The present invention relates preferably to the use of 4-bromo-N-[(E)-(2-methyl-1H-indol-3-yl)methyleneamino]benzenesulphonamide and 4-methyl-3-oxo-2-(3-pyridylmethylene) benzo[3,4-b]furan-6-yl-4-chlorobenzenesulphonate (compounds 5 and 6, respectively), which are compounds that can inhibit the toxic activity of sphingomyelinase D from Loxosceles venom, controlling the development of cutaneous and systemic loxoscelism; reducing haemolysis; inhibiting the formation of skin lesions; inhibiting skin necrosis; inhibiting intracellular signaling pathways and the production of reactive oxygen species. In addition to the therapeutic potential thereof, said inhibitors can be used to study the activity of sphingomyelinases and phospholipases D. The present invention also relates to a pharmaceutical composition for treating loxoscelism, reducing haemolysis, inhibiting the formation of skin lesions, inhibiting skin necrosis, inhibiting intracellular signaling pathways and the production of reactive oxygen species, comprising said compounds and a pharmaceutically acceptable carrier.