Doxyson

FDA-Approved Indications:

• Respiratory Tract Infections:
• Community-acquired pneumonia
• Acute bronchitis and chronic bronchitis exacerbations
• Sinusitis caused by susceptible organisms
• Sexually Transmitted Infections (STIs):
• Uncomplicated gonorrhea
• Chlamydia trachomatis infections
• Syphilis (in penicillin-allergic patients)
• Nongonococcal urethritis
• Pelvic inflammatory disease (PID)
• Zoonotic & Vector-borne Diseases:
• Lyme disease
• Rocky Mountain spotted fever
• Ehrlichiosis and anaplasmosis
• Tularemia
• Plague (as adjunct)
• Q fever
• Brucellosis
• Malaria:
• Malaria prophylaxis (especially in chloroquine-resistant areas)
• Treatment of uncomplicated malaria due to Plasmodium falciparum (in combination with quinine)
• Skin & Soft Tissue Infections:
• Acne vulgaris (moderate to severe)
• Rosacea
• MRSA skin infections (community-acquired strains)
• Ophthalmic Infections:
• Trachoma and inclusion conjunctivitis caused by Chlamydia trachomatis
• Gastrointestinal Infections:
• Cholera
• Traveler’s diarrhea caused by E. coli
• Campylobacter enteritis
• Helicobacter pylori (part of multidrug regimens)
• Anthrax:
• Inhalational post-exposure prophylaxis and treatment, including Bacillus anthracis

Clinically Accepted Off-Label Uses:

• Periodontitis: As part of adjunctive therapy in periodontal disease (low-dose doxycycline)
• Perioral Dermatitis
• Rickettsial diseases in children <8 years (short courses when benefits outweigh risks)
• Leptospirosis
• Filariasis and onchocerciasis (as anti-Wolbachia therapy)

Adults:

• Initial dose: 100 mg orally or IV twice daily on Day 1
• Maintenance dose: 100 mg once or twice daily depending on severity and indication

Common Regimens:

• Acne: 50–100 mg orally once or twice daily
• STIs: 100 mg orally twice daily for 7–14 days
• Malaria prophylaxis: 100 mg orally once daily, starting 1–2 days before travel and continuing for 4 weeks after return
• Malaria treatment (with quinine): 100 mg twice daily for 7 days
• Anthrax prophylaxis: 100 mg twice daily for 60 days

Pediatrics (>8 years of age):

• 2.2 mg/kg every 12 hours on Day 1, followed by 2.2 mg/kg once daily or divided every 12 hours.
• Maximum dose: Usually not to exceed 100 mg per dose.

Elderly:

• No routine dose adjustment required; monitor renal and hepatic function if compromised.

Renal Impairment:

• No dose adjustment generally required; doxycycline does not significantly accumulate in renal failure.

Hepatic Impairment:

• Use caution in severe hepatic dysfunction; consider dose reduction or longer dosing interval.

Administration Notes:

• Administer with plenty of fluids to prevent esophageal irritation.
• Avoid administration with dairy, iron, or antacids (contain calcium, magnesium, aluminum).
• IV form used when oral route is not possible.

Doxycycline is a broad-spectrum, bacteriostatic antibiotic belonging to the tetracycline class. It inhibits bacterial protein synthesis by binding reversibly to the 30S ribosomal subunit, preventing the addition of amino acids to growing peptide chains. This disrupts bacterial replication and metabolism. Its ability to penetrate bacterial cell walls and bind intracellularly allows activity against a wide range of Gram-positive and Gram-negative organisms, as well as atypical pathogens (e.g., Mycoplasma, Rickettsia, Chlamydia).

• Absorption: Oral bioavailability ~90–100%; minimally affected by food (though dairy/calcium reduces absorption).
• Distribution: Widely distributed in tissues, including lungs, prostate, and skin; crosses placenta and enters breast milk.
• Plasma Protein Binding: ~80–90%
• Metabolism: Minimal hepatic metabolism.
• Half-life: 16–22 hours (longer than tetracycline).
• Elimination: Primarily via feces (biliary route); ~35–40% renal excretion unchanged.
• Onset of Action: Therapeutic effects typically observed within 24–48 hours.

