Drug Interaction Report

ADJUST DOSING INTERVAL: Non-radioactive somatostatin analogs may interfere with the uptake of Ga-68 dotatate into neuroendocrine tumors by competitively binding to somatostatin receptors in tumor tissues. This may affect diagnostic imaging results.

MANAGEMENT: The manufacturer recommends imaging patients with gallium Ga-68 dotatate positron emission tomography (PET) just prior to dosing with long-acting somatostatin analogs. Short-acting formulations of somatostatin analogs can be used up to 24 hours before imaging with gallium Ga-68 dotatate.

MONITOR: Due to their gastrointestinal pharmacologic effects, somatostatin analogs (e.g., octreotide, lanreotide) may variously affect the absorption of dietary nutrients and concomitantly administered oral medications. Somatostatin analogs have been shown to prolong gastrointestinal transit time and inhibit intestinal absorption of some nutrients such as fat. Clinical data are limited, however. In case reports, octreotide has been reported to reduce the relative bioavailability of cyclosporine. Transplant rejection and significant reductions in cyclosporine levels, sometimes to undetectable levels, have been reported in association with the interaction. Vitamin K absorption was not affected when concomitantly administered with lanreotide according to the manufacturer.

MANAGEMENT: Clinicians should be aware of the potential for altered absorption of concomitantly administered oral medications during treatment with somatostatin analogs. Blood levels and clinical response should be monitored, particularly for drugs that have a narrow therapeutic index, and the dosages adjusted as necessary.