Module 6: Top 25 Veterinary-Only Prescription Drugs
Part 2: Hormonal Drugs and Selected Individual Agents
Diethylstilbestrol (DES) Summary
Dosage by Species
- Dogs: Tapered administration starting with0.02 mg/kg (not to exceed 1 mg) orally every 24 hours for 3–5 days initially, then decreased to every other day, and finally decreased to the longest dosing interval that controls incontinence (once weekly for most dogs).
Pharmacokinetic Parameters
| Parameter | Dogs |
| T ½ (hr) | 24 |
| Vd (L/kg) | NR* (>5 in primates) |
| Protein binding (%) | 95 |
| *NR = Not reported. | |
Contraindications/Warnings
- Do not administer concurrently with other estrogens (e.g., estriol).
- Not for use in cats.
- Carcinogenic and teratogenic in humans.
Pregnancy Category
- Category X.
Drug Interactions
| Drug(s) | Interaction |
CYP3A4 Inhibitors
|
CYP3A4 and p-glycoprotein transporter inhibition causes estrogens (including DES) to accumulate |
CYP3A4 Inducers
|
Increase metabolism of estrogens (including DES) |
| Corticosteroids | Estrogens (including DES) may inhibit metabolism of steroids or displace from plasma proteins, necessitating adjustment of corticosteroid dosing |
| Highly protein-bound drugs | DES may displace or be displaced by other highly protein-bound drugs |
| Warfarin | Estrogen (including DES) decreases warfarin levels |
Storage/Stability
- Store compounded capsules in a moisture-resistant and light-resistant container at room temperature (59°F–86°F).
Estriol Summary
Brand Name: Incurin
Manufacturer: Merck Animal Health
Source: http://www.merck-animal-health-usa.com/products/96-59930-4/productdetails_130_163463.aspx
Available Dosage Forms
- Scored tablets: 1 mg supplied in blister packs of 30 tablets
Dosage by Species
- Dogs: Tapered dosage starting with2 mg orally every 24 hours for 14 days, then 1 mg orally every 24 hours for 7 days, then 0.5 mg orally every 24 hours for 7 days. When the lowest effective dose is determined, it can be administered every 48 hours or as infrequently as possible to control incontinence.
Pharmacokinetic Parameters
| Parameter | Dogs |
| T ½ (hr) | 8–12 |
| Vd (L/kg) | NR* (>5 in primates) |
| Protein binding (%) | 95 |
| *NR = Not reported. | |
Contraindications/Warnings
- Do not administer concurrently with other estrogens (e.g., diethylstilbestrol).
- Not for use in cats.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
CYP3A4 Inhibitors
|
CYP3A4 and p-glycoprotein transporter inhibition causes estrogens (including estriol) to accumulate |
CYP3A4 Inducers
|
Increase metabolism of estrogens (including estriol) |
| Corticosteroids | Estrogens (including estriol) may inhibit metabolism of steroids or displace from plasma proteins, necessitating adjustment of corticosteroid dosing |
| Highly protein-bound drugs | Estriol may displace or be displaced by other highly protein-bound drugs |
| Warfarin | Estrogen (including estriol) decreases warfarin levels |
Storage/Stability
- Store at or below 77°F, with excursions permitted to 104°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-325.
Phenylpropanolamine Summary
Brand Name: Proin
Manufacturer: PRN Pharmacal
Source: https://www.valleyvet.com/ct_detail.html?pgguid=3709570e-ae33-4dbb-ac22-aa599889c086
Available Dosage Forms
- Chewable liver-flavored scored tablets: 25 mg, 50 mg, 75 mg
Dosage by Species
- Dogs: 2 mg/kg orally every 8–24 hours.
- Cats: 1–2.2 mg/kg orally every 8–24 hours; not recommended for use in cats.
Pharmacokinetic Parameters
| Parameter | Dogs |
| T ½ (hr) | 3.5 |
| Vd (L/kg) | NR* |
| Protein binding (%) | NR |
| *NR = Not reported. | |
Contraindications/Warnings
- Use with caution (if at all) in animals with glaucoma, prostatic hypertrophy, hyperthyroidism, diabetes mellitus, cardiovascular disorders, renal insufficiency, or hypertension.
- Do not use in dogs with urinary tract infections; important clinical signs may be masked.
