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Continuing Education: Common Medications Used in Veterinary Practice
Continuing Education
Common Medications Used in Veterinary Practice
Authors
Karen L. Kier, PhD, MSc, R.Ph., BCPS, BCACP, CTTS, Professor of Pharmacy Practice, Director of Drug and Health Information Center, Raabe College of Pharmacy, Ohio Northern University; and Travis Pees, DVM Owner/Veterinary Practice, Ada Animal Hospital, Ada, OH
Dr. Karen Kier and Dr. Travis Pees have no relevant financial relationships to disclose.
Goal
The goal of this lesson is to provide information on the most common human medications used in small animal veterinary practice and resources for pharmacists.
Objectives
At the completion of this activity, the participant will be able to: 1. Select the indication(s), pharmacologic action(s), clinical applications, dosing regimens, and mode of administration for each drug; 2. List the most relevant adverse effects, warnings, precautions, contraindications, and significant drug interactions reported with these medications; 3. List important counseling information to convey to pet owners who will be administering these medications; and 4. Identify resources for veterinary medications.
Background
In the 1800s, Robert Virchow identified the correlation between human and veterinary medicine. He noted in a publication that “between animal and human medicine there is no dividing line, nor should there be.”
In an effort to show the inter-dependence of humans, animals, and the environment, the movement, “One World, One Medicine, One Health,” was initiated with support from the American Veterinary Medical Association and the American Medical Association. It recognizes the global and public health impact of humans and animals. This impact goes beyond concerns of antibiotic resistance and ventures into diseases transmitted from animals to humans throughout the world. Many medications routinely prescribed for humans can be effectively used in veterinary practice, and pharmacists can legally dispense them pursuant to a prescription from a licensed veterinarian. Pharmacists also compound many medications for veterinary use. In 2015, FDA estimated that over 75,000 pharmacies in the U.S. compound
Table 1 Selected veterinary medication references
Merck Veterinary Manual: http://www.merck vetmanual.com/
Plumb’s Veterinary Drug Handbook 8th edition (2015). Wiley. Veterinary Pharmacology & Therapeutics (2017). Wiley. Veterinary Product Database: https://www. drugs.com/vet/ FDA Center for Veterinary Medicine: https:// www.fda.gov/AboutFDA/ CentersOffices/OfficeofFoods/CVM/default.htm
One Health Initiative will unite human and veterinary medicine: http://onehealthinitiative. com/
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approximately 6.3 million veterinary prescriptions per year. Common veterinary resources include Plumb’s Veterinary Drug Handbook and Veterinary Pharmacology and Therapeutics. In 2015, FDA withdrew its 2003 Compliance Policy Guide 608.400 titled, “Compounding of Drugs for Use in Animals” and replaced it with Guidance for Industry No. 230 “Compounding Animal Drugs from Bulk Drug Substances.” This document provides direction to pharmacies on compounding for veterinary practice, but does not provide clinical information. Pharmacists who dispense veterinary compounds should periodically refer to FDA’s Center for Veterinary Medicine (CVM) website for updates at https://www.fda.gov/ AboutFDA/CentersOffices/OfficeofFoods/ CVM/ default.htm. FDA’s CVM approves drugs for animal use and does not regulate veterinarians or offlabel use of human medications for animal use.
This lesson will provide information on human medications that are commonly used in small animal veterinary practice. Dosages, with monitoring information when appropriate, will primarily be listed for cats and dogs. Brand names are listed for identification; other brands and generics may be available.
