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Cotrimoxazole is a combination of trimethoprim and sulfamethoxazole. Cotrimoxazole is used to treat a variety of bacterial infections such as uncomplicated UTIs, respiratory tract infections, and gastrointestinal infections.


Primary Characterstics

. It is of Synthetic origin and belongs to Sulphonamide, Trimethoprim. It belongs to Antibiotic, Sulphonamide Derivative pharmacological group.The Molecular Weight of Co-Trimoxazole is 253.21.
Its pKa is 5.6.


Oral absorption of Co-Trimoxazole is found to be 90% ±5. Volume of distribution is found to be 12-18, 70-100 litre and plasma protien binding is 42-66%. and metabolism is reported 60-70%. Renal Excretion accounts for 70% and plasma half life is 9-10 hr.



Co-Trimoxazole is contraindicated in conditions like Impaired renal function,Haematological disorders,Liver parenchymal damage,Hypersensitivity.

Drug Interactions

Co-Trimoxazole is known to interact with other drugs, the details of drug interactions is as follows:

Cyclosporin A
Phenytoin (Na)
Procainamide (HCl)
Warfarin (Na)

These interactions are sometimes beneficial and sometimes may pose threats to life. Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.

Interference in Pathology

  • Overstimation of serum creatinine with alkaline picrate reaction.

Side Effects

The severe or irreversible adverse effects of Co-Trimoxazole, which give rise to further complications include Thrombocytopenia, Aplastic anemia, Hemolytic anemia, Aplastic anemia, Hemolytic anemia, Stevens johnson syndrome, Stevens johnson syndrome, Leucopenia, Neutropenia, Agranulocytosis, Interstitial nephritis, Acute renal failure, Methemoglobinemia, Hemolytic anemia, Megaloblastic anemia, Crystalluria, Methemoglobinemia, Aplastic anemia.

The symptomatic adverse reactions produced by Co-Trimoxazole are more or less tolerable and if they become severe, they can be treated symptomatically, these include Nausea, Vomiting, Skin reactions, Skin rashes, GI symptoms, Exfoliative dermatitis, Skin rashes.

Available Brands

No Brands Available.


Co-Trimoxazole's dosage details are as follows:
Dose Single Dose Frequency Route Instructions

Adult Dosage

2.88 mg2.9 (2.88)12 hourlyPO2 divided doses in serve infection
960 mg960 (960)12 hourlyPO

Paedriatic Dosage ( 20 Kg. )

24 mg/kg24 (24)12 hourlyOral-
24 mg/kg24 (24)12 hourlySlow IV-

Neonatal Dosage ( 3 Kg. )

15 to 30 mg/kg22 (22.5)12 hourlyoral
15 to 30 mg/kg22 (22.5)12 hourlySlow intravenous

High Risk Groups

Drug should not be given to Pregnant Mothers, patients suffering from Liver Malfunction, Geriatrics, and Neonates.

If prescribing authority justifies the benefits of the drug against the possible damages he/she should reevaluate them and consult the reference material and previous studies.

Warning / Precautions

Co-trimoxazole should be used with caution in patients with history of hypersensitivity to it or to sulphonamides or trimethomprim. Avoid use in patients with hepatic impairment. It should be used with caution in patients with known renal impairment and special measures should be adopted. Regular monthly blood counts, urinalyses and renal function tests should be carried out in patients receiving prolonged treatment with co-trimoxazole. Folate supplementation may be necessary in patients predisposed to folate deficiency, such as elderly patients and when high dose of co-trimoxazole are given for a prolonged period. Drug should be discontinued at first appearance of skin rash. Exercise caution when treating patients with severe hepatic parenchymal damage. It should be given with caution in patients with severe allergy or bronchial asthma.

Storage Conditions

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