undecylenic acid /un′desilen″ik/ , a topical antifungal agent. ▪ INDICATIONS: It is prescribed in the treatment of athlete’s foot and ringworm. ▪ CONTRAINDICATIONS: Known hypersensitivity to this drug prohibits its use. It is not used in the eyes or on mucous membranes. Caution is advised when the patient is diabetic. ▪ ADVERSE EFFECTS: Among the more serious adverse effects are skin irritation and hypersensitivity reactions.