Generic name: Oxytetracycline (ox-it-tet-ra-sye-kleen)
Brand names: Inj.Steclin
Dosage form: 5% (50-mg/mL) injection
Drug class: Antibiotics
Pharmacology and Mechanism of Action:
Tetracyclines are primarily bacteriostatic antibiotics that inhibit protein synthesis by reversibly binding to the 30S subunit of the ribosome in susceptible organisms. This binding prevents aminoacyl-tRNA from attaching to the ribosome, thereby halting translation.
As a drug class, tetracyclines are effective against a wide range of organisms, including most mycoplasmas, spirochetes (such as the causative agent of Lyme disease), Chlamydia, and Rickettsia. They also exhibit activity against certain gram-positive bacteria, including some strains of staphylococci and streptococci, though resistance among these organisms is on the rise.
Among gram-positive organisms typically susceptible to tetracyclines are Actinomyces spp., Bacillus anthracis, Clostridium perfringens and C. tetani, Listeria monocytogenes, and Nocardia. In terms of gram-negative bacteria, tetracyclines usually show both in vitro and in vivo activity against Bordetella spp., Brucella, Bartonella, Haemophilus spp., Pasteurella multocida, Shigella, and Yersinia pestis.
However, many or most strains of Escherichia coli, Klebsiella, Bacteroides, Enterobacter, Proteus, and Pseudomonas aeruginosa are generally resistant to tetracyclines. Despite this, tetracycline compounds that achieve high urinary concentrations (such as tetracycline and oxytetracycline) have been associated with successful treatment outcomes in dogs with urinary tract infections caused by P. aeruginosa, despite its usual resistance in vitro.
Pharmacokinetics:
Oxytetracycline and tetracycline are well-absorbed orally in fasting animals, with bioavailability ranging from 60–80%, though food or dairy can significantly reduce absorption (by up to 50% or more). After IM injection, oxytetracycline reaches peak levels within 30 minutes to several hours, depending on the injection site and formulation. The long-acting form (LA-200®) is absorbed more slowly.
Tetracyclines distribute widely throughout the body, reaching organs and fluids such as the heart, lungs, kidneys, bile, urine, saliva, and even eye fluids, but CSF penetration is poor. Doxycycline and minocycline penetrate the prostate and eye tissues more effectively than oxytetracycline. These drugs cross the placenta and enter milk, with higher concentrations in inflamed mammary glands.Plasma protein binding is 10–40%.
Volume of distribution for oxytetracycline varies by species:
- Small animals: ~2.1 L/kg
- Horses: ~1.4 L/kg
- Cattle: ~0.8 L/kg
Route of elimination: Excretion is primarily through the kidneys (glomerular filtration) with most of the drug eliminated unchanged. Impaired renal function can lead to drug accumulation. Oxytetracycline is also excreted into the GI tract, where it may become inactive through chelation.
Elimination half-life by species:
- Dogs and cats: 4–6 hours
- Cattle: 4.3–9.7 hours
- Horses: 10.5 hours
- Swine: 6.7 hours
- Sheep: 3.6 hours
Indications and Clinical Uses:
Instructions for Use:
Contraindications & Precautions for Oxytetracycline:
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Contraindicated in animals with known hypersensitivity to oxytetracycline or other tetracyclines.
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Use with caution during pregnancy: Tetracyclines can retard fetal bone development and discolor deciduous teeth. They should only be used in the last half of pregnancy if benefits outweigh risks. Oxytetracycline and tetracycline pose higher risks for these effects than doxycycline or minocycline.
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Use cautiously in patients with renal or hepatic impairment. Dose reductions and close monitoring of kidney and liver function are recommended.
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Avoid combining with other nephrotoxic or hepatotoxic drugs.
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For long-term therapy, consider monitoring serum drug levels.
- Oxytetracycline and tetracycline given to young animals can cause a yellow,brown, or gray discoloration of bones and teeth.
Adverse Effects & Warnings:
Ruminants:
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High oral doses can depress rumen microflora and cause ruminoreticular stasis.
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Rapid IV injection of propylene glycol-based products may cause intravascular hemolysis and hemoglobinuria.
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In calves, these formulations may also cause cardiodepression.
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IM injections may lead to local reactions, including yellow staining and tissue necrosis.
Small Animals:
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Common side effects: nausea, vomiting, anorexia, and diarrhea.
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Cats are particularly sensitive and may show colic, fever, hair loss, and depression with oral tetracycline or oxytetracycline.
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Rare reports suggest urolith formation in dogs with long-term use.
Horses:
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Stressed horses (e.g., post-surgery or trauma) may develop severe diarrhea, especially after oral tetracycline.
General Risks:
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Superinfections (overgrowth of non-susceptible bacteria or fungi) may occur with long-term use.
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Other potential but less common adverse effects include:
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Photosensitivity reactions
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Hepatotoxicity (rare)
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Blood dyscrasias (rare)
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Drug Interactions: Bacteriostatic drugs, like the tetracyclines, may interfere with bactericidal activity of the penicillins, cephalosporins, and aminoglycosides; there is some controversy regarding the actual clinical significance of this interaction.
