Doxycycline

Doxycycline is a broad-spectrum antibiotic from the tetracycline group. It is used to treat numerous bacterial infections, including chlamydia, mycoplasma infections, acne, Lyme disease and malaria prophylaxis.

For chlamydia infections, doxycycline is an equivalent alternative to azithromycin. Treatment lasts 7 days, which requires more discipline in taking the medication.

Doxycycline is characterized by good tissue penetration and a broad spectrum of activity.

Doxycycline has a bacteriostatic effect by inhibiting protein synthesis:

Mechanism of action: The antibiotic binds to the 30S subunit of bacterial ribosomes and prevents the attachment of aminoacyl-tRNA. This blocks protein biosynthesis, and the bacteria can no longer multiply.

Special features of doxycycline:

• Good intracellular penetration
• Effective against many gram-positive and gram-negative bacteria
• Also effective against atypical pathogens (chlamydia, mycoplasma, rickettsia)
• Long half-life (12-25 hours) – only needs to be taken 1-2x daily

Additional effect: Doxycycline also has anti-inflammatory properties, which is why it is used for acne and rosacea.

Doxycycline is suitable for:

• Chlamydia infection (7-day therapy)
• Urethritis (inflammation of the urethra)
• Epididymitis (inflammation of the epididymis)
• Pelvic inflammatory disease (inflammation of the lower abdomen)
• Lymphogranuloma venereum
• Acne and rosacea
• Lyme disease
• Malaria prophylaxis

Advantages over azithromycin:

• Better efficacy against mycoplasma

Not suitable for:

• Pregnancy
• Children under 8 years of age
• Severe hepatic insufficiency

For chlamydia/STIs:

• 100 mg twice daily for 7 days
• Or 200 mg once daily for 7 days

For acne:

• 50-100 mg daily over several weeks/months

For malaria prophylaxis:

• 100 mg daily, starting 1–2 days before arriving in the malaria area and continuing until 4 weeks after leaving it

Available strengths:

• 50 mg tablets/capsules
• 100 mg tablets/capsules
• 200 mg tablets (single dose per day)

How to take it correctly:

• Take with a full glass of water
• Stay upright – do not lie down right away (to protect the esophagus)
• Take with or after a meal (better tolerability)
• Do not take together with dairy products, antacids or iron supplements (keep 2-3 hours apart)

For chlamydia:

• 100 mg in the morning and evening for 7 days
• Complete the entire course

Important:

• Use sun protection during treatment (photosensitization)
• No unprotected sex for 7 days after the end of treatment
• Have your partner treated as well

Doxycycline must not be taken in cases of:

• Hypersensitivity to tetracyclines
• Pregnancy – risk to the child's teeth and bones
• Children under 8 years of age
• Severe hepatic insufficiency

Caution is advised in cases of:

• Breastfeeding
• Myasthenia gravis
• Systemic lupus erythematosus
• Impaired kidney function

Special warning: Tetracyclines can cause permanent tooth discoloration and tooth enamel defects in children.

Common (1-10%):

• Nausea
• Diarrhea
• Abdominal pain
• Photosensitivity (tendency to sunburn)
• Vaginal yeast infection

Uncommon (0.1-1%):

• Headache
• Dizziness
• Skin rash
• Itching
• Esophagitis (inflammation of the esophagus)

Rare but serious:

• Severe allergic reactions
• Increased intracranial pressure (pseudotumor cerebri)
• Liver damage
• Severe skin reactions

Photosensitivity: Increased sensitivity to sunlight is an important side effect. Sun protection (SPF 30+) and avoiding intense sun are important during treatment.

Absorption reduced by:

• Dairy products (calcium)
• Antacids (aluminum, magnesium)
• Iron supplements
• Minerals with divalent cations

→ Keep 2-3 hours apart!

Interactions with:

• Warfarin – increased bleeding tendency
• Retinoids (isotretinoin) – increased intracranial pressure
• Barbiturates, carbamazepine – accelerated breakdown of doxycycline
• Cyclosporine – increased toxicity

Hormonal contraception: With short-term use, probably no relevant effect on the pill, but caution is advised in case of vomiting or diarrhea.