Sulphamethoxazole

It is a combination of Sulfonamides exhibiting maximum synergism (Trimethoprim 80 mg with Sulfamethoxazole 400 mg). Additional organisms covered by the combination are salmonella typhi, Serratia, Klebsiella, Yersinia enterocolitica, Pneumocystis carinii and many Sulfonamide resistant strains of staph aureus, strep. pyogenes, shigella, enter pathogenic E.coli, H. influenzae and gonococci

Indications

Urinary tract, Respiratory tract Infections. Typhoid, bacterial diarrhoeas and dysentery, Septicaemias, Gonorrhoea, Chancroid, whooping cough and for prophylaxis and therapeutic treatment of severe infection of Pneumocystis carinii in neutropenic patients.

Dosage

Trimethoprim Sulfamethoxazole. 80 mg+400 Trimethoprim Sulfamethoxazole. 80 mg+400 mg tab: 2BD for 2 days then 1BD, 160 mg+800 mg tab: Double strength (D.S) 1BD, 20 mg + 100 mg paediatric tab 1BD, 40 mg + 200 mg per 5 ml susp: infant 2.5 ml, children 1-5 yrs 5 ml, 6-12 yrs 10 ml (all B.D), 160 mg + 800 mg per 3 ml for i.m.inj 12 hrly, 80 mg + 400 mg per 5 ml for i.v inj 10-15 ml B.D

Contra-Indications

Hypersensitivity to either sulphonamides or trimethoprim. Not to be used in premature or infants of few weeks. Marked liver parenchymal damage, blood dyscrasias and severe renal insufficiency, unless blood levels can be closely monitored.

Special Precautions

Patients with history of allergies, urinary obstruction, blood dyscrasias, hepatic and renal impairment, bronchial asthma. Not to be used in pregnancy because of the possible teratogenic effects of inducing folate deficiency. Paediatrics: Reduced dose necessary. Not recommended in infants under 6 weeks. Pregnancy: Contraindicated. Lactation: Use with caution. Elderly: Possibility of side effects.

Side Effects

Allergic reactions include rash, fever, hepatitis, agranulocytosis, purpura, aplastic anaemia, peripheral neuritis. Skin reactions including erythema multiforme bullosa & toxic epidermal necrolysis. Other side effects include Crystalluria causing renal colic, heaematuria, oliguria, less serious effects include malaise, headache, nausea or vomiting, diarrhoea, mental depression & rarely cyanosis.

Drug Interactions

Co-administration with pyrimethamine causes megaloblastic anaemia.