Doxt-SL 100: Uses, How It Works, Side Effects
Also known as: Doxt-SL, Doxt SL 100, Doxt-SL 100 mg, Doxycycline 100 mg
Doxt-SL 100 is a prescription tablet containing 100 mg of doxycycline, a tetracycline antibiotic used to treat certain bacterial infections, such as some chest, urinary tract, gum and sexually transmitted infections. It works only against bacteria, so it does not help colds, flu or other viral infections. It is taken only on a doctor's prescription, and the full course should be finished as prescribed. It is usually avoided in pregnancy and in young children.
- Active ingredient
- Doxycycline 100 mg
- Type of medicine
- Tetracycline antibiotics
- Starts working in
- Many infections start to improve within a few days
- Effect lasts
- About 18 to 22 hours; usually taken once or twice a day
- With or without food
- Take with a full glass of water; follow the label about food
- Alcohol
- Best avoided; alcohol can stop it working properly
- Pregnancy
- Usually avoided; ask your doctor
- Habit-forming
- No
- Made by
- VERIFY on pack
Pharmacist review in progress. This page is based on the sources listed below and is being checked by our registered pharmacist.
On this page
- What is Doxt-SL 100 used for?
- How does Doxt-SL 100 work?
- How to take Doxt-SL 100
- Side effects of Doxt-SL 100
- Who should be careful
- Medicines and things that interact with Doxt-SL 100
- If someone takes too much
- Storage
- Regulatory status in India
- Other brands with the same medicine
- Other strengths and forms
- Common questions
What is Doxt-SL 100 used for?
Doxt-SL 100 is a prescription antibiotic. It is used, on a doctor's advice, to treat certain bacterial infections.
- Treating some bacterial chest (respiratory tract) infections
- Treating some bacterial urinary tract infections
- Treating some gum and sexually transmitted infections
- Other bacterial infections listed on the Indian pack insert, and in some people as part of acne treatment or to help prevent malaria, when a doctor judges it suitable
How does Doxt-SL 100 work?
Doxycycline attaches to the small (30S) part of the bacterial ribosome, the machinery bacteria use to build proteins. Without new proteins the bacteria cannot grow or multiply, and the body's defences clear the infection.
What happens in your body after you take it
You swallow the tablet
The tablet dissolves in the gut and doxycycline is absorbed into the blood. Taking it with a full glass of water helps it to reach the stomach and not irritate the food pipe.
It travels in the blood
Doxycycline spreads widely through the body and reaches the lungs, urinary tract, gums and skin, where infections can sit.
It blocks the bacteria's protein making
In the bacteria it attaches to the 30S part of the ribosome and stops the cell from building new proteins.
The bacteria cannot grow
Without new proteins the bacteria stop growing and multiplying, and the body's defences clear the infection. It has no effect on viruses.
The body clears it
Doxycycline is removed through the gut and the kidneys. Its half-life is about 18 to 22 hours, so a once or twice a day schedule keeps the effect going.
How to take Doxt-SL 100
Take Doxt-SL 100 exactly as your doctor has prescribed or as printed on the pack. Your doctor decides the dose and the number of days, which depend on the infection. The first-day dose is sometimes higher.
- It is usually taken once or twice a day, at the same time each day.
- Swallow it with a full glass of water while sitting or standing, and stay upright for at least 30 minutes. Do not take it just before lying down. If the pack says the tablet is a dispersible one, follow the pack instructions.
- Keep it apart from antacids, iron, zinc, and calcium or magnesium supplements, which can stop it being absorbed.
- Take the full course your doctor prescribed, even if you feel better sooner.
- If you miss a dose, take it when you remember unless the next dose is nearly due; never take two together.
Side effects of Doxt-SL 100
Most people take doxycycline without serious problems. Headache, feeling sick and a rash are common side effects, but a few side effects need medical help.
Uncommon or mild
- Feeling sick (nausea) or being sick (vomiting)
- Headache
- Rash
- Diarrhoea or loss of appetite
- Sore throat or discomfort when swallowing
Rare but serious: get medical help
- Signs of a severe allergic reaction: swelling of the face, lips, tongue or throat, difficulty breathing, hives or collapse. Get emergency help straight away
- Skin that burns or reacts strongly in sunlight, with rash, itching or redness
- Pain or difficulty swallowing, or chest pain after taking the tablet (possible food pipe irritation or ulcer)
- Severe or watery diarrhoea, or diarrhoea with blood, which can be a sign of a gut infection called C. difficile, even weeks after the course
- A severe headache with blurred vision, which can be a sign of raised pressure around the brain
- A severe skin reaction, such as blistering or peeling skin
- Tiredness, easy bruising or frequent infections (possible blood changes), or yellow skin or eyes
Who should be careful
Doxt-SL 100 is not suitable for everyone. Tell your doctor about your health and your other medicines before taking it.
When the label says not to use it
- Allergy to doxycycline or any other tetracycline antibiotic
- A serious allergic reaction to any ingredient of the tablet
- It treats bacterial infections only. It does not work for colds, flu or other viral infections, and taking it when it is not needed adds to antibiotic resistance
- Pregnancy: it is usually avoided because it can affect the baby's teeth and bones; tell your doctor if you are pregnant or planning a pregnancy. Breastfeeding: ask your doctor
- Children: it is usually not given to young children because it can leave lasting stains on developing teeth; your doctor decides
- Allergy to doxycycline or any other tetracycline antibiotic such as minocycline
- Sunlight: it can make skin burn easily, so cover up, use sunscreen and avoid sunbeds
- Liver or kidney disease, lupus, or myasthenia gravis: tell your doctor
- Alcohol dependence or heavy drinking: it can lower doxycycline levels
- A history of food pipe problems or trouble swallowing
- Acne treatment with isotretinoin or other retinoids: the combination is avoided
Medicines and things that interact with Doxt-SL 100
Some medicines and supplements change how doxycycline is absorbed or how long it works. Tell your doctor or pharmacist about everything you take.
