Tetracycline is a time-tested, broad-spectrum antibiotic belonging to the tetracycline class, widely utilized in clinical practice for its efficacy against a diverse range of gram-positive and gram-negative bacteria, as well as atypical pathogens. It functions by inhibiting bacterial protein synthesis, effectively halting microbial proliferation and enabling the host immune system to clear the infection. This agent is particularly valued for its utility in treating acne vulgaris, respiratory tract infections, and certain zoonotic diseases, making it a versatile tool in both outpatient and inpatient settings. Its well-documented pharmacokinetic profile and oral bioavailability support its continued relevance in modern antimicrobial therapy.

Features

• Active Ingredient: Tetracycline hydrochloride
• Drug Class: Tetracycline antibiotic
• Available Forms: Oral capsules (250 mg, 500 mg), tablets
• Mechanism of Action: Binds to the 30S ribosomal subunit, inhibiting aminoacyl-tRNA attachment
• Spectrum of Activity: Effective against many gram-positive and gram-negative bacteria, Rickettsia, Chlamydia, Mycoplasma pneumoniae, and some protozoa
• Half-Life: Approximately 8–11 hours
• Administration: Oral

Benefits

• Provides broad-spectrum coverage against a wide array of pathogenic bacteria
• Effective in the management of moderate to severe inflammatory acne through anti-inflammatory and antibacterial actions
• Useful in treating respiratory infections, including those caused by atypical pathogens
• Can be employed for the prophylaxis and treatment of zoonotic infections such as Lyme disease and Rocky Mountain spotted fever
• Offers an oral formulation that supports outpatient treatment and adherence
• Cost-effective compared to many newer broad-spectrum antibiotics

Common use

Tetracycline is commonly prescribed for bacterial infections including acne vulgaris, respiratory tract infections (e.g., pneumonia, bronchitis), urinary tract infections, sexually transmitted infections such as chlamydia, and tick-borne illnesses including Lyme disease and ehrlichiosis. It is also used off-label for rosacea and as a prophylactic agent in individuals with exposure to certain infectious agents. Its use in Helicobacter pylori eradication regimens, in combination with other agents, is another established application.

Dosage and direction

Dosage must be individualized based on the type and severity of infection, renal function, and patient characteristics. For most infections in adults, the typical dose is 500 mg twice daily or 250 mg four times daily. For acne vulgaris, lower doses such as 500 mg to 1 gram daily in divided doses are often used. Administration should occur on an empty stomach (1 hour before or 2 hours after meals) to maximize absorption. Avoid concomitant intake of dairy products, antacids, or iron supplements, as these can significantly reduce bioavailability. Treatment duration varies; complete the full course as prescribed even if symptoms improve earlier.

Precautions

Use with caution in patients with renal impairment; dosage adjustment may be necessary. Tetracycline may cause photosensitivity—advise patients to limit sun exposure and use sunscreen. It is not recommended during pregnancy or in children under 8 years due to the risk of permanent tooth discoloration and enamel hypoplasia. May cause esophageal irritation; instruct patients to take with a full glass of water and remain upright for at least 30 minutes after ingestion. Monitor for superinfection or Clostridioides difficile-associated diarrhea.

Contraindications

Hypersensitivity to tetracycline or any component of the formulation. Contraindicated in pregnancy and breastfeeding due to effects on fetal bone and tooth development. Do not use in children under 8 years of age. Avoid in patients with severe hepatic dysfunction. Concomitant use with isotretinoin is contraindicated due to increased risk of benign intracranial hypertension.

Possible side effect

Common side effects include gastrointestinal disturbances such as nausea, vomiting, diarrhea, and epigastric discomfort. Photosensitivity reactions, manifesting as severe sunburn, may occur. Less frequently, glossitis, stomatitis, black hairy tongue, and esophageal ulceration have been reported. Rare but serious adverse effects include hepatotoxicity, pancreatitis, blood dyscrasias, and pseudotumor cerebri. Discoloration of teeth and inhibition of bone growth may occur if used during tooth development or pregnancy.

Drug interaction

Tetracycline may interact with antacids, calcium, iron, magnesium, and zinc supplements, reducing its absorption. Concurrent use with warfarin may potentiate anticoagulant effect. It may decrease the efficacy of oral contraceptives; advise alternative contraception. Coadministration with methoxyflurane may result in fatal renal toxicity. Penicillins may antagonize the antibacterial effects of tetracyclines. Avoid with retinoids due to additive risk of intracranial hypertension.

Missed dose

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double the dose to catch up. Maintaining consistent serum levels is important for efficacy, so try to adhere to the prescribed schedule. If multiple doses are missed, contact a healthcare provider for guidance.

Overdose

Overdose may lead to nausea, vomiting, and diarrhea. In severe cases, hepatotoxicity or pancreatitis could occur. There is no specific antidote; management is supportive and includes gastric lavage if ingestion was recent, along with symptomatic treatment. Hemodialysis is not effective for removal. Contact a poison control center or seek emergency medical attention immediately.

Storage

Store at room temperature (15–30°C or 59–86°F) in a tightly closed container, protected from light and moisture. Keep out of reach of children and pets. Do not use after the expiration date printed on the packaging.

Disclaimer

This information is for educational purposes and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, changing, or stopping any medication. The content provided is based on current medical literature but may not cover all possible uses, directions, precautions, or interactions.

Reviews

“Tetracycline has been a cornerstone in my dermatology practice for decades, particularly for inflammatory acne. Patients often see significant improvement within weeks, though sun protection counseling is essential.” — Dr. Eleanor Vance, MD, Dermatologist
“As an infectious disease specialist, I value tetracycline for its role in treating rickettsial infections and Lyme disease. It’s reliable and well-tolerated when used appropriately.” — Dr. Marcus Thorne, MD
“Effective for my recurrent bronchitis, but must remember to take it on an empty stomach. Had some initial nausea but it subsided.” — Patient, 42
“Used for chlamydia treatment as per CDC guidelines. Worked quickly with no side effects. Finished the course as directed.” — Patient, 28
“Prescribed for rosacea off-label. Noticeable reduction in redness and papules over 2 months.” — Patient, 51