Pharmacology for Cats and Dogs

By Rebecca J. Anderson, PhD

For a long while, Fluffy had not been feeling quite herself. The 15-year-old calico was tired, frequently irritable and just didn’t want to play. Fluffy suffered from chronic kidney disease, and like many older cats with kidney disease, her blood pressure was too high. The family’s veterinarian was concerned because hypertension often accelerates kidney deterioration, leading to kidney failure. He invited Fluffy’s owners to have her participate in an experimental study, which was testing a new antihypertensive treatment for cats.

Comparative Pharmacology

There are about 1,600 drugs specifically labeled for veterinary use, compared to about 20,000 drugs approved for people (1). In fact, for many animal species, there are diseases and conditions for which no suitable veterinary drug is available. Veterinarians, like physicians, may legally prescribe human drugs for conditions (and species) not approved by the Food and Drug Administration (FDA). In the veterinary community, off-label prescriptions are called “extra label” use (1, 2)

The basic principles of drug action are identical across veterinary and human pharmacology (2). But estimating the optimal dosing regimen for an animal using a human drug is often little more than guesswork. Each animal species (and breed) may respond with different pharmacokinetics, pharmacodynamics, and adverse effects.

Developing a new animal drug follows a similar process as that for human pharmaceuticals, and the FDA requires the same level and amount of data for approval. But animal healthcare companies face challenges and complications that do not occur with human pharmaceuticals (2). Animal species (and breeds) vary in size, behavior, metabolism, and lifespan. Those factors largely account for the differences in pharmacokinetics and toxicity profiles. Drug assessment, particularly regarding side effects, is further complicated because animals cannot directly communicate with investigators (2).

For these reasons, the FDA requires that a veterinary drug label must include species-specific dosing instructions, and the label may also impose restrictions that are not part of a human drug label (2).

The review and approval process is handled by the FDA’s Center for Veterinary Medicine. The agency evaluates and regulates new drugs for seven “major” species (cats, dogs, horses, cattle, pigs, chickens, and turkeys), as well as all “minor” species, including fish, ferrets, goats, sheep, birds, rabbits, guinea pigs, reptiles, zoo animals, wildlife, and bees, among others (1, 2).

Because of the species differences and other variables not present in human pharmacology, the cornerstone of veterinary medicine is “comparative pharmacology.” That is, the systematic study of how different species (and breeds) handle and respond to a drug.

Fluffy Steps Up

Telmisartan (Micardis) is a non-peptide angiotensin II receptor blocker and was already approved by the FDA to treat people with hypertension. So, the purpose of Fluffy’s clinical trial was to confirm that the appropriate dose adjustments had been made for optimal treatment of cats.

Considerable data had already been collected from preclinical animal studies that had been conducted to support the original human drug approval of telmisartan. Only two additional issues needed to be addressed.

The FDA requires data from one well-controlled trial showing that the drug works in the “target animal species” (1). Often, such as in this case, the trial is a field study, which evaluates how the drug performs when the animal is in its normal environment (that is, under “field” conditions).

Fluffy’s owners agreed to enroll her in the study. She was one of 221 cats in the placebo-controlled, double-blind trial (3). Her owners were taught how to administer the drug solution, which Fluffy slurped daily at home.

Fortunately, Fluffy was in the group receiving telmisartan, and after four weeks of treatment, her blood pressure dropped significantly to near-normal. The investigators continued to follow Fluffy for six months. Each day, she took a maintenance dose of telmisartan, and her blood pressure remained under control (3)

During development of telmisartan for human use, much of the adverse effect data and specialized safety test results had already been compiled from laboratory animals (mainly rodents and dogs), as well as from people. The only remaining requirement to get regulatory approval of veterinary telmisartan was data showing that the drug was safe in cats (4).

Typically for a target species safety study, a small number of healthy animals are used, so that investigators can easily identify species-specific side effects and establish the safety margin (1). The study must be conducted under Good Laboratory Practices, and the standard study design recommended by the FDA is extremely detailed and specific. Drug companies rarely deviate from it (4, 5). Assessment of drug safety is based on observations of animal behavior, blood tests, and necropsy, pathology, and histopathology of tissues and organs (1).

