Hepatic, renal & hematologic effects. GI effects eg, nausea, abdominal pain, vomiting, pseudomembranous colitis, epigastric distress, anorexia. Central & peripheral nervous system effects eg, tiredness, drowsiness, headache, dizziness, ataxia, confusion, muscular weakness, visual disturbances, peripheral neuropathy. Skin & allergic effects eg, rash, fever, urticaria, pruritus. Rifampicin: Endocrine effects. Ethambutol: Acute gout (rare).