Treatment of Diabetes and Other Endocrine Disorders
Acarbose (Precose®) can be used in both cats and dogs as an adjuvant to diet therapy for controlling blood glucose. This drug is not used as monotherapy to treat diabetes mellitus in cats or dogs because the glucose lowering effect is mild. Acarbose has minimal systemic absorption in humans (~2 percent) and in dogs (~4 percent). The mechanism of action of acarbose for humans and animals is the same. It inhibits pancreatic alphaamylase and alpha-glucosidases in the small intestine. Due to the local effect in the gastrointestinal (GI) tract, the major side effects for both cats and dogs are diarrhea, loose stools, and flatulence. It is recommended to administer this medication with feeding times and not on an empty stomach. Acarbose can reduce the absorption of digoxin in animals, and should not be used in animals on digoxin. The initial dose for acarbose in dogs is 12.5–25 mg orally with each meal. After two weeks, the dose may be increased to 50 mg, and up to 100 mg in dogs weighing over 25 kg. Cats can receive 12.5 mg twice daily with meals. Tablets may be split or crushed and put in food immediately prior to feeding. If diarrhea is severe, the owner needs to contact the veterinarian.
Blood glucose can drop when used in combination with other agents such as insulin. Owners can be counseled on signs of low blood sugar such as seizures, back leg weakness, muscle twitching, or fatigue. Glimepiride (Amaryl®) is an oral sulfonylurea used to manage non-insulin dependent diabetes mellitus (NIDDM) in cats. The dose is 1–2 mg per day given once daily. Glipizide (Glucotrol®) is an oral sulfonylurea used to manage non-insulin dependent diabetes mellitus (NIDDM) in cats. The dose is 2.5–5 mg given twice per day. Owners should be counseled that full effect may take four to eight weeks. The most common side effects are GI-related. Liver enzymes during therapy should be monitored for cats.
Glyburide (Diabeta®, Micronase®) is an oral sulfonylurea used to manage non-insulin dependent diabetes mellitus (NIDDM) in cats. The initial dose is 0.625 mg once daily. Weight, urine glucose, and blood glucose should be monitored during therapy. Liver enzymes and complete blood counts should be performed periodically during therapy. Liothyronine sodium (Cytomel®) is a second-line alternative to levothyroxine for thyroid disorders. Levothyroxine is availale
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as a veterinary product. Liothyronine is a shorter duration T3 that can be used if the animal does not respond to levothyroxine. Thyroid hormone blood levels should guide treatment. The dose for both cats and dogs is similar at 4–4.4 mcg given two to three times per day.
Metformin hydrochloride
(Glucophage®) is a biguanide anti-diabetic agent that has been investigated for insulin resistance, but data are limited. Metformin has been reported to be toxic for some animals, including cats. Therefore, other alternatives for animals should be tried first.
Treatment of Cardiovascular Conditions
Amiodarone HCl (Cordarone®) is used to treat and control arrhythmias. It is reserved for treating animals when other agents have failed, primarily due to limited clinical data and the side effect profile. The most common side effects in animals are GI and liver related. Amiodarone has numerous drug interactions, as noted in humans. So far this drug has been studied in dogs, cats, and horses. Amiodarone has a long half-life in animals as well as humans.
The dose in cats and dogs is 5–10 mg/ kg orally every 12 hours. Owners need to be counseled on proper administration and the need for followup appointments with the veterinarian. For more accurate dosing, the pharmacist may need to compound an oral suspension from the tablets.