The target animal safety study for telmisartan was conducted in healthy, normotensive cats. After 6 months of dosing, the cats exhibited no troublesome side effects, and the data were also used to establish the safety margin of telmisartan in cats. In 2018, the FDA approved veterinary telmisartan (Semintra). In doing so, telmisartan became the only angiotensin receptor blocker approved for first-line treatment of hypertension in cats.

Prescription veterinary drugs, like telmisartan, can be dispensed or prescribed only by a licensed veterinarian. If a drug label’s directions are clear enough for lay people to administer the drug safely and appropriately to the animal, the FDA can permit the drug to be available over the counter (1).

But Not Vice Versa

Physicians are discouraged from prescribing veterinary drugs for human use, even though the practice is legal. Veterinary drugs are often manufactured in highly concentrated form to accommodate large animals, and the likelihood of overdosing people is a serious concern (6)

For example, ivermectin was approved in 1981 as a veterinary medicine. It is widely used to treat worms and other parasites in livestock (6). Subsequently, ivermectin (Stromectol) was approved to treat river blindness, a parasitic infection that is prevalent in Africa. The standard treatment to protect people from acquiring river blindness is a 3- to 12-mg dose given once per year.

The average ivermectin dose in cattle is 80-160 mg. So, people are more likely to overdose by taking the veterinary formulation. Ivermectin’s overdose effects include nausea, vomiting, diarrhea, seizures, coma, and sometimes death.

During the COVID-19 pandemic, off-label use of veterinary ivermectin garnered some media attention, but there was never any data showing it was effective for treating or preventing COVID-19. Concerned about the public’s health, FDA officials posted a nowfamous tweet: “You are not a horse. You are not a cow. Seriously, y’all. Stop it….Using ivermectin to treat COVID-19 can be dangerous and even lethal” (7)

Encouraging New Animal Drugs

About 70% of American households own pets, totaling nearly 280 million, including 65 million cats and 85 million dogs (2, 8). Pets have close interactions with their owners, and they are increasingly treated like members of the family. Some are comfort or service animals and provide an important wellness function for people. Consequently, many pets receive a high level of medical care, which increasingly resembles human healthcare (9).

Despite the increased demand for veterinary drugs, the animal healthcare industry has had little incentive to invest in new drug development (2). HealthforAnimals reported that in 2015, it took 6.5 years and $22.5 million to bring a new veterinary drug to market (8). The profit margin on those drugs remains far less than the profitability of a new human pharmaceutical (2)

To reduce the financial burden on animal healthcare companies, the FDA’s regulatory requirements were amended. Greater flexibility is now permitted in the types of “adequate, well-controlled” trials that are required to establish efficacy and safety. Also, three or five years of patent exclusivity after market approval (depending on certain criteria) has been added to offset the time required to develop a new veterinary drug. Finally, the FDA adopted a phased review process, which created efficiencies for the reviewers, shortened the regulatory review time, and increased the likelihood that the veterinary drug will be approved (2).

New Drugs for Animals

Among the companies that have taken advantage of these incentives is Pfizer Animal Health, which recently developed maropitant specifically for veterinary use. Maropitant is a selective neurokinin-1 receptor inhibitor. It binds to receptors in the chemoreceptor trigger zone and the medullary vomiting center, which receive inputs from the many neurological pathways that trigger vomiting. Because of this central mechanism of action, researchers hoped that maropitant would block a broad range of nauseous and emetic stimuli (10)

In a series of studies in laboratory-bred dogs and placebo-controlled field trials with pet dogs, Pfizersponsored investigators showed that, indeed, maropitant had broad efficacy. It prevented vomiting induced by chemotherapy, viral diseases, food and toxin ingestion, intestinal inflammation, opiates, and motion sickness. The results also showed that maropitant prevented vomiting as effectively as, or better than, the commercially available antiemetics (2, 10, 11).

