The feline medicine cabinet: drug therapy for cats (Proceedings)

Cats handle drugs in a different fashion than dogs. While this is not a surprise, there are some drugs that every practitioner should be aware of that work really well for their feline patients. The focus of this discussion will be to highlight these drugs and their uses, showing why they deserve to be in the feline medicine cabinet. Case studies will be utilized.

Prednisolone

Prednisone is converted to prednisolone in the liver. Prednisolone is the active form of the drug. While the cat can make this conversion from prednisone to prednisolone, the conversion varies from cat to cat. Some cats do not convert enough prednisone to prednisolone to effectively treat the disease, appearing to be treatment failures. Using prednisolone skips this extra step and often the cats respond more reliably to prednisolone. Lower doses of prednisolone may also be effective for long-term control of disease (asthma, inflammatory bowel disease, etc.). Cats handle corticosteriods much better than our canine patients, with fewer reported side effects.

Dose: Varies widely depending on the disease being treated

     • Neoplasia (lymphoma): 10 mg per cat daily, often used in conjunction with other drugs

     • Immune-mediated diseases: 1-2 mg/kg q 12 hours to start, decreasing to lowest effective dose

     • Inflammatory disease: 1–2 mg/kg once daily, decreasing to lowest effective dose

Budesonide

Budesonide is a potent glucocorticoid (15 times more potent than prednisolone). Its "topical" anti-inflammatory effects are particularly useful in controlling inflammatory bowel disease in cats. The drug is absorbed systemically, but steroid side-effects are minimized by the high first-pass metabolism effect through the liver. The drug usually needs to be compounded for our feline patients.

Dose: 1 mg PO once daily

Piroxicam

This drug is a strong non-steroidal anti-inflammatory drug (NSAID) that can be used to control pain and swelling in a wide variety of diseases. It should never be combined with corticosteroids or other NSAIDs due to the risk of gastrointestinal ulceration. I will use this drug in cats to treat inflammation in the nose, lungs, and bladder. This drug also controls pain due to osteoarthritis and neoplasia in cats. It has also been used as adjunctive treatment of some cancers (transitional cell carcinoma, adenocarcinomas). This drug is not recommended for use in cats with kidney disease. Concurrent use of GI protectants is generally not needed. The long-term daily use of piroxicam is cats has been found to be well-tolerated.

Dose: 0.3 mg/kg PO q 24-48 hours with food

Tramadol

Tramadol is drug used for its analgesic effects. It is a centrally acting opiate agonist that is not a controlled substance. It can be used alone or in conjunction with other drugs (corticosteroids, NSAIDs). This drug can have some sedating effects, which can be minimized with lower doses. The drug is safe to use in cats with renal disease.

Dose: ⅛ to ¼ of a 50 mg tablet (6.25 – 12.5) PO q 12-24 hours; 4 mg/kg PO q 12-24 hours

Doxycycline

This antibiotic is useful for treating a wide variety of bacterial and other unusual infections in cats. I particularly like to use this drug in cats with nasal disease (to treat secondary infections), possible Mycoplasma infections, anemias of unknown etiology (erythrocytic mycoplasmal infections, Ehrlichia spp.), Chlamydia psittaci, polyarthritis, Mycobacteria, L-form bacterial infections. This drug also seems to have some anti-inflammatory effects. It is important to make sure the drug is given with food or water, as significant ulceration and stricture of the esophagus have been reported. Alternatively, the drug can be compounded into a liquid suspension.

Dose: 5 mg/kg PO q 12-24 hours with food

Calcitriol

Renal secondary hyperparathyroidism is a concern in our feline patients with chronic renal failure. Calcitriol production is decreased as renal tubular function decreases. Calcitriol supplementation effectively controls secondary hyperparathyroidism. There is also some clinical evidence that suggests these cats experience improved appetite, brighter attitude, and a more active, longer life span.

This drug should only be used in patients with a normal serum phosphorus level. Phosphate binders can be used concurrently with this drug. If calcium-based phosphate binders are used, serum calcium levels should be closely monitored. Aluminum-based phosphate binders might be a better choice for these patients.

Dose: 2.5-3.5 nanograms/kg orally every 24 hours; better to give at night on an empty stomach. Intermittent dosing is also a popular option, giving 3.5 times the daily dose every 3.5 days, given on an empty stomach.

