DOXYCYCLINE BIOTECH 100 is a prescription, sugar-free, film-coated tablet that contains 100 mg of doxycycline, a broad-spectrum antibiotic in the tetracycline family. Doctors use it to treat many different bacterial infections affecting the chest, urinary tract, eyes, and certain infections spread by ticks, lice, or animals. It is also used for some less common infections named in the source, such as cholera and brucellosis. Because this medicine is Schedule 4 (S4) in South Africa, it must be used exactly as directed by a healthcare provider.

What it is and what it is used for

What it is
DOXYCYCLINE BIOTECH 100 contains doxycycline, an antibiotic in the tetracycline group. It is designed to stop the growth of bacteria that cause infections.

What it is used for
Your healthcare provider may prescribe DOXYCYCLINE BIOTECH 100 for:

Respiratory tract infections, including:
- Sinusitis
- Inflammation of the pharynx
- Lung infections caused by Mycoplasma
- Parrot fever (psittacosis)
- Chronic bronchitis
Urinary tract infections
Sexually transmitted diseases
Infections of the eye
Other infections, including:
- Malaria
- Cholera
- Brucellosis
- Leptospirosis
- Fevers caused by lice or ticks
Rickettsial infections, such as Q fever and tick fever
Rabbit fever (tularaemia), yaws (a tropical skin infection), and long-term infections that form sores or abscesses in soft tissue

Note: Use only for conditions your healthcare provider diagnoses and prescribes.

How it works

Doxycycline slows down or stops bacteria from multiplying by blocking the way they make essential proteins. Without these proteins, bacteria cannot grow or spread, and your immune system can clear the infection. Because doxycycline is “broad-spectrum,” it is active against many different bacteria mentioned in the source.

Who should NOT use this medicine

Do not take DOXYCYCLINE BIOTECH 100 if any of the following apply:

You are allergic to doxycycline hyclate, any tetracycline, or any ingredient in the tablet.
You have some form of kidney (renal) disease.
You are pregnant or breastfeeding.
You are younger than 12 years (risk of permanent tooth discolouration).
You have systemic lupus erythematosus (an inflammatory disease of connective tissue).

Children: This medicine should not be used in children under 12 years.

If you are unsure, speak to your doctor or pharmacist before taking the first dose.

Warnings and precautions (Read before use)

Tell your healthcare provider about all your medical conditions and medicines. Take special care in the following situations:

Sunlight/UV exposure: Doxycycline can increase skin sensitivity. Avoid direct sun and tanning lamps. Stop and seek advice if you develop a rash or severe sunburn.
Liver disease or medicines affecting the liver: You may need monitoring.
Severe kidney problems: Extra caution is advised.
Serious skin reactions: Seek urgent help if you develop symptoms such as red target-like patches, widespread rash with blisters or peeling (these include erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis).
Stomach or bowel problems: If you have diarrhoea during or after treatment—especially severe, prolonged, or bloody diarrhoea—contact your doctor immediately. This can be a sign of bowel inflammation (pseudomembranous colitis) that may occur after antibiotics.
Porphyria: Use only under medical advice due to risk of worsening symptoms.
Retinoids (including isotretinoin): Taking these with doxycycline can raise pressure inside the skull (symptoms: severe headache, visual changes). Do not use together unless your doctor is supervising closely.
Frail or elderly patients: May require closer monitoring.
Fungal infections: Those with vaginal or blood fungal infections may be at risk of worsening thrush; tell your doctor if you develop symptoms.
Oesophagitis/gullet irritation: This can occur if the tablet lodges in the oesophagus. Reduce risk by swallowing with a full glass of water, staying upright, and avoiding lying down for at least 30 minutes after each dose.
Sexually transmitted infections (e.g., syphilis): Special diagnostic follow-up may be required; tell your doctor if you are being treated for STIs.
Myasthenia gravis: Use with caution (muscle weakness can affect swallowing and breathing).
Systemic lupus erythematosus (SLE): Listed under “Do not use”; this condition can worsen.
Jarisch–Herxheimer reaction (JHR): If treated for spirochetal infections (such as syphilis, Lyme disease, leptospirosis, or relapsing fever), you may develop fever, chills, headache, muscle pain, or a skin rash within 24 hours of starting antibiotics. This is usually self-limiting but tell your doctor if it occurs.

Driving and using machines
Do not drive or operate machinery if you experience visual disturbances (such as blurred vision) while taking doxycycline. Only resume these activities once you feel fully safe to do so.

Pregnancy, planning pregnancy, and breastfeeding

Do not use DOXYCYCLINE BIOTECH 100 if you are pregnant or breastfeeding. If you are pregnant, planning a pregnancy, or think you might be pregnant, speak to your doctor, pharmacist, or another healthcare provider before taking this medicine. The source also notes that pregnancy increases susceptibility to severe doxycycline-induced liver damage.