Likewise, the target animal safety studies in dogs showed that maropitant is safer than the other antiemetic drugs used in veterinary medicine. Although neurokinin-1 receptors are involved in a wide range of physiological and behavioral responses, the low doses of maropitant used to control vomiting do not cause adverse effects associated with those other physiological functions (2).

In 2007, the FDA approved maropitant (Cerenia) as a veterinary prescription drug to manage vomiting in dogs (10).

Pfizer Animal Health then sponsored another series of studies in cats. Under both laboratory conditions and in field trials with pet cats, maropitant was effective in preventing vomiting induced by various noxious stimuli, including motion sickness (2, 12). The target animal safety studies showed, like dogs, that there was a wide margin of safety between the effective dose and the appearance of adverse effects in cats (12). Based on these data, FDA approved maropitant for cats in 2012.

The comparative pharmacology results from these studies reinforced the view that animal clinical trials must be species-specific. Maropitant has a higher oral bioavailability and a longer half-life in cats than in dogs (2). Consequently, the drug label for cats specifies a dose that is one-half the dose listed on the label for dogs.

Helping Human Drug Development

Small pharmaceutical companies often lack development resources and sometimes turn to veterinarians to assist with preliminary efficacy testing of their drug candidates before launching clinical trials in people. Investigators at veterinary schools are especially helpful when the target disease or medical condition cannot be easily simulated in the laboratory. For example, Plex Pharmaceuticals in San Diego, Calif., recently received Small Business Innovation Research grants from the U.S. National Eye Institute to test their novel anti-cataract compounds (13). The protein, alpha-Acrystallin, is a major component of the eye lens and helps to maintain its transparency. Damage or aging can cause aggregation of this protein, and protein aggregation in the lens leads to the formation of cataracts (13).

The Plex lead compound, CAP4196, had produced promising results in treating other protein aggregation diseases. The Plex researchers developed a topical eye drop formulation, and they wanted to confirm its efficacy in animals with cataracts before beginning human clinical trials.

Age-related cataracts are a major health problem in dogs. By age 13, almost 80% of dogs develop cataracts (14). Surgery is the only remedy currently available.

Plex partnered with researchers at the Univ. of California, Davis, School of Veterinary Medicine to test the CAP4196 formulation. The UC Davis veterinarians are recruiting 24 pet dogs for the trial. Each dog must be at least eight years old and have age-related cataracts. The randomized, placebo-controlled study will follow CAP4196 treatment at two different doses for 9 months (14)

The Plex researchers hope that the data from the UC Davis trial, along with other preclinical and regulatoryrequired studies, will be sufficient to gain FDA clearance to start Phase I clinical trials of CAP4196 in patients with cataracts (13).

Repurposing a Drug

Sometimes, investigational drugs intended for people are redirected to veterinary medicine. For example, when Gilead Sciences decided to discontinue its human clinical trials of rabacfosadine, the small biotech firm, VetDC, acquired the veterinary rights to the drug (15). In 2019, VetDC licensed the compound to Elanco Animal Health, a global leader in animal healthcare products, for further development and commercialization (16)

Rabacfosadine is a nucleotide analog that preferentially targets lymphoid cells and causes cell death by inhibiting DNA polymerases. One-quarter of all dogs will be diagnosed with cancer in their lifetime, and lymphoma is one of the most common types of cancer seen by veterinarians (15, 16).

The efficacy of rabacfosadine in dogs was established in a masked, randomized, placebo-controlled clinical trial (16). Researchers at several veterinary schools recruited 158 pet dogs of various breeds. Each dog had been diagnosed with multicentric lymphoma. For the dog to be included in the trial, researchers needed to be able to externally measure at least one peripheral lymph node tumor (16).

