Dramatic changes in muscle contractile and structural properties after 2 botulinum toxin injections

• Published in: Muscle & nerve Vol. 52; no. 4; pp. 649 - 657
• Main Authors: Minamoto, Viviane B., Suzuki, Kentaro P., Bremner, Shannon N., Lieber, Richard L., Ward, Samuel R.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.10.2015
• Subjects: Animals; Botox; Botulinum Toxins, Type A - pharmacology; Collagen - metabolism; denervation; Drug Administration Schedule; fiber type; Functional Laterality; Gene Expression Regulation - drug effects; Injections, Intramuscular; Lipid Metabolism - drug effects; Male; Muscle Contraction - drug effects; muscle physiology; Muscle, Skeletal - drug effects; Myosin Heavy Chains - metabolism; Neuromuscular Agents - pharmacology; neurotoxin; Protein Isoforms - metabolism; Rats; Time Factors; muscle physiology; neurotoxin; fiber type; denervation; Botox
• ISSN: 0148-639X; 1097-4598; 1097-4598
• DOI: 10.1002/mus.24576

ABSTRACT Introduction: Botulinum toxin is frequently administered serially to maintain therapeutic muscle paralysis, but the effect of repeated doses on muscle function are largely unknown. This study characterized the muscle response to 2 onabotulinum toxin (BoNT) injections separated by 3 months. Methods: Animal subjects received a single toxin injection (n = 8), 2 BoNT injections separated by 3 months (n = 14), or 1 BoNT and 1 saline injection separated by 3 months (n = 8). Results: The functional effect of 2 serial injections was exponentially greater than the effect of a single injection. While both groups treated with a single BoNT injection had decreased torque in the injected leg by approximately 50% relative to contralateral legs, the double BoNT injected group had decreased torque by over 95% relative to the preinjection level. Both single and double BoNT injections produced clear signs of fiber‐type grouping. Conclusions: These experiments demonstrate a disproportionately greater effect of repeated BoNT injections. Muscle Nerve 52: 649–657, 2015