eflornithine, drug used to treat late-stage African trypanosomiasis (sleeping sickness). Eflornithine is effective only against Trypanosoma brucei gambiense, which causes Gambian (or West African) sleeping sickness. It is not effective against T. brucei rhodesiense, which causes Rhodesian (or East African) sleeping sickness. Eflornithine is also used to treat excessive facial hair growth, particularly in women.
Throughout the 1990s the expense and lack of availability of eflornithine limited its use. However, in the early 2000s demand for eflornithine significantly increased because it was found to be more effective than melarsoprol in the treatment of late-stage Gambian sleeping sickness. For Gambian sleeping sickness, eflornithine is administered by intravenous injection. For facial hair reduction, it is self-applied as a topical cream.
Eflornithine exerts its effects by inhibiting an enzyme called ornithine decarboxylase, which catalyzes the synthesis of polyamine-based compounds involved in cell division and cell differentiation. Polyamines are essential for DNA synthesis, cell division, and growth in both normal and parasitic cells. Thus, eflornithine disrupts parasite growth and replication and ultimately causes parasite death. In the case of hair, irreversible inhibition of ornithine decarboxylase within hair follicles slows hair growth.
In order to circumvent the evolution of eflornithine-resistant trypanosomes, combination therapies have been developed. The most effective of these is the combination of eflornithine with nifurtimox, a nitrofuran compound that is used in the treatment of Chagas disease, which is caused by T. cruzi, an organism closely related to T. brucei.
Because eflornithine was shown to block the proliferation of tumor cells, its use in the treatment of certain cancers has been investigated. However, the results of such studies have been mixed. The most promising anticancer use of eflornithine is as a topical chemopreventative agent for people at high risk of skin cancer.