Doxycycline Drug Profile

What is Doxycycline?

Doxycycline is a broad-spectrum antibiotic belonging to the tetracycline class of medications. It works by inhibiting bacterial protein synthesis and is commonly prescribed to treat various bacterial infections, including respiratory tract infections, skin conditions, and certain sexually transmitted infections. This medication is also used for malaria prevention in travelers to endemic areas.

Uses

Doxycycline is approved for treating several bacterial infections and conditions:

• Respiratory tract infections: Including pneumonia, bronchitis, and sinusitis caused by susceptible bacteria
• Skin and soft tissue infections: Such as cellulitis, wound infections, and severe acne when other treatments have failed
• Sexually transmitted infections: Including chlamydia, gonorrhea, and syphilis, particularly in patients allergic to penicillin
• Tick-borne diseases: Treatment of Rocky Mountain spotted fever, Lyme disease, and ehrlichiosis
• Malaria prevention: Used as prophylaxis for travelers to areas with chloroquine-resistant malaria

How it works

Doxycycline works by binding to the 30S ribosomal subunit of bacteria, preventing them from producing essential proteins needed for growth and reproduction. This bacteriostatic action stops bacterial multiplication, allowing the body’s immune system to eliminate the infection. The medication is effective against both gram-positive and gram-negative bacteria, as well as some atypical organisms like mycoplasma and chlamydia.

Side effects

Common side effects include:

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• Nausea and vomiting
• Diarrhea or loose stools
• Stomach upset or abdominal pain
• Loss of appetite
• Headache
• Dizziness
• Skin sensitivity to sunlight (photosensitivity)
• Vaginal yeast infections in women

Serious side effects requiring immediate medical attention:

• Severe diarrhea or signs of C. difficile infection
• Severe skin reactions or blistering
• Signs of liver problems (yellowing of skin or eyes, dark urine)
• Increased pressure in the skull (severe headache, vision changes)
• Severe allergic reactions (difficulty breathing, swelling of face or throat)

Warnings and precautions

• Pregnancy and children: Doxycycline should not be used during pregnancy or in children under 8 years old, as it can cause permanent tooth discoloration and affect bone development
• Kidney impairment: Patients with severe kidney disease may need dose adjustments or alternative antibiotics, as the medication can worsen kidney function
• Sun exposure: Increased risk of severe sunburn; patients should avoid prolonged sun exposure and use sunscreen
• Esophageal irritation: Take with plenty of water and remain upright for at least 30 minutes after taking to prevent esophageal ulceration
• Superinfections: Long-term use may lead to overgrowth of resistant bacteria or fungi

Interactions

• Antacids and iron supplements: Reduce doxycycline absorption; take 2-3 hours apart from the antibiotic
• Warfarin: May increase bleeding risk by enhancing anticoagulant effects
• Oral contraceptives: May reduce effectiveness of birth control pills; use additional contraceptive methods
• Digoxin: Can increase digoxin levels, potentially causing toxicity
• Calcium and dairy products: Significantly reduce drug absorption; avoid taking together
• Phenytoin and carbamazepine: These seizure medications can reduce doxycycline effectiveness
• Isotretinoin: Combination may increase risk of increased intracranial pressure
• Live bacterial vaccines: Doxycycline may reduce vaccine effectiveness

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Dosage

Typical adult dosages vary depending on the condition being treated. For most infections, the usual dose is 100 mg twice daily or 200 mg once daily. For acne treatment, doses typically range from 40-100 mg daily. Malaria prevention usually requires 100 mg daily, starting 1-2 days before travel and continuing for 4 weeks after leaving the malaria area. The medication should be taken with a full glass of water and can be taken with food to reduce stomach upset. Dosage should always be determined by a healthcare provider based on the specific condition, patient factors, and response to treatment.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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