Doxycycline oral and injectable antibiotics for bacterial infections

Doxycycline is a broad-spectrum antibacterial medication available in oral and injectable forms. It is used to treat various bacterial infections by interfering with bacterial growth. This medicine includes multiple formulations such as film-coated tablets, capsules, and powder for injection, with strengths ranging from 50 mg to 150 mg. It is produced by several pharmaceutical manufacturers.

Doxycycline is prescribed to treat infections caused by susceptible bacteria. It is used for:

• Rickettsial infections including Rocky Mountain spotted fever, typhus, Q fever, rickettsialpox, and other tick fevers.
• Respiratory tract infections caused by Mycoplasma pneumoniae.
• Sexually transmitted infections such as lymphogranuloma venereum, inclusion conjunctivitis, uncomplicated urethral, endocervical, or rectal infections caused by Chlamydia trachomatis, nongonococcal urethritis due to Ureaplasma urealyticum, and uncomplicated gonorrhea when penicillin is contraindicated.
• Psittacosis (ornithosis) caused by Chlamydophila psittaci.
• Relapsing fever caused by Borrelia recurrentis.
• Gram-negative infections such as chancroid (Haemophilus ducreyi), plague (Yersinia pestis), tularemia (Francisella tularensis), cholera (Vibrio cholerae), Campylobacter fetus infections, brucellosis (with streptomycin), bartonellosis, and granuloma inguinale.
• Gram-negative and gram-positive infections when susceptibility is confirmed, including Escherichia coli, Enterobacter aerogenes, Shigella species, Acinetobacter species, Haemophilus influenzae, Klebsiella species, Streptococcus pneumoniae, and anthrax (Bacillus anthracis), including inhalational anthrax post-exposure prophylaxis.
• Alternative treatment for syphilis and yaws caused by Treponema pallidum subspecies when penicillin is contraindicated.
• Other infections like listeriosis, Vincent's infection, actinomycosis, clostridial infections, and as adjunct therapy for acute intestinal amebiasis.
• Prophylaxis of malaria due to Plasmodium falciparum in short-term travelers to areas with resistant malaria strains.
• Severe acne as adjunctive therapy.

Doxycycline; Doxycycline hyclate

Doxycycline belongs to the tetracycline class of antibiotics and works by inhibiting bacterial protein synthesis. This action prevents bacteria from growing and reproducing, thereby treating and controlling bacterial infections. It has a high degree of lipid solubility and low affinity for calcium binding, ensuring stability in the human body. It is effective only against susceptible bacteria, so culture and susceptibility testing is often recommended to guide therapy.

Adults

• Initial oral dose is typically 200 mg on the first day, given as 100 mg every 12 hours, followed by 100 mg once daily maintenance. For severe infections, 100 mg may be given every 12 hours.
• In uncomplicated gonococcal infections (except anorectal infections in men): 100 mg orally twice daily for 7 days, or as an alternative single visit dose, 300 mg stat followed one hour later by a second 300 mg dose.
• Acute epididymo-orchitis from N. gonorrhoeae: 100 mg orally twice daily for at least 10 days.
• Primary and secondary syphilis: 300 mg daily in divided doses for at least 10 days.
• Chlamydial infections: 100 mg twice daily for at least 7 days.
• Inhalational anthrax post-exposure prophylaxis: 100 mg twice daily for 60 days.

Pediatrics

• For children under 45 kg with severe or life-threatening infections (e.g., anthrax, Rocky Mountain spotted fever): 2.2 mg/kg every 12 hours.
• For children over 8 years and weighing less than 45 kg with less severe disease: 4.4 mg/kg divided into two doses on the first day, followed by 2.2 mg/kg once daily or divided twice daily maintenance dose.
• Children over 45 kg should receive adult dosing.

Administration Notes

• Take with adequate fluids to prevent esophageal irritation and ulceration. Avoid taking immediately before lying down.
• If stomach irritation occurs, doxycycline can be taken with food or milk; food and milk do not markedly affect absorption.
• Dosage adjustments are generally not required for renal impairment.
• For injectable doxycycline, infuse over 1 to 4 hours; do not inject intramuscularly or subcutaneously.

Hypersensitivity to doxycycline or any tetracycline class drug.

Tooth discoloration: Use during tooth development (last half of pregnancy, infancy, and children

Clostridioides difficile-associated diarrhea (CDAD): May occur with use and can be severe or fatal. Monitor patients with diarrhea during and up to 2 months after treatment.

Severe skin reactions: Include exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, and DRESS. Discontinue immediately if these occur.

Intracranial hypertension (pseudotumor cerebri): Associated with doxycycline. Symptoms include headache, blurred vision, diplopia, and vision loss. If visual changes occur, discontinue and perform ophthalmologic evaluation.

Photosensitivity: May cause exaggerated sunburn. Avoid excessive sunlight or UV exposure; discontinue if skin redness occurs.

Pregnancy and nursing: Potential fetal harm; crosses placenta and is excreted in breast milk. Avoid unless benefits justify risks.

Other: May increase blood urea nitrogen (BUN) due to anti-anabolic effects. Avoid rapid IV injection; prolonged infusion recommended to reduce thrombophlebitis risk.

Common adverse reactions: Gastrointestinal upset (nausea, vomiting, diarrhea, glossitis, dysphagia), esophagitis, inflammatory lesions (with fungal overgrowth), photosensitivity, and skin rash.

Serious but less common reactions: Severe skin reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis), hypersensitivity reactions (urticaria, angioedema, anaphylaxis), hematological effects (hemolytic anemia, thrombocytopenia, neutropenia), psychiatric symptoms (depression, anxiety, hallucinations), hepatotoxicity, and intracranial hypertension.

Other: Brown-black microscopic thyroid discoloration with prolonged use, reversible tooth coloration with professional cleaning.

• May decrease effectiveness of oral contraceptives.
• Absorption impaired by antacids containing aluminum, calcium, magnesium; iron preparations; and bismuth subsalicylate.
• Barbiturates, carbamazepine, phenytoin, and rifampin shorten doxycycline half-life, reducing concentration.
• May depress plasma prothrombin activity; anticoagulant doses may require adjustment.
• Should not be used concurrently with penicillin as bacteriostatic effect may interfere with penicillin's bactericidal action.
• Concurrent use with methoxyflurane (Penthrane®) can cause fatal renal toxicity and should be avoided.

Pregnancy

Use during pregnancy, especially in the last half and in early pregnancy, may cause fetal harm including tooth discoloration and skeletal development toxicity. Use only if benefits outweigh risks.

Lactation

Doxycycline is excreted in breast milk. Short-term use may be acceptable, but prolonged exposure risks to nursing infants are unknown. Consider discontinuing nursing or drug.

In case of overdose, discontinue drug and provide supportive treatment. Dialysis is not effective in removing doxycycline.