Amlodipine (Norvasc®) is a calcium channel blocker used to treat hypertension in both humans and animals. Amlodipine appears to be more effective in managing hypertension in cats than in dogs. It can be used in dogs with kidney disease, but other agents may be preferred. Amlodipine is considered a drug of first choice in managing hypertension in cats, and it can prevent serious long-term consequences if started early in the disease process. Side effects are minimal, but can include lethargy, increased heart rate and weight loss in cats. Dogs have been reported to develop gingival hyperplasia, which has also been reported in humans. In cats, amlodipine can be dosed 0.625–1.25 mg orally once daily. In dogs, the dose is 0.1–0.5 mg/kg once daily given orally. Again, an oral suspension can be compounded to more accurately dose both cats and dogs. Diltiazem hydrochloride is a calcium channel blocker that is used to treat hypertension and arrhythmias such as atrial fibrillation. Diltiazem has a negative inotropic effect in both humans and animals, and can result in an exacerbation of congestive heart failure (CHF). The drug should be used in caution in older animals, as well as those who have pre-existing CHF. Blood pressure and heart rate should be monitored while on therapy. The dose in dogs is 1–2 mg/kg three times per day. The daily dose for cats is 7.5 mg divided into two to three doses per day. Verapamil hydrochloride is a calcium channel blocker similar in efficacy to diltiazem for small animals. It has been used in both cats and dogs for supraventricular arrhythmias. The side effect profile is similar to diltiazem. The dose for dogs is 1–5 mg/kg three times daily. Cats can receive 0.5–1 mg/kg every eight hours. Atenolol (Tenormin®) is a selective betablocker that can be used to treat hypertension and tachyarrhythmias. Due to the selectivity of atenolol, it can often be used in small animals who have cardiovascular conditions com-bined with asthma. This concept is similar in humans as well. Atenolol has a negative inotropic effect in animals and can exacerbate CHF in both cats and dogs. Atenolol should be used with caution in animals with renal dysfunction and/or brittle diabetes mellitus. Counseling owners on the importance of adherence is critical. Also, owners should be counseled not to abruptly stop atenolol because animals, like humans,
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can have rebound hypertension if doses are missed or the drug is discontinued. If the animal develops side effects such as cough, lethargy, or shortness of breath, the veterinarian should be notified. The usual dose for dogs is 0.25–1 mg/kg orally every 12 hours. The dose for cats is 6.25–12.5 mg daily, divided into two doses. Carvedilol (Coreg®) is a nonselective betablocker with alpha-1 adrenergic blocking activity. As with humans, this drug has been used to treat CHF. The data for carvedilol are not as extensive as other betablockers in CHF. Dosing has been provided for dogs, but not cats. The dose is titrated up to reach the desired effect. The dose in dogs is 0.2–0.8 mg/kg twice daily with food.
Metoprolol tartrate and Metoprolol
succinate (Lopressor®, Toprol XL®) are selective betablockers that can be used like atenolol in both cats and dogs, especially those with a history of respiratory disorders. Animals with arrhythmias often require higher doses than those with CHF. As with the other betablockers, metoprolol should be titrated from a lower dose upward for control of symptoms. Propranolol hydrochloride (Inderal®) is a nonselective betablocker used as an antiarrhythmic medication for both cats and dogs. Doses vary on the condition and usually will be titrated upward to achieve therapeutic effect. Owners should be counseled to notify the veterinarian if any respiratory side effects occur. Sotalol hydrochloride (Betapace®) is a nonselective betablocker used to manage arrhythmias in both cats and dogs. The dose needs to be titrated to the desired effect. Doses vary from 1 mg/kg up to daily doses of 80 mg depending on the animal and the condition. Adherence is an important aspect of treatment for owners to understand.
Benazepril hydrochloride (Lotensin®) is an angiotensin converting-enzyme (ACE) inhibitor that is indicated for treating hypertension and CHF in both dogs and cats. It can offer some renoprotective effects in some disease states as well. The side effect profile can include hypotension, renal dysfunction, and increases in serum potassium. Dogs and cats are given similar doses at 0.25–1 mg/kg once daily. Owners should be counseled on the need to be adherent to the medication schedule and to not stop the medication abruptly. Captopril is another ACE inhibitor that has been used in small animals. However, due to the short half-life and the side effect profile, it has been largely replaced by other ACE inhibitor medications such as benazepril and enalapril. Table 2 lists resources for obtaining animal formulations for various medications including captopril suspension. Some require subscription or membership to access.
