ash ▁or ▁system ic ▁sympt oms ▁ ▁formation ▁of ▁r ash ▁with ▁system ic ▁sympt oms ▁ ▁severe ▁skin ▁or ▁hyp ers ens itivity ▁re actions ▁Additionally , ▁the ▁U . S . ▁F DA ▁recomm ends ▁close ▁monitoring ▁during ▁the ▁first ▁ 6 ▁weeks ▁of ▁ther apy ▁for ▁the ▁above ▁sympt oms ▁as ▁there ▁is ▁high ▁risk ▁during ▁this ▁time . ▁Cont in ued ▁monitoring ▁is ▁recommended ▁for ▁up ▁to ▁the ▁first ▁ 1 8 ▁weeks ▁of ▁treatment . ▁If ▁a ▁patient ▁experiences ▁he pat itis ▁plus ▁r ash ▁or ▁other ▁system ic ▁sympt oms , ▁or ▁severe ▁hyp ers ens itivity ▁or ▁skin ▁r ash , ▁ne vi rap ine ▁should ▁not ▁be ▁restart ed . ▁ ▁D rug ▁interactions ▁Ne vi rap ine ▁is ▁a ▁substr ate ▁for ▁li ver ▁C Y P 3 A ▁and ▁C Y P 2 B 6 ▁en zym es . ▁Con com it ant ▁administration ▁of ▁dru gs ▁that ▁are ▁in hib itors ▁of ▁these ▁en zym es ▁may ▁increase ▁ser um ▁ne vi rap ine ▁levels ▁significantly . ▁Some ▁examples ▁of ▁these ▁dru gs ▁include ▁rit on av ir , ▁fos am pr en av ir , ▁and ▁flu con az ole . ▁On ▁the ▁other ▁hand , ▁dru gs ▁that ▁are ▁indu cers ▁of ▁these ▁en zym es ▁such ▁as ▁rif amp ic in ▁may ▁lower ▁ser um ▁ne vi rap ine ▁levels .[ 1 8 ] ▁ ▁In ▁addition , ▁con com it ant ▁use ▁of ▁ ▁St . ▁John '