In patients with impaired renal function, the dosage should be reduced or the interval between doses prolonged in order to prevent cumulation in the blood. Determination of plasma drug concentrations is recommended in such patients.
Regular blood count is advisable whenever Comazole is given for prolonged periods, especially in elderly, there is possibility of haematological changes indicative of folic acid deficiency; these are reversible by folinic acid therapy.
An adequate output should be maintained at all times. Treatment must be discontinued immediately if skin rash appears.
Blood dyscrasias; death associated with the administration of sulphonamides have been reported from hypersensitivity reactions, agranulocytosis, aplastic anaemia and other blood dyscrasias.
Clinical signs such as sore throat, fever, pallor, purpura or jaundice may be early indications of blood disorders. Complete blood count should be done frequently in patients receiving sulphonamides. Trimethoprim has been reported to interfere with haematopoiesis in occasional patients.
Group A-beta haemolysis streptococcal tonsillo-pharyngitis; Patients treated with trimethoprim and sulphamethoxazole have a greater incidence of bacteriological failure than those treated with penicillin, as evidenced by failure to eradicate this organism from the tonsilopharyngeal area.
Superinfections: Possible overgrowth of non-susceptible organism, including fungi should be looked for when any sulphonamide is administered. Should this occur treatment should be discontinued and appropriate therapy instituted.
Severe allergy or bronchial asthma: Sulphonamides should be given with caution to these patients, with a critical appraisal of benefit versus risk.
Comazole also should be given with caution to patients with impaired hepatic function and to those patients with severe allergy or bronchial asthma. In G6PD, hemolysis may occur (dose related).
Because of the risk of crystalluria, an adequate fluid intake should be maintained and the administration of alkalis may be necessary, if very large doses are used.