- Do not administer to dogs undergoing food allergy trials or known to be allergic to liver, garlic, or whey.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| Aspirin | Phenylpropanolamine may potentiate antiplatelet effect |
| Monamine oxidase (MAO) inhibitors (e.g., amitraz, selegiline) | Pressor effects of phenylpropanolamine may be enhanced by MAO inhibitors |
| NSAIDs | May increase the pressor effects of phenylpropanolamine |
| Tricyclic antidepressants | May increase the pressor effects of phenylpropanolamine |
Storage/Stability
- Store at controlled room temperature (68°F–77°F). Excursions are permitted between 59°F and 104°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-324.
Trilostane Summary
Brand Name: Vetoryl
Manufacturer: Dechra
Available Dosage Forms
- Capsules: 5 mg, 10 mg, 30 mg, 60 mg
Dosage by Species
- Dogs (hyperadrenocorticism): 2.2–6.7 mg/kg orally every 24 hour; therapy may be initiated with ~1 mg/kg orally every 12 hours to minimize adverse effects.
- Dogs (Alopecia X): 3 mg/kg orally every 12 hours for 4–6 months.
- Cats: 0.5–12 mg/kg orally every 24 hours or every 12 hours.
- Horses: 120–240 mg orally every 24 hours.
Pharmacokinetic Parameters
| Parameter | Dogs |
| T ½ (hr) | 8 |
| Vd (L/kg) | NR* (0.13 in rats) |
| Protein binding (%) | NR |
| *NR = Not reported. | |
Contraindications/Warnings
- Do not use in pregnant animals.
- Do not use in animals with primary hepatic disease or renal insufficiency.
- Intolerance to trilostane therapy or overdosage has resulted in death. Pet owners should consult a veterinarian immediately if any signs of possible toxicity are observed.
Pregnancy Category
- Category X: inhibition of progesterone synthesis can result in miscarriage.
Drug Interactions
| Drug(s) | Interaction |
| ACE inhibitors | May increase risk of hyperkalemia |
| Ketoconazole Mitotane |
Further decrease cortisol production and may lead to hypoadrenocorticism |
| Potassium salts (bromide, chloride, citrate, gluconate) | May increase risk of hyperkalemia |
| Potassium-sparing diuretics | May increase risk of hyperkalemia |
Storage/Stability
- Store at controlled room temperature (77°F). Excursions are permitted between 59°F and 86°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-291.
Pergolide Mesylate Summary
Brand Name: Prascend
Manufacturer: Boehringer Ingelheim
Source: https://www.valleyvet.com/ct_detail.html?pgguid=e0f4888c-86de-4ce9-9013-6d947df697a8
Available Dosage Forms
- Scored oral tablet: 1 mg
Compounded Formulations
- Pergolide Compounded Oral Suspension, Veterinary, USP (1 mg/mL)
Dosage by Species
- Horses: 2–4 µg/kg orally every 24 hours, rounded to the nearest 0.5 mg (½ tablet).
Pharmacokinetic Parameters
| Parameter | Horses |
| T ½ (hr) | 5.86 |
| Vd (L/kg) | 3.08 |
| Protein binding (%) | 90 |
Contraindications/Warnings
- Contraindicated in horses with allergy to ergot derivatives.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| Dopamine antagonists (domperidone, metoclopramide, phenothiazines) | Antagonize the effects of pergolide |
| Highly protein-bound drugs (carprofen, doxycycline, furosemide, ketoconazole) | May displace or be displaced by pergolide |
Storage/Stability
- Store at or below 77°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-331.
- ARCI (Association of Racing Commissioners International) has classified pergolide mesylate as a Class 3 substance.
Domperidone Summary
Brand Name: Equidone
Manufacturer: Dechra Animal Products
Source: http://www.dechra-us.com/products/horse/equidone-gel
Available Dosage Forms
- Oral gel: 110 mg/mL in a 26-mL oral dosing syringe (approximately 5 doses for the average adult mare)
Dosage by Species
- Horses (prevention of fescue toxicosis): 1.1 mg/kg orally every 24 hours, starting 10–15 days before expected foaling date. Treatment may continue for up to 5 days after foaling.
- Horses (diagnosis of PPID): 2.5 mg/kg orally as a single dose; ACTH level 4 hours post dosing.
