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Doxycycline
Antibiotic — TetracyclineNigerian brand names:VibramycinDoxylinDoxyBiodoxiDoxymax
Reviewed by the PMC Medical Team · Promise Medical Centre
Overview
Doxycycline is a broad-spectrum antibiotic belonging to the tetracycline class. It works by inhibiting bacterial protein synthesis, stopping bacteria from growing and multiplying. It is effective against a wide range of bacteria and some parasites, including those responsible for malaria, typhus, chlamydia, and Lyme disease. In Nigeria, doxycycline is widely used for malaria prophylaxis in travellers and as an alternative or adjunct in malaria treatment, as well as for sexually transmitted infections and respiratory tract infections.
Uses
Doxycycline is used to treat and prevent:
- Malaria prophylaxis: Prevention of Plasmodium falciparum malaria in travellers to malaria-endemic areas
- Respiratory tract infections: Community-acquired pneumonia, atypical pneumonia (Mycoplasma, Chlamydia pneumoniae)
- Sexually transmitted infections (STIs): Chlamydia, non-gonococcal urethritis, pelvic inflammatory disease (PID)
- Skin infections: Acne vulgaris (moderate to severe), infected skin conditions
- Rickettsia infections: Typhus fever, Rocky Mountain spotted fever
- Leptospirosis prevention and treatment
- Cholera treatment (with rehydration)
- Anthrax (post-exposure prophylaxis and treatment)
- Some cases of typhoid fever
How to Use
Take doxycycline exactly as prescribed.
Dosage:
- Most infections (adults): 100 mg twice daily on the first day, then 100 mg once or twice daily
- Malaria prophylaxis: 100 mg once daily, starting 1–2 days before travel, throughout the trip, and for 4 weeks after returning
- Acne: 50–100 mg once or twice daily (often long-term, months)
Taking it correctly:
- Take with a full glass of water (at least 200 mL)
- Take with food or milk to reduce stomach irritation — food does not significantly reduce absorption for doxycycline (unlike older tetracyclines)
- Take each dose at the same time daily
- Remain upright (do not lie down) for at least 30 minutes after taking doxycycline — lying down immediately can cause severe oesophageal (gullet) irritation or ulceration
- Complete the full course of treatment
Side Effects
Common side effects:
- Nausea, vomiting, or stomach upset — taking with food helps
- Diarrhoea
- Photosensitivity (sun sensitivity): Skin burns more easily in sunlight — use sunscreen, wear protective clothing, avoid prolonged sun exposure. This is especially important in sunny Nigeria
- Oesophageal irritation or ulceration — prevented by taking with water and staying upright
- Discolouration of teeth (a concern in children under 8 — see Warnings)
Serious side effects (rare):
- Severe allergic reactions (rash, hives, difficulty breathing, swelling)
- Clostridium difficile diarrhoea (severe, bloody, watery diarrhoea)
- Raised intracranial pressure (headache, visual changes) — especially in women of childbearing age
- Liver toxicity with prolonged high-dose use
Warnings & Precautions
Do not use doxycycline if you:
- Are pregnant: Can cause permanent yellow-brown discolouration of developing foetal teeth and bone growth suppression
- Are breastfeeding: Enters breast milk and may affect infant bone and tooth development
- Are a child under 8 years old: Can permanently stain developing teeth yellow-brown and affect bone growth — not used in young children except in life-threatening situations (e.g., anthrax, Rocky Mountain spotted fever)
Important warnings:
- Sun protection is essential: Doxycycline causes photosensitivity — patients in Nigeria, where UV exposure is high year-round, must use sunscreen (SPF 30+) and protective clothing. Severe sunburn can occur within minutes of sun exposure
- Take with water and stay upright: Swallow with at least a full glass of water. Do not take immediately before bed. Doxycycline tablets can stick in the oesophagus and cause painful ulceration if not swallowed correctly
- Expiry date: NEVER use expired doxycycline — degraded tetracyclines can cause a serious kidney condition (Fanconi syndrome)
- Acne: Long-term acne treatment should be reviewed regularly for antibiotic resistance and alternative therapies
Drug Interactions
Important interactions:
- Antacids containing calcium, magnesium, or aluminium (e.g., Gaviscon, Maalox): Significantly reduce doxycycline absorption — take doxycycline 2 hours before or 6 hours after antacids
- Iron supplements and dairy products: Reduce absorption — take 2–3 hours apart
- Bismuth subsalicylate: Reduces absorption
- Penicillin antibiotics: Doxycycline may reduce the bactericidal effect of penicillins — avoid combination where possible
- Warfarin: Doxycycline can increase anticoagulant effect — monitor INR
- Oral contraceptives: May reduce contraceptive efficacy in rare cases — use additional contraception during treatment
- Retinoids (isotretinoin, acitretin): Combination increases risk of raised intracranial pressure — contraindicated
- Methotrexate: Doxycycline can increase methotrexate toxicity
- Antiepileptics (phenytoin, carbamazepine, phenobarbitone): Reduce doxycycline blood levels — may need higher dose
Storage
Store at room temperature (below 30°C) in a dry place, away from light and moisture. Never use expired doxycycline. Keep out of reach of children.
Buy only NAFDAC-registered medications
Nigeria has a significant problem with counterfeit and substandard drugs. Always purchase medications from a licensed pharmacy and check the NAFDAC registration number on the package — verify at nafdac.gov.ng.