Tetracycline

What is Tetracycline?

Tetracycline is a broad-spectrum antibiotic that belongs to the tetracycline class of antibiotics. It is used to treat a wide variety of bacterial infections, including respiratory tract infections, skin infections, and certain sexually transmitted diseases. This medication has been widely used since the 1950s and remains an important treatment option for many bacterial conditions.

Uses

Tetracycline is prescribed for several bacterial infections and conditions:

• Respiratory tract infections: Including pneumonia, bronchitis, and other bacterial infections of the lungs and airways
• Skin and soft tissue infections: Such as acne vulgaris, cellulitis, and wound infections caused by susceptible bacteria
• Sexually transmitted infections: Including chlamydia, gonorrhea, and syphilis, particularly in patients allergic to penicillin
• Urinary tract infections: Caused by bacteria sensitive to tetracycline
• Eye infections: Including trachoma and conjunctivitis caused by susceptible organisms

How it works

Tetracycline works by inhibiting bacterial protein synthesis, which is essential for bacterial growth and reproduction. It binds to the 30S ribosomal subunit in bacteria, preventing the attachment of amino acids to the growing protein chain. This bacteriostatic action stops bacteria from multiplying, allowing the body’s immune system to eliminate the infection.

Side effects

Common side effects include:

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• Nausea and vomiting
• Diarrhea
• Stomach upset or abdominal pain
• Loss of appetite
• Headache
• Dizziness
• Skin sensitivity to sunlight (photosensitivity)
• Vaginal yeast infections

Serious side effects to watch for:

• Severe diarrhea or signs of C. difficile infection
• Severe skin reactions or blistering
• Signs of liver problems (yellowing of skin or eyes, dark urine)
• Severe headache with vision changes
• Allergic reactions including difficulty breathing or swelling

Warnings and precautions

• Pregnancy and children: Tetracycline should not be used during pregnancy or in children under 8 years old, as it can cause permanent tooth discoloration and affect bone development
• Kidney impairment: Dosage adjustments may be necessary for patients with kidney disease, as the drug is primarily eliminated through the kidneys
• Sun exposure: Patients should avoid prolonged sun exposure and use sunscreen, as tetracycline increases sensitivity to UV light
• Dairy and supplements: Avoid taking with dairy products, calcium, iron, or magnesium supplements, as these can significantly reduce absorption
• Liver function: Use with caution in patients with liver disease, and monitor liver function during extended treatment

Interactions

Tetracycline has several important drug and supplement interactions:

• Antacids containing aluminum, calcium, or magnesium: Significantly reduce tetracycline absorption when taken together
• Iron supplements: Can form complexes with tetracycline, reducing the effectiveness of both medications
• Warfarin: Tetracycline may enhance the anticoagulant effect, increasing bleeding risk
• Oral contraceptives: May reduce the effectiveness of birth control pills
• Digoxin: Tetracycline can increase digoxin levels in some patients
• Dairy products: Calcium in milk and dairy can chelate tetracycline, reducing absorption
• Penicillin antibiotics: May antagonize the bactericidal effects of penicillin
• Retinoids: Concurrent use may increase the risk of intracranial pressure

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Dosage

Typical adult dosages vary depending on the condition being treated. For most infections, the usual dose is 250-500 mg taken four times daily, or 500 mg taken twice daily. For acne treatment, lower doses of 250-500 mg daily may be prescribed for extended periods. Tetracycline should be taken on an empty stomach, at least one hour before or two hours after meals, with a full glass of water. Patients should remain upright for at least 30 minutes after taking the medication to prevent esophageal irritation. Dosage and duration of treatment should always be determined by a healthcare provider based on the specific infection, patient factors, and response to treatment.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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