Pharmacokinetic Parameters
| Parameter | Horses |
| T ½ (hr) | 6 |
| Vd (L/kg) | NR* (6.3 in humans) |
| Protein binding (%) | 93 |
*NR = Not reported.
Contraindications/Warnings
- Accurate breeding date and expected foaling date are needed for safe use. Domperidone may lead to premature birth, low birth weight foals, or foal morbidity if administered more than 15 days before the expected foaling date.
- Domperidone causes false positives on the milk calcium test used to predict foaling.
- Do not use in horses with gastrointestinal obstruction (domperidone is a prokinetic agent).
Pregnancy Category
- Safe use in breeding, pregnant, or lactating mares has not been determined (other than in last 45 days of pregnancy and first 15 days of lactation).
Drug Interactions
| Drug(s) | Interaction |
| CYP3A4 and pGp inhibitors (azole antifungals, cimetidine, dexamethasone, macrolides, metronidazole, omeprazole, ranitidine) | Increase blood levels of domperidone |
| Dopamine agonists (bromocriptine, pergolide) | Antagonize effects of domperidone |
| Highly protein-bound drugs | Domperidone may displace or be displaced by other highly protein-bound drugs |
Storage/Stability
- Store at controlled room temperature (77°F). Excursions are permitted between 59°F and 86°F.
- Recap dosing syringe after each use.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-314.
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Oclacitinib Maleate Summary
Brand Name: Apoquel
Manufacturer: Zoetis Animal Health
Source: http://www.veterinarypracticenews.com/May-2014/Shortage-Of-Apoquel-Allergy-Drug-To-Last-Into-2015/
Available Dosage Forms
- Oral film-coated tablets: 3.6 mg, 5.4 mg, 16 mg
Dosage by Species
- Dogs: 0.4–0.6 mg/kg orally every 12 hours for 14 days, then every 24 hours (often accomplished by administering half of the dose in the morning and half in the evening, rather than the whole dose once daily).
- Cats: 0.4–0.6 mg/kg orally every 12 hours; not labeled for use in cats.
Pharmacokinetic Parameters
| Parameter | Dogs |
| T ½ (hr) | 4 |
| Vd (L/kg) | 0.942 |
| Protein binding (%) | 66.3–69.7 |
Contraindications/Warnings
- Not for use in breeding dogs or pregnant or lactating bitches.
- Do not use in dogs younger than 12 months of age.
- Do not use in dogs with serious infections or neoplasia.
- Concurrent use with glucocorticoids, cyclosporine, or other systemic immunosuppressive agents has not been evaluated and may increase risks from immunosuppression.
Pregnancy Category
- Category X.
Drug Interactions
- No drug interactions were observed when oclacitinib was administered concurrently with endoparasiticides, ectoparasiticides, antimicrobial agents, or anti-inflammatory agents during field studies.13
- Although not evaluated directly, it is possible that concurrent use with glucocorticoids, cyclosporine, or other systemic immunosuppressive agents could increase risks from immunosuppression.
Storage/Stability
- Store at controlled room temperature between 68°F and 77°F. Excursions are permitted between 59F° and 104°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-345.
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Maropitant Summary
Brand Name: Cerenia
Manufacturer: Zoetis Animal Health
Source: https://www.zoetisus.com/products/dogs/cerenia.aspx
Available Dosage Forms
- Oral scored tablets: 16 mg, 24 mg, 60 mg, 160 mg
- Injectable solution: 10 mg/mL
Dosage by Species
- Dogs (acute vomiting): 2 mg/kg orally or 1 mg/kg by subcutaneous or intravenous injection every 24 hours.
- Dogs (motion sickness): 8 mg/kg orally every 24 hours for a total of two doses. Dogs must be fasted 1 hour before administration; administration must occur 2 hours before travel (owner must remove access to food 3 hours before travel).
- Cats: 1 mg/kg by subcutaneous or intravenous injection every 24 hours.
Pharmacokinetic Parameters
| Parameter | Dogs | Cats |
| T ½ (hr) | 4 (2 mg/kg dose) 5.5 (8 mg/kg dose) |
9 (subcutaneous) |
| Vd (L/kg) | 0.25 | 0.25 |
| Protein binding (%) | 99.5 | 99.5 |
Contraindications/Warnings
- Do not use in puppies younger than 16 weeks of age because of a higher risk of myelosuppression.