Every three weeks, the owners brought their pets to the clinic for a 30-minute intravenous infusion of rabacfosadine (or placebo solution), for a total of five doses over 15 weeks (16). Complete or partial responses were observed in 73% of the rabacfosadine-treated dogs. The compound was not only more effective, but also required less frequent dosing than human cancer drugs, which are the only alternatives for dogs with lymphoma (15)

The target animal safety assessment was based on three studies using healthy beagles. Because of their demeanor and uniform size, beagles are specifically bred for laboratory studies and toxicology testing. Rabacfosadine was well-tolerated at the doses used for cancer treatment.

In 2021, the FDA gave full approval of rabacfosadine (Tanovea) as a prescription drug for the treatment of lymphoma in dogs. In so doing, rabacfosadine became one of the most comprehensively studied treatment options for dogs with lymphoma (16).

Veterinary Pharmacology Research

Pharmacologists at veterinary schools conduct a wide range of research, from comparative pharmacology studies to experimental therapeutics. Sometimes, their basic research findings serve as the starting point for development of a new veterinary drug by an animal health company or a new treatment option for practicing veterinarians. In some cases, those discoveries are also leveraged to improve human therapeutics.

For example, veterinarians at Cummings School of Veterinary Medicine (Tufts Univ.) discovered genes in dogs that are biomarkers for canine compulsive disorder. These genes correlate with an increased incidence of stereotypical behaviors such as tail chasing (9)

In one series of studies, the Tufts researchers collaborated with colleagues at Harvard, MIT, and the Univ. of Massachusetts Medical School to search for behavior-associated genes in Doberman pinschers. Up to 30% of Dobermans display compulsive behaviors such as incessant licking of flanks or sucking on blankets (17)

In Dobermans that exhibited compulsive behavior, the researchers found a mutation in CDH2, a gene on chromosome seven. This canine gene codes for the same protein that is coded by a corresponding gene on chromosome 18 in humans. Mutations of chromosome 18 are associated with various human psychiatric disorders (17)

Researchers in China found this same gene, CDH2, was associated with the compulsive circling behavior in Belgian Malinois. Interestingly, German shepherds, a breed similar to Malinois, are also known to circle compulsively (17).

CDH2 is involved with the development of glutamate receptors, and dysfunction of glutamate neurotransmission has been associated with obsessive compulsive disorder (OCD) symptoms in humans (18).

With this in mind, Nicholas Dodman and colleagues at Tufts found that memantine, an Alzheimer’s drug that blocks brain glutamate, significantly reduced the compulsive behaviors of dogs (17).

Michael Jenike at McLean Hospital in Belmont, Mass., followed up with a pilot study in 44 OCD patients who had not responded to SSRIs, the standard-of-care treatment for OCD (17). Half of the OCD patients were given memantine, and the other half received standard cognitive behavioral therapy. Only the memantinetreated patients exhibited significant decreases in their OCD symptoms (19)

Subsequent clinical trials confirmed the efficacy of memantine, and Tufts patented memantine as a new treatment for OCD (17).

Until now, investigational psychiatric drugs that showed impressive efficacy in animal models have often failed in patients with psychiatric disorders. Because of this lack of predictive correlation, the pharmaceutical industry has reduced research and development of new psychiatric drugs over the past 50 years (20).

The results from the Tufts genomic studies in dogs and the therapeutic efficacy of memantine in both dogs and patients demonstrate the value of canine compulsive disorder as a valid model of OCD in people (9). It also suggests that a genomics approach may lead to better and more predictive animal models of the complicated neural networks associated with psychiatric disorders (20).

Innovative Therapeutics

In addition to genomic and other basic science studies, researchers at veterinary schools also explore innovative therapeutic regimens for animals. For example, veterinary researchers are investigating new drug combinations for osteosarcoma (bone cancer).

Large, long-legged dog breeds are especially prone to develop osteosarcoma, an aggressive and malignant form of cancer that affects more than 10,000 dogs in the U.S. each year (21). The annual incidence of bone cancer in people is much less: about 1,000 cases, mostly children and young adults (21)

Because of the small number of human cases, conducting clinical trials in people with osteosarcoma is challenging, and there is little incentive to fund those trials (22). Consequently, no new drugs or treatment regimens for osteosarcoma have been own immune system can be activated to recognize and kill osteosarcoma cells. Combining drugs that activate the immune system in complementary ways could potentiate their cancer-killing effect.

