Injection of Botulinum Immune Globulin to Reduce Side Effects from Botulinum Toxin
Botulinum toxin (Botox) injections are an accepted and effective treatment for blepharospasm of the eyelid and for strabismus. However, ptosis and diplopia are common side effects, occurring in 15 to 25% of patients injected. This limits dosage and is bother some and sometimes incapacitating to patients, causing some to seek alternative methods of treatment. Our aim in this study was to investigate the effect of botulinum human antitoxin (immune globulin) on the nerve terminals of the eyelid following Botox injection for blepharospasm, to eliminate or reduce ptosis. We developed human-based antitoxin for use in this study, as a safer and more dependable product than the equine product used in previous studies. All patients enrolled in this study had received previous Botox injections for blepharospasm and had experienced side effects. The patients all signed informed-consent forms with the understanding that if there was a reduction of beneficial effect of the Botox in reducing symptoms of blepharospasm, the injected eyelid muscle would be reinjected with Botox the following week.
Antitoxin Dose Studies
The first study assessed the dose of immune globulin to use. The eyelid muscles of both eyes were injected with Botox as usual. Immune globulin was then injected into the orbicularis muscles of one eye. Results were assessed by measuring or estimating the pre- and post-injec tion orbicularis force in both eyes. We found that doses between 3.2 x 10-3 and 3.2 x 10-2 Interna tional Units of antitoxin per unit of toxin were effective in blocking the toxin effect .
In a second study we assessed the timing of injection. The maximum effect of the immune globulin in blocking unwanted side effects was found in injections performed within 2.5 hours of Botox injection. Injections performed more than 24 hours after Botox injection had no effect.
Blocking the Side Effects
In a third study we tested the effectiveness of immune globulin in blocking side effects of Botox injections in these doses. Twenty blepharospasm patients received injections of immune globulin into the levator muscle of the eye which had previously had ptosis immediately after Botox injection as usual. Patients were re-examined or interviewed by telephone one week after injection to compare the two eyes and to determine if the immune globulin prevented the development of ptosis. Three patients (15%) developed ptosis in the immune globulin injected eye. Thirty-five percent developed ptosis in the fellow eye, about the same incidence as before for this eye. In nine repeat injections, ptosis developed in the immune globulin injected eye in one case (11%) and in the fellow eye in 3 (33%).
No hemorrhage, loss of vision or systemic effect of the antitoxin was noted.
Based on these results, we are offering immune globulin as an experimental adjunct to Botox injection for patients who have a history of side effects.
Supported by the National Eye Institute.