Is Drowsiness A Side Effect Of Doxolin Drugs?

hI DOCOTOR my father is 60 years old suffering from wheezing hard breathing he has a history of tuberclosis in 2001. now its negative, he has been prescribed with doxolin tablet and duolin rota caps yearterday by a chest speacilist he ifeeling very drowsy and losses his memory is it normal is doxolin a very heavy drug howvere he is taking only half tablet in the morning and half in the night. Pls advise.