Table 2: Chemotherapy drugs affecting gonadal function used in boys and adolescents.

Relation to cell cycle	Mechanism of action	Drug class	Drug	Risk of prolonged infertility in adulthood
Non-cell-cycle specific	Direct damage of nucleic acids (DNA and RNA) Induction of apoptosis	Alkylating agents	Cyclophosphamide Ifosfamide Busulfan Melphalan Chlorambucil Procarbazine BCNU CCNU	High
	Induction of DNA strand breaks	Antitumour antibiotics	Bleomycin Actinomycin	Low
Cell-cycle specific	Inhibition of nucleic acid synthesis (DNA and RNA) Inhibition of cell proliferation (mitosis and meiosis) Deamination of proteins	Antimetabolites	Methotrexate Mercaptopurine	Low
		Vinca alkaloids	Vincristine Vinblastine	Low
		Podophyllotoxins	Asparaginase	Low

BCNU = bischloroethyl nitrosourea; CCNU = chloroethyl cyclohexyl nitrosourea.