Tafenoquine is a relatively new anti-malarial medication which is chemically related to primaquine. Tafenoquine is not related to mefloquine and acts quite differently in the body.
The Army Malaria Institute (AMI) conducted a study of tafenoquine in ADF troops deploying to Timor-Leste in 2000 and 2001, and a smaller study in 1998/99 in soldiers deploying to Bougainville. The abstract of the Bougainville study is available here and the full text article is available on request to ADF.Malaria@defence.gov.au.
Prior to its use in ADF personnel, tafenoquine had been tested in over 1,000 people in Africa and South East Asia. Those earlier studies showed that tafenoquine was safe, well-tolerated and effective against malaria. The most common side effects reported were gastrointestinal (nausea, vomiting and diarrhoea) and headache. These symptoms were mild and resolved quickly.
Uncommonly, an eye condition, vortex keratopathy (small deposits in the cornea), has been associated with tafenoquine use. This condition is also associated with other medications, such as chloroquine, which was used widely for malaria management before drug resistance became a problem, and some medications used to treat heart conditions and cancer. The condition does not affect vision and has no symptoms. It is benign and resolves completely after tafenoquine is stopped.
Tafenoquine has not been shown to have any neurotoxic or neuropsychiatric side effects. Like primaquine, the main concern in using tafenoquine is in people who lack the G6PD enzyme. In those people, tafenoquine can cause red blood cell problems, causing anaemia. All ADF personnel are tested for this enzyme on entry.
The main advantage of tafenoquine is that it is effective for both prevention and treatment of malaria and is longer acting than primaquine, so fewer doses are needed thus improving compliance.
To date more than 4000 people, both military and civilian, have taken tafenoquine in clinical studies around the world. Tafenoquine has successfully treated relapsing malaria (i.e. continued infections long after exposure) when combined with another medication called chloroquine. At this point tafenoquine remains a medication that is only used within voluntary clinical studies.
Malaria is a complex disease with different medications being effective in different parts of the infection cycle and against different kinds of the malaria parasite. The parasite evolves over time and develops resistance to certain medications, thus making them less effective. This is why new medications need to be continuously developed and tested.