Doxycycline

Doxycycline is a tetracycline-type antibiotic used to treat a wide range of bacterial infections. It belongs to the broad-spectrum antibiotic class and works by stopping the growth of bacteria. Doxycycline is available as capsules, tablets, and dispersible tablets in the UK and is prescribed for conditions including acne, rosacea, chest infections, sexually transmitted infections, urinary tract infections, and as a preventative treatment for malaria. It is a prescription-only medicine (POM) and is widely available on the NHS.

Doxycycline is used to treat many bacterial infections including acne vulgaris, rosacea, chlamydia and other sexually transmitted infections, lower respiratory tract infections such as pneumonia, Lyme disease, sinusitis, and certain dental infections. It is also used as malaria prophylaxis for travellers visiting areas where Plasmodium falciparum malaria is present. Additionally, Doxycycline is sometimes prescribed off-label for chronic conditions like periodontitis at a sub-antimicrobial dose.

Doxycycline works by inhibiting bacterial protein synthesis. It binds to the 30S ribosomal subunit of bacteria, preventing the attachment of transfer RNA (tRNA) to the messenger RNA–ribosome complex. This stops the bacteria from producing essential proteins needed for growth and reproduction, effectively halting the infection. Doxycycline is bacteriostatic, meaning it stops bacteria from multiplying rather than killing them directly, allowing the body’s immune system to clear the infection.

Yes, Doxycycline is readily available on the NHS and is one of the most commonly prescribed antibiotics in the UK. It is relatively inexpensive as a generic medication. Doxycycline can also be obtained through private prescriptions and online prescribing services such as NowPatient. For malaria prevention, it may sometimes need to be purchased privately as not all GP practices prescribe antimalarials on the NHS.

Doxycycline should not be taken by children under 12 years of age as it can cause permanent tooth discolouration and affect bone development. It is contraindicated in pregnancy and breastfeeding. People with a known allergy to tetracycline antibiotics must avoid Doxycycline. Those with severe liver disease should use it with caution. Patients with lupus (SLE) may experience photosensitivity reactions. You should inform your prescriber about any kidney problems, myasthenia gravis, or porphyria before taking Doxycycline.

The usual dose of Doxycycline depends on the condition being treated. For most infections, the standard dose is 200 mg on the first day (given as a single dose or 100 mg twice daily), followed by 100 mg once daily. For acne, the typical dose is 100 mg daily for at least 6 to 12 weeks. For malaria prophylaxis, the dose is 100 mg once daily, starting 1–2 days before travel, continuing throughout the trip and for 4 weeks after returning. For chlamydia, the usual course is 100 mg twice daily for 7 days. Always follow your prescriber’s specific instructions.

Yes, Doxycycline capsules and tablets should be taken with or after food and with a full glass of water. Taking Doxycycline on an empty stomach is more likely to cause nausea and stomach irritation. You should swallow the capsule whole while sitting or standing upright and avoid lying down for at least 30 minutes afterwards to prevent oesophageal irritation and ulceration. Do not take Doxycycline with milk, antacids, iron supplements, or calcium products as these reduce its absorption.

If you miss a dose of Doxycycline, take it as soon as you remember unless it is nearly time for your next dose. Do not take a double dose to make up for a missed one. If you are using Doxycycline for malaria prevention and miss a dose, take it as soon as you remember and continue as normal. If you frequently forget doses, try setting a daily alarm. Missing doses of antibiotics can reduce their effectiveness and contribute to antibiotic resistance.

Common side effects of Doxycycline (affecting 1 in 10 to 1 in 100 people) include nausea, vomiting, diarrhoea, and abdominal pain, particularly if taken on an empty stomach. Photosensitivity (increased sensitivity to sunlight) is a well-known side effect — you may burn more easily. Oral thrush and vaginal thrush can occur due to disruption of normal bacterial flora. Headache is also commonly reported. These side effects are usually mild and temporary.

Yes, photosensitivity is one of the most notable side effects of Doxycycline. You may develop an exaggerated sunburn reaction even with relatively brief sun exposure. To reduce this risk, use a high-factor sunscreen (SPF 30 or above), wear protective clothing, and avoid prolonged sun exposure or sunbeds while taking Doxycycline and for a few days after stopping. This is particularly important for those using Doxycycline for malaria prophylaxis in sunny destinations. If you develop a severe skin reaction, contact your doctor.

Rare but serious side effects of Doxycycline include severe headache with blurred vision, which could indicate raised intracranial pressure (benign intracranial hypertension) — seek urgent medical attention if this occurs. Severe allergic reactions (anaphylaxis) with swelling of the face, lips, or tongue require emergency help. Oesophageal ulceration can occur if the capsule gets stuck — symptoms include painful swallowing or chest pain. Liver damage (hepatotoxicity) is very rare but possible. Clostridioides difficile-associated diarrhoea (severe, watery or bloody diarrhoea) should be reported immediately.

Doxycycline has several important drug interactions. Antacids containing aluminium, calcium, or magnesium, and iron supplements significantly reduce Doxycycline absorption — leave at least 2–3 hours between doses. Warfarin’s anticoagulant effect may be enhanced by Doxycycline, requiring INR monitoring. Rifampicin, carbamazepine, phenytoin, and barbiturates can reduce Doxycycline levels through enzyme induction. Ciclosporin levels may be increased. Oral typhoid vaccine (Vivotif) should be completed at least 3 days before starting Doxycycline. Retinoids such as isotretinoin should not be used concurrently due to the risk of benign intracranial hypertension.

While there is no absolute contraindication, it is generally advisable to limit alcohol consumption while taking Doxycycline. Heavy alcohol use can increase the rate at which your body breaks down Doxycycline, potentially reducing its effectiveness. Alcohol can also worsen the gastrointestinal side effects of Doxycycline such as nausea and stomach upset. If you are taking Doxycycline for a serious infection, it is best to avoid alcohol until you have completed the course.

According to current FSRH and BNF guidance, standard antibiotic courses of Doxycycline do not reduce the effectiveness of combined or progestogen-only contraceptive pills, provided the antibiotic does not cause vomiting or severe diarrhoea. Additional contraceptive precautions are not routinely required. However, if Doxycycline causes vomiting within 2 hours of taking your pill, or severe diarrhoea, you should follow the missed pill rules in your contraceptive’s patient information leaflet. Enzyme-inducing antibiotics (such as rifampicin) do affect contraceptive efficacy, but Doxycycline is not enzyme-inducing.

No, Doxycycline should not be used during pregnancy. Tetracyclines can cause permanent discolouration of developing teeth and may affect bone growth in the foetus, particularly if taken during the second and third trimesters. Doxycycline is also excreted in breast milk and should be avoided while breastfeeding for the same reasons. If you discover you are pregnant while taking Doxycycline, stop the medication and contact your doctor immediately. Alternative antibiotics that are safe in pregnancy, such as amoxicillin or erythromycin, can usually be prescribed instead.

You can obtain a prescription for Doxycycline from your GP, a sexual health clinic (GUM clinic), or through an online prescribing service such as NowPatient. For malaria prophylaxis, you can get a prescription from your GP, a travel clinic, or an online pharmacy. NowPatient offers a convenient online consultation where a qualified UK prescriber can assess your suitability and issue a prescription with home delivery. Some pharmacies also offer Doxycycline for malaria prevention through their travel health services.