Which of the following drugs is used to treat giardiasis in patients 1 year of age and older?

A) nitazoxanide
B) pyrimethamine
C) benznidazole
D) nifurtimox

A) nitazoxanide
A) Nitazoxanide is used to treat giardiasis in patients over 1 year of age and older. It is also used for diarrhea that is caused by Cryptosporidium parvum in patients between 1 and 11 years of age.