What medications do veterinarians use in broodmares and why? And are they completely safe?Broodmares get ill or injured just like any other horse. But when treating the mare, thought must also be given to what is safe for her developing fetus or nursing foal. | Shelley PaulsonDespite careful management, broodmares still face injury and illness during pregnancy. When medical issues arise, treatment decisions carry added weight because of the fetus, raising questions about which medications are known to be safe in pregnant mares.C. Scott Bailey, DVM, MS, Dipl. ACT, associate professor at Cornell Universitys College of Veterinary Medicine, in Ithaca, New York, says few medications have been specifically studied in broodmares.The exceptions are a few common antibiotics and firocoxib in their ability to penetrate to the foal, says Bailey. Studies show that common antibiotics and firocoxib do reach the foal. But early research didnt detect flunixin meglumine (Banamine) in fetal fluids, and crystalline ceftiofur (Excede, an antibiotic) did not appear to reach the foal. In reality, though, we have to assume every drug we give is going to reach the foal unless demonstrated otherwise. The placenta is designed for the efficient transfer of all manner of things. This doesnt, however, mean drugs administered to mares are going to cause a toxic effect to the foal.Despite the lack of safety data on many medications in broodmares, this population still needs treatment when necessary. In this article well describe common medical conditions affecting broodmares, along with some of the most widely used medications. This discussion builds on a previous article in The Horse, What Medications Are Safe for Broodmares?Common Conditions Affecting BroodmaresRebecca Mouncey, BVetMed, PhD, PGCert, FHEA, MRCVS, of the Royal Veterinary College, in Hatfield, England, and colleagues recently reviewed data from 275 pregnancies on seven stud farms over two breeding seasons (Mouncey et al., 2022). They recorded the occurrence of veterinary-attended episodes of illness and medications prescribed during those episodes.Overall, 34% of the 203 pregnancies with available data needed veterinary intervention at least once during the study period.In one study of equine pregnancies, musculoskeletal injury occurred in 22.7% of cases. | Adobe StockTop conditions recorded for those 203 pregnancies were:Musculoskeletal injuries in 22.7% of the pregnancies, occurring around 140 to 215 days of gestation (specific examples included trauma, 9.8%; cellulitis, 7.4%; and foot pain/abscess/laminitis, 6.4%)Placentitis (inflammation of the mares placenta, 4.9%)Colic (abdominal pain, 4.4%)Conjunctivitis/corneal ulcer (inflammation or ulceration of structures within the eye, 2.5%)Bailey confirms these are common conditions seen in broodmares, based on his six years spent working at Claiborne Farm, in Paris, Kentucky.Laminitis is high on the list of conditions broodmares require treatment for because some mares are already subclinically laminitic prior to pregnancy, says Bailey. In other words, they dont have obvious clinical signs of the condition, which occurs when the tissues that suspend the coffin bone within the hoof become damaged and inflamed. We then have added weight during pregnancy, and they can become clinically laminitic. Broodmares also become insulin resistant in late pregnancy, which probably worsens the situation.Common Medications Used in Pregnant BroodmaresIn the study by Mouncey et al., veterinarians prescribed medications in almost half (47%) of the 203 pregnancies in mares diagnosed with conditions listed above. The most prescribed medications included antibiotics in one-quarter of the pregnancies. Trimethoprim/sulfonamides were most frequently prescribed (13% of pregnancies), followed by tetracyclines (7%), penicillins (6%), and aminoglycosides (5%). Vets rarely prescribed cephalosporins and fluoroquinolones.Bailey says, I do not use either fluoroquinolones (e.g., enrofloxacin) or tetracyclines in pregnant broodmares. Tetracyclines have been associated with changes in tooth enamel in all species, while fluoroquinolone use has raised concerns about joint pathology (disease or damage) in foals. This antibiotic should be avoided unless the practitioner doesnt have another choice, he adds.Common non-steroidal anti-inflammatory drugs (NSAIDs) were the second-most-administered medication, with veterinarians most frequently reaching for phenylbutazone (Bute). Overall, they prescribed NSAIDs in 23.1% of the pregnancies, and phenylbutazone was the most commonly used, given in 15% of the pregnancies. Veterinarians also prescribed Banamine and aspirin.Mouncey et al. also reported practitioners using other medications, including altrenogest to treat placentitis or mastitis. Only rarely did they use local anesthetics, omeprazole, prednisolone, and triamcinolone.These data show that the occurrence of disease and medication usage during gestation are high, report the researchers. And yet despite how commonly veterinarians prescribe medications for pregnant broodmaresagain, almost half of all pregnancies included in this retrospective studythe profession lacks safety data on these medications in this population.Many older broodmares deal with osteoarthritis pain. | Adobe StockFocus on LamenessIn addition to the musculoskeletal trauma mentioned above, broodmares often have evidence of osteoarthritis (OA). This degenerative disease is common in all types of horses, including pregnant broodmares that have retired from their athletic careers or those still in competition and taking a season off to breed. We know OA is a painful condition that negatively affects quality of life. Therefore, keeping affected