Purpose: To determine the distribution of the toxin among individual muscles after
intramuscular injection of
botulinum toxin
gel. Methods: One eye of 7 New Zealand white rabbits was randomized into group A, and the contralateral eye was into group B. Eyes in group A received medial rectus intramuscular injection of 2.5 IU of 125I-BTX-A gel in 0.1ml, and those in group B received equivalent amount of 125I-BTX-A solution by medial rectus intramuscular injection. Four rectus muscles and the levator palpebrae superioris were harvested and the
radioactivity of muscles was measured 16 hours after the injection. Results: In group A, the radioactivity of per gram medial rectus was significantly higher than that of other muscles (P < 0.01), and there was no statistically significant difference in the radioactivity of per gram muscles among other muscles (P> 0.05). In group B, the radioactivity of per gram medial rectus and levator palpebrae superioris was significantly higher than that of other muscles respectively (P < 0.05), and the difference in the radioactivity of per gram muscles between medial rectus and levator palpebrae superioris was not statistically significant (P > 0.05). The radioactivity of per gram medial rectus in group A was higher than that in group B (t=3.731 ,P=0.01), and there was no significant difference in the radioactivity of per gram muscles among other homonymous muscles (P> 0.05). Conclusion: The toxin dispersed principally in the injected muscle and the local concentration of the toxin was much high following intramuscular injection of
botulinum toxin gel. Eye Science 2005;21:52-55.