An important component of reproductive pharmacology encompasses the effect of treatment on the fetus or neonate of medication administered to pregnant or lactating animals that are nursing. Many factors influence the ability of a drug to cross the placenta, including placental architecture of the particular species, but in general, drugs that are lipid-soluble, nonionized, and of low molecular weight can be expected to cross the placenta readily. Among antimicrobials, aminoglycosides are associated with nephrotoxicity and ototoxicity in the fetus, fluoroquinolones may affect developing cartilage, and tetracyclines affect bone and tooth development. Teratogenicity has been associated with the use of the antifungal agents griseofulvin and ketoconazole in pregnant animals. All cancer chemotherapeutic agents are potentially harmful to developing fetuses. Glucocorticoids may induce palatoschisis or other defects in puppies.

Any administration of medication to lactating animals requires consideration of the excretion of the drug or its metabolites in milk and of the effects on suckling neonates. Milk produced for human consumption must be free of potentially harmful residues, and all relevant laws and regulations regarding usage and appropriate withdrawal times should be followed.

Last full review/revision March 2012 by Robert O. Gilbert, BVSc, MMedVet, DACT, MRCVS