Botulinum toxin injection into the trapezius muscle of cynomolgus monkeys: Comparison of serotype A with B

Abstract

Objective : To compare the magnitude and duration of muscle paralysis induced by botulinum toxin (BoNT) type A and type B in cynomolgus monkeys. Methods : Twenty-two monkeys were injected with one of five doses of BoNT-A, BoNT-B or a placebo in each of their trapezius muscles. Compound muscle action potentials (CMAP) were measured at baseline and 2, 4, 8, 12 and 16 weeks post-injection in all animals and at 20 and 24 weeks post-injection in the two highest dose groups. Toxins were injected and data scored with the investigators “blinded” to the dose and serotype used in each muscle. Results : At 2 weeks, the degree of paralysis for each dose pair was approximately equivalent, with a range across doses of 60–95%. A clear dose–recovery relationship was observed, with longer paralysis associated with higher BoNT doses. At the lowest doses tested (i.e., 0.5 U of BoNT-A and 16 U of BoNT-B), recovery, defined as a decrement of less than 20%, was evident by 12–16 weeks in all monkeys; at the highest doses (i.e., 10 U of BoNT-A and 500 U of BoNT-B), the same degree of recovery was documented only after 24 weeks. Conclusions : The duration of induced paralysis is related to the BoNT dose and the initial degree of paralysis for both serotypes. When BoNT doses that produce approximately equivalent initial paralytic effects are compared, the duration of action is similar across serotypes.