Enalapril maleate (Vasotec®) is an ACE inhibitor used for the management of hypertension and CHF. In addition, it has a reno-protective effect for some disease states in animals. This medication should be avoided in both pregnancy and lactation. A basic metabolic panel should be monitored with long-term therapy. There are several veterinary products available for enalapril. The dose for dogs is 0.25–1 mg/kg every 12 to 24 hours. Cats can receive 1.25–2.5 mg once daily. Lisinopril (Prinivil®, Zestril®) is an ACE inhibitor, similar to the other ACEs, used to manage hypertension and heart failure. Oral suspension formulations are available. The dose for cats and dogs is 0.25–5 mg/kg once daily. Ramipril (Altace®) is an additional ACE inhibitor used to manage hypertension and heart failure. Dosing is started at 0.125 mg daily and titrated up until therapeutic outcome is reached or side effects are limiting. Irbesartan (Avapro®) is an angiotensinII receptor blocker (ARB) that has been
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investigated to treat dogs with hypertension secondary to renal dysfunction. ARBs would be an alternative for dogs who have failed ACE inhibitor therapy. Irbesartan is dosed at 5 mg/kg every 12 to 24 hours. Blood pressure, heart rate, and electrolytes should be monitored in the canine during therapy. Clopidogrel bisulfate (Plavix®) is indicated as an anti-platelet agent to reduce thrombosis in animals as well as humans. Compounding formulations for the suspension are available. As with humans, this drug can increase the risk of bleeding as well as cause GI irritation, so counseling the owner to administer with food is important. Clopidogrel interacts with some proton pump inhibitors and can decrease antiplatelet activity. The dose is similar for cats and dogs at 1–3 mg/kg daily with a dosage reduction to 0.5–1 mg/kg if combined with aspirin for dual antiplatelet therapy. Warfain sodium (Coumadin®) can be used as an anticoagulant for preventing thrombosis in small animals. As with humans, warfarin therapy takes a strong commitment to adherence and monitoring parameters. The drug-drug interactions are the same as humans, as well as the control of vitamin K intake in foods and supplements. Dosing is individualized. Digoxin (Lanoxin®) is a cardiac glycoside used for managing CHF and arrhythmias such as atrial fibrillation and atrial flutter. Digoxin has a narrow therapeutic index in both animals and humans requiring monitoring of blood levels, as well as symptoms of toxicity. Humans and animals display similar signs of toxicity. Animals may have a loss of appetite, vomiting, diarrhea, and behavioral changes if blood levels get too high. The dose for dogs is 0.005–0.0075 mg/kg every 12 hours, while cats are dosed every other day with 0.007 mg/kg. Hydralazine (Apresoline®) is a potent vasodilator used to treat hypertension and CHF. It is used in the animal model for afterload reduction in CHF. This agent would be considered for management in animals who have failed other medications or could benefit from adding an additional drug to improve control. In both dogs and cats, hydralazine requires close monitoring. This drug can cause sodium and water retention, and owners need to watch for weight gain and swelling. Diuretics can be used in combination. The dose is titrated upwards to achieve improvement in CHF. Hydrocholorthiazide is a thiazide diuretic that can be used in animals to treat hypertension, diabetes insipidus, calcium oxalate stones, and heart failure. Electrolytes and uric acid should be monitored in these animals while on therapy. In cats, 1–2 mg/kg every 12 hours can be used for heart failure, while doses of 1–6 mg/kg every 12 hours can be used for dogs. Medication adherence and laboratory monitoring are essential components of counseling. Spironolactone (Aldactone®) is a potassium-sparing diuretic that can be used as an additional agent in refractory CHF. The side effects are similar in animals as humans, such as increases in serum potassium. As in humans, this drug has been used to treat ascites in small animals. Doses will vary with the animal, the condition, and the response to therapy. Prazosin hydrochloride (Minipress®) is an alpha-1 adrenergic blocker that can be used for managing CHF, pulmonary hypertension, and hypertension in dogs. The dose is based on weight and varies with condition. The medication should be given with food when possible.