horses comfortable remains paramount, regardless of their job.For broodmares there is pasture sound and there is athletically sound, says Bailey. I think its okay for pregnant broodmares to be pasture sound. Its acceptable to have some level of lameness, but if it gets to the point that the mare is not engaging in normal activities that horses enjoy then treatment is most certainly indicated.Practitioners often use intra-articular corticosteroids, which are administered directly into the arthritic joint in athletic horses to reduce the inflammation and improve comfort. However, Bailey says corticosteroids are, in his opinion, contraindicated in broodmares.I do not give steroids to pregnant mares, he says. There are scientific and clinical data showing steroids administered at time of breeding affect follicular dynamics. He adds that giving corticosteroids in late pregnancy could also contribute to laminitis.In lieu of traditional intra-articular corticosteroids, practitioners could reach for other therapies such as orthobiologics. These treatments use the bodys own healing properties to manage musculoskeletal disorders. Examples include stem cell therapy, platelet-rich plasma (PRP), and interleukin-1 receptor antagonist protein (IRAP).Im not concerned about using orthobiologics for joint disease in pregnant broodmares. There arent any contraindicated to my knowledge, Bailey says. But I would recommend only using autologous products obtained from the patient themselves rather than autogenous that are obtained from a donor horse. Autogenous products may have a potential immunologic problem that could affect pregnancy.Veterinarians might also consider the newer polyacrylamide hydrogels (available in a 2.5% and 4% concentration). These are technically medical devices rather than medications and are designed to remain in or be incorporated into the joint following injection. Good clinical evidence supports their use, and they are gaining popularity among equine practitioners (Pluim and Frippiat, 2025).Bailey says some retired broodmares with OA stay on NSAIDs continuously.If the mare is so lame that she isnt exercising or eating or (shes) being ostracized by the herd, treating her pain is going to decrease her cortisol and stress levels and is better than allowing her to suffer without NSAIDs, he notes.Managing Laminitis During a Mares PregnancyStephen OGrady, DVM, MRCVS, of Virginia Therapeutic Farriery, in Keswick, proposes that a key to managing laminitis in pregnant broodmares is getting the pain under control.My choice is firocoxib until you get their feet under control with farriery, which is really the cornerstone of managing laminitis, OGrady says.With significant pain, OGrady says his go-to has always been Banamine combined with acetaminophen (which is a pain reliever, not an NSAID).Other medications OGrady uses in heavy mares foundering early in pregnancy are the sodium-glucose co-transporter-2 inhibitors (SGLT2is). These help lower blood glucose levels and rapidly decrease body weight in horses with equine metabolic syndrome.Most knowledge on the safety of any medications for pregnant broodmares has been extrapolated from other species or accumulated through clinical experience: Administration of NSAIDs has been linked to various fetal disturbances and developmental disorders in people, mice, rats, and rabbits, and thus NSAIDs should be used according to careful risk-benefit considerations, wrote Hallman et al. (2023), a group of veterinary researchers from the University of Helsinki Faculty of Veterinary Medicine, in Finland.Extrapolating from other species, however, is not an ideal practice because the equine placenta is markedly dissimilar from those of other species, especially humans. Drugs are likely to cross the placenta differently among species.Why take the risk with medications not proven to be safe? The consequences of untreated/undertreated laminitis extend beyond discomfort. As relayed by Hallman et al. (2023) based on work performed by Pazinato et al. (2017), compared with healthy broodmares, pregnant mares with chronic laminitis have:Shorter gestation lengthsLower placental weightsLower foal birth weightsHigher heart ratesHypertensionAbnormalities of the placental vasculatureFurther, as reported by Hallman et al., Pain and the concomitant (naturally occurring) stress response have been shown to lower blood progestogen levels and may therefore predispose the mare to fetal loss especially during early pregnancy.Take-Home MessageTo defend use of medications in pregnant broodmares without full safety data, Bailey says, In a mare with laminitis, the stress has a greater effect than any medication does. We need to make the mare comfortable. I generally administer the drugs that I need to treat the mare and assume the pregnancy and foal will be fine.Current evidence points to gaps in understanding medication use during pregnancy in horses. As Mouncey et al. writes, Given the high levels of medication usage reported in this study, findings support the need for work to further understanding of medication usage during gestation in Thoroughbreds, particularly evaluation of associations with offspring health outcomes.This article is from the Spring 2026 issue ofThe Horse: Your Guide to Equine Health Care. We at The Horse work to provide you with the latest and most reliable news and information on equine health, care, management, and welfare through our magazine and TheHorse.com. Your subscription helps The Horse continue to offer this vital resource to horse owners of all breeds, disciplines, and experience levels. To access current issues included in your subscription, please sign in to theAppleorGoogleapps ORclick herefor the desktop version.