The blood glucose lowering effects of tolbutamide
may be increased by chloramphenicol
and acute hypoglycaemia can occur. Other sulphony- lureas are often predicted to interact similarly, but there does not seem to be any direct evidence of this.
An increased blood glucose lowering effect should be expected if both drugs are given but few patients experience a severe effect. Monitor concurrent use carefully and reduce the dosage of the sulphonylurea as necessary. No interaction would be expected with topical chloramphenicol
because the systemic absorption is likely to be small.