Doxycycline

What is Doxycycline?

Doxycycline is a broad-spectrum tetracycline antibiotic used to treat a wide range of bacterial infections. It is the preferred first-line antibiotic for Chlamydia trachomatis infection (chlamydia) and non-gonococcal urethritis (NGU) in non-pregnant adults, per WHO and European STI treatment guidelines, and is also widely used for selected respiratory infections, acne, Lyme disease, and malaria prophylaxis.

Doxycycline is listed on the WHO Model List of Essential Medicines and is one of the most widely prescribed antibiotics globally. It is available as doxycycline hyclate and doxycycline monohydrate; check the formulation and instructions of the prescribed product.

How does Doxycycline work?

Doxycycline inhibits bacterial protein synthesis by binding reversibly to the 30S ribosomal subunit of bacteria. This blocks the attachment of aminoacyl-tRNA to the messenger RNA-ribosome complex, preventing the addition of new amino acids to growing polypeptide chains.

The result is:

• Inhibition of protein synthesis: Bacteria cannot produce the proteins essential for growth, metabolism, and replication
• Bacteriostatic activity: Doxycycline stops bacterial growth and reproduction rather than directly killing bacteria, allowing the immune system to clear the infection
• Broad spectrum: Active against a wide range of gram-positive, gram-negative, and atypical organisms including intracellular pathogens such as Chlamydia, Mycoplasma, and Rickettsia species

Doxycycline’s ability to treat intracellular organisms (bacteria that live inside host cells) is clinically important — Chlamydia trachomatis is an obligate intracellular pathogen, and intracellular Rickettsia species cause tick-borne diseases also treated with doxycycline.

Pharmacokinetic properties:

• High oral bioavailability (~93%), nearly equivalent to intravenous dosing
• Long half-life (~18–22 hours), allowing twice-daily dosing
• Widely distributed in tissues, including into the genital tract
• Eliminated via bile and faeces (unlike most antibiotics excreted by the kidneys — less dose adjustment needed in renal impairment)

Who is Doxycycline for?

Doxycycline is the preferred treatment for:

• Chlamydia (Chlamydia trachomatis): First-line treatment for uncomplicated genital chlamydia in non-pregnant adults (100 mg twice daily for 7 days)
• Non-gonococcal urethritis (NGU): First-line treatment, usually caused by Chlamydia trachomatis or Mycoplasma genitalium
• Lymphogranuloma venereum (LGV): Caused by Chlamydia trachomatis serovars L1–L3; treated with doxycycline 100 mg twice daily for 21 days
• Pelvic inflammatory disease (PID): Used as part of combination regimens
• Syphilis: Second-line option for patients allergic to penicillin (2–4 weeks depending on stage)
• Epididymo-orchitis: When caused by Chlamydia trachomatis
• Lyme disease, acne, respiratory infections, and malaria prophylaxis: Common non-STI uses where doxycycline is also first-line or alternative therapy

Doxycycline is not appropriate for:

• Pregnant women (a doctor must select an alternative under current guidance)
• Patients with known tetracycline allergy
• Viral or fungal infections

This article covers adult use. The Spanish Vibracina label has specific paediatric restrictions and exceptional indications; it does not impose an absolute prohibition for everyone under 12. This article provides no paediatric regimens and does not change platform access eligibility.

Dosage

Doxycycline capsules/tablets should be swallowed with a full glass of water and taken in an upright position (not immediately before lying down) to prevent oesophageal irritation.

Side effects

Common side effects (affecting 1 to 10 in 100 people)

• Nausea
• Vomiting
• Diarrhoea
• Abdominal pain
• Photosensitivity (increased sensitivity to sunlight — use sunscreen and avoid prolonged sun exposure during treatment)

Less common side effects

• Oesophageal irritation or ulceration (take with adequate water and do not lie down immediately after)
• Headache
• Dizziness
• Vaginal thrush (candidiasis) — antibiotic disruption of normal flora
• Skin rash

Serious side effects (rare)

• Severe photosensitivity reactions: Avoid direct sunlight and UV exposure during treatment
• Intracranial hypertension (pseudotumour cerebri): Rare — persistent headache, visual changes, or vomiting should be assessed by a doctor
• Serious allergic reactions: Including anaphylaxis, angioedema
• Clostridioides difficile colitis: Severe persistent diarrhoea

Doxycycline vs alternative antibiotics for chlamydia

Doxycycline vs Azithromycin: Doxycycline is preferred; azithromycin is an alternative in selected circumstances for uncomplicated genital chlamydia. A 2021 meta-analysis and updated European guidelines favour doxycycline as the preferred option for genital chlamydia due to higher microbiological cure rates, particularly for rectal infection. Azithromycin single-dose remains an alternative when adherence to a 7-day course is a concern.

Online assessment for Doxycycline

Doxycycline is a prescription-only medicine (POM) in all EU member states. It cannot legally be dispensed without a valid prescription from a licensed medical professional.

Prescrivia operates as a technology intermediary: we do not prescribe medicines, employ doctors, or sell medicines. Our platform connects patients with independent doctors who can conduct confidential online health assessments.

Availability of an online assessment, prescribing, dispensing and delivery depends on the medicine, country and applicable law. Spain prohibits distance sale of prescription medicines; a catalogue entry or cross-border prescription does not establish a right to delivery. An in-person examination or testing may be required.

The process, where legally and clinically available:

1. Complete a health assessment: Provide details of your symptoms, recent STI testing, sexual history, and any relevant allergies or current medications.
2. Doctor review: An independent doctor reviews your assessment. If doxycycline is clinically appropriate, they may issue a prescription.
3. Pharmacy fulfilment: The prescription is sent to a pharmacy partner to assess dispensing and any supply under the applicable country rules.

Important: Prescrivia does not guarantee that a prescription will be issued. A positive chlamydia test or strong clinical indication is typically required. All prescribing decisions are made independently by qualified medical professionals.

Important safety information

Do not take Doxycycline if you:

• Are pregnant or breastfeeding
• Have a known allergy to tetracycline antibiotics
• Are taking isotretinoin (increased risk of intracranial hypertension)

Tell your doctor before taking Doxycycline if you:

• Have liver disease
• Have systemic lupus erythematosus (SLE) — photosensitivity risk is increased
• Are taking antacids, calcium supplements, iron, or bismuth-containing products (take at least 2–3 hours apart)
• Are taking warfarin (monitoring of anticoagulation may be needed)
• Are taking oral contraceptives (additional contraceptive precautions are not required, but discuss with your doctor)

Partner notification: If diagnosed with chlamydia or another STI, sexual partners from the preceding 6 months should be informed, offered testing, and treated. This is essential to prevent reinfection.

Test of cure: A test of cure is not routinely recommended after standard treatment for uncomplicated chlamydia, but may be advised if adherence was uncertain. Pregnancy requires an appropriate alternative treatment and follow-up; this does not authorise doxycycline use in pregnancy.

Sources

• Product information / clinical reference 1
• Product information / clinical reference 2

Medical information on this page is based on the following sources:

• World Health Organization (WHO). WHO Guidelines for the Treatment of Chlamydia trachomatis. 2016. who.int
• European STI Guidelines Editorial Board. 2015 European guideline on the management of Chlamydia trachomatis infections. Journal of the European Academy of Dermatology and Venereology.
• World Health Organization (WHO). WHO Model List of Essential Medicines. 22nd edition, 2021.
• Dombrowski JC, et al. Doxycycline versus azithromycin for the treatment of rectal chlamydia in men who have sex with men. Clinical Infectious Diseases. 2021.

The content-edit date does not certify a clinical review. It is provided for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for advice relevant to your individual health circumstances.