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Sympathotropic drugs and the distribution of 99mTc-hydroxymethylene diphosphonate. Experimental studies in the mouse
M Cronhjort1, C Jonsson, H Jacobsson
1Department of Diagnostic Radiology, Karolinska Hospital, Stockholm, Sweden.
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 beta-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 beta-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.