In November 2020, Jellybean’s owners enrolled her in a clinical trial at Tufts Univ. School of Veterinary Medicine (23). They signed an Informed Consent Form and were trained to administer the drugs. Every day, they stuffed three pills in Jellybean’s favorite chickenflavored treats. By Christmas, Jellybean’s tumors had begun to shrink, and they haven’t come back. Now five years old, Jellybean walks with ease, as if she had never had metastatic cancer (23).

The drug combo that Jellybean received was toceranib (Palladia), losartan, and ladarixin.

Toceranib is a tyrosine kinase receptor inhibitor approved for treating dog tumors. It directly kills tumor cells. Toceranib is also an angiogenesis inhibitor and decreases the blood supply to the tumor.

Losartan is an angiotensin II receptor blocker approved to treat hypertension. But at a tenfold higher dose, it also blocks the recruitment of immune cells that stimulate tumor growth (23, 24) developed in over 35 years. On the other hand, the high incidence of osteosarcoma in dogs offers an opportunity to accelerate this research and drug testing (22, 23).

Ladarixin is an experimental (unapproved) inhibitor of IL-8 receptors. It inhibits the recruitment of neutrophils.

Jellybean, a two-year-old Labrador-retriever mixed breed was diagnosed with bone cancer in her hind leg (23). The standard treatment is amputation followed by four rounds of chemotherapy with carboplatin. But despite amputation and chemotherapy, metastases to various organs occur in ~90% of dogs (23)

Jellybean’s case was typical. After undergoing amputation and chemotherapy, her cancer quickly spread to her lungs. A dog’s average survival time is about two months after metastases are detected (23) But Jellybean had another treatment option.

Evidence has accumulated from both laboratory studies and human clinical trials that an individual’s

The complementary mechanisms of these three drugs enhance the immune system’s ability to target and kill tumor cells.

The response of Jellybean and other dogs to the three-drug regimen was encouraging. But delaying treatment until after amputation and completion of chemotherapy permitted residual tumor cells to become drug-resistant and metastasize (23)

The Tufts researchers thought that the drug combo would work even better if treatment began earlier (23). In a follow-up study, which is ongoing, the researchers administer the toceranib-losartan-ladarixin regimen prior to amputation. At this early stage, any residual tumor cells are assumed to be more vulnerable to attack by immune cells. Hopefully, the drug combo will prevent the cancer from spreading to the lungs and other organs.

In parallel with this trial, academic researchers at Children’s Hospital Colorado launched a Phase I clinical trial (NCT03900793). This ongoing dose-escalation study is recruiting 41 children and young adults who suffer from resistant or recurrent osteosarcoma. The patients are receiving losartan and sunitinib (Sutent), a tyrosine kinase inhibitor that has been approved for human use and is analogous to the veterinary-approved toceranib.

Pet Clinical Trials

As these examples suggest, researchers now recognize that pet dogs and cats have advantages over lab-raised animals for assessing human drugs. Pets are exposed to much of the same environment as humans. They share the same homes, consume the same water and foods, and are exposed to a number of the same hazards (21-23, 25)

Because of their high level of medical care, the pets’ detailed medical records are often available (25) Unlike humans, there are fewer medical confidentiality concerns (e.g., HIPAA regulations), making data sharing easier (22)

Cats are 90% genetically identical to humans, and dogs are 95% identical. Not surprisingly, similar genetics and a similar living environment make pets and their owners vulnerable to many of the same health risks (26). Like humans, cats and dogs naturally acquire diseases, such as obesity, diabetes, heart disease, and cancer (23, 26). Laboratory rodents, on the other hand, must be manipulated to induce a disease condition, and they have proven to be less reliable in predicting human responses to drug treatment (22, 23).

