The complete guide to doxycycline
- How doxycycline works
- What doxycycline is used for
- Doxycycline for chlamydia
- What forms and strengths are available in the UK
- Who typically should not take doxycycline
- How to access it in the UK
How doxycycline works
Doxycycline works by interfering with the ability of bacteria to produce proteins. To reproduce, bacteria need to produce proteins. Doxycycline works by blocking this process, leaving the bacteria unable to multiply. With the infection no longer spreading, the body's own immune system can clear the bacteria over the course of treatment.
This approach, slowing bacterial growth rather than killing bacteria directly, is why doxycycline is described as a bacteriostatic antibiotic. It is effective against a broad range of bacterial infections, including some types of bacteria that other common antibiotics cannot reach, which is part of the reason it has remained in clinical use for so long.
Good to know
Doxycycline only works against bacterial infections. It has no effect on viral infections such as colds, flu, or COVID-19. Using antibiotics when they are not needed contributes to antibiotic resistance, which is a significant public health concern. Doxycycline should only be taken when prescribed for a confirmed or suspected bacterial infection.
What doxycycline is used for
Doxycycline has one of the broadest indication profiles of any antibiotic currently licensed in the UK.
Respiratory tract infections
Doxycycline is licensed for pneumonia and other lower respiratory tract infections caused by susceptible organisms including Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, and Mycoplasma pneumoniae. It is also used in the treatment of chronic bronchitis and sinusitis.
Sexually transmitted infections
Doxycycline is licensed for several sexually transmitted infections, including infections caused by Chlamydia trachomatis (uncomplicated urethral, endocervical, or rectal infections), non-gonococcal urethritis caused by Ureaplasma urealyticum, and conditions including chancroid, granuloma inguinale, and lymphogranuloma venereum. It is also listed as an alternative treatment option for gonorrhoea and syphilis.
Urinary tract infections
Doxycycline is licensed for urinary tract infections caused by susceptible organisms including Klebsiella species, Enterobacter species, Escherichia coli, and Streptococcus faecalis.
Skin infections
Doxycycline is licensed for acne vulgaris where antibiotic therapy is considered necessary by a prescriber.
Ophthalmic infections
Licensed uses include infections caused by susceptible strains of gonococci, staphylococci, and Haemophilus influenzae, as well as trachoma and inclusion conjunctivitis.
Rickettsial infections
Doxycycline is effective against rickettsial diseases including Rocky Mountain spotted fever, typhus, Q fever, and Coxiella endocarditis.
Other infections and prophylaxis
Further licensed uses include brucellosis, cholera, bubonic plague, relapsing fever, tularaemia, melioidosis, and acute intestinal amoebiasis. Doxycycline is also licensed for prophylaxis in scrub typhus, travellers' diarrhoea, leptospirosis, and malaria (in accordance with current guidelines).
Good to know
The breadth of doxycycline's indications reflects its activity against an unusually wide range of organisms, including bacteria that other antibiotic classes cannot treat. This is one of the reasons it has remained clinically useful for several decades.
Doxycycline for chlamydia
Chlamydia is one of the most common reasons doxycycline is prescribed in the UK. It is recommended by the British Association for Sexual Health and HIV (BASHH) as the first-line antibiotic treatment for uncomplicated chlamydia infections of the urethra, cervix, and rectum.
Doxycycline is effective against Chlamydia trachomatis because the bacterium's biology makes it susceptible to the protein synthesis inhibition that doxycycline provides. The standard treatment involves a course of tablets taken twice daily for seven days.
Specific dosing guidance should always come from your prescriber or the patient information leaflet supplied with your medication.
Available forms and strengths
Doxycycline is available in the UK in several forms and strengths, depending on the manufacturer and the specific indication.
- 100 mg capsules: The most commonly prescribed form for conditions including chlamydia and other infections in adults. Capsules are taken orally with water.
- 100 mg dispersible tablets (Vibramycin-D): A dispersible tablet form that is dissolved in water before taking. This form may be preferred for people at higher risk of oesophageal irritation from standard capsules, such as older patients or those with swallowing difficulties.
- 50 mg capsules: A lower-strength formulation used for conditions such as acne vulgaris, where a lower daily dose is prescribed over a longer period.
