Short communication: fasting increases serum concentrations of bilirubin in patients receiving atazanavir: results from a pilot study.

Unconjugated hyperbilirubinemia resulting from therapy with atazanavir is physiologically related to hyperbilirubinemia in Gilbert's syndrome (GS). In patients with GS, changes in diet have a significant impact on bilirubinemia. Our aim was to investigate whether changes in diet affect the level of serum bilirubin in patients receiving atazanavir. Thirty patients on stable therapy with ritonavir-boosted atazanavir without evidence of GS were enrolled. Hemolysis and chronic hepatitis were excluded. After a baseline period of normal intake of calories, the patients were randomized to follow a 24-h 400-calorie diet (fasting), then a 48-h period of normal calorie intake and, afterward, a 24-h period of a high-calorie diet, or the same interventions in inverse order. Serum bilirubin concentrations were measured before and after each intervention. A high adherence to the recommended diet was observed. The mean unconjugated bilirubin concentration before the high-calorie diet was 2.79±1.53 mg/dl and after such intervention it was 2.70±1.40 mg/dl. The mean difference between preintervention and postintervention was -0.08±0.69 mg/dl (p=NS). The mean unconjugated bilirubin concentration before the fasting diet was 2.31±1.23 mg/dl and it was 3.84±1.90 mg/dl after. The mean difference between prefasting and postfasting was 1.53±1.17 mg/dl (p=0.001). According to these results, short periods of fasting seem to increase the unconjugated bilirubin concentration in patients on atazanavir. A high-calorie diet did not have any impact in bilirubin probably because most patients follow similar diets in their everyday life.