoxin in a small percentage of patients, potentially leading to toxicity.
- Divalent or Trivalent Cations (Antacids, Calcium, Iron, Magnesium, Zinc, Bismuth) · Chelation occurs, significantly decreasing the oral absorption of the tetracycline. Separate administration by at least 1-2 hours.
- Warfarin · May depress plasma prothrombin activity; anticoagulant dosage may need adjustment.
Monitorización
- Clinical efficacy (resolution of infection)
- Gastrointestinal signs (vomiting, diarrhea, anorexia)
- Renal function (BUN, creatinine) and hepatic function, especially with prolonged use or in compromised patients
- Fluid and electrolyte status if severe GI distress occurs
Sobredosis
Tetracyclines are generally well tolerated after acute overdoses. * **Oral Overdose:** Most likely associated with gastrointestinal disturbances (vomiting, anorexia, diarrhea). If severe emesis or diarrhea develops, monitor and replace fluids and electrolytes. * **Chronic Overdose:** May lead to drug accumulation and nephrotoxicity. * **Ruminants:** High oral doses can cause ruminal microflora depression and ruminoreticular stasis. * **Intravenous Overdose:** Rapid IV injection of undiluted propylene glycol-based products can cause intravascular hemolysis and hemoglobinuria. Rapid IV injection can also induce transient collapse and cardiac arrhythmias due to chelation with intravascular calcium ions.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.