Cotrimoxazole

Question 1

What is the FDC aid cotrimoxazole ?
MOA

Answer 1

Mechanism of Action
Para-aminobenzoic acid (PABA)
Folate synthetase <
• Sulfamethoxazole
Dihydrofolic acid (DHFA)
Dihydrofolate reductase «
Trimethoprim
Tetrahydrofolic acid (THFA)•
Cotrimoxazole (sulphamethoxazole and trimethoprim in a dose ratio

Question 2

Therapeutic uses of cotrimaxazole ?

Answer 2

Therapeutic Uses
1. Urinary tract infection (UTI): Cotrimoxazole is effective for the treatment of acute uncomplicated lower UTIs due to gram-negative organisms such as E. coli, Protes and Enterobacter spp. The usual dose is 800 mg sulphamethoxazole plus 160 mg of trimethoprim (cotri-moxazole double-strength tablet) b.d. for 3 days. It is useful for chronic and recurrent lower UTIs especially in women. Cotrimoxazole can be used in the treatment of bacterial prosta-tifis as it is concentrated in prostatic tissue.
2. Respiratory tract infections: Cotrimoxazole is useful for acute and chronic bronchitis due to H. influenzae and Moraxella catarrhalis. It is also useful for acute maxillary sinusitis and otitis media.
3. Bacterial diarrhoeas: Cotrimoxazole may be used for GI infections due to Shigella, E. coli and Salmonella spp. But FQs are the preferred agents.
4. P. jiroveci infection: High doses of cotrimoxazole are used for treatment of infection due to
P. jiroveci in immunocompromised patients. It is used for treatment (one double strength tablet every 4 6 hours for 3’weeks) as well as prophylaxis of P. jiroveci pneumonia. Pent-amidine, clindamycin, primaquine and atovaquone are the alternative drugs for P. jiroveci infection.
5. Nocardiosis: Cotrimoxazole has been used in the treatment of infection due to Nocardia spp.
6. Chancroid: It is caused by H. ducreyi. The drug of choice is azithromycin. Cotrimoxazole is equally effective. The alternative drugs are ceftriaxone and ciprofloxacin.
7. Typhoid fever*: Preferred drug is azithromycin’ (oral) and ceftriaxone (parenteral). Other drugs are cotrimoxazole, cefepime, ciprofloxacin and

Question 3

Adverse effects of cotrimoxazole ?

Answer 3

Adverse Effects :-
Cotrimoxazole is well tolerated in most patients. Most of the adverse effects are same as those of sulfonamides. The common adverse effects are skin rashes and gastrointestinal (GI) distur-bances. Exfoliative dermatitis, erythema multiforme and Stevens-Johnson syndrome are rare.
GI symptoms include nausea, vomiting, glossitis and stomatitis. Megaloblastic anaemia due to folate deficiency may occur rarely, especially in alcoholics and malnourished persons. Bone marrow suppression with leucopenia, neutropenia and thrombocytopenia occurs rarely. Cotri-moxazole is contraindicated in pregnancy.