bacterial infection
"Was prescribed (basically, handed a packet of pills) metronidazole by the company doctor on the Pacific island where I'm currently doing volunteer work. Five day course. By day two my dizziness and nausea had turned into uncoordinated gait and problems with fine motor control; that night I woke up panicking and completely dissociated from my surroundings. Went to another doctor who happens to be living in the same village as me, she told me I was having a rare and very serious sensitively to the drug. Miserable experience, but like I said, very rare. I'm sharing because the second doctor told me I was on it too long: if you experience any loss of balance or coordination on these drugs, even if you don't feel bad, you need to see a doctor."