check carefully (one)clozapine increases results of letibotulinumtoxinA by pharmacodynamic synergism. Use Caution/check. prescription drugs with anticholinergic effects may potentiate botulinum toxin effects, which may result in abnormal neuromuscular weakness and heighten systemic anticholinergic outcomes. incobotulinumtoxinA, letibotulinumtoxinA