Interactions

Always tell your healthcare provider about all medicines you take, including complementary or traditional products. The following interactions are listed in the source:

Antacids and mineral supplements containing aluminium, calcium, or magnesium, and products with iron, bismuth, or zinc:
Do not take at the same time as DOXYCYCLINE BIOTECH 100 because they can reduce absorption.
Warfarin and other anticoagulants:
Doxycycline may affect blood-thinning control; monitoring may be required.
Epilepsy medicines such as phenobarbital, carbamazepine, primidone, and phenytoin:
These may alter doxycycline metabolism and reduce its effect.
Penicillins:
Penicillins should not be used with doxycycline as they may block doxycycline’s action.
Oral contraceptives (“the Pill”):
Doxycycline may reduce effectiveness. Use additional contraception while taking it and as advised by your healthcare provider.
Methoxyflurane (anaesthetic):
Tell your doctor or dentist you are taking doxycycline if you are due for a procedure.
Alcohol:
Alcohol may reduce doxycycline’s effect by changing how quickly it is cleared from the body. Avoid alcohol during treatment.
Ciclosporin:
Requires appropriate monitoring if used together.
Rifampicin (for tuberculosis):
May reduce doxycycline’s effect, leading to sub-therapeutic levels.
Isotretinoin or other systemic retinoids:
Increases risk of raised pressure inside the skull; avoid using together unless specifically advised by your doctor.

Food, drink, and alcohol

Take with a full glass of water.
Take either one hour before meals or two hours after meals.
Do not drink alcohol while taking this medicine.

How to take (Step-by-step)

Follow your prescriber’s instructions exactly. Do not share your antibiotic with anyone else.

Check your dose.
- Usual adult regimen: 100 mg twice on the first day, then 100 mg once daily thereafter.
- Your healthcare provider will decide how long you need treatment.
When to take it.
- Take by mouth one hour before meals or two hours after meals.
How to take it.
- Swallow the film-coated tablet whole with a full glass of water.
- Take the tablet sitting or standing.
- Do not lie down for at least 30 minutes after each dose.
While on treatment.
- Complete the full course even if you feel better earlier, unless your doctor tells you to stop.
- Avoid direct sunlight or UV exposure.
- Do not drink alcohol.
- Check for interactions before taking antacids, iron, zinc, bismuth, calcium, or magnesium products; if your prescriber advises continued use, ask about spacing these several hours away from doxycycline.
If you think the medicine is too strong or too weak.
- Speak to your doctor or pharmacist; do not adjust the dose on your own.

Missed dose

Do not take a double dose to make up for a forgotten tablet.
Take the next dose at the usual time and continue as directed.

Overdose

If you (or someone else) take more than prescribed, contact your doctor, pharmacist, the nearest hospital, or a poison centre immediately.

Stopping treatment early

Do not stop early unless your doctor instructs you to. Stopping too soon can allow the infection to come back or worsen.

Dosing table

Age group	Dose on Day 1	Ongoing daily dose	How to take	Notes
Adults and adolescents (≥12 years)	100 mg twice daily	100 mg once daily	By mouth with a full glass of water, upright, 1 hour before or 2 hours after meals	Doctor decides duration. Do not lie down for ≥30 minutes after taking.
Children <12 years	Do not use	—	—	Risk of permanent tooth discolouration.

Maximum daily dose and weight-based paediatric doses are not specified in the source.

Possible side effects

DOXYCYCLINE BIOTECH 100 can cause side effects, although not everyone gets them. If your general health worsens while taking it, contact your healthcare provider.

Serious—seek urgent help

Stop the medicine and get medical help immediately if you have any of the following:

Swelling of the hands, feet, ankles, face, lips, mouth, or throat; difficulty swallowing or breathing
Rash or itching with signs of allergy
Fainting
Yellowing of the skin or eyes (jaundice)

Contact your doctor urgently or go to casualty if you notice:

Severe, persistent, or bloody diarrhoea (may occur during treatment or up to 2–3 months after the last dose), possibly with stomach pain or fever—this can be a sign of serious bowel inflammation
Skin becomes very sensitive to light (rash, itching, redness, or severe sunburn after sunlight or sunbed exposure)
Low blood pressure
Inflammation around the heart (pericarditis) or fast heart rate
Worsening of systemic lupus erythematosus (SLE)
Serum sickness
Shortness of breath (dyspnoea) or blood vessel inflammation
Fever, swollen lymph nodes, or skin rash—possible DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms), which can be severe and life-threatening
Severe skin reactions such as erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis (widespread rash with blisters, peeling, and systemic symptoms)
Jarisch–Herxheimer reaction (fever, chills, headache, muscle pain, skin rash) shortly after starting treatment for certain infections (usually self-limiting; inform your doctor)

Important: Using expired doxycycline may lead to a Fanconi-type syndrome (symptoms can include excessive urination and thirst, nausea, vomiting, and specific laboratory abnormalities). Check expiry dates and return unused medicine to your pharmacist.

