What Is Doxycycline?
Doxycycline is a broad‑spectrum antibiotic belonging to the tetracycline class. Its active ingredient, doxycycline hyclate, interferes with bacterial protein synthesis by binding to the 30S ribosomal subunit. This halts the production of essential proteins, effectively stopping bacterial growth and allowing the immune system to clear the infection.
In the United Kingdom it is licensed for a range of bacterial infections: chlamydia, gonorrhoea, acne vulgaris, rosacea, respiratory tract infections, urinary tract infections, and certain tick‑borne illnesses such as Lyme disease. The medication can also be used off‑label as an antimalarial prophylaxis in endemic areas.
While the drug is generic, many UK pharmacies stock branded versions produced by companies such as Pfizer (Vibramycin) or generic manufacturers listed on the NHS BNF. Its long history—first introduced in 1960s—has made it widely available and cost‑effective.
Forms and Dosages
Doxycycline is supplied mainly in tablet and capsule form. The most common strength is 100 mg, but 50 mg and 200 mg options exist for specialised indications such as acne or severe infections.
- Capsules (100 mg) – scored for easy splitting if a lower dose is required; they are not coated.
- Tablets (100 mg) – smooth, unscored, typically taken whole with water.
- Injectable formulation – 200 mg/mL in saline, used in hospital settings for severe infections or when oral intake is not possible.
Capsules can be split to achieve a 50 mg dose; tablets should only be divided if they are scored and the patient is instructed to do so by a pharmacist. The typical regimen for chlamydia is two capsules per day (morning and evening) for seven days, totaling fourteen capsules.
Who Can Take It?
Doxycycline is suitable for both men and women across all adult age groups. However, it is not recommended for children under 8 years old due to the risk of permanent tooth discoloration and bone growth interference.
Elderly patients may experience increased sensitivity or a higher likelihood of gastrointestinal upset; dose adjustments are rarely necessary but should be discussed with a clinician.
Pregnancy and lactation are contraindications because doxycycline can affect fetal bone development and has low safety data in breast‑feeding infants. Women who are pregnant, trying to conceive, or nursing should seek alternative therapies.
How to Take Doxycycline
Take the medication exactly as prescribed: two 100 mg doses each day, spaced at least eight hours apart. For chlamydia treatment, start immediately after a positive test result and finish all capsules even if symptoms subside early.
- With food or milk? Food can reduce stomach upset; taking with a glass of water is essential to prevent irritation.
- Timing? Consistency matters—take at the same times each day to maintain steady blood levels.
- Missed dose? If you forget one, take it as soon as remembered. Do not double up on the next scheduled dose.
After completing the course, a follow‑up test is advised three months later if under 25 years old to confirm cure and prevent reinfection.
How It Works
Imagine the bacteria as factories that need raw materials to produce vital components. Doxycycline blocks the machinery (ribosomes) responsible for building proteins, effectively putting a stop sign on bacterial production lines. Without new proteins, bacteria cannot multiply or survive, allowing your immune system to eliminate them.
Contraindications
- Allergy to tetracyclines: severe hypersensitivity reactions such as rash, swelling, or anaphylaxis.
- Pregnancy and lactation (see above).
- Severe liver disease: the drug is hepatically metabolised; impaired function can raise serum levels.
- Patients on certain medications: warfarin (risk of increased bleeding), fluoroquinolones, or other antibiotics that may have additive GI side effects.
Interactions
- Calcium‑rich foods, dairy products, antacids containing magnesium or aluminum – can bind doxycycline and reduce absorption.
- Grapefruit juice – may increase serum levels, raising the risk of side effects.
- Alcohol – heightens gastrointestinal irritation; best avoided during therapy.
- NSAIDs or aspirin – potential additive GI upset.
- Blood thinners (warfarin) – monitor INR closely if co‑prescribed.
Side Effects
Common: nausea, mild diarrhoea, headache, and photosensitivity. These usually resolve after a few days of treatment.
Less common: vomiting, abdominal pain, or allergic skin reactions such as rash.
Serious (seek immediate medical help): severe allergic reaction (difficulty breathing, swelling), persistent diarrhoea > 48 h, or signs of liver dysfunction (jaundice, dark urine).
Overdose Risks
An accidental ingestion of more than the prescribed daily dose can lead to nausea, vomiting, abdominal pain, and in extreme cases seizures or kidney damage. If you suspect an overdose, call 111 or go straight to A&E. Immediate medical attention is crucial.
Price and Availability
The cost depends on quantity and pharmacy choice. For a standard 14‑capsule course of 100 mg capsules, the retail price in the UK averages around £6.50 when ordered online through Dr Fox (delivery fee £2.90). In physical pharmacies, prices range from £10 to £18 for comparable packages.
Factors influencing cost include:
- Dosage strength: higher concentrations (200 mg) are pricier per tablet but may reduce the total number needed.
- Quantity: bulk orders or subscription services often offer discounts.
- Prescription status: pharmacies require a prescription, which can add an administrative fee; online clinics incorporate this into their service charge.
Buying Drugs without Prescription (UK)
Doxycycline is strictly prescription‑only in the United Kingdom. However, licensed online services such as Medicade.co.uk provide a streamlined process: you complete an online health questionnaire, receive an electronic prescription from a registered doctor, and have the medication delivered to your address.
| City | Estimated Delivery Time |
|---|---|
| London | 2–3 business days |
| Manchester | 3–4 business days |
| Birmingham | 3–5 business days |
| Leeds | 3–5 business days |
| Glasgow | 4–6 business days |
Alternatives
For chlamydia, the standard alternative is a single dose of 1 g azithromycin. Azithromycin offers convenience (one‑time dosing) but has higher rates of gastrointestinal upset and may be less effective against certain resistant strains.
Natural options such as cranberry extract or probiotics are sometimes used to support gut flora but have no proven antibacterial activity against chlamydia. They can be considered complementary rather than replacement therapy.
Precautions
- Sun protection: doxycycline increases photosensitivity; wear sunscreen and protective clothing when outdoors.
- Storage: keep the medication in a cool, dry place away from direct sunlight. Do not expose it to heat or moisture.
- Inform your doctor if you are taking calcium supplements, antacids, or have a history of kidney disease.
- Never share your dose with others; antibiotics must be prescribed individually.
FAQ
- Can I take doxycycline while pregnant?
- No. It is contraindicated during pregnancy and lactation due to potential fetal harm.
- What if I miss a dose?
- Take it as soon as you remember; skip the next scheduled dose if it's close to the time for the following one.
- Is there a risk of antibiotic resistance?
- Yes. Complete the full course even if symptoms improve early to minimise the development of resistant bacteria.
Reviewed by a medical professional Isabel D White.