Treatment of CNS and Behavioral Issues
Acetaminophen (Tylenol® and generics) can be used for mild pain management in dogs, rabbits, hamsters, Guinea pigs, and mice. It is contraindicated in, and toxic to,
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cats and potentially ferrets. It has a narrow therapeutic window for dogs who do not metabolize it as well as humans, and it should be dosed carefully with specific counseling for owners to not exceed daily recommendations. Acetaminophen is not recommended for dogs who are pregnant or nursing. For short-term analgesia, acetaminophen in dogs can be dosed 10–15 mg/kg every 12 hours for five days. Long-term management can start at 5 mg/ kg per day, but should not exceed 20 mg/ kg per day. Dogs can suffer hepatotoxicity like humans when too much acetaminophen and its metabolites accumulate in the body. Acetaminophen is contraindicated for dogs taking other medications reported to alter liver function. Overdosage or acute toxicity can be treated similar to humans with acetylcysteine. Acetaminophen can be combined with narcotic analgesics or tramadol if pain is not controlled with the single entity product. Acetaminophen can be given as a suspension, solution, or chewable tablet. For small animals like rabbits, acetaminophen can be added to their drinking water. With chronic therapy, owners should be aware that liver, renal, and hematologic monitoring by the veterinarian might be necessary. Owners should be counseled on proper dosing so not to exceed limits, as well as on follow-up appointments for laboratory monitoring. Amantadine (Symmetrel®) has been investigated for treatment of chronic pain in both dogs and cats. It is used as adjuvant therapy to nonsteroidal anti-inflammatory drugs (NSAIDs). The mechanism for treating pain is not related to its antiviral properties, but rather for its NmethylD-aspartate receptor (NMDA) antagonist actions. Amantadine has a very narrow therapeutic window in animals. Owners should be counseled on proper dosing administration. In both cats and dogs, 3–5 mg/kg orally once daily can been added to NSAID therapy. The medication should be given with food to decrease the GI side effects. It is not recommended for animals that are pregnant. Amantadine is available as tablets and as an oral syrup. It might be best to compound the tablets into a liquid or add a flavoring to the oral syrup to mask the bad taste.
Fentanyl Transdermal (Duragesic®) is a CII controlled substance, available as a patch, used to control post-operative pain in dogs, cats, rabbits, horses, pigs, sheep, and goats. In addition, it can be used to manage severe chronic pain. The dose/patch size is based on the weight of the animal. There are specific recommendations for patch placement for each species of animals. Owner counseling is essential for the application, removal, and proper disposal of the patch. Alprazolam (Xanax®) is a benzodiazepine used in both cats and dogs to help control behavioral issues. Alprazolam can cause physical dependence in animals. Adverse effects can include sedation, increased appetite, and ataxia (staggering). In addition, it can cause idiosyncratic drug reactions of aggressiveness or CNS excitement. Benzodiazepines have been shown to interfere with learning and may alter the animal’s ability to be trained. Alprazolam may cause impairment in working animals, and this should be considered prior to administering. As in humans, alprazolam can accumulate in elderly dogs and cats as well as those with liver or kidney dysfunction. Alprazolam is commercially available as a solution, tablets, or oral disintegrating tablets. When dosing on an as needed basis, counsel owners to give the medication approximately one hour before a known stimula-tor event such as storms, traveling, or office visits. For dogs, doses can range from 0.01–0.4 mg/kg every four hours as needed, not to exceed 2–4 mg per day depending on the dog’s age and condition. For cats, doses range from 0.05–0.25 mg/ kg every eight to 12 hours as needed.
