This imbalance can affect a joint in varied ways such as at the ankle with foot position (always points toes or up on toes when walking) or at the wrist with hand position (hand in flexion with problems grasping). After a contracture occurs (not able to bring the joint through its full range of motion, even with forceful / prolonged stretching) it can be hard to re-establish full range of motion at that joint without surgery.
Postmarketing safety data from BOTOX and other approved botulinum toxins suggest that botulinum toxin effects may, in some cases, be observed beyond the site of local injection. The symptoms are consistent with the mechanism of action of botulinum toxin and may include asthenia, generalized muscle weakness, diplopia, ptosis, dysphagia, dysphonia, dysarthria, urinary incontinence, and breathing difficulties. These symptoms have been reported hours to weeks after injection. Swallowing and breathing difficulti es can be life threatening and there have been reports of death related to spread of toxin effects. The risk of symptoms is probably greatest in children treated for spasticity but symptoms can also occur in adults treated for spasticity and other conditions, and partic ularly in those patients who have an underlying condition that would predispose them to these symptoms. In unapproved uses, including spasticity in children, and in approved indications, symptoms consistent with spread of toxin effect have been reported at do ses comparable to or lower than doses used to treat cervical dystonia and spasticity. Patients or caregivers should be advised to seek immediate medical care if swallowing, speech or respiratory disorders occur.
On July 29, 2016, Food and Drug Administration (FDA), of the United States of America approved abobotulinumtoxinA for injection for the treatment of lower limb spasticity in pediatric patients two years of age and older.[20] AbobotulinumtoxinA is the first and only FDA-approved botulinum toxin for the treatment of pediatric lower limb spasticity. In the United States of America, the FDA approves the text of the labels of prescription medicines. The FDA approves which medical conditions the drug manufacturer may sell the drug for. However, those approved by the FDA to prescribe these drugs may freely prescribe them for any condition they wish, called off-label use. Botulinum toxins have been used off-label for several pediatric conditions, including infantile esotropia.[21]
Spread of toxin effects. The effect of botulinum toxin may affect areas away from the injection site and cause serious symptoms including: loss of strength and all-over muscle weakness, double vision, blurred vision and drooping eyelids, hoarseness or change or loss of voice, trouble saying words clearly, loss of bladder control, trouble breathing, and trouble swallowing.
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