Cotrimoxazole (Trimethoprim + Sulfamethoxazole) is a combination antibiotic tablet used to treat ocular toxoplasmosis, an eye infection affecting the retina.
| Drug class | Systemic Antibiotic |
|---|---|
| Type | Combination |
| Forms | Tablet |
| Common strength | 800 mg + 160 mg (DS) |
| Common Indian brands | Septran, Bactrim |
| Prescription status | Prescription |
What Cotrimoxazole (Trimethoprim + Sulfamethoxazole) is used for
Cotrimoxazole (Trimethoprim + Sulfamethoxazole) is a systemic antibiotic medicine prescribed by ophthalmologists at Pristine Eye Hospitals to treat specific eye conditions. It is taken by mouth as a tablet.
- Ocular Toxoplasmosis (Retinochoroiditis): This medicine is most commonly used in India to treat ocular toxoplasmosis, which is an infection of the retina and choroid (the layers at the back of your eye). This infection is caused by a parasite and can lead to inflammation and vision problems.
How it works
Cotrimoxazole is a combination medicine that contains two active ingredients: Trimethoprim and Sulfamethoxazole. Together, these ingredients work to kill the Toxoplasma parasite, which is responsible for causing ocular toxoplasmosis in the retina. By eliminating the parasite, the medicine helps to reduce the infection and inflammation in your eye.
How it’s used
Cotrimoxazole is prescribed as a tablet to be taken by mouth. It is very important to follow your ophthalmologist’s instructions precisely for the best results and to prevent the infection from worsening or recurring.
The typical dosing for ocular toxoplasmosis is:
- Dosage: One DS (Double Strength) tablet (800 mg + 160 mg) taken twice a day.
- Duration: This treatment usually continues for 6 weeks.
- Combination Therapy: Your doctor will usually prescribe a steroid medicine to be started 48 hours after you begin taking Cotrimoxazole. This combination therapy is crucial for effective treatment.
Always take the tablet with a glass of water, and try to take it at the same times each day to maintain a consistent level of medicine in your body. Do not stop taking the medicine even if your symptoms improve, unless specifically advised by your doctor. Completing the full course of treatment is essential to fully clear the infection and prevent its return.
Always follow your ophthalmologist’s exact instructions.
Brands available in India
- Septran
- Bactrim
Brand availability and pricing vary; confirm with your pharmacist.
Good to know
Prescription eye medicine — use only as directed by a qualified ophthalmologist. This page is for general education and is not a substitute for professional medical advice, diagnosis or a prescription. Do not self-medicate or reuse an old prescription.
Precautions & side effects
Before starting Cotrimoxazole, and while you are taking it, please be aware of the following important precautions:
- Steroid Use: It is critically important that steroids are NEVER given alone to treat toxoplasmosis. They must always be used alongside anti-parasitic cover like Cotrimoxazole. Your ophthalmologist will manage this combination carefully.
- Allergies: If you have a known allergy to sulfa drugs (medicines containing ‘sulfa’), you must inform your doctor. Cotrimoxazole contains sulfamethoxazole, and an allergic reaction can be serious.
- Pregnancy: This medicine should be avoided during pregnancy. If you are pregnant, planning to become pregnant, or breastfeeding, please inform your ophthalmologist immediately.
- Prescription Only: Cotrimoxazole is a prescription medicine. Use it only as directed by a qualified ophthalmologist. Do not self-medicate or use an old prescription.
- General Health: Always inform your doctor about all your medical conditions, other medicines you are taking (including over-the-counter drugs, vitamins, and herbal supplements), and any past medical history, especially kidney or liver problems.
If you experience any unusual or severe side effects, contact Pristine Eye Hospitals or your ophthalmologist immediately.
Understanding Ocular Toxoplasmosis
Ocular toxoplasmosis is an infection of the eye caused by a parasite called Toxoplasma gondii. This parasite is quite common and can be found in undercooked meat, contaminated water, or cat faeces. While many people who are exposed to the parasite may not develop any symptoms, in some cases, it can travel to the eye and cause inflammation, particularly in the retina and choroid (the light-sensitive tissue at the back of your eye). This condition is known as retinochoroiditis.
When the retina is affected, it can lead to symptoms such as blurred vision, floaters (small spots or lines that seem to drift across your vision), pain, redness, and sensitivity to light. If left untreated, ocular toxoplasmosis can cause permanent damage to your vision. Early diagnosis and appropriate treatment, often involving medicines like Cotrimoxazole, are crucial to manage the infection and preserve your eyesight. Your ophthalmologist will perform a thorough examination, including looking at the back of your eye, to diagnose this condition accurately.
General Advice for Taking Oral Medicines for Eye Conditions
Taking oral medicines like Cotrimoxazole for an eye condition requires careful attention to ensure effectiveness and safety. Always follow your ophthalmologist’s instructions precisely. Here are some general tips:
- Adherence is Key: Take your medicine exactly as prescribed – the correct dose, at the correct times, and for the full duration. Do not skip doses or stop taking the medicine early, even if you start feeling better. Stopping early can lead to the infection returning or becoming harder to treat.