- Antacids with aluminium, calcium or magnesium, bismuth, iron, zinc and multivitamins with minerals: they reduce absorption, so keep them well apart from doxycycline as your pharmacist advises
- Isotretinoin and other vitamin A related acne medicines: the combination can raise pressure around the brain and is avoided
- Warfarin and other blood thinners: the blood-thinning effect may increase, so your doctor may check your clotting more often
- Penicillin antibiotics: avoid taking them together unless your doctor has prescribed both
- Oral contraceptives: their effect may be reduced; ask your doctor about extra protection
- Carbamazepine, phenytoin and barbiturates: they shorten how long doxycycline stays in the body
- Alcohol: can stop doxycycline from working properly
If someone takes too much
Taking one extra tablet by mistake is unlikely to be serious, but larger amounts can cause sickness and vomiting. If someone has taken much more than prescribed, call 112 or go to the nearest hospital and take the medicine pack with you.
Storage
Store in a cool, dry place below 30 C, protected from light and moisture, in the original strip and out of the reach of children. Do not use after the expiry date. Check the pack for the exact storage instructions.
Regulatory status in India
Approved for sale in India as a prescription medicine. Single-ingredient doxycycline is not on the CDSCO list of medicines banned under section 26A of the Drugs and Cosmetics Act. Several fixed-dose combinations that include doxycycline are prohibited (for example with serratiopeptidase, with neomycin, or in a kit with serratiopeptidase and diclofenac), so check the ingredient list on the pack. Doxt-SL 100 should contain doxycycline only; confirm on the pack.
Other brands with the same medicine
Doxycycline 100 mg tablets and capsules are sold under other brand names and as generic medicines. They contain the same medicine, but the salt form and the type of tablet can differ, so check the label. Some products combine doxycycline with other ingredients, and several such combinations are banned in India, so do not switch without asking your doctor or pharmacist.
Other strengths and forms
Doxycycline is also sold in other strengths, as capsules, dispersible tablets and delayed-release tablets, which are taken differently. The strength and contents are printed on the pack, so check the label of the one you have.
Common questions
Is Doxt-SL 100 a prescription medicine?
Yes. Doxycycline is a prescription-only antibiotic in India. It should be taken only if a doctor has prescribed it, and it should not be started, stopped or changed without the doctor's advice.
Is Doxt-SL 100 an antibiotic for cold, flu or viral fever?
No. Doxt-SL 100 acts only on bacteria, and colds, flu and many fevers are caused by viruses. Taking it for them does not speed recovery, adds side effects and adds to antibiotic resistance. A doctor decides whether an infection is bacterial and needs an antibiotic.
How should Doxt-SL 100 be taken?
Swallow it with a full glass of water while sitting or standing, and stay upright for at least 30 minutes, to avoid irritating the food pipe. Keep it apart from antacids, iron and zinc. If the pack says dispersible tablet, follow its instructions. Follow the label or your doctor's advice.
Should I finish the whole course of Doxt-SL 100?
Take the full course your doctor prescribed, even if you feel better sooner, because stopping early can let the infection come back. The exception is a serious side effect or allergic reaction: stop and contact your doctor straight away. Never keep leftover tablets or share them.
Can I go out in the sun while taking Doxt-SL 100?
Take care. Doxycycline can make skin burn easily, causing rash, itching or redness. Cover your skin, wear a hat, use a high-factor sunscreen and avoid sunbeds. On brown or black skin the reaction can be harder to see. Tell your doctor if your skin reacts.
Can Doxt-SL 100 be taken in pregnancy, by children or while breastfeeding?
It is usually avoided in pregnancy and in young children because it can stain developing teeth and affect bone growth, and ask your doctor about breastfeeding. A doctor may still prescribe it if the benefit outweighs the risk. Tell your doctor if you are pregnant or may be.
Can I drink alcohol while taking Doxt-SL 100?
Alcohol can stop doxycycline working properly, especially with heavy drinking, so it is best avoided during the course. Ask your doctor or pharmacist if you are unsure.
What is the difference between Doxt-SL 100 and doxycycline?
Doxt-SL is a brand name; doxycycline is the medicine inside it. Other brands contain the same medicine, but the salt form and the type of tablet can differ. Check the strength and ingredient list on the pack, and ask your pharmacist before switching products.
Sources
- Doxycycline hyclate tablets and capsules: prescribing information (DailyMed label revised 4/2025). DailyMed, US National Library of Medicine
- Doxycycline. NHS (UK)
- Side effects of doxycycline. NHS (UK)
- ATC/DDD Index: J01AA Tetracyclines. WHO Collaborating Centre for Drug Statistics Methodology
- List of drugs prohibited for manufacture and sale through gazette notifications under section 26A of the Drugs & Cosmetics Act 1940. Central Drugs Standard Control Organisation (CDSCO)
- The Drugs Rules, 1945 (consolidated, September 2024 edition), Schedule H: prescription drugs. Central Drugs Standard Control Organisation (CDSCO)