Effects of acepromazine on three-phase 99mTc-MDP bone imaging in 11 horses.

This research investigates the effect of a drug called acepromazine on bone imaging in horses. The objective of the study was to observe changes in the count density during a bone scan after injecting acepromazine, which is known to cause increased blood flow. The study found significant differences, notably, the onset of vascular phase occurred earlier with acepromazine but it didn’t affect the density of bone-phase scintigrams.

Study Overview

• The study involved skeletal scintigraphy on 11 adult horses in two separate sessions. Scintigraphy is a diagnostic test where a two-dimensional picture is taken after a radioactive tracer is injected into the body. The goal of this experiment was to observe the effects of acepromazine on the count density of the bone scans. Acepromazine was administered intravenously during one of the sessions.
• The study aimed at investigating acepromazine’s effects mainly because horses undergoing this procedure often show decreased uptake of radiopharmaceutical substances in their limbs, which reduces the effectiveness of scintigraphy as a diagnostic tool.

Findings

• The study found that the use of acepromazine resulted in a statistically significant average difference of 12 seconds for initial blood flow and 21 seconds for peak flow. Essentially, both the initial and peak blood flow transpired earlier when acepromazine was administered.
• The bone to soft tissue ratios during the soft tissue and bone phases of the scan did not see significant changes between procedures. Conversely, the drug was found to influence the count density during the vascular phase of the scintigram due to the increased peripheral blood flow it caused.
• However, despite the increased peripheral blood flow, acepromazine did not influence the count density of the bone phase scintigrams, as per the findings of this research.

Implications

• The findings of this research suggest that acepromazine’s vasodilating effect ( causing an increase in blood flow) readily influences the count density during the vascular phase of the bone scan. This is particularly important and useful when an earlier onset of the vascular phase during the three-phase bone scan is desired.
• Nevertheless, the research indicates that the application of acepromazine doesn’t affect the count density during the bone phase of the scan. This means that while the drug could alter the timing of the scan phases, it won’t necessarily improve the diagnostic value of scintigraphy in relation to bone-density readings.