Ursodiol (Actigall)

Ursodeoxycholic acid is a therapeutic bile acid used for stimulation of bile flow in cholestatic disease and immune modulation in inflammatory liver diseases. It is believed to have hepatoprotective effects. This drug is useful in cats with hepatic lipidosis or inflammatory liver diseases.

Dose: 10-15 mg/kg q 24 hours with food.

Benazepril (Lotensin)

Benazepril is an ACE-inhibitor that is recommended for use in patients with high blood pressure and proteinuria. Many of our renal failure patients would benefit from this drug. While some clinicians prescribe this drug in all their feline renal failure patients, I prefer to document blood pressure concerns and/or proteinuria first.

Dose: 0.25 – 0.5 mg/kg q 12 - 24 hours.

Amlodipine (Norvasc)

Amlodipine is a calcium-channel blocker that is used to treat high blood pressure in cats. Since most of the drug's vasodilating actions are peripheral, it is has minimal cardiac effects and is not used as a first line of therapy in cardiac disease.

Dose: 0.625 – 1.25 mg once daily, though cats with severe hypertension or large body size may require twice daily dosing.

Lantus - Insulin Glargine

This is the "insulin du Jour", but it is very effective at controlling diabetes mellitus in cats. Insulin Glargine is a long-lasting human insulin analog produced by recombinant DNA technology using a non-pathogenic strain of E coli. This insulin requires U-100 syringes. The bottle of insulin may remain potent for 2-6 months once opened.

Study results: Diabetic cats treated with Lantus had lower serum fructosamine levels and achieved diabetic remission earlier than cats treated with PZI or lente.

Dose: 0.25 – 0.5 U/kg q 12 - 24 hours. Adjust dose as needed. Dose may decrease after 2 weeks of starting therapy (or sooner) in new diabetic patients.Higher probability of diabetic remission using higher BID dosing.Low risk of clinical hypoglycemia. Glargine has a very long duration of action whether dosed once or twice daily.

Fluticasone inhaler (Flovent)

Fluticasone is a glucocorticoid that has potent anti-inflammatory effects. It is commonly used as an aerosol for the treatment of feline asthma patients. Though some drug is absorbed systemically, steroid side-effects are minimal.

Dose: Fluticasone 220mcg (1 puff) q 12 – 24 hours. Treatment can be combined with albuterol inhaler as needed for symptomatic relief and oral corticosteroids for more severe cases.

Cyproheptadine

This antihistamine has a unique side effect in our feline patients. It is commonly used as an appetite stimulant. I will often use this drug to "jump start" a pet's appetite as I definitively treat the pet's underlying disease which is contributing to the anorexia. The drug is also useful as an adjunct treatment in feline asthma, as it also possesses serotonin antagonistic properties, decreases smooth muscle contraction and may cause bronchodilation. Cyproheptadine is also the antidote for serotonin syndrome. A possible side effect of this drug is estrus-like behavior, which resolves with discontinuation of the drug.

Dose: 1-2 mg PO q 12 hours

Mirtazipine

This drug is a tetracyclic antidepressant which ultimately increases norepinephrine levels and antagonizes several serotonin (5HT) receptor subtypes. The antagonism of the 5HT3 receptors effectively decreases nausea and vomiting. The increased levels of norepinephrine tend to increase appetite. The result is a patient who feels better (less nausea and vomiting) and has an improved appetite. Side effects can include vocalization and sedation. If this drug is used with tramadol, there is an increased risk of serotonin syndrome. Do not use this drug with monoamine oxidase inhibitors (ex: selegiline) as this also increases the risk of serotonin syndrome.

Serotonin syndrome is a potentially life threatening multi-systemic disorder caused by over stimulation of serotonin receptors within the CNS and other systems. Clinical signs may include vomiting, diarrhea, seizures, hyperthermia, hyperesthesia, depression, mydriasis, vocalization, death, blindness, hypersalivation, dyspnea, ataxia/paresis, disorientation, hyperreflexia, and coma. The antidote is cyproheptadine (2-4 mg/cat orally or rectally).

Dose: 3.75 mg (¼ of a 15 mg tablet) once every 2-3 days. If adverse reactions occur, reduce the dose by ¼ to ½. Alternatively, some practitioners choose to have the drug compounded and dose at 1 mg daily.

Meclizine

This is an excellent drug to use in cats with vestibular disease. This drug is an antihistamine that has antiemetic properties as well as anti-motion-sickness properties that are not completely understood. Side effects are few, though sedation can occur in some cats. The drug is available OTC.

