Allergic reactions, including rash, pruritus & anaphylaxis. GI effects eg, heartburn, eructation, abdominal pain & cramps, diarrhea, vomiting, nausea & anorexia; hepatic dysfunction w/ abnormal LFT including hyperbilirubinemia; deterioration of acneiform vulgaris or eruption of acneiform exanthema. Riboflavin: Bright yellow urine discoloration. Niacinamide: Strong vasodilator effects (flushing, dizziness or faintness). Pyridoxine: Peripheral sensory neuropathies. Ascorbic acid: Stone formation, crystalluria & oxalosis.