Is medication safe during your dog’s pregnancy?

by Dr. Mikel Delgado, PhD

In the early stages of puppy development in utero (shortly after fertilization and through the embryonic stage), exposure to certain chemicals can be dangerous. Teratogens are substances that can interfere with fetal development, increasing the risks of birth defects or neonatal fatalities if the dam is exposed to them, especially in the first few weeks of pregnancy. 

Pregnancy causes physical changes in dogs such as increased renal function, increased blood flow to the skin, and decreased movement of the digestive system, which in turn can affect physical responses to medications and how well they are absorbed. Some drugs are also able to cross the placental barrier and directly affect the fetus.

For that reason, only medications and supplements that are proven to be safe for pregnant bitches should be used during a dogs' pregnancy. There may be times where life-saving or pain-controlling medication is necessary, and many medications are considered safe during pregnancy.  

If you have questions about whether a medication is safe for your pregnant dog, ask your veterinarian. They can let you know if the product has been tested on pregnant dogs and what the safety profile of the medication is. Your veterinarian can also explain the risks of a specific medication, and whether your dog’s health warrants taking a medication despite any risks.

Medications to generally avoid during pregnancy

Some medications are considered riskier than others, and should generally be avoided during pregnancy. These include:

• Steroids 
• Non-steroidal anti-inflammatory drugs (NSAIDs)
• Certain antibiotics such as metronidazole, tetracycline and doxycycline
• Hormones including testosterones, progestins, prostaglandins, progesterones, and estrogens
• Antifungals including ketoconazole, itraconazole, and fluconazole 
• Imidacloprid (Advantage®)
• Any nutritional supplements or herbal medications that have not been evaluated by the FDA

Medications considered generally safe during pregnancy 

• Some antibiotics, including penicillin G, ampicillin, amoxicillin, and erythromycin
• Insulin
• Thyroxine
• Localized anesthesia
• Some opioid pain relievers such as methadone, morphine and hydromorphone
• Most dewormers and flea and tick preventatives

Always check with your veterinarian before administering medications to your pregnant bitch.

What about parasite control?

Always check with your veterinarian before administering medications to your dogs. 

Most forms of parasite control, including Revolution and Frontline, are considered safe for use in pregnant dogs. Imidacloprid (Advantage®) is one example of an antiparasitic that is not typically recommended for use during pregnancy.

Many dewormers, including Fenbendazole (Panacur), are safe for use in pregnant dogs. Most heartworm products are also generally considered safe for pregnant dogs and should be continued throughout pregnancy. The risks of not deworming your pregnant bitch are high; parasites can be transferred to the puppies in the womb and after birth via nursing. Many parasites such as roundworm and hookworm can be deadly to puppies.

If you have concerns about using antiparasitics with your pregnant dog, talk to your veterinarian. You may be able to adjust the timing of treatment, avoiding the first three weeks of pregnancy when the fetus is most sensitive to the effects of medications. 

What about vaccinations?

The best time to vaccinate your breeding bitch is at least two weeks prior to breeding. During gestation, vaccines can be dangerous to a developing fetus. The exception to this guidance is the canine herpesvirus (CHV) vaccine, which is currently only available in Europe. Preliminary research demonstrated that the CHV vaccine decreased mortality rate among exposed puppies.

What about anesthesia and pain control?

Anesthesia and pain control are based on need. Surgical procedures require both. For example, a dog who has received a surgical artificial insemination should be given post-operative pain control. This is completely safe as there is no embryo yet.  

During pregnancy, there are two situations that might require anesthesia and/or pain control: a non-pregnancy related emergency situation, and a pregnancy-related situation (such as a cesarean section, planned or unplanned). In the case of a non-pregnancy related emergency, inform your veterinarian about your dog’s pregnancy status and expected due date. Both anesthesia and pain control can be safe for your dog and puppies, and your veterinarian can help determine how to ensure your dog’s safety and comfort while minimizing risks to puppies.

References and resources

DVM 360: Anesthesia for pregnancy or cesarean section and for neonates

VCA: Imidacloprid - Topical

VIN: Pregnant Dog Care

WSAVA Global Pain Council Pain Management Protocol: Pregnant or Lactating Patients

Greer, M. L. (2014). Canine reproduction and neonatology. CRC Press.

Kushnir, Y., & Epstein, A. (2012). Anesthesia for the pregnant cat and dog. Isr. J. Vet. Med, 67(1), 19-23.

Poulet, H., Guigal, P. M., Soulier, M., Leroy, V., Fayet, G., Minke, J., & Chappuis Merial, G. (2001). Protection of puppies against canine herpesvirus by vaccination of the dams. Veterinary Record, 148(22), 691-695.

Rebuelto, M., & Loza, M. E. (2010). Antibiotic treatment of dogs and cats during pregnancy. Veterinary Medicine International, 2010.