Activity of the combination of isoniazid, protionamide and dapsone against Mycobacterium leprae and some other mycobacteria.

No additive effect was found at the addition of isoniazid to either dapsone or protionamide against M. leprae and against highly dapsone-sensitive in vitro growing Mycobacterium sp. strains. It is concluded that the indication of the administration of isoniazid in leprosy is extremely limited and could only be envisaged as a companion drug in combined therapy of dapsone-resistant multibacillary leprosy in light-skinned people, when aminoglycosides cannot be administered.