Sympathotropic Drugs and the Distribution of 99m Tc-Hydroxymethylene Diphosphonate

Abstract

Objective: the uptake of bone-seeking radiopharmaceuticals depends on the blood flow, which is influenced by the sympathetic nervous system. Our aim was to study the effect of sympathomimetic drugs on the distribution of bone-seeking agents.

Material and Methods: Various sympathomimetic and β-blocking drugs were injected in mice at different times in relation to the administration of ^99mTc-HDP Three hours after this, venous blood and various organs were removed and their activities were related to the administered activity. A kinetic study of the whole-body activity retention after administration of terbutaline was also made.

Results: the biodistribution of ^99mTc-HDP was similar after the administration of sympathomimetics and of β-antagonists. All drugs gave rise to an increased soft tissue activity and a decreased bone activity, corresponding to a lowered quality of the potential bone scan. Terbutaline gave rise to an increased excretion of ^99mTc-HDP. the mechanisms behind the findings cannot be entirely explained.

Conclusion: Drug interference with the sympathetic nervous system causes undesirable effects on the biodistribution of ^99mTc-HDP in the mouse. Studies in humans are necessary to evaluate whether clinical treatment with sympathotropic drugs affects the bone scintigram.