<s>[INST] Hi i had low back pain and for that i done an operation in back bone.after 7 months again im having back pain sometimes when i wakeup from bed in early morning.now doctor prescribed to have hifenac sr tablet for 1 day.can i have that tablet.any side effects? [/INST] Hifenec is a safe drug usually.  It does not cause any moajor reaction.  But us shod be taken more long time, ci mean it should  not be taken for months.  For Your back pain for one month it is ok to take one tablet. </s>