Sulphamethoxazole + Trimethoprim
Uses of Sulphamethoxazole + Trimethoprim
Sulphamethoxazole + Trimethoprim is primarily used to manage bacterial infections. It belongs to the group of combination antibacterial medicines.
This medicine is also indicated for managing urinary tract infections, acute otitis media, bronchitis, traveller's diarrhoea, shigellosis, and Pneumocystis jirovecii pneumonia.
Side effects of Sulphamethoxazole + Trimethoprim
Gastrointestinal disturbances
Allergic skin reactions
Headache
Dizziness
How Sulphamethoxazole + Trimethoprim works
- Sulphamethoxazole + Trimethoprim works by blocking two consecutive steps in the process bacteria use to produce folate, a nutrient essential for bacterial growth and reproduction.
- Sulphamethoxazole belongs to the sulphonamide class of antibiotics. It works by blocking an enzyme bacteria need to begin producing folate from a precursor compound, preventing the first step in the folate production pathway.
- Trimethoprim is a folic acid antagonist. It blocks a different enzyme further along the same pathway, preventing bacteria from converting an intermediate compound into tetrahydrofolic acid - the active form of folate that bacteria require to grow and multiply.
- By blocking two separate, sequential steps in the same essential pathway, this combination disrupts bacterial folate production far more effectively than either medicine could alone. Since bacteria cannot produce DNA, RNA, or proteins without adequate folate, this dual blockade halts bacterial growth and reproduction, helping the body clear the infection.
- Human cells obtain folate from dietary sources rather than producing it internally in this way, which is why this combination selectively targets bacteria with limited effect on human cells.
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Written By
Doctor of Medicine
Reviewed By
BAMS, FMC, MD Resident
Expert Advice
Dosage Forms Available
Sulphamethoxazole + Trimethoprim is available in the form of tablets and as a suspension for oral administration.
This combination can also be administered intravenously as an infusion.
Age and Dose Restrictions
This medicine is meant for adults and children over 6 weeks of age.
Contraindications
Sulphamethoxazole + Trimethoprim is contraindicated in patients with known hypersensitivity to sulphamethoxazole, trimethoprim or any component of the formulation.
It is also contraindicated in patients with documented megaloblastic anaemia due to folate deficiency.
Other Medications to Avoid
This combination may interact with anticoagulants (e.g., warfarin, heparin), medications affecting folate metabolism (e.g., methotrexate, pyrimethamine), cardiac glycosides (e.g., digoxin, digitoxin), antiepileptic medications (e.g., phenytoin, phenobarbital), medicines used to manage diabetes (e.g., glibenclamide, glipizide), antibiotics (e.g., rifampicin), medicines for HIV infections (e.g., zidovudine, lamivudine), potassium-sparing diuretics (e.g., spironolactone), steroids (e.g., prednisolone), ACE inhibitors (e.g., captopril, enalapril), and immunosuppressants (e.g., ciclosporin, azathioprine).
Overdose and Missed Dose
- An overdose of Sulphamethoxazole + Trimethoprim can cause symptoms ranging from nausea, vomiting, and dizziness to more severe effects such as crystalluria (crystals in the urine), kidney problems, or blood disorders. If you suspect an overdose, contact your doctor immediately.
If you forget to take a dose of this medicine, take it as soon as you remember. However, if it is nearly time for your next dose, skip the missed one and continue with your regular schedule. Do not take a double dose to make up for the missed dose. Continue taking the medicine for the full prescribed duration, even if symptoms improve earlier.
Management of Side Effects
Most side effects are temporary and generally harmless, resolving after discontinuing this medicine. However, if you experience severe side effects or worsening symptoms, consult your doctor.
For gastrointestinal disturbances such as nausea or diarrhoea, try taking this medicine with food.
Avoid excessive exposure to sunlight and wear sunscreen to manage photosensitivity reactions.
Use in Driving and Operating Machinery
This medication may cause dizziness. Hence, driving or operating heavy machinery is not advised until you know how this medicine affects you.
Use in Pregnancy and Lactation
It is advisable to consult your doctor before using Sulphamethoxazole + Trimethoprim during pregnancy and breastfeeding.
Caution in Other Conditions
Sulphamethoxazole + Trimethoprim should be used with caution in patients with severe renal impairment or hepatic dysfunction.
This medicine should also be used with care in patients with folate deficiency.
Special Dietary and Lifestyle Recommendations
Maintain good personal hygiene to prevent recurrent urinary tract infections, one of the conditions managed by Sulphamethoxazole + Trimethoprim.
Stay hydrated by drinking plenty of fluids. This helps to clear bacteria from your urinary tract, reducing the risk of infection.
Frequently asked questions
Is Sulphamethoxazole + Trimethoprim a steroid?
No, Sulphamethoxazole + Trimethoprim is not a steroid. It is a combination of two antibiotics - a sulfonamide antibiotic (sulphamethoxazole) and a folic acid antagonist (trimethoprim).
Can Sulphamethoxazole + Trimethoprim interfere with my sleep?
Sulphamethoxazole + Trimethoprim is not commonly known to interfere with sleep. If you experience sleep issues, consult your doctor.
Will taking Sulphamethoxazole + Trimethoprim affect my fertility?
Sulphamethoxazole + Trimethoprim is not commonly known to affect fertility. If you have specific concerns, consult your doctor.
Can I take Sulphamethoxazole + Trimethoprim every day?
This combination medicine is usually prescribed for a specific duration depending upon the type and severity of the infection. Regular use should be as per your doctor's recommendation.
How long does it take for Sulphamethoxazole + Trimethoprim to start working?
This will depend on the type of infection being addressed, but some improvement is usually seen within a few days of starting the medication. However, it is essential to complete the full duration of treatment prescribed by your doctor.
When should I take Sulphamethoxazole + Trimethoprim?
The medicine can be taken with or without food, as prescribed by your doctor. It is important to follow your doctor's instructions on when and how often to take it.
Is there a specific test or medical monitoring required while taking Sulphamethoxazole + Trimethoprim?
In case of prolonged therapy with Sulphamethoxazole + Trimethoprim, regular monitoring of blood counts and kidney and liver function may be necessary.
Sulphamethoxazole + Trimethoprim in other salts
List of medicines for Sulphamethoxazole + Trimethoprim
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