Doxycycline Biotech is doxycycline 100 mg, a tetracycline antibiotic. It treats chest infections, acne, sexually transmitted infections, tick bite fever and skin infections, and it is used to prevent malaria. It causes severe sunburn and must be swallowed upright with plenty of water.
What is Doxycycline Biotech?
Biotech is the manufacturer; doxycycline is the medicine. The South African Medicine Price Registry lists Doxycycline Biotech as a Schedule 4 tablet containing doxycycline 100 mg. Doxycycline is registered here under several other names, and being given a different brand is ordinary substitution.
Doxycycline is a tetracycline. It binds to the bacterial ribosome and blocks protein synthesis, so bacteria cannot multiply and the immune system clears them.
Two features make it particularly useful:
It penetrates cells well, which is why it works against organisms that live inside human cells — chlamydia, rickettsia (which cause tick bite fever), and the atypical bacteria behind some pneumonias. Many antibiotics cannot reach those.
It is broad-spectrum and taken once or twice daily.
Doxycycline also has an anti-inflammatory effect independent of its antibacterial action, which is why low doses are used in acne and rosacea — there the benefit is as much about reducing inflammation as about killing bacteria.
In South Africa it has a particular relevance for tick bite fever, which is common and which doxycycline treats effectively.
What is Doxycycline Biotech commonly used for?
- Tick bite fever (African tick bite fever) — doxycycline is the treatment of choice, and it works quickly.
- Acne, at lower doses over months, for the anti-inflammatory effect.
- Rosacea, similarly.
- Chlamydia, and as part of treatment for pelvic inflammatory disease. Partners need treating too, or reinfection follows.
- Chest infections, including atypical pneumonia caused by Mycoplasma or Chlamydophila.
- Sinusitis and bronchitis, where appropriate.
- Skin and soft tissue infections.
- Malaria prevention for travellers, taken daily before, during and for four weeks after travel.
- Leptospirosis, brucellosis, Q fever and other less common infections.
- Periodontal disease, in dental use.
- Some bites, and cholera and plague in specific settings.
It does not treat colds, flu or most sore throats and coughs, which are viral.
Complete the course. For acne, that course is measured in months, not days — improvement takes six to twelve weeks, and stopping at four because nothing has happened is the commonest reason people conclude it did not work.
How Doxycycline Biotech fits into this medicine category
| Group | Examples | Typical role |
|---|---|---|
| Tetracyclines | Doxycycline, minocycline, lymecycline | Tick bite fever, acne, chlamydia, atypical pneumonia |
| Macrolides | Azithromycin (Azrotrin), erythromycin | Atypical infections; alternative in pregnancy |
| Aminopenicillins | Amoxicillin | Broad first-line cover |
| Penicillin + inhibitor | Co-amoxiclav | Where resistance defeats amoxicillin |
| Nitroimidazoles | Metronidazole | Anaerobes; often paired with doxycycline in PID |
| Antimalarials | Doxycycline, atovaquone-proguanil, mefloquine | Malaria prevention |
See the antibiotics and antimicrobials hub.
What to check before using Doxycycline Biotech
Two practical rules matter more than anything else with doxycycline, and both are about avoiding harm rather than making it work.
Sun sensitivity is severe and it is not a minor caution. Doxycycline causes marked photosensitivity — people get badly burnt after exposure that would normally be harmless. In South African sun this is a real risk. Use high-factor sunscreen, cover up, avoid the midday sun, and do not use sunbeds. This matters especially for people on months-long acne courses, and for travellers taking it for malaria prevention in exactly the settings where sun exposure is highest.
Swallow it upright with a full glass of water, and stay upright for at least 30 minutes. Doxycycline causes oesophageal ulceration if a tablet lodges in the food pipe — a painful and well-documented problem, most often when taken lying down or at bedtime with a sip of water.
Absorption is blocked by metal ions. Separate doxycycline by two to three hours from antacids, dairy products, and supplements containing calcium, magnesium, iron or zinc. Getting this wrong can render the antibiotic useless.
Also tell your doctor or pharmacist if you:
- Are pregnant or breastfeeding. Doxycycline is contraindicated in pregnancy — tetracyclines affect developing bones and teeth.
- Are treating a child under 8, where tetracyclines can permanently stain teeth. Doxycycline is used in children in specific serious infections where the benefit outweighs that.
- Have liver disease or kidney disease.
- Have myasthenia gravis, lupus, or porphyria.
- Take warfarin — doxycycline can increase its effect.
- Take anti-epileptics (carbamazepine, phenytoin, phenobarbital) or rifampicin, which reduce doxycycline levels.
- Take isotretinoin — the combination should be avoided.
Take it with food if it upsets your stomach; unlike older tetracyclines, food does not significantly reduce doxycycline absorption.
Possible cautions and when to ask a pharmacist or doctor
Common effects are nausea, vomiting, diarrhoea, abdominal discomfort and photosensitivity. Thrush — oral or vaginal — is common after a course.
Get emergency help for:
- Difficulty or pain on swallowing, or pain behind the breastbone — possible oesophageal ulceration. Stop and seek advice.
- Severe sunburn or blistering after limited sun exposure.
- Swelling of the face, lips or tongue, difficulty breathing, or a widespread blistering rash.
- Severe, watery or bloody diarrhoea, especially with fever, during or in the weeks after the course.
- Severe headache with visual disturbance — raised pressure inside the skull is a rare but recognised effect of tetracyclines.
- Yellowing of the skin or eyes, or severe abdominal pain.
Contact your doctor if:
- The infection is not improving after two to three days, or fever climbs.
- Tick bite fever symptoms worsen — spreading rash, severe headache, confusion or breathlessness.
- Acne is not improving after two to three months, or is scarring — scarring is far easier to prevent than to treat.
- You are treating an STI and your partner has not been treated.
- You develop thrush afterwards.
- You are on malaria prevention and develop fever during or after travel. Any fever after travel in a malaria area is malaria until proven otherwise, whatever prophylaxis you took, and needs same-day testing.
Related medicine guides
Frequently asked questions
What is Doxycycline Biotech 100 used for? Tick bite fever, acne and rosacea, chlamydia and pelvic inflammatory disease, chest and skin infections, and malaria prevention. It contains doxycycline 100 mg.
Is Biotech the medicine? No. Biotech is the manufacturer; doxycycline is the active ingredient.
Why must I stay upright after taking it? A tablet lodging in the food pipe causes ulceration. Take it with a full glass of water and stay upright for at least 30 minutes.
Why does it make me burn so easily? Doxycycline causes marked photosensitivity. Use high-factor sunscreen, cover up and avoid midday sun — this matters especially in South Africa.
Can I take it with milk or an antacid? Separate them by two to three hours. Calcium, magnesium, iron and zinc bind doxycycline and stop it being absorbed.
Can I take it in pregnancy? No. Doxycycline is contraindicated in pregnancy because tetracyclines affect developing bones and teeth.
How long does acne treatment take? Six to twelve weeks before meaningful improvement, and courses run for months. Stopping early is the commonest reason it appears not to work.
Does it prevent malaria completely? No prophylaxis is 100% effective. Any fever during or after travel in a malaria area needs same-day testing regardless.