CAPS and trigeminal neuralgia: A well-known antiepileptic phenytoin (hydantoin derivative; 5,5-diphenylhydantoin; Figure 4(a); which is known to inhibit voltage-gated Na+ channels [24] and to relieve paroxysm in trigeminal neuralgia [18]) at 0.1 mM (a maximally soluble concentration) inhibited frog CAPs in a partially reversible manner (Figure 4(b)(A)).