Melarsoprol is a drug used to treat African trypanosomiasis and other diseases caused by parasites in the same genus. It works by blocking the action of an enzyme the parasite requires to make energy. Although it is readily available in areas where the disease is endemic, in the United States it is only available from the CDC.
Although melarsoprol is effective in over 95% of even late stage cases, it is treated as a drug of last resort because of its numerous side effects. First and foremost, it is an arsenic compound and many of the side effects are identical to arsenic poisoning. These include fever, loss of consciousness, convulsions, rash, nausea, vomiting and blood in the stool. It can also damage the heart and kidneys. In over 5% of cases, it can trigger an encephalopathy. Patients must be closely monitored before and during treatment, including frequent blood tests and lumbar puncture to check white blood cell levels.
Melarsoprol also has several counter-indications. In patients with a rare genetic condition, it can destroy red blood cells. It is also contraindicated where there are existing liver or kidney issues, a history of heart conditions, existing neurological disorders, or leprosy. It is not recommended for pregnant women and in such cases, treatment is postponed until delivery of the newborn.