Cotrimoxazole is bactericidal in vitro to a wide range of Gram-positive and Gram-negative organisms, including Streptococcus, Staphylococcus, Pneumococcus, Neisseria, B. catarrhalis, Escherichia coli, Klebsiella, Proteus spp., Haemophilus, Salmonella, Shigella, Vibrio cholerae, Brucella, Pneumocystis carinii, Nocardia and Bordetella. A particularly high degree of activity is exhibited against Haemophilus influenzae, E. coli and Proteus spp., making Cotrimoxazole particularly suitable for the treatment of chronic bronchitis and urinary tract infections. Cotrimoxazole exerts its bactericidal action by the sequential blockade of two bacterial enzyme systems in the biosynthesis of Folinic acid in the micro-organisms. The synergy thus produced accounts for the high degree of bactericidal activity.

Indications are :

• Respiratory tract infections, including acute and chronic bronchitis (treatment and prophylaxis), bronchiectasis, lung abscess, lobar and broncho-pneumonia, Pneumocystis carinii pneumonitis, sinusitis and otitis media.
• Genito-urinary tract infections, including urethritis, acute and chronic cystitis, pyelonephritis, prostatitis and gonorrhoea.
• Gastro-intestinal tract infections, caused by Salmonella typhi and Salmonella paratyphi, including the chronic carrier state.
• Other infections, caused by a wide range of organisms confirmed to be susceptible to Cotrimoxazole and where the therapeutic benefits are considered to outweigh the possible occurrence of adverse events.
• Such infections include acute and chronic osteomyelitis, acute brucellosis, skin infections including pyoderma, abscesses and wound infections, septicaemia, bacillary dysentery and cholera (as an adjuvant to fluid and electrolyte replacement), nocardiosis and mycetoma.

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 month-5 years: 1 teaspoonful twice daily.
• 6 weeks-6 months: 0.5 teaspoonful twice daily.

• Hypersensitivity to trimethoprim or sulphonamides.
• Patients with documented megaloblastic anaemia due to folate deficiency.
• Patients showing marked liver parenchymal damage, blood dyscrasia, severe renal insufficiency, glucose 6-phosphate dehydrogenase deficiency.

The side effects like crystalluria, allergic reactions, haemolysis, thrombocytopenia, neutropenia, agranulocytosis etc. have been reported rarely with Sulphamethoxazole-Trimethoprim combination. Other side effects are less serious in nature such as malaise, headache, nausea and vomiting. These are normally transient and do not require withdrawal of treatment.

Prolonged full dose treatment with sulfamethoxazole-trimethoprim combination is associated with the risk of macrocytic anaemia due to the drug’s interference in the conversion of Folic acid into Folinic acid. If this occurs, it can be reversed by giving Folinic acid. Care should be taken when giving this combination to diabetic patients receiving sulphonylurea drug for possible potentiation of action of sulphonylurea.

Pregnancy & Lactation

Pregnancy and during the nursing period, because sulphonamides pass the placenta and are excreted in the breast milk and may cause kernicterus.