- Use with caution in animals with cardiovascular disease; maropitant can prolong the QT interval.
- Use with caution in animals with compromised hepatic function.
- Keep potential toxins away from pets treated with maropitant. It is not possible to induce vomiting in animals receiving maropitant.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| Drugs that induce hepatic microsomal enzymes (phenobarbital, rifampin) | May lower blood levels of maropitant |
| Drugs that inhibit hepatic microsomal enzymes (azole antifungal agents, macrolides, metronidazole, omeprazole) | May increase blood levels of maropitant |
| Highly protein-bound drugs (carprofen, cefovecin, doxycycline, furosemide, ketoconazole) | May displace or be displaced by maropitant |
Storage/Stability
- Store tablets at controlled room temperature (68°F–77°F). Excursions are permitted between 59°F and 86°F.
- Store injectable solution at controlled room temperature (68°F–77°F). Excursions are permitted between 59°F and 86°F. After first vial puncture, store solution at refrigerated temperature (36°F–46°F). Use within 90 days of first vial puncture; stopper may be punctured a maximum of 25 times.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-262 (tablets), #141-263 (injection).
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Cisapride Summary
Compounded Formulations
- Cisapride Compounded Oral Suspension, Veterinary, USP (10 mg/mL)
- Cisapride Compounded Injection, Veterinary, USP (3 mg/mL)
Dosage by Species
- Dogs: 0.5–1 mg/kg orally or by intravenous injection every 8 hours.
- Cats: 2.5–7.5 mg (not weight-based) orally every 8–12 hours; 1 mg/kg by intravenous injection every 8–12 hours.
- Horses: 0.1–0.4 mg/kg by intravenous injection every 8–12 hours.17
- Mice, Rats, Gerbils, Hamsters, Guinea Pigs, Chinchillas, Rabbits: 0.1–0.5 mg/kg orally every 12 hours.18
Pharmacokinetic Parameters
| Parameter | Dogs | Cats | Horses |
| T ½ (hr) | 8–10 | 8–10 | 8–10 |
| Vd (L/kg) | NR* (180 in humans) | NR | NR |
| Protein binding (%) | 97.5 | 97.5 | 97.5 |
*NR = Not reported.
Contraindications/Warnings
- Contraindicated in animals with gastrointestinal obstruction, hemorrhage, or perforation.
Pregnancy Category
- Category C.
Drug Interactions
| Drug(s) | Interaction |
| CYP3A4 inducers | Decreased blood levels of cisapride |
| CYP3A4 inhibitors | Potential elevation of cisapride blood levels; this has not been observed or studied in animals |
| Highly protein-bound drugs | Cisapride may displace or be displaced by other highly protein-bound drugs |
Storage/Stability
- Store compounded oral suspension and injection in the refrigerator (36°F–46°F).
- Shake oral suspension well before administering.
Regulatory Considerations
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Potassium Bromide Summary
Compounded Formulations
- Potassium Bromide Compounded Oral Solution, Veterinary, USP (250mg/mL)
Dosage by Species
- Dogs (loading dose): 400–600 mg/kg orally, administered as several daily doses over 1–5 days. Administer with food.
- Dogs (maintenance dose): 30–35 mg/kg orally every 24 hours or divided into 2 equal doses. Administer with food.
Pharmacokinetic Parameters
| Parameter | Dogs | Cats |
| T ½ | 16–46 days | 10 days |
| Vd (L/kg) | 0.2–0.4 | NR* |
| Protein binding (%) | low | low |
*NR = Not reported.
Contraindications/Warnings
- Bromide toxicity (bromism) may occur at blood levels exceeding 2.5 mg/mL.
- Do not administer solution with evidence of precipitation (bromide crystals) to avoid bromide toxicity.
- Hyperkalemia is possible during the initial loading period. Foods and supplements that contain potassium—as well as potassium-sparing diuretics—should be avoided.