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Amitriptyline (Elavil®) is a tricyclic antidepressant (TCA) used in animals for behavioral condi-tions such as generalized anxiety and separation anxiety in dogs; and anxiety and excess grooming in cats. Other treatments have been investigated including as an adjuvant for neuropathic pain, as well as treatment of itching. The side effect profile is similar to humans with both sedating and anticholinergic properties including constipation and urinary retention. This agent is not recommended in pregnant animals. This drug classification can have a significant toxicity profile in overdose situations resulting in life-threatening arrhythmias. Accurate dosing is essential, as well as keeping the medication away from pets and children. It is important to dispense this medication in a child-protective container. The dosing for dogs ranges from 0.25–2 mg/kg orally every 12 to 24 hours, and for cats the dose range is 0.5–1 mg/kg orally every 12 hours. Doxepin hydrochloride (Sinequan®) is a tricyclic antidepressant used for psychogenic dermatoses in small animals with anxiety. Owners should be counseled that it may take several weeks of therapy before seeing improvement in behavior. Doxepin has anticholinergic effects similar to amitriptyline and can have a significant overdose profile. The dose in dogs is 3–5 mg/kg every 12 hours. The dose for cats is 0.5–1 mg/kg every 12 to 24 hours. Imipramine (Tofranil®) is a TCA that can be used to treat cataplexy and urinary incontinence in cats and dogs. Doses of 5–15 mg daily divided into two doses can be used in dogs. The dose for cats is 2.5–5 mg daily divided into two doses. Imipramine has similar warnings as the other TCA agents. Fluoxetine (Prozac®) is a selective serotonin reuptake inhibitor (SSRI) that is available in veterinary formulations to treat behavioral problems such as separation anxiety, conflict-related aggression, urine marking, generalized anxiety disorders, and noise aversion. It may take several days to weeks to see improvement in symptoms. When the desired effect is achieved, the drug can be slowly tapered, or long-term therapy prescribed. Dosing strategies vary widely depending on the species, as well as the condition being treated. Side effects can include behavioral changes, anorexia, and GI distress. Fluoxetine should be used cautiously in animals with pre-existing seizures or diabetes.
Fluvoxamine maleate (Luvox®) is an SSRI that is used to manage behavioral issues in both cats and dogs. As with other TCA and SSRI medications, it can take several weeks to months to see improvement. The side effect profile is similar to the other SSRI medications. It is recommended that this product not be used in pregnant animals due to concerns for teratogenicity. Efficacy is enhanced when a behavior modification program is combined with drug therapy. Paroxetine hydrochloride (Paxil®) is another SSRI alternative that can be used for behavioral issues in both cats and dogs. The dose for cats and dogs is 0.5–1 mg/ kg daily. Animals should be monitored for changes in behavior, as well as for changes in sleep patterns. Animals should be weighed at each visit to determine if the animal’s appetite is altered. Sertraline hydrochloride (Zoloft®) is another SSRI alternative for treating behavioral disorders with a similar side effect profile. The dose for dogs is 0.25–4 mg/kg once daily. Cats can be treated at 0.25–1.5 mg/kg daily. Baclofen (Lioresal®) is a GABA derivative muscle relaxant indicated to treat urinary retention in dogs. This drug is not used in cats. Owners need to be counseled on the CNS depressant effects of this medication, and not to mix it with any other medications that have similar effects. Counseling on proper dosing and consequences of overdosing the animal is
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also important. Suspension formulations are available to help owners administer the proper dose. Side effects for dogs can include sedation, weakness, GI irritation, salivation, and itching. It is important to not stop this medication abruptly, and to call the veterinarian with any concerns, especially unwanted side effects. Dogs should be monitored for liver function and blood glucose. Buspirone hydrochloride (BuSpar®) is an anxiolytic used to treat behavioral issues, especially fears and phobias. Buspirone can be used to treat fears related to thunderstorms, but often at higher doses. Therapy can take up to one week to affect behavioral change and should not be used to manage acute episodes. Side effects can include an increase in aggression, as well as other CNS changes. Sedation is usually less with buspirone than with other anxiolytics. Cardiovascular changes are another potential side effect. Dogs can be given 2.5–15 mg per day in two to three divided doses. Cats can be given 2.5–5 mg per day in two to three divided doses.
