Brown-brown is a purported form of cocaine or amphetamine insufflation mixed with smokeless gunpowder.
This powder often contains nitroglycerin, a drug prescribed for heart conditions, which might cause vasodilation, permitting the cocaine or amphetamine insufflation to move more freely through the body.
[1][2] Brown-brown is reportedly given to child soldiers before West African armed conflicts.
[3] One former child soldier, Michel Chikwanine, has written a graphic novel with Jessica Dee Humphreys called Child Soldier, about the experience of being captured at the age of 5 by rebel fighters in the Democratic Republic of Congo, including being given brown-brown.
[4] "The rebel soldier who had hit me used a long, jagged knife to cut my wrist and rubbed powder into the wound.