L-Eflornithine monohydrochloride is primarily used in the treatment of African trypanosomiasis, also known as sleeping sickness. It works by inhibiting ornithine decarboxylase, an enzyme crucial for the growth and replication of the parasite Trypanosoma brucei gambiense. This makes it an effective agent in reducing the parasite load in patients, particularly in the second stage of the disease when the central nervous system is affected. It is often administered in combination with other antiparasitic drugs to enhance its efficacy and reduce the risk of resistance.

In addition to its antiparasitic applications, it is also utilized in dermatology as a topical cream to reduce unwanted facial hair in women. By inhibiting the same enzyme in hair follicles, it slows down hair growth, providing a non-invasive option for managing hirsutism. This dual application highlights its versatility in both medical and cosmetic fields.