- Bromides usually are administered as oral liquids. Solid dosage forms—especially large gelatin capsules—could lodge in the esophagus and cause erosion.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| Benzodiazepines Opioids |
Increased risk of sedation and respiratory depression |
| Chloride (fluctuations in chloride intake) | Too much chloride decreases bromide blood levels and risks breakthrough seizures; too little risks increased bromide blood levels and toxicity |
| Diuretics | May lower bromide blood levels via increased excretion |
| Drugs that lower seizure threshold (methylxanthines, phenothiazines, xylazine) | May cause breakthrough seizures |
| Potassium-sparing diuretics | May risk hyperkalemia |
Storage/Stability
- Store potassium bromide in a moisture-resistant container at room temperature (59°F–86°F) or in the refrigerator (36°F–46°F).
Regulatory Considerations
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Pimobendan Summary
Brand Name: Vetmedin
Manufacturer: Boehringer Ingelheim
Source: http://www.vetmedin.com/safety_and_dosing/dosage.aspx
Available Dosage Forms
- Oral beef-flavored scored tablets: 1.25 mg, 2.5 mg, 5 mg, 10 mg
Dosage by Species
- Dogs: 0.25 mg/kg orally every 12 hours (labeled dose); 0.3 mg/kg orally every 8 hours (ACVIM).
- Cats: 0.25 mg/kg orally every 12 hours; typical dose per cat is 1.25 mg.
Pharmacokinetic Parameters
| Parameter | Dogs | Cats |
| T ½ (hr) | 0.5–2 | 1.3 |
| Vd (L/kg) | 2.6 | 8.2 |
| Protein binding (%) | >90 | NR* |
| *NR = Not reported. | ||
Contraindications/Warnings
- For use in dogs diagnosed with congestive heart failure only. Laboratory studies in normal dogs showed cardiovascular pathology when pimobendan was administered at higher doses.
- Do not administer to animals with hypertrophic cardiomyopathy, aortic stenosis, or any other clinical condition in which an augmentation of cardiac output is inappropriate for functional or anatomical reasons.
- Safe use of pimobendan has not been evaluated in dogs younger than 6 months of age or dogs with diabetes or other serious metabolic disease.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| Highly protein-bound drugs | Pimobendan may displace or be displaced by other highly protein-bound drugs |
| Other phosphodiesterase inhibitors (pentoxifylline, sildenafil, theophylline) | May potentiate effect or compete with pimobendan |
| Proton pump inhibitors (esomeprazole, omeprazole, pantoprazole) | Pimobendan requires an acidic environment for absorption; increasing gastric pH may reduce oral bioavailability of pimobendan |
Storage/Stability
- Store at room temperature (68°F–77°F). Excursions are permitted between 59°F and 86°F.
Regulatory Considerations
- New Animal Drug Application (NADA) #141-273.
- ARCI (Association of Racing Commissioners International) has not classified this drug.
Clenbuterol Summary
Brand Name: Ventipulmin
Manufacturer: Boehringer Ingelheim
Source: https://www.valleyvet.com/ct_detail.html?pgguid=2e87bed2-7b6a-11d5-a192-00b0d0204ae5
Available Dosage Forms
- Oral solution: 72.5 µg/mL
Dosage by Species
- Horses (airway obstruction): 0.8 µg/kg orally every 12 hours.
- Horses (pregnant mares with dystocia): 10 mL orally as a single dose.
Pharmacokinetic Parameters
| Parameter | Horses |
| T ½ (hr) | 10–13 |
| Vd (L/kg) | 1.6 |
| Protein binding (%) | 97 |
Contraindications/Warnings
- Use in food-producing animals is prohibited.
- Use with caution in horses with cardiac disease because of risk of tachycardia.
Pregnancy Category
- Safe use in breeding or lactating animals has not been determined.
Drug Interactions
| Drug(s) | Interaction |
| β-blockers (atenolol, metoprolol, propranolol) | Antagonize effects of clenbuterol |
| Digoxin | Increases risk of arrhythmias |
| Highly protein-bound drugs | Clenbuterol may displace or be displaced by other highly protein-bound drugs |
| Other bronchodilators (albuterol, terbutaline) | May increase adverse effects associated with clenbuterol |
Storage/Stability
- Store at or below 77°F. Avoid freezing.
Regulatory Considerations
- New Animal Drug Application (NADA) #140-973.
- ARCI (Association of Racing Commissioners International) has classified clenbuterol as a Class 3 substance.