Drug Interactions between delavirdine and Lescol XL

ADJUST DOSE: Coadministration with delavirdine may increase the plasma concentrations of fluvastatin. The proposed mechanism is delavirdine inhibition of CYP450 2C9 and 3A4, the isoenzymes responsible for the metabolic clearance of fluvastatin. Although the interaction has not been specifically studied, high levels of HMG-CoA reductase inhibitory activity in plasma is known to be associated with an increased risk of musculoskeletal toxicity. Myopathy manifested as muscle pain and/or weakness associated with grossly elevated creatine kinase exceeding ten times the upper limit of normal has been reported occasionally. Rhabdomyolysis has also occurred rarely, which may be accompanied by acute renal failure secondary to myoglobinuria and may result in death.

MANAGEMENT: Caution is advised if fluvastatin is prescribed in combination with delavirdine. The lowest possible dosage of fluvastatin should be used. All patients treated with HMG-CoA reductase inhibitors should be advised to promptly report any unexplained muscle pain, tenderness, or weakness, particularly if accompanied by malaise or fever. Therapy should be discontinued if creatine kinase is markedly elevated in the absence of strenuous exercise or if myopathy is otherwise suspected or diagnosed. Pravastatin is not expected to interact with delavirdine and may be a suitable alternative in patients receiving delavirdine.