Nuclear Cardiology Boards Practice Test

Which medication inhibits binding of Tc-99m pertechnetate to hemoglobin inside red blood cells?

Methyldopa Hydralazine Prazosin Digoxin

Correct Answer:

Methyldopa

Explanation:

Labeling red blood cells with Tc-99m pertechnetate depends on reduced technetium binding to hemoglobin inside intact red cells. Certain medications can alter the red cell environment and hinder this binding. Methyldopa is known to inhibit Tc-99m pertechnetate from binding to hemoglobin inside red blood cells, reducing labeling efficiency. The mechanism likely involves changes in the red cell milieu or oxidation state of hemoglobin that impede the binding of reduced technetium. The other drugs listed do not typically affect this labeling process, so they don’t interfere with pertechnetate binding to Hb.

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