An important component of reproductive pharmacology is the effect that treatment with a medication administered to pregnant dams or to lactating, nursing dams has on the fetus or neonate. Many factors influence the ability of a drug to cross the placenta, including placental architecture of the particular species. In general, drugs that are lipid-soluble, nonionized, and of low molecular weight cross the placenta readily.
The potential effects of pharmacotherapeutics on pregnancy and neonatal development are being increasingly studied in domestic animals; frequently, however, inferences must be made from studies in other animal species or in humans. Many drugs are known to be teratogenic during pregnancy; these should be avoided (see the table ).
Safety of Selected Drugs During Pregnancy in Domestic Animals
Drug | Class | Teratogenic or Adverse Effect | Comments |
|---|---|---|---|
Antimicrobials | |||
Amikacin | Aminoglycoside | Possible ototoxicosis or nephrotoxicosis, especially at high doses. | |
Chloramphenicol | Phenicol | Ocular malformations (congenital cataracts); can decrease protein synthesis (bone marrow). Fetal hemolysis described in human pregnancies. | Prohibited in food animals in the US. |
Ciprofloxacin | Fluoroquinolone | Possible articular cartilage defects. | Of greatest consequence when neonate is weight-bearing soon after birth. Extralabel use prohibited in food animals in the US. |
Doxycycline | Tetracycline | Bone and teeth malformations and teeth discoloration. | Potential teratogen, particularly in last half of pregnancy. |
Enrofloxacin | Fluoroquinolone | Possible articular cartilage defects. | Of greatest consequence when neonate is weight-bearing soon after birth. Extralabel use prohibited in food animals in US. |
Metronidazole | Nitroimidazole | Possible fetal resorption and pregnancy loss, fetal hepatotoxicosis, congenital defects (including exencephaly), visceral hernias, and tail defects documented in laboratory animals. | Prohibited in food animals in the US. |
Streptomycin | Aminoglycoside | Ototoxicosis and possible nephrotoxicosis, especially at high doses. | |
Tetracycline | Tetracycline | Bone and teeth malformations and teeth discoloration. | |
Antifungals | |||
Griseofulvin | Miscellaneous antifungal | Multiple congenital abnormalities reported with skeletal and brain malformations, palatoschisis, jaw malformations, cyclopia, anophthalmia, atresia ani, atresia coli, absence of atrioventricular valves, absence of external nares. | Signs have been best documented in cats. |
Ketoconazole | Azole | Multiple skeletal malformations, limb defects, fetal resorption, fetal mummification, and stillbirths. | |
Endocrine Drugs | |||
Altrenogest | Progestin | Possible masculinization of female fetuses. | |
Betamethasone | Glucocorticoid | Associated with palatoschisis and other congenital malformations. Can induce premature labor or abortion. In humans, corticosteroids have been shown to potentially cause intrauterine growth restriction and decreased birth weight. | |
Cortisone | Glucocorticoid | Associated with palatoschisis and other congenital malformations. Can induce premature labor or abortion. In humans, corticosteroids have been shown to potentially cause intrauterine growth restriction and decreased birth weight. | |
Dexamethasone | Glucocorticoid | Associated with palatoschisis and other congenital malformations. Can induce premature labor or abortion. In humans, corticosteroids have been shown to potentially cause intrauterine growth restriction and decreased birth weight. | |
Diethylstilbestrol (DES) | Estrogen | Malformation of genitourinary system. Possible pregnancy loss (abortion) reported in dogs. | Prohibited in food animals in the US |
Estradiol cypionate (ECP) | Estrogen | Malformation of genitourinary system. Possible pregnancy loss (abortion) reported in dogs. | |
Prednisolone | Glucocorticoid | Associated with palatoschisis and other congenital malformations. Can induce premature labor or abortion. | |
Prednisone | Glucocorticoid | Associated with palatoschisis and other congenital malformations. Can induce premature labor or abortion. | |
Testosterone | Androgen | Possible masculinization of female fetuses. | |
Pregnant humans should handle with care many drugs intended for animals, especially those that are known to cause pregnancy loss, that induce premature delivery, or that are teratogenic. Whenever possible, handling of these drugs should avoided. The recommendation is to consult the National Institute for Occupational Safety and Health (NIOSH) List of Hazardous Drugs in Healthcare Settings and to follow the FDA's labeling instructions for medications with known risks for pregnancy, lactation, and females and males of reproductive potential.
Any administration of medication to lactating animals requires consideration of excretion of the drug or its metabolites in milk and of the effects on suckling neonates. Research on how the exposure of mothers to various medications affects nursing neonates has been limited, and inferences are frequently made from possible effects known in humans.
Pearls & Pitfalls
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The National Institute of Child Health and Human Development's Drugs and Lactation Database (LactMed) provides information about known effects in humans and animals from exposure during nursing or milk consumption. 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.
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Also see pet owner content regarding drugs used to treat urinary tract and reproductive tract disorders.