Ketorolac tromethamine (Toradol®) is a nonsteroidal anti-inflammatory (NSAID) used for short-term pain relief. It is a potent NSAID that inhibits both COX-I and COX-2 receptors. Ketorolac needs to be given with food to decrease the GI distress. It has an increased risk of GI bleeding and owners should be counseled on signs and symptoms including blood in the stool or black feces. The dose for dogs is 0.3 mg/kg given twice daily. In cats, ketorolac is dosed 0.25 mg/kg every eight to 12 hours. Carbamazepine (Tegretol®) has been used to treat seizures, behavioral disorders, and neuropathic pain. Carbamazepine is considered a thirdline agent especially for seizures in small animals. Absorption can be incomplete making it hard to control symptoms. The sus pension formulation offers better absorption and is recommended. Clonazepam (Klonopin®) is a benzodiazepine indicated for anxiety and seizures in both cats and dogs. Cats are at an increased risk of liver damage, so owners should be counseled to call the veterinarian immediately if they note loss of appetite, weight loss, vomiting, or yellowing of the whites of the eyes. Dogs may develop a tolerance with long-term use and lose therapeutic benefit. If owners see this in their animal, they should contact the veterinarian. Side effects include sedation and ataxia. Adherence to the medication should be stressed to owners. Dosage for dogs is 1–2 mg/kg every 12 hours, while the dose for cats is 0.05–0.2 mg/kg every 12 hours. Diazepam (Valium®) is a benzodiazepine used to manage anxiety, muscle spasms, and seizures. It has also been used as a hypnotic and a means to stimulate appetite in animals. Cats need to be monitored for liver damage, while dogs are prone to developing tolerance to diazepam’s effects. This drug can cause a change in behavior and should be monitored closely. Since absorption can be variable in animals, it can be difficult to predict outcomes. Daily dosage in dogs is 2–10 mg divided into three doses. The dose in cats is 0.2–0.4 mg/kg every 12 to 24 hours. Lorazepam (Ativan®) is a benzodiazepine
Table 2 Selected compounding resources for pharmacists
PCCA: www.pccarx.com Medisca: www.medisca.com
Letco Medical: www.letcomedical.com
Humco Compounding: www.humco. com P&C Pharma: pandcpharma.com Spectrum Pharmacy Products: www.spectrumrx.com American Veterinary Medical As-sociation: https://www.avma.org/KB/Resources/ Reference/Pages/Com-pounding.aspx
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that can be used as an alternative to diazepam for acute treatment of seizures. It is also used to manage behavioral disorders in both cats and dogs. One of the advantages of lorazepam is that it is not metabolized in the liver and may provide a safer alternative in animals with liver dysfunction. The dose for cats is 0.03–0.08 mg/kg given orally every 12 hours. The dose for dogs is 0.02–0.1 mg/kg every eight to 24 hours.
Gabapentin (Neurontin®) has been investigated as an anticonvulsant and for treatment of pain in both cats and dogs. Commercially available solutions contain xylitol which can be toxic to dogs. Therefore, pharmacists should compound an oral suspension from commercially available tablets. A formulation is available without xylitol. Doses vary widely between treatment for seizures and pain management. Side effects of ataxia or excessive sedation should be reported to the veterinarian.
Pregabalin (Lyrica®) has been investigated for seizures and neuropathic pain in small animals. Studies are limited. Doses of 3–4 mg/kg twice daily have been tried in dogs for seizures, while 1–2 mg/kg every 12 hours has been tried in cats.
Levetiracetam (Keppra®) is an anticonvulsant that can be added to other seizure therapy in both dogs and cats. It is commonly used in combination, but has been tried as monotherapy when animals have failed other drugs or had intolerable side effects. Side effects include sedation and loss of appetite. The dose for dogs and cats is 20 mg/kg every eight hours. Therapeutic blood levels, complete blood counts and basic metabolic panels should be monitored.
