Chlortetracycline, the first tetracycline antibiotic, was discovered in 1945 by Benjamin M. Duggar at Lederle Laboratories from the soil bacterium Streptomyces aureofaciens. It was named Aureomycin because of the golden color of the bacteria and was launched on the market in 1948. Shortly thereafter, other tetracyclines, such as oxytetracycline (Terramycin) and tetracycline, were developed. Chlortetracycline (CTC) is a broad-spectrum antibiotic and the first identified member of the tetracycline class. It acts as a bacteriostatic agent by inhibiting bacterial protein synthesis and is widely used in both human and veterinary medicine.
BRAND NAMES
Chlortetracycline is marketed under well-known brand names such as Aureomycin and Panmycin.
Aureomycin: One of the earliest commercially available tetracycline antibiotics, commonly prescribed for a wide range of bacterial infections. It is available in oral tablet, capsule, and liquid forms.
Panmycin: Another brand formulation of chlortetracycline, often used interchangeably with Aureomycin depending on the region or manufacturer.
MECHANISM OF ACTION
Chlortetracycline is a tetracycline antibiotic that inhibits bacterial protein synthesis. It binds to the 30S ribosomal subunit, preventing aminoacyl-tRNA from attaching. This stops bacterial growth, making it bacteriostatic rather than bactericidal. It is effective against a broad range of Gram-positive and Gram-negative bacteria. Its action is less effective against anaerobic bacteria.
PHARMACOKINETICS
Absorption: Chlortetracycline is absorbed incompletely from the gastrointestinal tract. Absorption is reduced when taken with dairy, antacids, or iron supplements.
Distribution: It is widely distributed in body tissues and fluids but crosses the placenta and enters breast milk.
Metabolism: Minimal metabolism occurs in the liver; most of the drug remains unchanged.
Excretion: It is primarily excreted via urine and feces, with some enterohepatic circulation.
PHARMACODYNAMICS
Chlortetracycline inhibits bacterial protein synthesis by binding to the bacterial 30S ribosome. Its bacteriostatic effect slows bacterial growth, allowing the immune system to clear the infection. The drug works best in actively dividing bacteria. Resistance can develop with prolonged or inappropriate use. Its activity is reduced in acidic environments or in the presence of divalent cations.
Administration
Chlortetracycline is usually administered orally as tablets, capsules, or liquid suspensions. Dosing should follow the healthcare provider’s instructions to ensure efficacy. It is generally taken on an empty stomach to improve absorption. Some topical forms are applied directly to the skin for localized infections. Adequate hydration is recommended to prevent esophageal irritation.
Dosage and Strength
Typical oral doses range from 250 mg to 500 mg every 6–12 hours, depending on the infection type. Pediatric doses are adjusted based on body weight. The course usually lasts 7–14 days but may be longer for severe infections. Dosage adjustments may be needed in renal impairment. Overuse or prolonged therapy increases the risk of resistance.
DRUG INTERACTIONS
Chlortetracycline interacts with antacids, calcium, iron, magnesium, and zinc, reducing absorption. It may enhance the effects of anticoagulants like warfarin. Concomitant use with penicillin may reduce efficacy of both antibiotics. It can interact with oral contraceptives, potentially reducing contraceptive effectiveness. Monitoring and spacing administration times can minimize interactions.
FOOD INTERACTIONS
Absorption is reduced when taken with dairy products or calcium-fortified foods. Iron-rich meals and antacids can also decrease effectiveness. It is best taken with a full glass of water on an empty stomach. Alcohol does not significantly affect its absorption but should be avoided to reduce gastrointestinal irritation. Grapefruit juice has minimal impact on chlortetracycline levels.
CONTRAINDICATIONS
Chlortetracycline should not be used in patients with hypersensitivity to tetracyclines. It is contraindicated in children under 8 years due to risk of tooth discoloration. Pregnancy is a cautionary period as the drug may affect fetal bone and teeth development. Severe liver or kidney disease may require avoiding its use. Patients with a history of esophageal irritation from medications should take precautions.
SIDE EFFECTS
Nausea, vomiting, and diarrhea.
Abdominal discomfort or stomach upset.
Photosensitivity, causing increased risk of sunburn.
Fungal or bacterial superinfections with long-term use.
Rare liver toxicity or kidney impairment.
Tooth discoloration and enamel hypoplasia in children.
OVERDOSE
Symptoms of overdose include severe nausea, vomiting, diarrhea, and dehydration. Electrolyte imbalances may occur in serious cases. Supportive care is the main treatment, including fluid and electrolyte management. Activated charcoal may be considered if ingestion was recent. Close monitoring in a medical facility is recommended for severe overdose.
TOXICITY
Chlortetracycline toxicity primarily results from gastrointestinal irritation and hepatotoxicity. Long-term use can lead to renal toxicity, especially in patients with pre-existing kidney issues. Photosensitivity reactions may become severe with prolonged exposure. Disruption of gut microbiota can cause superinfections. Immediate discontinuation and supportive care are essential in cases of severe toxicity.
