Doxycycline

Oral Antibiotics

Drug class: Tetracycline Antibiotic

Doxycycline (VIBRAMYCIN)（中文：多西環素）

Pronunciation

Doxycycline 100mg

Common Strengths

• 100 mg

Drug Trade Name

Vibramycin

Drug Usage

Doxycycline is a broad-spectrum antibiotic used to treat various bacterial infections, including:

• respiratory tract infections
• urinary tract infections
• Acne and rosacea
• Sexually transmitted infections (e.g. chlamydia, gonorrhea, syphilis)
• Malaria prophylaxis
• Infections caused by mites, ticks, or lice
• Anthrax treatment and prophylaxis

Mechanism of Action

Doxycycline works by inhibiting bacterial protein synthesis. It binds to the 30s ribosomal subunit of bacteria, preventing the addition of amino acids to the growing peptide chain. This action stops bacterial growth and reproduction.

Route of Administration

Doxycycline can be administered via:

• Oral (tablets or capsules)

Dosages

General Adult Dosage:

• Initial: 200 mg on the first day (may be divided into 100 mg every 12 hours)
• Maintenance: 100 mg once daily

Side Effects

Frequency	Adverse reactions
Common Side Effects	Nausea and vomiting
	Diarrhea
	Stomach pain
	Photosensitivity
Serious Side Effects	Severe allergic reactions (hives, difficulty breathing)
	Liver problems (jaundice)
	Blood disorders (low white blood cell counts)
	Esophageal irritation or ulceration

Pharmacokinetics

• Doxycycline is rapidly absorbed after oral administration.
• Onset Time: Effects can be seen within 1 to 2 hours.
• Duration of action: The half-life ranges from 15 to 30 hours.

Drug Precautions

Pregnancy

Not recommended during pregnancy due to risks of tooth and bone development issues in the fetus.

Breastfeeding

Short-term use is generally considered safe; however, long-term use may affect infant bone development.

Children and Elderly

Not recommended for children under 8 years due to risks of permanent teeth discoloration. Use with caution in elderly patients with renal impairment.

Drug Monitoring Items

Monitor liver function tests and complete blood counts during prolonged therapy.

Drug Interactions

Avoid concurrent use with:

• Antacids containing aluminum, calcium, or magnesium (reduce absorption). The recommended separation time for doxycycline when taken with these antacids is as follows:
  • Take doxycycline at least 1 to 2 hours before consuming antacids containing aluminum, calcium, or magnesium.
  • Alternatively, take doxycycline 1 to 2 hours after these antacids.
  • This timing helps prevent the formation of insoluble complexes that can significantly reduce the absorption of doxycycline in the gastrointestinal tract.
• Supplements containing minerals like zinc or magnesium should be avoided close to doxycycline administration due to potential absorption.
• Anticoagulants: Doxycycline can enhance the effects of blood thinners like warfarin, increasing the risk of bleeding.
• Other Antibiotics: It can interfere with the effectiveness of penicillin antibiotics (e.g., amoxicillin).
• Anticonvulsants: Medications such as phenytoin (Dilantin) and carbamazepine (Tegretol) can accelerate the metabolism of doxycycline, potentially reducing its effectiveness.
• Vitamin A Derivatives: Acne treatments containing isotretinoin may increase the risk of increased intracranial pressure when taken with doxycycline.

FAQ

How Should I Take the Tablet?

Swallow whole with plenty of water; do not crush or chew. It can be taken with food to minimize stomach irritation.

What Should I Avoid while Taking?

Avoid sun exposure without protection due to increased photosensitivity. Also, avoid taking antacids or supplements containing calcium or iron close to the time of taking doxycycline.

What Happens if I Miss a Dose?

Take it as soon as you remember unless it is almost time for your next dose. Do not double doses.