Topiramate (Topamax®) has been investigated in small animals to help control seizure activity. Dosing in dogs has been tried at 2–10 mg/kg every 12 hours. The dose in cats has been 12.5–25 mg divided into two to three doses per day. Owners should be counseled on the need for adherence in animals with seizures, and to report lack of seizure control or anything unusual to the veterinary clinic. Chlorpromazine (Thorazine®) is a phenothiazine used as an antiemetic and a sedative. Chlorpromazine has also been used successfully in managing motion sickness in cats. Interestingly, some breeds of dogs with the MDR1 (multi-drug resistance) mutation have an increased sensitivity to pain medications, antibiotics, loperamide, and ivermectin. Dogs at risk, such as collies and Australian shepherds, can exhibit excess sedation with chlorpromazine. At higher doses, cats can experience extrapyramidal side effects such as tremors, shivers, rigidity, and loss of the righting reflex. Owners should be counseled on these side effects. Doses in dogs are 4–8 mg per day in two divided doses, while cats can receive 2 mg per day in two divided doses.
Methylphenidate (Ritalin®) is an amphetamine-related stimulant that can be used to treat cataplexy/narcolepsy or hyperactivity in dogs. Adverse events can include over-stimulation or the development of aggressive behaviors. As in humans, this drug can cause a decrease in appetite and weight. Dogs should be monitored for changes in appetite and weight loss. Doses can vary, but 5–10 mg per day is sufficient for small to medium dogs. Large dogs may require up to 20–40 mg per day. Tramadol hydrochloride (Ultram®) has been investigated for pain management in small animals including cats and dogs. It has similar drug interactions and side effects as seen in humans. Dosing in cats has been tried at 1–2 mg/kg every 12 hours. In dogs, the dose is 2–5 mg/kg given two to three times per day.
Compounding Resources for Pharmacists
There are a variety of companies that
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provide compounding training, products, services, equipment, devices, ingredients, and resources. Some require subscription or membership to access. They are included in Table 2.
The USP Compounding Compendium (http:// www.usp. org/products/usp-compoundingcompendium) offers compounding practitioners convenient access to all compounding-related General Chapters and monographs from the United States Pharmacopeia and the National Formulary (USP–NF). It also features more than 40 supporting general chapters and more than 170 compounding monographs along with USP–NF General Notices and Requirements. FDA’s Center for Veterinary Medicine (https://www.fda.gov/AboutFDA/ CentersOffices/OfficeofFoods/CVM/default. htm) protects human and animal health, regulat-ing the safety and effectiveness of animal drugs on the market. The International Academy of Compounding Pharmacists (IACP) is an association representing more than 4,000 pharmacists, technicians, students, and members of the compounding community who focus upon the specialty practice of pharmacy compounding. Compounding pharmacists work directly with prescribers including physicians, nurse practitioners and veterinarians to create customized medication solutions for patients and animals whose healthcare needs cannot be met by manufactured medications. For more information, visit www.iacprx.org.
Conclusion
In the U.S., many human medications are available for use in animals that do not have a veterinary product counterparts. Some drugs, like NSAIDs used for pain and arthritis, have veterinary alternatives that are more effective in animals than the human products. Establishing a good working relationship with local veterinarians can provide an opportunity for pharmacists to provide a valuable service to the community. Pharmacists can compound products to better provide accurate dosing, as well as dosage forms that are better tolerated for animals. Pharmacies have established themselves as a veterinary medication resource and market their services to the public. Pharmacists are in a unique position to counsel pet owners on medications used in their pets. The authors, the Ohio Pharmacists Foundation and the Ohio Pharmacists Association disclaim any liability to you or your patients resulting from reliance solely upon the information contained herein. Bibliography for additional reading and inquiry is available upon request. This lesson is a knowledge-based CPE activity and is targeted to pharmacists in all practice settings. Disclosure: The OPF trustees and other individuals responsible for planning OPF continuing pharmacy education activities have no relevant financial relationships to disclose. n
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Release date: 4-15-18 Expiration date: 4-15-21
CPE Hours: 1.5 (0.15 CEU)
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