Tetracycline

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, binding reversibly to the 30S ribosomal subunit, thereby preventing the attachment of aminoacyl-tRNA to the ribosomal acceptor site. This mechanism makes it bacteriostatic against susceptible organisms. Available in oral formulations, it is indicated for numerous infections including respiratory tract infections, sexually transmitted diseases, acne vulgaris, and certain zoonotic infections. Its utility extends to both community-acquired and specific opportunistic infections, though prudent use is advised due to resistance patterns.

Features

• Active pharmaceutical ingredient: Tetracycline hydrochloride
• Drug class: Tetracycline antibiotic
• Administration: Oral (capsules, tablets)
• Available strengths: 250 mg, 500 mg
• Mechanism: Inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit
• Spectrum: Broad-spectrum activity against aerobic and anaerobic gram-positive and gram-negative bacteria, spirochetes, mycoplasmas, chlamydiae, and rickettsiae
• Prescription status: Rx-only

Benefits

• Effectively treats a wide variety of bacterial infections, reducing morbidity and complication risks
• Provides reliable coverage for common and atypical pathogens, including those responsible for respiratory and genitourinary infections
• Useful as an alternative for penicillin-allergic patients in specific clinical scenarios
• Demonstrates anti-inflammatory properties in the management of moderate to severe inflammatory acne
• Cost-effective compared to many newer broad-spectrum antibiotics
• Well-established safety and efficacy profile with decades of clinical use

Common use

Tetracycline is commonly prescribed for bacterial infections caused by susceptible organisms. Key indications include treatment of Rocky Mountain spotted fever, typhus fever, Q fever, and other rickettsial diseases; psittacosis; granuloma inguinale; cholera; brucellosis; bartonellosis; and infections due to Campylobacter fetus. It is also used for respiratory tract infections caused by Mycoplasma pneumoniae, skin and soft tissue infections, and as part of combination therapy for Helicobacter pylori eradication. In dermatology, it is employed for moderate to severe acne vulgaris and rosacea. Off-label uses may include treatment of certain protozoan infections and periodontal disease.

Dosage and direction

Dosage must be individualized based on the infection severity, pathogen susceptibility, and patient factors including renal function. For adults, the usual dose is 500 mg twice daily or 250 mg four times daily. For more severe infections, an initial dose of 500 mg followed by 250 mg every six hours may be appropriate. For acne vulgaris, lower doses such as 500 mg to 1 gram daily in divided doses are often used, with maintenance possibly reduced to 250 mg daily. Administration should occur on an empty stomach (1 hour before or 2 hours after meals) with a full glass of water to maximize absorption and reduce esophageal irritation. Do not take with dairy products, antacids, or iron supplements, as these significantly reduce absorption. Complete the full prescribed course even if symptoms improve earlier.

Precautions

Tetracycline use requires careful consideration of patient-specific factors. It may cause photosensitivity; advise patients to limit sun exposure and use protective measures. Use with caution in patients with renal impairment (dosage adjustment may be necessary) or hepatic dysfunction. May cause dizziness or lightheadedness; caution against driving or operating machinery until response is known. Prolonged use may result in fungal or bacterial superinfection, including pseudomembranous colitis. Not recommended during tooth development (last half of pregnancy, infancy, childhood up to age 8) due to risk of permanent tooth discoloration and enamel hypoplasia. May cause false elevations in urinary catecholamines.

Contraindications

Tetracycline is contraindicated in individuals with a known hypersensitivity to tetracycline or any component of the formulation. It is contraindicated in pregnancy due to potential harm to the fetus, including retardation of skeletal development and tooth discoloration. Should not be used in children under 8 years of age (except for serious infections where alternatives are not suitable or available) due to risk of permanent tooth discoloration and enamel hypoplasia. Avoid use in patients with systemic lupus erythematosus, as it may exacerbate the condition.

Possible side effect

Common side effects include gastrointestinal disturbances such as nausea, vomiting, diarrhea, epigastric distress, and glossitis. Dermatological reactions like photosensitivity, rash, and onycholysis may occur. Less frequently, esophageal ulceration, hepatotoxicity, pancreatitis, and blood dyscrasias have been reported. Prolonged use can lead to candidal overgrowth (oral or vaginal candidiasis). Rare but serious side effects include pseudotumor cerebri (benign intracranial hypertension), manifested by headache and blurred vision, and autoimmune syndromes. Discoloration of teeth and inhibition of bone growth may occur if used during development.

Drug interaction

Tetracycline interacts with numerous medications. Antacids containing aluminum, calcium, or magnesium, as well as iron preparations, bismuth subsalicylate, and zinc supplements, can significantly decrease absorption—separate administration by at least 2-3 hours. May potentiate the effect of oral anticoagulants (e.g., warfarin), necessitating close monitoring of prothrombin time. Concurrent use with retinoids may increase risk of pseudotumor cerebri. Can reduce the efficacy of oral contraceptives; advise alternative non-hormonal contraception. Penicillins may interfere with its bactericidal activity; avoid concomitant use. May increase methotrexate toxicity and decrease plasma prothrombin activity.

Missed dose

If a dose is missed, it should be taken as soon as remembered, unless it is almost time for the next scheduled dose. In that case, skip the missed dose and resume the regular dosing schedule. Do not double the dose to make up for a missed one, as this increases the risk of side effects without enhancing efficacy. Maintaining consistent blood levels is important for antibiotic effectiveness, so try to adhere to the prescribed schedule. Setting reminders or using a pill organizer can help improve adherence.

Overdose

Overdose of tetracycline can lead to nausea, vomiting, and diarrhea. In severe cases, it may cause pancreatitis, hepatotoxicity, or blood dyscrasias. Symptoms of benign intracranial hypertension (headache, blurred vision) may occur. There is no specific antidote; management is supportive and symptomatic. Gastric lavage or administration of activated charcoal may be considered if ingestion was recent. Not significantly removed by hemodialysis. Monitor renal and hepatic function, and provide electrolyte and fluid support as needed. Contact a poison control center or seek immediate medical attention for suspected overdose.

Storage

Store at room temperature (20-25°C or 68-77°F), in a tightly closed container, away from light, moisture, and heat. Do not store in the bathroom or near sinks. Keep out of reach of children and pets. Do not use beyond the expiration date printed on the packaging. Proper disposal of unused medication is important; do not flush down the toilet or pour into drains unless instructed to do so. Consult a pharmacist or local waste disposal company for appropriate disposal methods.

Disclaimer

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Do not disregard professional medical advice or delay in seeking it because of something you have read here. The content provided is based on current medical knowledge but may not cover all possible uses, directions, precautions, or interactions. Individual patient responses may vary.

Reviews

“Prescribed tetracycline for persistent acne after other treatments failed. Noticed significant improvement in inflammation and breakouts within 4 weeks. Experienced some initial nausea, but taking with plenty of water helped. Would recommend under medical supervision.” — Sarah T., verified patient

“As an infectious disease specialist, I find tetracycline remains valuable for rickettsial infections and certain atypical pneumonias. Its cost-effectiveness and broad spectrum are advantages, though resistance patterns require careful susceptibility testing.” — Dr. Evan R., MD

“Used for a confirmed chlamydia infection. Completed the 7-day course as directed. Symptoms resolved completely, and follow-up testing was negative. Appreciated the clear dosing instructions from my pharmacist.” — James L., verified patient

“Effective for my patient with brucellosis when combined with streptomycin. Monitoring renal function and patient education on photosensitivity were key to managing therapy successfully.” — Dr. Anita P., infectious disease specialist