For example, only 15% of cancer drug candidates survive to Phase III after successful preclinical testing in laboratory animals. Only half of the cancer drugs in Phase III trials will be approved for clinical use, giving an overall success rate of less than 8% (20).

Researchers now know that many naturally occurring cancers that affect dogs and cats (including osteosarcoma, breast and prostate cancers, nonHodgkin’s lymphoma, head and neck cancer, and melanoma) share features with human cancers (23, 25). Those animal tumors not only look the same as human tumors microscopically, but also mutations in the same genes often drive emergence and spread of the cancer (22). Given those similarities, it is perhaps not surprising that pet and human cancers seem to respond to treatments in similar ways (23)

Cancer trials in pets also provide data that have fewer uncontrolled variables that might interfere with interpreting drug efficacy. Cancer patients typically must fail the standard of care (often chemotherapy) before enrolling. Also, because it is considered unethical to give a cancer patient only an experimental drug (that might not work), they are usually given the best-known effective treatment, in combination with the experimental drug (22)

By contrast, pets can enroll in an animal clinical trial without having their immune system already compromised by earlier (failed) treatments and without an accompanying standard-of-care drug. This makes the efficacy data easier to interpret.

Over the past decade, great progress has been made in accumulating comparative genomic data, fostering collaboration between veterinarians and oncologists, and attracting funding for pet clinical trials.

The Comparative Oncology Program

About four million dogs in the U.S. are diagnosed with cancer every year, and this large pool of pets promises to speed development of cancer treatments that will benefit both them and their owners (21). This approach is called comparative oncology (25).

In 2003, the U.S. National Cancer Institute (NCI) launched the Comparative Oncology Program. Under the Program, NCI works collaboratively with academic researchers at 20 veterinary schools in the U.S. and 2 in Canada to study the biology of a variety of cancers and to assess novel treatments (25). The Program is now funded under the White House’s Cancer Moonshot Initiative and oversees dozens of pet clinical trials (21, 22).

NCI and the participating academic veterinary clinics collaborate to design and implement these pet clinical trials, which closely mimic the procedures that are used to recruit, enroll, and treat people in a clinical trial.

To participate, the pets must meet strict enrollment criteria. Their owners must sign an Informed Consent Form and follow the protocol procedures stipulated for their pet. Board-certified veterinary oncologists at the veterinary schools are responsible for conducting the trial and monitoring the pets’ health (25)

The results from these cutting-edge trials give researchers valuable information on investigational drug pharmacokinetics, pharmacodynamics, dose strength, dosing schedule, biomarkers, toxicity, and various histology endpoints. This comparative oncology information is then used to design additional trials to establish the compounds’ efficacy and safety. Those results will hopefully benefit both animals and people with cancer (25).

Cutting-Edge Trials

For example, investigators at Case Western Reserve Univ. discovered BG34-200, a 200-k Dalton glucose polysaccharide that was derived from oats. BG34-200 dramatically increases the level of immune factors (i.e., gamma-interferon and TNF-alpha) at the tumor site. In addition, the compound mobilizes tumor-reactive T cells systemically (27). Unlike many chemotherapy drugs, BG34-200 can be prepared in both oral and injectable formulations.

In laboratory mice that have been manipulated to express advanced melanoma, BG34-200 significantly inhibited tumor growth and improved survival (28). These results suggested that immunotherapy with BG34200 might be an effective alternative for patients with advanced melanoma, that is, melanomas that have failed to respond to current standard-of-care treatments (28)

To confirm the compound’s efficacy and provide greater justification for human clinical trials, the NCI Comparative Oncology Program is sponsoring a study at the Univ. of Pennsylvania: “Pilot assessment of BG34-200 in spontaneous canine cancers” (COTC029). Up to 10 dogs weighing more than 15 kg are being recruited for the trial. Each dog must be diagnosed with an initial or recurrent solid tumor larger than 2 cm.

This pilot study will evaluate the safety of BG34-200, as well as its ability to stimulate the dogs’ immune system, to recognize cancer cells and attack them. In addition to malignant melanoma, the study will also explore the compound’s efficacy against other tumor types, such as mammary tumors, soft tissue sarcoma, and osteosarcoma.

