Cotrimoxazole is a bactericidal agent in vitro with activity against a broad range of Gram-positive and Gram-negative organisms, including Streptococcus, Staphylococcus, Pneumococcus, Neisseria, Moraxella catarrhalis, Escherichia coli, Klebsiella, Proteus spp., Haemophilus, Salmonella, Shigella, Vibrio cholerae, Brucella, Pneumocystis carinii, Nocardia, and Bordetella. It shows particularly strong activity against Haemophilus influenzae, E. coli, and Proteus spp., making it especially useful in chronic bronchitis and urinary tract infections. Cotrimoxazole acts by sequential inhibition of two bacterial enzyme systems involved in folinic acid synthesis, resulting in a synergistic bactericidal effect.

This combination is indicated in:

• Respiratory tract infections, including acute and chronic bronchitis (treatment and prevention), bronchiectasis, lung abscess, lobar and bronchopneumonia, Pneumocystis carinii pneumonia, sinusitis, and otitis media.
• Genito-urinary tract infections, including urethritis, acute and chronic cystitis, pyelonephritis, prostatitis, and gonorrhoea.
• Gastrointestinal infections caused by Salmonella typhi and Salmonella paratyphi, including chronic carrier states.
• Other infections caused by susceptible organisms where the expected benefits outweigh potential risks, such as osteomyelitis, acute brucellosis, skin infections (pyoderma, abscesses, wound infections), septicaemia, bacillary dysentery, cholera (as adjunct to fluid and electrolyte therapy), nocardiosis, and mycetoma.

Cotrimoxazole is a broad-spectrum bactericidal combination effective against many Gram-positive and Gram-negative bacteria and certain protozoa. It contains Trimethoprim and Sulphamethoxazole in a 1:5 ratio. This combination exerts its bactericidal effect by sequential inhibition of two key bacterial enzymes involved in folinic acid synthesis, leading to enhanced antimicrobial activity.

Cotrimoxazole double strength tablet: Over 12 years

• For mild to moderate infections: 1 tablet twice daily.
• For severe infections: 1.5 tablets twice daily.
• Long term therapy (>14 days): 0.5 tablet twice daily.
• Gonorrhoea: 2 tablets every 12 hours for two days or 2.5 tablets followed by a further dose of 2.5 tablets after 8 hours.

Cotrimoxazole tablet: Over 12 years

• For mild to moderate infections: 2 tablets twice daily.
• For severe infections: 2 tablets thrice daily.
• Long term therapy (>14 days): 1 tablet twice daily.

Cotrimoxazole suspension: Under 12 years

• 6–12 years: 2 teaspoonful twice daily.
• 6 months–5 years: 1 teaspoonful twice daily.
• 6 weeks–6 months: 0.5 teaspoonful twice daily.

• Cotrimoxazole is contraindicated in patients with known hypersensitivity to trimethoprim or sulphonamides.
• It should not be used in individuals with documented megaloblastic anaemia due to folate deficiency.
• Use is also contraindicated in patients with significant hepatic parenchymal damage, blood dyscrasias, severe renal impairment, or glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Rare adverse reactions include crystalluria, allergic reactions, haemolysis, thrombocytopenia, neutropenia, and agranulocytosis. More common but less severe effects include malaise, headache, nausea, and vomiting. These are usually mild and transient and typically do not require discontinuation of therapy.

Use during pregnancy and breastfeeding is not recommended. Sulphonamides cross the placenta and are excreted into breast milk, which may lead to kernicterus in the newborn.

Long-term use at full doses may lead to macrocytic anaemia due to interference with folic acid metabolism. This condition can be reversed by administering folinic acid. Caution is advised when using this combination in diabetic patients taking sulphonylureas, as it may enhance the hypoglycaemic effect of these drugs.

Anti-diarrhoeal antimicrobial drugs, Sulphonamides & Trimethoprim

Store below 30°C, protected from light and moisture. Keep out of reach of children.