- Timing: Try to take your tablets at the same time each day. This helps maintain a consistent level of the medicine in your body, which is important for fighting the infection effectively. If you miss a dose, take it as soon as you remember, unless it’s almost time for your next dose. In that case, skip the missed dose and continue with your regular schedule. Do not double the dose to catch up.
- With or Without Food: Your doctor or pharmacist will advise whether to take your medicine with food or on an empty stomach. Follow this advice closely.
- Hydration: Drink plenty of water unless advised otherwise by your doctor. This can help with the absorption of some medicines and reduce the risk of certain side effects.
- Storage: Store your medicine in a cool, dry place, away from direct sunlight and moisture. Keep it out of reach of children and pets. Do not store medicines in the bathroom cabinet as humidity can affect them.
- Disposal: Once your treatment is complete, or if the medicine expires, dispose of it safely. Do not flush it down the toilet or throw it in the regular trash. Ask your pharmacist for advice on proper disposal.
When to Seek Medical Help
While taking any medicine, it’s important to be aware of when to contact your doctor or seek immediate medical attention. For eye conditions and systemic treatments like Cotrimoxazole, be vigilant for the following:
- Worsening Symptoms: If your eye symptoms (like blurred vision, pain, redness, or light sensitivity) worsen or do not improve after a few days of starting the medicine, contact Pristine Eye Hospitals.
- New or Severe Side Effects: If you experience any severe or unusual side effects, such as a rash, severe itching, difficulty breathing, swelling of the face or throat, or any other concerning symptoms, seek immediate medical attention. These could be signs of an allergic reaction.
- Vision Changes: Any sudden or significant changes in your vision, such as a sudden loss of vision, flashes of light, or a sudden increase in floaters, warrant immediate medical consultation.
- Fever or General Malaise: If you develop a fever, chills, or feel generally unwell while on treatment, inform your doctor.
- Questions or Concerns: If you have any questions about your medicine, its dosage, or any aspect of your treatment, do not hesitate to contact your ophthalmologist or the staff at Pristine Eye Hospitals. It’s always better to clarify doubts than to make assumptions.
Remember, your ophthalmologist is your best resource for managing your eye health. Regular follow-up appointments are essential to monitor your progress and adjust your treatment if necessary.
Frequently asked questions
What is Cotrimoxazole (Trimethoprim + Sulfamethoxazole) used for?
Cotrimoxazole (Trimethoprim + Sulfamethoxazole) is a systemic antibiotic tablet primarily used to treat ocular toxoplasmosis, which is an infection of the retina and choroid in the eye caused by a parasite.
How does Cotrimoxazole (Trimethoprim + Sulfamethoxazole) work?
This medicine works by killing the Toxoplasma parasite that causes the infection in the retina. It is a combination of two ingredients, Trimethoprim and Sulfamethoxazole, which work together to eliminate the parasite.
What are the common Indian brands for Cotrimoxazole (Trimethoprim + Sulfamethoxazole)?
In India, common brands for Cotrimoxazole (Trimethoprim + Sulfamethoxazole) include Septran and Bactrim.
How should I take Cotrimoxazole (Trimethoprim + Sulfamethoxazole)?
You should take one DS (Double Strength) tablet (800 mg + 160 mg) twice a day for 6 weeks, or as directed by your ophthalmologist. It is usually prescribed along with a steroid, which is started 48 hours after you begin taking Cotrimoxazole.
Do I need a prescription for Cotrimoxazole (Trimethoprim + Sulfamethoxazole)?
Yes, Cotrimoxazole (Trimethoprim + Sulfamethoxazole) is a prescription medicine and should only be used as directed by a qualified ophthalmologist. Do not self-medicate.
What are the key precautions I should be aware of when taking Cotrimoxazole (Trimethoprim + Sulfamethoxazole)?
Important precautions include: steroids must never be given alone for toxoplasmosis (always with anti-parasitic cover), avoid if you have a sulfa allergy, and it should be avoided during pregnancy. Always inform your doctor about your medical history and other medications.
References
- Trimethoprim-Sulfamethoxazole – StatPearls – NCBI Bookshelf – NIH
- Ocular Toxoplasmosis: A Refresher – American Academy of Ophthalmology
- Co-trimoxazole: MedlinePlus Drug Information
- Antimicrobial Drug Prophylaxis for Recurrent Ocular Toxoplasmosis – MDPI
- Learn about eye health – National Eye Institute (NIH)
Medically reviewed by Dr. C Jagadesh Reddy, Chief Surgeon: Cornea, Cataract and Refractive Surgery — last reviewed 2026-07-28.
This page is for general education only and is not a substitute for professional medical advice, diagnosis or treatment. Never self-medicate or reuse an old prescription. Always consult a qualified ophthalmologist before starting, changing or stopping any eye medicine.