[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Tetracyclines](https://durgical.com/en/pharmacology/classes/tetracyclines/) › Doxycycline [Pharmacology](https://durgical.com/en/pharmacology/) · [Tetracyclines](https://durgical.com/en/pharmacology/classes/tetracyclines/) # Doxycycline The most used tetracycline: for rickettsial fevers, chlamydia, leptospirosis, cholera and malaria prevention. Taken upright with water, away from minerals. Updated 2026-11-01 - Class: [Tetracyclines](https://durgical.com/en/pharmacology/classes/tetracyclines/) - Target: Bacterial ribosome, 30S subunit (16S rRNA, A site) - ATC code: J01AA02 - WHO Model List of Essential Medicines ◆**Bacterial ribosome, 30S subunit (16S rRNA, A site)**Doxycycline ⓘ The figure shows doxycycline bound to the 30S ribosomal subunit of Escherichia coli. **Target in 3D:** Bacterial ribosome, 30S subunit (16S rRNA, A site). PDB structure 9SX2 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/9SX2) · Drag to rotate · pinch to zoom ## Mechanism of action Doxycycline binds the 16S rRNA of the 30S subunit and blocks aminoacyl-tRNA from entering the A site, so the protein chain cannot grow. It is mainly bacteriostatic and reaches intracellular bacteria such as Rickettsia and Chlamydia. - Absorbed almost completely by mouth - Enters the bacterium and binds the 30S subunit - Aminoacyl-tRNA cannot reach the A site - Protein synthesis and growth stop ## Pharmacokinetics **Absorption** About 90% absorbed by mouth; food changes it little, but calcium, magnesium, aluminium and iron reduce it. **Distribution** Wide, including intracellular sites. **Elimination** Urine and faeces; it can be used in kidney failure without dose change. **Half-life** About 18–22 hours, similar in severe kidney failure. ## Indications - Chlamydia trachomatis infection (WHO first choice), including lymphogranuloma venereum [Chlamydia infection →](https://durgical.com/en/conditions/chlamydia-infection/) - Leptospirosis and rickettsial fevers (spotted fever, typhus, Q fever) [Leptospirosis →](https://durgical.com/en/conditions/leptospirosis/) - Prevention of Plasmodium falciparum malaria in travellers [Malaria →](https://durgical.com/en/conditions/malaria/) - Community-acquired pneumonia (WHO second choice) [Community-acquired pneumonia →](https://durgical.com/en/conditions/community-acquired-pneumonia/) - Syphilis when penicillin cannot be used [Syphilis →](https://durgical.com/en/conditions/syphilis/) - Cholera (WHO first choice) and anthrax after exposure ## Adverse effects ### Common - Nausea and stomach upset - Photosensitivity (exaggerated sunburn) - Oesophageal irritation or ulcer if swallowed without water - Vaginal yeast infection ### Serious (rare, important) - Permanent tooth discoloration if used during tooth development - Intracranial hypertension (headache, blurred vision) - Severe skin reactions and C. difficile colitis - Liver injury (rare) ## Contraindications - Allergy to any tetracycline - Second half of pregnancy and children up to 8 years, except severe disease (e.g. spotted fever, anthrax) without alternatives ## Key interactions **Antacids, calcium, magnesium, iron, bismuth** Chelate doxycycline and lower absorption; doses are spaced. **Warfarin** Tetracyclines can increase its effect. **Carbamazepine, phenytoin, barbiturates, rifampicin** Shorten doxycycline's half-life. **Isotretinoin** Both can raise intracranial pressure; combined use is avoided. ## What is monitored - Headache or visual change (intracranial hypertension) - Skin after sun exposure - INR on warfarin ## Administration and safety - Swallow with a full glass of water and stay upright for a while; not at bedtime - Separate from antacids, minerals and iron - The IV form is protected from light and infused slowly ## Nursing care - Teach sun protection - Teach to report painful swallowing, severe headache or blurred vision - Ask about pregnancy and the child's age - For malaria prevention, explain that it is continued after leaving the risk area as prescribed ## Pregnancy and breastfeeding Avoided in the second half of pregnancy because it stains the baby's teeth and affects bone growth. ## Memory aid «Doxy for the Ds and the bugs that hide»: dengue-like fevers that are really rickettsial or leptospiral, and chlamydia hiding inside cells. ## Test yourself Think of the answer, then tap the question to see it. ## Why is doxycycline swallowed with plenty of water while upright? A capsule or tablet that stays in the oesophagus causes irritation and ulcers. ## Which antimalarial use does doxycycline have? Prevention of Plasmodium falciparum malaria in travellers. ## Does doxycycline need a dose change in kidney failure? No; its half-life stays similar, because it is also cleared in the faeces. ## Which minerals cut doxycycline absorption? Calcium, magnesium, aluminium and iron. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/doxycycline/) ## Related drugs - [Minocycline](https://durgical.com/en/pharmacology/minocycline/) - [Tetracycline](https://durgical.com/en/pharmacology/tetracycline/) - [Azithromycin](https://durgical.com/en/pharmacology/azithromycin/) ## Related conditions - [Chlamydia infection](https://durgical.com/en/conditions/chlamydia-infection/) - [Leptospirosis](https://durgical.com/en/conditions/leptospirosis/) - [Malaria](https://durgical.com/en/conditions/malaria/) - [Community-acquired pneumonia](https://durgical.com/en/conditions/community-acquired-pneumonia/) - [Syphilis](https://durgical.com/en/conditions/syphilis/) [← Back to the class: Tetracyclines](https://durgical.com/en/pharmacology/classes/tetracyclines/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - DOXYCYCLINE HYCLATE capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=fbc1924f-d647-465a-b8b2-25de332c5896) (DailyMed (U.S. National Library of Medicine), 2026); [Doxycycline: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682063.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/?query=doxycycline) (World Health Organization, 2025); [30S Doxycycline Bound E. coli Ribosome](https://www.rcsb.org/structure/9SX2) (RCSB Protein Data Bank, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/doxycycline/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/doxycycline/