Antibiotic — Tetracycline Pregnancy: Contra-indicated in pregnancy and lactation (see contraindications).

Doxycycline

Brand names: Vibramycin, Doxycycline Hyclate

Doxycycline is a tetracycline antibiotic used in obstetrics and gynaecology principally for pelvic inflammatory disease and certain sexually transmitted infections such as chlamydia.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Genito-urinary / STI regimens (adults): uncomplicated urethral, endocervical or rectal Chlamydia trachomatis infection, non-gonococcal urethritis (Ureaplasma urealyticum), and uncomplicated gonococcal infection (except anorectal in men) — 100 mg twice daily for 7 days. Acute epididymo-orchitis (C. trachomatis or N. gonorrhoeae) — 100 mg twice daily for 10 days. Primary and secondary syphilis (non-pregnant, penicillin-allergic) — 200 mg orally twice daily for two weeks.

Route: Oral

Frequency: Twice daily (indication-specific durations above)

Max: Not stated as an absolute ceiling (indication-specific regimens)

General acute-infection regimen: 200 mg on the first day (single or divided doses) then 100 mg/day maintenance; 200 mg daily throughout for more severe infections. Doxycycline is CONTRAINDICATED in pregnancy and in nursing mothers (tetracyclines cross to teeth/skeleton and are excreted in milk) — of particular relevance in obstetric/gynaecological practice; use a pregnancy test and non-tetracycline alternatives where pregnancy is possible. Elderly: usual dosages, no special precautions. Other labelled indications (acne 50 mg daily 6-12 weeks; malaria prophylaxis 100 mg daily; relapsing fever; Rocky Mountain spotted fever 100 mg every 12 h) also apply per the SPC.

Paediatric dose

Dose: 4.4 mg/kg

Route: Oral

Frequency: Initial 4.4 mg/kg (single or 2 divided doses) on day 1, then maintenance 2.2 mg/kg (single or 2 divided doses); up to 4.4 mg/kg throughout for more severe infections

Max: Children over 45 kg: use the adult dose

Applies to children aged 8 to <12 years weighing 45 kg or less, only where other drugs are unavailable/ineffective/contraindicated (careful justification). CONTRAINDICATED / do NOT use under 8 years (permanent tooth discolouration) except severe/life-threatening infection with no alternative. Not for use in pregnancy/lactation. Paediatric dosing is safety-critical — verify against a current children's formulary.

Dose adjustments

Renal

No dosage adjustment necessary in renal impairment (usual recommended doses do not lead to accumulation)

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

Contraindications

Hypersensitivity to the active substance, to other tetracyclines, or to any of the excipients
Pregnancy (predominantly effects on teeth and skeletal development)
Nursing mothers (tetracyclines excreted into milk)

Side effects

Infections: vaginal (Candida) infection; inflammatory monilial lesions in the anogenital region
Gastrointestinal: nausea/vomiting, dyspepsia; (rare) pancreatitis, C. difficile/pseudomembranous colitis, oesophageal ulcer/oesophagitis
Skin: photosensitivity reaction, rash; serious reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, DRESS)
Hypersensitivity (anaphylactic shock/reaction, angioedema, urticaria); Jarisch-Herxheimer reaction
Nervous system: headache; benign intracranial hypertension (pseudotumor cerebri); Hepatobiliary: hepatitis, hepatotoxicity, jaundice

Clinical monograph

How it works

Inhibits bacterial protein synthesis by binding the 30S ribosomal subunit, giving a broad bacteriostatic spectrum including atypical and intracellular organisms.

Prescribing in practice

Contraindicated in pregnancy and avoided while breastfeeding because of the risk of dental staining and effects on developing bone in the child.
Often combined with other agents (such as metronidazole and a cephalosporin) in pelvic inflammatory disease regimens for broader anaerobic and gonococcal cover.
Absorption is reduced by calcium, iron, antacids and dairy, which should be separated from dosing.

Monitoring

Routine laboratory monitoring is not required for short courses; review clinical response and ensure partner notification and follow-up for sexually transmitted infections.

Counselling the patient

Take with plenty of water while sitting or standing upright to reduce the risk of oesophageal irritation.
Use sun protection as the skin may become more sensitive to sunlight.
Complete the full course and attend follow-up testing where advised.

Evidence & guidelines

Doxycycline-based regimens for pelvic inflammatory disease and chlamydia are recommended in BASHH and NICE guidance.

Reference: BASHH Chlamydia Guidelines (2018); BASHH PID Guidelines (2019); RCOG (2022); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators