Doxycycline

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Doxycycline on Prescriptsy

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Doxycycline is a broad-spectrum tetracycline antibiotic widely prescribed in the United Kingdom for a diverse range of indications.

It is used to treat bacterial infections including acne vulgaris, sexually transmitted infections (most notably chlamydia), Lyme disease, lower respiratory tract infections, skin and soft tissue infections, and periodontal disease.

Doxycycline is also a first-line option for malaria prophylaxis in travellers visiting endemic regions.

It is available as capsules, tablets, and dispersible tablets and is a prescription-only medicine (POM) available on the NHS.

Doxycycline has been in clinical use since the 1960s and remains one of the most commonly prescribed antibiotics worldwide due to its broad spectrum of activity, well-established safety profile, convenient once or twice-daily dosing, and the fact that it can be used in patients with renal impairment (unlike most other tetracyclines).

In the UK, it is the tetracycline of choice for most indications where a tetracycline is appropriate.

This page provides a comprehensive clinical overview of how doxycycline works, its licensed indications, dosing regimens, side effects, important safety information, and how to obtain a prescription in the UK.

Important safety information about doxycycline

Before starting treatment, note the following essential safety points.

• Doxycycline must not be taken during pregnancy or breastfeeding. It can cause permanent tooth discolouration and bone growth problems in the developing baby or infant.
• Doxycycline causes photosensitivity. Avoid prolonged sun exposure and sunbeds, and use high-factor sunscreen during treatment.
• Take doxycycline with plenty of water while sitting or standing upright to prevent oesophageal ulceration. Do not lie down for at least 30 minutes after taking a dose.
• Do not take doxycycline at the same time as antacids, iron or calcium supplements, or dairy products. Separate by at least 2 to 3 hours.
• Do not take doxycycline with isotretinoin or acitretin, as the combination increases the risk of raised intracranial pressure.

Understanding how antibiotics work against bacterial infections

Bacteria are single-celled microorganisms that can cause disease by invading tissues, releasing toxins, or triggering an inflammatory immune response.

Antibiotics work by targeting biological processes that are essential to bacterial survival but absent or sufficiently different in human cells.

Doxycycline targets bacterial protein synthesis, a fundamental process required for bacterial growth and replication.

By blocking this process, doxycycline halts bacterial multiplication (bacteriostatic action) and allows the body's immune system to clear the remaining organisms.

The importance of completing a prescribed antibiotic course and using antibiotics only when clinically indicated cannot be overstated. Antimicrobial resistance (AMR) is a growing global health threat.

In the UK, the National Action Plan on AMR emphasises antimicrobial stewardship, which includes prescribing antibiotics at the correct dose and for the correct duration, and avoiding unnecessary prescriptions.

When doxycycline is prescribed for acne, it should always be used alongside non-antibiotic topical agents (such as benzoyl peroxide or a retinoid) to reduce the risk of resistance development.

How doxycycline works: mechanism of action

Doxycycline is a semi-synthetic tetracycline antibiotic that exerts its antibacterial effect by inhibiting protein synthesis.

It enters bacterial cells through outer membrane porin channels (in Gram-negative organisms) and via energy-dependent active transport mechanisms.

Once inside the cell, doxycycline binds reversibly to the 30S ribosomal subunit at the aminoacyl-tRNA acceptor site.

This prevents the binding of aminoacyl-tRNA to the ribosome-mRNA complex, blocking the addition of new amino acids to the growing polypeptide chain and halting protein synthesis.

Because doxycycline prevents bacterial growth rather than directly killing bacteria, it is classified as bacteriostatic. At higher concentrations and against certain organisms, it may achieve bactericidal activity.

The clinical outcome depends on the interaction between the antibiotic, the infecting organism, and the host immune response.

Doxycycline has additional pharmacological properties relevant to its use in acne and inflammatory conditions. It inhibits matrix metalloproteinases (MMPs), enzymes involved in tissue breakdown and remodelling.

It reduces neutrophil chemotaxis (the migration of inflammatory white blood cells to sites of infection or inflammation) and suppresses pro-inflammatory cytokine production.

These anti-inflammatory effects contribute to its efficacy in acne at sub-antimicrobial doses and have led to interest in doxycycline for other inflammatory conditions.

The spectrum of activity includes Gram-positive bacteria (Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes), Gram-negative bacteria (Haemophilus influenzae, Neisseria gonorrhoeae, Escherichia coli), atypical organisms (Chlamydia trachomatis, Mycoplasma pneumoniae, Coxiella burnetii, Rickettsia species), spirochaetes (Borrelia burgdorferi causing Lyme disease, Treponema pallidum causing syphilis), and Plasmodium species (malaria parasites).

Clinical indications and UK prescribing guidance

Acne vulgaris

Doxycycline is the most commonly prescribed oral antibiotic for moderate to severe inflammatory acne in UK clinical practice.

NICE CKS on acne vulgaris recommends oral antibiotics alongside a topical retinoid or benzoyl peroxide when topical treatment alone has not produced an adequate response after 8 to 12 weeks.

Doxycycline 100 mg daily for up to 3 months is the recommended first-line oral antibiotic.

If acne does not respond to two courses of different oral antibiotics, referral to a dermatologist for consideration of isotretinoin is appropriate.

Sexually transmitted infections

Doxycycline 100 mg twice daily for 7 days is the recommended first-line treatment for uncomplicated genital chlamydia in the current BASHH guidelines.

It is also used in the treatment of non-gonococcal urethritis, pelvic inflammatory disease (as part of a combination regimen), lymphogranuloma venereum, and early syphilis (as an alternative to benzathine penicillin in penicillin-allergic patients).

Doxycycline 100 mg twice daily for 14 days is a recommended regimen for early syphilis in patients unable to tolerate penicillin.

Lyme disease

NICE guideline NG95 recommends doxycycline 100 mg twice daily for 21 days as first-line treatment for erythema migrans (the characteristic expanding red rash of early Lyme disease) in adults and children over 12 years.

For Lyme disease with neurological, cardiac, or joint involvement, specialist advice should be sought regarding appropriate antimicrobial therapy.

Malaria prophylaxis

Doxycycline 100 mg daily is recommended for malaria prophylaxis by Public Health England (now the UK Health Security Agency) and the British National Formulary for travellers to areas with chloroquine-resistant Plasmodium falciparum.

Prophylaxis should begin 1 to 2 days before entering the malarious area, continue daily during the stay, and continue for 4 weeks after leaving.

Other options include atovaquone-proguanil (Malarone) and mefloquine; the choice depends on the destination, duration of travel, and individual patient factors.

Respiratory tract infections

Doxycycline is used for lower respiratory tract infections including community-acquired pneumonia caused by atypical organisms (Mycoplasma, Chlamydophila, Legionella), exacerbations of chronic obstructive pulmonary disease (COPD), and bronchitis.

It is also used in the treatment of Q fever (Coxiella burnetii) and rickettsial infections.

Dosage and administration

Standard dosing for most indications is 200 mg on the first day (as a loading dose), followed by 100 mg once daily.

For acne, the loading dose is often omitted and treatment begins at 100 mg daily. For chlamydia, the dose is 100 mg twice daily for 7 days.

For Lyme disease, 100 mg twice daily for 21 days. For malaria prophylaxis, 100 mg once daily throughout the travel period and for 4 weeks after return.

Take each dose with a full glass of water while sitting or standing upright. Take with or after food to reduce nausea.

Do not lie down for at least 30 minutes after swallowing the dose.

Avoid antacids, iron preparations, calcium supplements, and dairy products within 2 to 3 hours of your dose, as these form insoluble chelates with doxycycline and substantially reduce its absorption.

If you miss a dose, take it as soon as you remember.

If it is nearly time for your next dose, skip the missed dose and continue with your normal schedule. Do not double up.

Complete the full course as prescribed, even if you feel better before it is finished, unless your prescriber advises otherwise.

Side effects of doxycycline

Common side effects

Gastrointestinal effects are the most commonly reported side effects and include nausea, vomiting, diarrhoea, abdominal discomfort, and loss of appetite.

Taking doxycycline with food and plenty of water helps minimise these symptoms.

Photosensitivity is a well-known and common effect; patients may develop exaggerated sunburn even with brief sun exposure.

This can occur throughout the course and for several days after completing treatment.

Uncommon side effects

Oesophageal irritation and ulceration can cause retrosternal pain and difficulty swallowing. This is preventable with correct administration technique. Oral and vaginal thrush (candidiasis) may develop due to disruption of normal bacterial flora. Headache, dizziness, and blurred vision are occasionally reported.

Rare but serious side effects

Benign intracranial hypertension (pseudotumour cerebri) presents with severe persistent headache, visual disturbances (blurred vision, double vision, visual field loss), nausea, and pulsatile tinnitus.

This requires urgent medical assessment and immediate discontinuation of doxycycline.

The risk is increased when doxycycline is combined with systemic retinoids (isotretinoin, acitretin), which is why concurrent use is contraindicated.

Severe skin reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis are extremely rare. Drug-induced lupus erythematosus, hepatotoxicity, pancreatitis, and blood dyscrasias (thrombocytopenia, neutropenia, haemolytic anaemia) have been reported rarely with prolonged use.

When to seek medical advice

Contact your GP, pharmacist, or NHS 111 if you experience persistent or severe gastrointestinal symptoms, difficulty swallowing, or symptoms of thrush.

Seek urgent medical attention (call 999 or attend A&E) if you develop severe headache with visual changes, a widespread blistering skin rash, swelling of the face or throat, or difficulty breathing.

Report any suspected adverse reactions to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk .

Warnings and precautions

Pregnancy and breastfeeding

Doxycycline is absolutely contraindicated in pregnancy and breastfeeding.

Tetracyclines cross the placenta and accumulate in developing teeth and bones, causing permanent yellow-grey-brown discolouration of the teeth and potential inhibition of skeletal growth.

Women of childbearing potential should use effective contraception during treatment.

Photosensitivity

All patients taking doxycycline should be counselled about the risk of photosensitivity.

Use broad-spectrum sunscreen with SPF 30 or higher on all exposed skin, wear protective clothing including a hat, and avoid sunbeds.

If a severe phototoxic reaction occurs (painful, blistering sunburn), stop doxycycline and seek medical advice.

Oesophageal protection

Take each dose with a full glass (200 mL) of water while sitting or standing. Do not take doxycycline immediately before bed. If oesophageal symptoms (chest pain on swallowing, difficulty swallowing) develop, stop the medication and contact your prescriber.

Drug interactions

Antacids, iron, calcium, magnesium, zinc, and bismuth preparations reduce doxycycline absorption. Separate by at least 2 to 3 hours.

Enzyme-inducing drugs (rifampicin, carbamazepine, phenytoin, phenobarbital) reduce doxycycline plasma levels and may reduce efficacy.

Concurrent use with isotretinoin or acitretin is contraindicated due to the risk of benign intracranial hypertension. Doxycycline may potentiate the effect of warfarin; INR should be monitored.

Ciclosporin levels may increase during concurrent doxycycline use.

Antimicrobial stewardship

Complete the prescribed course unless advised otherwise by your doctor. Do not share antibiotics or keep unused supplies for future self-treatment.

For acne, always use doxycycline alongside a non-antibiotic topical agent (benzoyl peroxide or a topical retinoid) to reduce the development of resistant bacteria.

Limit treatment to the shortest effective course.

Doxycycline for different conditions: what to expect

For acne, noticeable improvement typically takes 4 to 6 weeks, with continued improvement over the full 3-month course.

For chlamydia, a 7-day course is usually curative; a test of cure may be recommended 3 to 5 weeks after treatment.

For Lyme disease, the 21-day course treats early infection effectively in the majority of cases; ongoing symptoms should be discussed with your GP.

For malaria prophylaxis, protection is effective provided the medication is taken consistently as prescribed.

How to get a doxycycline prescription in the UK

Doxycycline is a prescription-only medicine available through the NHS. For acne, your GP can prescribe it after assessing your skin and discussing previous treatments.

For sexually transmitted infections, your local sexual health clinic (GUM clinic) can prescribe and supply doxycycline, often on the same day.

For Lyme disease, your GP can prescribe treatment. For malaria prophylaxis, a travel health consultation with your GP practice, pharmacy travel clinic, or specialist travel clinic is recommended.

Authorised online prescribers registered with the General Pharmaceutical Council (GPhC) may also prescribe doxycycline following a structured clinical assessment.

The standard NHS prescription charge in England is currently 9.90 pounds per item; prescriptions are free in Scotland, Wales, and Northern Ireland.

Sources

• Doxycycline 100 mg Capsules, Summary of Product Characteristics (EMC)
• Doxycycline, British National Formulary (BNF)
• NICE CKS: Acne vulgaris
• NICE NG95: Lyme disease
• BASHH Guidelines
• Doxycycline, NHS
• MHRA Yellow Card Scheme