Common

Headache
Nausea or vomiting
Eating disorder (as described in the source)
Reddish-purple spots on lower legs, sore/swollen joints, tummy pain or blood in urine
Hives
Swelling of the legs or arms

Less common

Vaginal infection or vaginitis; thrush of the mouth or vagina
Blood disorders (changes in blood cell counts)—symptoms may include tiredness, easy bruising, or infections
Discolouration of thyroid tissue (does not affect thyroid function)
Porphyria with urine discolouration
Loss of appetite
Increased pressure in the skull (severe headaches, blurred/double vision, blind spots); permanent vision loss has been reported
Bulging fontanelle in infants
Anxiety
Tinnitus (ringing in the ears)
Flushing
Heartburn
Pancreatitis (severe upper abdominal pain)
Difficulty swallowing, stomach pain, diarrhoea
Inflammation/ulcers of the gullet (sore mouth, indigestion)
Oral thrush (redness, soreness)
Inflammation of the tongue
Soreness/itching of the rectal or genital area; inflammation around the vagina
Liver inflammation or damage; abnormal liver tests
Redness and peeling of the skin (dermatitis exfoliative)
Nail detachment
Joint or muscle aches
Increased urea in the blood

Frequency unknown

Vitamin deficiencies may occur
Discolouration of teeth

What to do if you get side effects

Mild effects: keep taking the medicine but inform your doctor or pharmacist.
Severe effects or allergic symptoms: stop the medicine and seek urgent help.
You can report side effects to SAHPRA using the Med Safety app (Medsafety X SAHPRA) or the eReporting platform listed on the SAHPRA website.

Storage and disposal

Store at or below 25 °C in a well-closed container.
Protect from light.
Keep out of sight and reach of children.
Do not use after the expiry date on the label or carton.
Return unused or expired tablets to your pharmacist.
Do not dispose of tablets in drains or toilets.

What the medicine contains

Active substance: Doxycycline (100 mg per tablet).
Other ingredients (excipients): Colloidal silicon dioxide, croscarmellose sodium, microcrystalline cellulose.
Tablet coating (TC/530027 Orange): Carnauba wax, hypromellose, polyethylene glycol/macrogol, sunset yellow FCF aluminium lake, and titanium dioxide.
Sugar status: Sugar-free.

Pack information and appearance

Tablet appearance: Round, light orange, film-coated, biconvex tablets, engraved “Dox” over “100” on one side; the other side is plain.
Blister packs: Alu/PVC strips of 14 tablets (1 strip) or 28 tablets (2 strips), in an outer carton or patient-ready pack.
Plastic bottles: White, opaque HDPE bottles of 100 or 250 tablets.
Note: Not all pack sizes and strengths may be marketed at the same time.

FAQs

Can I take DOXYCYCLINE BIOTECH 100 if I’m pregnant or breastfeeding?
No. Do not take this medicine if you are pregnant or breastfeeding. Speak to your healthcare provider for alternatives.

Can children use this medicine?
No. It should not be used in children under 12 years because of the risk of permanent tooth discolouration.

How should I take the tablet to protect my gullet (oesophagus)?
Swallow the tablet whole with a full glass of water, while sitting or standing. Do not lie down for at least 30 minutes after taking it.

When should I take it in relation to meals?
Take it one hour before meals or two hours after meals.

Can I drink alcohol while taking doxycycline?
No. The source advises you should not drink alcohol while on treatment, as it may reduce the medicine’s effect.

Does it interact with antacids or mineral supplements?
Yes. Products containing aluminium, calcium, magnesium, iron, bismuth, or zinc can reduce absorption. Do not take them at the same time as doxycycline.

Will doxycycline affect my oral contraceptive (“the Pill”)?
Yes, it may reduce effectiveness. Use additional contraceptive precautions as advised by your healthcare provider.

What if I develop bad diarrhoea during or after treatment?
Contact your doctor immediately—especially if diarrhoea is severe, prolonged, or bloody, or occurs with stomach pain or fever. This can indicate bowel inflammation after antibiotic use.

Is it safe to be out in the sun?
Use caution. Doxycycline can increase sun sensitivity. Avoid direct sunlight and sunbeds, and seek advice if you develop a rash or severe sunburn.

What infections is this medicine used for?
As prescribed for respiratory infections (such as sinusitis and chronic bronchitis), urinary tract infections, sexually transmitted diseases, eye infections, rickettsial infections (Q fever, tick fever), lice- or tick-borne fevers, malaria, cholera, brucellosis, leptospirosis, rabbit fever, yaws, and certain long-term soft-tissue infections, as listed in the source.

Militian Inessa Mesropovna

Education:
Sochi Medical College 2014 – 2017

Work experience:
2017 – to date Sochi Pharmacy – Pharmacist