The appropriate form and strength for your circumstances is determined by your prescriber and will be specified in your prescription. Always use the formulation and dose you have been prescribed, and read the patient information leaflet supplied with your specific product.
Who typically should not take doxycycline
Doxycycline is not suitable for everyone. The following groups are generally contraindicated or require careful prescriber assessment before starting treatment.
- Pregnancy: Doxycycline is contraindicated during pregnancy. Tetracyclines can affect the development of teeth and bones in the developing foetus.
- Breastfeeding: Doxycycline passes into breast milk and is contraindicated in breastfeeding mothers for the same reasons relating to tooth development.
- Children under 8 years: Doxycycline should not be used in children under 8 years of age due to the risk of permanent tooth discolouration. Use in children aged 8 to 12 years requires careful clinical justification.
- Known allergy: Doxycycline is contraindicated in anyone with a known hypersensitivity to doxycycline, other tetracycline antibiotics, or any of the excipients in the formulation.
This is not a complete list of all precautions and contraindications. Individual suitability is always determined by a prescriber following a medical assessment. Inform your prescriber of your full medical history, any allergies, and all other medicines you are taking before starting doxycycline.
Important !
Doxycycline interacts with several other medicines and supplements, including antacids containing aluminium, calcium, or magnesium, iron supplements, zinc supplements, and certain anticoagulants. These interactions can affect either how well doxycycline works or how other medicines behave in the body. Always disclose your full medication list to your prescriber.
How to access doxycycline in the UK
Doxycycline is a prescription-only medicine (POM) in the UK. It cannot be purchased without a valid prescription issued by a registered prescriber following a medical assessment.
- Via your GP: Your GP can assess whether doxycycline is appropriate for your condition and issue an NHS prescription. NHS prescriptions are subject to the standard prescription charge in England and are free for eligible patients in Scotland, Wales, and Northern Ireland.
- Via a sexual health clinic: For sexually transmitted infections including chlamydia, sexual health clinics can assess and prescribe doxycycline without the need for a GP referral. This service is free and confidential.
- Via a regulated online clinic: Private online clinics connect you with UK-registered prescribers who can conduct a medical assessment and approve a private prescription for doxycycline where appropriate.
Important !
Do not attempt to obtain doxycycline without a valid prescription, and do not use doxycycline prescribed for someone else. Always ensure any online provider is registered with the GPhC at gphc.org.uk before proceeding.
Conclusion
Doxycycline is a well-established, broad-spectrum antibiotic with a wide range of licensed uses in the UK, from respiratory and urinary tract infections to sexually transmitted infections and acne. Its effectiveness against Chlamydia trachomatis makes it the first-line antibiotic for chlamydia treatment in current UK clinical guidance.
As with all prescription medicines, its use requires a medical assessment to confirm suitability, appropriate dosing, and any relevant precautions or interactions. If you have questions about whether doxycycline is right for your circumstances, a UK-registered prescriber is the right first port of call.
FAQ
Is doxycycline the same as azithromycin for chlamydia?
Both doxycycline and azithromycin are antibiotics used to treat chlamydia, but they are different medicines with different mechanisms, courses, and dosing schedules. Doxycycline is currently the first-line recommendation in BASHH guidelines, typically taken twice daily for seven days. Azithromycin may be considered in specific circumstances, such as during pregnancy when doxycycline is contraindicated. The choice between them is a clinical decision made by a prescriber based on individual circumstances.
How long is a typical course of doxycycline for chlamydia?
The standard course for chlamydia is seven days, taken as 100 mg twice daily. The full course should always be completed even if symptoms resolve before the end of the seven days. For dosing details, see our doxycycline product page.
Can I take doxycycline if I am on the contraceptive pill?
Current guidance indicates that doxycycline does not significantly affect the reliability of hormonal contraception. However, if vomiting or diarrhoea occurs during your course, this may affect absorption of oral contraceptives. Follow the guidance in your contraceptive pill information leaflet in this situation and contact your prescriber if you are unsure.
Does doxycycline treat viral infections?
No. Doxycycline is an antibiotic and is only effective against bacterial infections. It has no effect on viral infections such as colds, flu, or COVID-19.
The DoktorABC medical advisory board
Dr. Roland Ruiken
Medical advisor, Norway
Dr. Viktor Simunovic
Medical advisor, Croatia