• Pregnancy:
  FDA Pregnancy Category D. Doxycycline can cause permanent tooth discoloration and inhibition of bone growth in the fetus. Avoid unless no safer alternatives are available and benefits clearly outweigh risks, especially in second and third trimesters.
• Lactation:
  Excreted in breast milk. Short-term use may be acceptable; however, risks of tooth discoloration and suppression of bone growth in infants exist. Avoid prolonged use during breastfeeding unless absolutely necessary.

• Primary Class: Antibiotic
• Subclass: Tetracycline-class bacteriostatic antibiotic (second-generation tetracycline derivative)

• Known hypersensitivity to doxycycline, tetracyclines, or any component of the formulation
• Children under 8 years of age (unless no alternative exists), due to risk of tooth discoloration and bone growth inhibition
• Pregnancy, especially second and third trimester (unless benefits outweigh risks)
• Severe hepatic impairment (relative contraindication depending on dose and duration)

• Tooth discoloration & bone growth retardation: Use with caution in children under 8 and during pregnancy.
• Photosensitivity: Increased risk of sunburn; advise sun protection.
• Intracranial hypertension (pseudotumor cerebri): Reported in adults and children; monitor for headache or vision changes.
• Esophagitis/esophageal ulceration: Ensure patient takes with water and remains upright for ≥30 minutes.
• Superinfection: May cause overgrowth of non-susceptible organisms including Candida and Clostridioides difficile.
• Hepatotoxicity: Rare, but dose-dependent; caution in hepatic impairment.
• Autoimmune syndromes: Rare reports of drug-induced lupus and vasculitis.

Common:

• GI: Nausea, vomiting, diarrhea, abdominal pain
• Skin: Photosensitivity, rash
• Musculoskeletal: Arthralgia (rare)
• General: Headache, dizziness

Serious/Rare:

• Hepatic: Elevated liver enzymes, hepatotoxicity
• Hematologic: Hemolytic anemia, thrombocytopenia, neutropenia (rare)
• Renal: Interstitial nephritis (rare)
• Neurologic: Benign intracranial hypertension (especially in females of childbearing age)
• Hypersensitivity: Anaphylaxis, serum sickness-like reaction
• Infectious: C. difficile-associated diarrhea or colitis

• Antacids, iron, calcium, magnesium supplements: Reduce absorption; separate by at least 2 hours.
• Oral contraceptives: May reduce effectiveness; recommend backup contraception.
• Anticoagulants (e.g., warfarin): Potentiates anticoagulant effect; monitor INR closely.
• Penicillins: Antagonistic effect; avoid concomitant use when bactericidal action is required.
• Barbiturates, carbamazepine, phenytoin: May decrease doxycycline half-life due to hepatic enzyme induction.
• Alcohol (chronic use): May reduce serum concentrations.

• CDC Guidelines (2021): Reaffirmed doxycycline as first-line therapy for chlamydia, rickettsial infections, and Lyme disease.
• WHO & FDA Updates: Continued approval for doxycycline in post-exposure anthrax prophylaxis and malaria prophylaxis.
• Pediatric Use Revision: CDC supports limited short-course doxycycline use in children under 8 for life-threatening rickettsial diseases.

• Tablets/Capsules:
• Store at 20°C to 25°C (68°F to 77°F).
• Protect from light and moisture.
• Keep in tightly closed containers.
• Reconstituted oral suspensions or IV preparations:
• Use immediately or as directed; do not freeze.
• Follow manufacturer guidelines for reconstitution and refrigeration (if applicable).
• Handling precautions:
• Avoid outdated doxycycline products, as degraded forms may cause nephrotoxicity (Fanconi-like syndrome).
• Keep out of reach of children.