Dose:
| Species | Indications | Dosage | Notes |
|---|---|---|---|
| Dogs | Systemic infections | 22 mg/kg PO every 8 hours for 7–14 days or 20 mg/kg IM every 7 days (repositol form) | May give with food if GI upset; avoid/reduce dose in renal/liver failure; avoid in young/pregnant animals |
| Salmon poisoning (Neorickettsia helmintheca) | 7 mg/kg IV every 8 hours for 3–5 days | ||
| Medial canthus syndrome (tear staining) | 25–50 mg PO once daily (2 weeks on/off/on) | ||
| Antibiotic-responsive diarrhea | 10–20 mg/kg PO every 8 hours | ||
| Cats | Hemotropic mycoplasmosis | 10–25 mg/kg PO or IV every 8 hours for 5–7 days | Oxytetracycline may not clear infection completely |
| Susceptible infections | 20 mg/kg PO every 8–12 hours | Avoid/reduce dose in renal/liver failure; avoid young/pregnant animals | |
| Inflammatory bowel disease | 10–20 mg/kg PO three times daily | ||
| Rabbits/Rodents/Small Mammals | Various infections | Rabbits: 15 mg/kg SC or IM every 8 hours; 15–50 mg/kg PO once daily; 1 mg/mL drinking water | For E. cuniculi in rabbits: 20 mg/kg SC once daily |
| Chinchillas | 50 mg/kg PO every 12 hours | ||
| Gerbils, Guinea pigs, Hamsters, Mice, Rats | Varied dosages PO or SC/IM | ||
| Cattle | Bacterial pneumonia (Pasteurella spp.) | 20 mg/kg SC or IM once; 6.6–11 mg/kg daily for 4 days max | Use caution IV; avoid IM in neck of small calves |
| Infectious bovine keratoconjunctivitis | 20 mg/kg once or twice followed by 2 g/calf/day for 10 days | PO or parenteral | |
| Anthrax | 4.4 mg/kg IM or IV daily | Do not use in healthy recently vaccinated animals | |
| Bovine anaplasmosis | Varies: 6.6–20 mg/kg IM every 21–28 days; daily treatments for carriers | Depot forms and repeated doses detailed | |
| Respiratory infections | 11–20 mg/kg IM/SC/IV daily or every 3–4 days (LA-200) | IM injections may cause myositis or abscesses | |
| Listeriosis | Up to 10 mg/kg daily for 5 days | High doses needed | |
| Horses | Foals systemic infections | 5–10 mg/kg IV every 12 hours or 10–20 mg/kg IV every 24 hours | Monitor kidney function |
| Equine ehrlichiosis | 6.6 mg/kg IV daily | Dilute and infuse slowly | |
| Lyme disease | 5–6.6 mg/kg IV every 12 hours for 3–4 weeks | Preferred treatment | |
| Potomac Horse Fever | 6.6 mg/kg IV twice daily for up to 5 days | ||
| Proliferative enteropathy | 5–6.6 mg/kg IV every 12 hours followed by doxycycline | ||
| Intrauterine infusion | 1–5 grams; povidone-based products only | Treatments usually daily or every other day for 3–7 days | |
| Swine | Bacterial pneumonia (Pasteurella multocida) | 20 mg/kg IM once or 6.6–11 mg/kg IM once daily | Treatment 24–48 hours after signs resolve; max 4 consecutive days |
| Infectious enteritis control in piglets | 6.6 mg/kg IM once around farrowing | ||
| Anthrax | 4.4 mg/kg IM or IV daily | Avoid use in recently vaccinated healthy animals | |
| General infections | 6–11 mg/kg IM or IV; 10–20 mg/kg PO every 6 hours | ||
| Sheep & Goats | Anthrax | 4.4 mg/kg IM or IV daily | Avoid use in recently vaccinated healthy animals |
| Enteritis and pneumonia | 22 mg/kg in water daily for 7–14 days | ||
| Campylobacteriosis in pregnant ewes | 20 mg/kg long-acting oxytetracycline or 250–300 mg/head/day feed | Treat all pregnant ewes during outbreak | |
| Birds | Chlamydiosis (Psittacosis) | 50 mg/kg IM every 3–5 days (LA-200®); or 200 mg/kg IM daily for 3–5 days | IM injections may cause severe local reactions |
| Reptiles | Ulcerative stomatitis (Vibrio) | 10 mg/kg PO once daily for 7 days | Used in turtles and tortoises |
Note: This drug is categorized as class: D Contraindicated. In canine and feline pregnancy these drugs have been shown to cause congenital malformations or embryotoxicity.]
Compatibility and Compounding Considerations for Oxytetracycline HCl
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Oxytetracycline HCl (regular, non-sustained release forms) is generally compatible with common IV infusion solutions such as D5W, 0.9% sodium chloride, and lactated Ringer’s.
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Stability decreases in solutions with pH greater than 6, especially those containing calcium. This instability is more prominent in propylene glycol-based veterinary injections compared to povidone-based ones.
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Compatible drugs include: colistimethate sodium, corticotropin, dimenhydrinate, regular insulin, isoproterenol HCl, methyldopate HCl, norepinephrine bitartrate, polymyxin B sulfate, potassium chloride, tetracycline HCl, and vitamin B complex with C.
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Drugs with reported incompatibility, conflicting data, or concentration/time-dependent compatibility include: amikacin sulfate, aminophylline, amphotericin B, calcium chloride/gluconate, carbenicillin disodium, cephalothin sodium, cephapirin sodium, chloramphenicol sodium succinate, erythromycin gluceptate, heparin sodium, hydrocortisone sodium succinate, iron dextran, methicillin sodium, methohexital sodium, oxacillin sodium, penicillin G potassium/sodium, pentobarbital sodium, phenobarbital sodium, and sodium bicarbonate.
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Compatibility depends on factors like pH, concentration, temperature, and diluent; consulting specialized references or a hospital pharmacist is advised for precise guidance.
Storage and Stability of Oxytetracycline HCl
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Store oxytetracycline HCl and related products in tight, light-resistant containers.
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Keep at temperatures below 40°C (104°F), preferably at room temperature (15–30°C).
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Avoid freezing unless otherwise specified by the manufacturer.