Tetracycline: Introduction, Types, Uses, Side Effects, and Drug Interactions

Introduction

Tetracycline is a broad-spectrum antibiotic that has been widely used for the past 50 years in the treatment of a wide variety of bacterial diseases.
It was first identified in the 1940s and is a type of antibiotic known as Streptomyces antibiotics.
The drugs operate by preventing protein synthesis in bacteria, which in turn prevents them from growing and spreading.
Based on their wide spectrum of activity, tetracyclines traditionally covered the treatment of respiratory tract infections, urinary tract infections, cutaneous diseases, and some parasitic diseases.
While newer antibiotics have been produced, tetracyclines continue to play an important role in modern medical applications.
Nevertheless, increasing resistance to tetracyclines by bacteria has, understandably, caused some reluctance to prescribe them so readily.

Types of Tetracyclines

The tetracyclines are a group of structurally similar antimicrobials with differences in potency, absorption, and half-life. The main types include:
Tetracycline (the original compound)

One of the oldest antibiotics belongs to this class.

Still utilised in some instances but less so because of resistance and newer derivatives available.

Doxycycline

Usually preferred to older tetracyclines for most indications due to its additional antianabolic and anti-inflammatory effects, and more palatable taste/less frequent dosing due to decreased lipophilicity.

Effective in variety of infections including respiratory and sexually transmitted infections.

Minocycline

Useful topically to penetrate and treat acne and other topical skin conditions and chronic resistant skin infections, 3% solution.

Occasionally employed in auto immune states on account of the antiinflammatory effects.

Tigecycline (a glycylcycline derivative)

Structurally similar to tetracyclines, but degradation-resistant against bacteria.

Typically in hospitals for serious infections.

Mechanism of Action

Tetracyclines do so by binding to the 30S ribosomal subunit of bacteria, preventing amino acids from being added to the growing peptide chain. This stops the bacteria from making protein, making it difficult for the bacteria to grow and multiply. Being mostly bacteriostatic (inhibit growth rather than kill outright), clearance of infection is profoundly dependent on the immune system.

Uses of Tetracyclines

Tetracyclines have a broad spectrum of clinical use. Their uses include:
Infections of the respiratory tract like pneumonia, bronchitis, sinusitis.

STIs (sexually transmitted infections), such as chlamydia, syphilis (alternative remedy) and pelvic inflammatory disease.

UTIs due to susceptible bacteria.

Skin diseases including acne, rosacea, and some bacterial skin infections.

Eye infections such as trachoma and conjunctivitis due to Chlamydia trachomatis.

Rickettsial disease such as Rocky Mountain spotted fever and typhus.

Zoonotic infections such as anthrax, plague, tularemia, and brucellosis.

Malaria prophylaxis and treatment in chloroquine-resistant locations (doxycycline in particular).

Gum infections (periodontal disease) kill oral bacteria.

Side Effects of Tetracyclines

Tetracyclines, like any drug, can lead to side effects. Most are mild; some can be serious.
Common Side Effects
Nausea, vomiting, and diarrhea

Loss of appetite

Sun sensitivity (higher chance of getting sunburn )

Lightheadedness, headache (more likely with minocycline)

Serious Side Effects
Tooth discoloration and enamel hypoplasia (particularly in children less than 8 years of age)

Reduced bone growth in children

Liver damage (particularly with high doses or long-term use)

Intracranial hypotension (infrequent but is possible)

An allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives)

They’re not safe for pregnant women, nursing mothers, or for young children as they can affect the growth of development of tooth and bone.

Drug Interactions

Tetracyclines may interact with other drugs, and unrelated drugs such as the antacid bismuth subsalicylate may also interact with tetracyclines. Some key interactions include:
Antacids and vitamins (calcium, magnesium, aluminum, iron, zinc)
– These chelate tetracyclines in the stomach to reduce absorption.

Patients are farther instructed not to consume any dairy foodstuffs or supplements for at least 2–3 hours after the dose.

Oral contraceptives

Could cause some of the birth control pills to be less effective which can lead to pregnancy.

Blood thinners (warfarin)

Tetracyclines increase the action of anticoagulants and so increasing blood clotting.

Penicillin antibiotics

May reduce the effectiveness of one another as tetracyclines are bacteriostatic and penicillins are bactericidal.

Retinoids (e.g., isotretinoin)

The concurrent use may increase the risk of intracranial hypertension.

Alcohol and liver-damaging drugs

Increase risk of hepatotoxicity when coadministered with tetracyclines.

Precautions and Contraindications

Some people should not take, or should take with caution, tetracyclines:
Pregnancy and breastfeeding: Pregnant or breastfeeding women should avoid Doxycycline Antimalarial Capsules as there exists the possibility of fetal harm when used during this time period and the development of teeth discoloration in infants.

Children younger than 8 years because of the danger of bone and tooth effects.

Patients with liver disease as tetracyclines, are extrahepatically metabolised.

Patients with kidney disease (with at least for the older compounds that are renally excreted).

Resistance Issues

Bacteria have also developed resistance to tetracyclines because of their overuse in medicine and agriculture.
Resistance mechanisms are driven by efflux pumps to remove the drug from bacteria, ribosomal protection protein, and enzymatic inactivation.
Accordingly, they are frequently used only for the treatment of specific infections for which the tetracyclines have been demonstrated to be effective (e.g., the treatment of gonorrhea) or in treatment regimens that result in low penetration of tetracyclines into human tissues.

Conclusion

Despite bacterial resistance and newer agents, tetracyclines are still worthwhile antibiotics.
Available in a broad spectrum, they remain important in the treatment of numerous infections, including respiratory, urinary, zoonotic, sexually transmitted, and dermatologic infections.
But they all have side effects, not to mention contraindications in children and pregnant women, and possible medications that could be causing problems.
Prudent use is critical for maintaining their efficacy for upcoming generations

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