Each week during the six- to seven-week treatment period, pet owners will bring their dogs to the Univ. of Pennsylvania clinic, where veterinary oncologists will measure the tumor size and assess drug-related side effects.

Recognizing the great promise of immunotherapy drugs to treat cancer, NCI established a network of five veterinary schools in 2017 to conduct clinical trials specifically of cancer immunotherapy drugs in pet dogs (29). In 2022, five additional academic sites were added. Currently, the cutting-edge immunotherapy treatments being investigated at these ten sites include drug combinations to treat dogs with lymphoma, osteosarcoma, and hemangiosarcoma (29).

To ensure the quality and accessibility of data from each dog trial conducted by this network, the School of Veterinary Medicine at the Univ. of Pennsylvania was designated as the Data Coordinating Center. The Center compiles data from all of the participating veterinary academic sites, ensures consistency in data collection across sites, harmonizes and integrates the data, and enables researchers to identify important common signals. This aggregated and high-quality data will allow both veterinarians and physicians to make evidence-based decisions when selecting treatment plans for their cancer patients (29).

Pet Prominence

The first wave of veterinary schools in the U.S. arose in the 1860s at land grant colleges (30). Because the curriculum emphasized agriculture, engineering, and the “practical arts,” the land grant colleges were located in predominantly rural agricultural areas. Consequently, veterinary students at these schools had little exposure to the centers of medical education, which were largely contained within universities in urban areas (30).

The main focus of veterinary education, practice, and research in the land grant colleges was related to the health and well-being of livestock and horses (31) Veterinary students consisted mainly of farm-reared boys, because of their intimate knowledge of farm animals (30). Companion animals were not considered a priority for either veterinary education or research (31)

Farm experience was the dominant admissions criterion, and there was a strong bias against admitting veterinary students from urban areas (30). At some veterinary schools, applicants had to validate their farm proficiency by harnessing work horses, backing two-wheeled wagons with a tractor, and placing milking machines on cows (32). Given this situation, few women were admitted to veterinary schools in the 19th and early 20th centuries (32).

The emergence and evolution of veterinary pharmacology paralleled changes in society and attitudes toward animals (6). In the mid-20th century, veterinary medicine shifted from a predominantly large animal practice to increasing consideration of companion animals. As pets became more integral family members, their health became a greater concern, and pet owners were more willing to invest in pet care (6, 31).

In 2022, spending on veterinary care reached $35 billion (9, 33). Much of this is spent on prescription and over-the-counter drugs (9). The median lifetime drug expenditures for a dog are $5,154 and for a cat are $5,325 (8).

Increased pet owner demands encouraged more veterinarians to specialize in companion animal care, which in turn, drove veterinary college faculties to, slowly but steadily, increase coursework on small animal medicine (31). At the same time, thanks to the passage of Title IX in 1972, the barriers to acceptance of women students into veterinary schools were relaxed (31)

The number of female veterinary students increased dramatically, and this trend continued over the following decades. By 2000, the gender ratio of veterinary students settled at ~80% women and 20% men. As a result, over half of practicing veterinarians are now women (31).

Many of those women are drawn to veterinary positions in pet hospitals or group veterinary practices in urban areas, both of which cater mainly to cats and dogs. Large animal veterinary medicine is still needed, and those veterinarians must comply with special regulations regarding drugs prescribed for foodproducing animals, such as cattle and chickens, and performance animals, such as racehorses. But that’s another story.

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Biosketch:

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Rebecca J. Anderson holds a bachelor’s in chemistry from Coe College and earned her doctorate in pharmacology from Georgetown University. She has 25 years of experience in pharmaceutical research and development and now works as a technical writer. Her most recent book is Nevirapine and the Quest to End Pediatric AIDS. Email rebeccanderson@msn.com

In the next issue of The Pharmacologist…

Dr. Anderson will feature Goodman and Gilman’s World War II.

Don't miss the January issue.