Dose: 12.5 mg per cat once daily

Propofol

ropofol is a short acting hypnotic agent that is used to induce general anesthesia in patients. A unique side effect of the drug is appetite stimulation. I tend to use this drug for short procedures (bone marrow aspirates, ultrasound guided biopsies). It is important to remember that this drug has little to no analgesic properties, so other drugs may be needed to provide control of pain. Rapid boluses may also induce apnea. A recent study showed that repeated administration of this drug does not cause clinically relevant hematologic changes and is not associated with any adverse effects. This is also a safe drug to use in cats with liver disease (hepatic lipidosis/feeding tube placement).

Dose: 4-6 mg/kg IV to effect Constant rate infusion: 0.1-0.6 mg/kg/min with IV fluids

Intranasal vaccines

Rhinitis is a frustrating disease. Stimulation of the local mucosal immunity with intranasal vaccines can decrease the severity and frequency of nasal congestion due to rhinitis. I have had several patients that have not experienced another relapse as long as they received an intranasal vaccination every 6 months. The initial vaccine is given and followed with a booster in 2-4 weeks. Further intranasal vaccines are given every 6 months, based on severity and control of clinical signs.

Transdermal medications

Great idea, but problematic.

Are we really sure the medicine is being absorbed? Compounding pharmacies are more than willing to make up drugs (almost any drug) in a transdermal preparation. Many of these preparations have no data that supports their efficacy.

And who is responsible for treatment failure? Not the compounding pharmacy. The prescribing doctor must take the blame. Do not prescribe any medications as transdermal administration unless there is research that supports the efficacy of the transdermal drug preparation. What about drug exposure to others in the family? Any person or animal that touches the drug is at risk of absorption and exposure to the drug. This concern is amplified for households with small children.

Bottom line: The prescribing veterinarian must assess the benefits and risks of transdermal drug delivery.

Selected readings

Bley CR, Roos M, Price J, et al: Clinical assessment of repeated propofol-associated anesthesia in cats. J Am Vet Med Assoc 231:1347-1353, 2007.

Bulman-Fleming JC, Turner TR, Rosenburg MP: Evaluation of adverse events in cats receiving long-term Piroxicam therapy for various neoplasms. J of Fel Med and Surg 12:262-268, 2010.

Johnson R: Compounding drugs. In Ettinger SJ, Feldman EC (eds): Textbook of Veterinary Internal Medicine, 6th ed. St. Louis, Elsevier Saunders, 2005, pp 512-514.

Leveille-Webster CR, Center SA: Chronic hepatitis: therapeutic considerations. In Bonagura JD(ed): Kirk's Current Veterinary Therapy XII Small Animal Practice, Philadelphia, W.B. Saunders, 1995, pp 749-756.

Marshall RD, Rand JS, Morton JM. Glargine and protamine zinc insulin have a longer duration of action and result in lower mean daily glucose concentrations than lente insulin in healthy cats, J Vet Pharmacol Therapeut 31:205-212, 2008.

Marshall RD, Rand JS, Morton JM. Insulin glargine has a long duration of effect following administration either once or twice daily in divided doses in healthy cats. J Feline Med Surg 10:488-494, 2008.

Marshall RD, Rand JS, Morton JM. Treatment of newly diagnosed diabetic cats with glargine insulin improves glycaemic control and results in higher probability of remission than protamine zinc and lente insulin. J Feline Med Surg 11: 683-691, 2009.

Mazzaferro EM: Small airway disease. In Lappin MR (ed): Feline Internal Medicine Secrets. Philadelphia, Hanley and Belfus, Inc., 2001, pp 37-42.

Plumb DC: Veterinary Drug Handbook, 6th ed. Stockholm, Wisconsin, PharmaVet Inc., 2008.

Posner LP, et al: Use of Propofol for general anesthesia in cats with primary hepatic lipidosis. J Am Vet Med Assoc 232:1841-1843, 2008.

Robinson EP, Sanderson SL, Machon RG: Propofol: a new sedative-hypnotic anesthetic agent. In Bonagura JD (ed): Kirk's Current Veterinary Therapy XII Small Animal Practice, Philadelphia, W.B. Saunders, 1995, pp 77-81.

Tuzio H: Acute and chronic renal failure. In Lappin MR (ed): Feline Internal Medicine Secrets. Philadelphia, Hanley and Belfus, Inc., 2001, pp 183-202.