title: Crotoxin in humans: analysis of the effects on extraocular and facial muscles.
abstract: OBJECTIVE
  Crotoxin is the main neurotoxin of South American rattlesnake Crotalus durissus terrificus. The neurotoxic action is characterized by a presynaptic blockade. The purpose of this research is to assess the ability of crotoxin to induce temporary paralysis of extraocular and facial muscles in humans.
  
  
  METHODS
  Doses of crotoxin used ranged from 2 to 5 units (U), each unit corresponding to one LD50. We first applied 2U of crotoxin in one of the extraocular muscles of 3 amaurotic individuals to be submitted to ocular evisceration. In the second stage, we applied crotoxin in 12 extraocular muscles of 9 patients with strabismic amblyopia. In the last stage, crotoxin was used in the treatment of blepharospasm in another 3 patients.
  
  
  RESULTS
  No patient showed any systemic side effect or change in vision or any eye structure problem after the procedure. The only local side effects observed were slight conjunctival hyperemia, which recovered spontaneously. In 2 patients there was no change in ocular deviation after 2U crotoxin application. Limitation of the muscle action was observed in 8 of the 12 applications. The change in ocular deviation after application of 2U of crotoxin (9 injections) was in average 15.7 prism diopters (PD). When the dose was 4U (2 applications) the change was in average 37.5 PD and a single application of 5U produced a change of 16 PD in ocular deviation. This effect lasted from 1 to 3 months. Two of the 3 patients with blepharospasm had the hemifacial spasm improved with crotoxin, which returned after 2 months.
  
  
  CONCLUSIONS
  This study provides data suggesting that crotoxin may be a useful new therapeutic option for the treatment of strabismus and blepharospasm. We expect that with further studies crotoxin could be an option for many other medical areas.
authors.affiliation: Universidade Federal de Minas Gerais - UFMG, Belo Horizonte, MG, Brazil. gbarrosribeiro@gmail.com
authors.forename: Geraldo de Barros
authors.initials: Gde B
authors.lastname: Ribeiro
authors.forename: Henderson Celestino de
authors.initials: HC
authors.lastname: Almeida
authors.forename: David Toledo
authors.initials: DT
authors.lastname: Velarde
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001764:Blepharospasm / Q000188:drug therapy; D003439:Crotoxin / Q000008:administration & dosage* / Q000009:adverse effects; D005152:Facial Muscles / Q000187:drug effects*; D005260:Female; D006801:Humans; D056965:Injections, Intraocular; D008297:Male; D051379:Mice; D008875:Middle Aged; D009466:Neuromuscular Blocking Agents / Q000008:administration & dosage* / Q000009:adverse effects; D009801:Oculomotor Muscles / Q000187:drug effects*; D009886:Ophthalmoplegia / Q000188:drug therapy*; D013285:Strabismus / Q000188:drug therapy; D055815:Young Adult
chemical_list: D009466:Neuromuscular Blocking Agents; D003439:Crotoxin