DRUGS TO AVOID IN CATS
Aspirin and Tylenol, for example, can be FATAL to cats Under dosing drugs, such as antibiotics, can lead to an ordinary infection becoming resistant to treatment. There, please DO NOT administer any drug or medication to your cat without the specific instruction from your veterinarian.
Early, thorough diagnosis and treatment by a qualified veterinarian will provide any animal the greatest chance for cure or control of specific problems. One of the greatest frustrations for veterinarians (and clients too) is to be called upon to treat a patient which has been "treated" by an owner over a period of time. Often home therapy allows a condition to become advanced, resistant to treatment or the strength of the patient becomes weakened as to make it very difficult if not impossible, to render a cure. This cure could have been obtained if care had been sought in a forthright fashion. In these cases, the cost of treatment is often greatly increased due to the more intensive nature of the care then required.
The following is a list of home medications that should not be used in cats. It is not meant to be a comprehensive list, but rather to provide caution against many medications often contained in home medicine cabinets.
ACETAMINOPHEN AND PHENACETIN
Sources Many prescription and over-the-counter brands of analgesic and antipyretic drugs contain acetaminophen or its ethyl ether, phenacetin. Examples are Tylenol, SineAid, SineOff, Anacin-3, Comtrex, Daytril, Nyquil, Allerest, and Vanquish.
Mechanism of action Phenacetin is metabolized to acetaminophen. Acetammophen is metabolized by enzymes of the cytochrome P-450 series to intermediate products: nonreactive glucuronides and sulfates (which are conjugated and eliminated in the urine), and reactive metabolites, which are metabolized with glutathione to nontoxic mercapturic acid (which is eliminated). If the toxic metabolites accumulate as a result of insufficient glucuronide or sulfate metabolism or insufficient glutathione, they are converted to toxic macromolecules that directly cause cellular death. Cats lack glucuronyl transferase and inefficiently form glucuronic acid and sulfate conjugates, leaving more acetaminophen or phenacetin to be metabolized to toxic metabolites. The glutathione stores are rapidly depleted in cats, leaving a large amount of toxic metabolites. Methemoglobinernia occurs.
Clinical signs Acute signs in cats are related to methemoglobin formation, whereas acute signs in the dog are related to hepatic damage. Toxicity is mainly seen in cats when even a small amount of acetarninophen is ingested (half of a 325 mg tablet for a 3.5 kg cat); dogs can usually tolerate dosages up to 100 mg/kg. Signs include cyanosis (which is caused by methemoglobinemia), dyspnea, facial edema (a hallmark of acetaminophen poisoning mechanism unknown), depression, hypothermia, vomiting. Signs may progress to weakness, coma, and subsequently death. Increased ALT from hepatic damage may be seen.
Treatment Since the toxic metabolites bind preferentially with glutathione rather than cell macromolecules, supplying a glutathione precursor is an important part of treatment. N-Acetylcysteine provides the cysteine needed for glutathione synthesis and also increases serum sulfate levels, which supplies sulfate for conjugation. Ascorbic acid is used to change methemoglobin to reduced hemoglobin. Acetarninophen is rapidly absorbed and reaches peak blood levels within 30 to 60 minutes; emesis is performed immediately after ingestion (if possible), and a saline cathartic is given. Steroids should not be given because they have been reported to cause a dose-dependent increase in mortality. Antihistamines have been reported to be contraindicated.
ANTIHISTAMINES AND DECONGESTANTS (PSEUDOEPHIDRINE, CONTACT, BENADRYL, CHLOR-TRIMATON, etc.) Dosages are not well established in cats for these drugs, and these should not be used without express consent from a veterinarian. These drugs can cause depression, , hyperexcitability, , vomiting, fever, muscle tremors, rapid or depressed heart rates, disorientation, and seizures.
ASPIRIN (ACETYLSALICYLIC ACID, SALICYLATE) Pepto-Bismol
Sources Many analgesic, antiinflammatory, antipyretic, and anticliartheal (Pepto-Bismol) agents that contain salicylates are sold as OTC preparations. Some keratolytic products contain salicylates.
Mechanism of action Acetylsalicylic acid inhibits cyclooxygenase, which then inhibits production of certain prostaglandins, including protective prostaglandins of the E series. High levels are known to directly stimulate the respiratory center (early) to cause an initial respiratory alkalosis. High doses are also known to uncouple' oxidative phosphorylation and may cause hyperglycemia and glycosuria.
Clinical signs The biologic half-life of aspirin is 7.5 to 8 hours in dogs and 38 to 45 hours in cats at a dose of 25 mg/kg/day. The toxic dose in cats is >25 mg/kg/day in cats and >50 mg/kg/day in dogs. Signs are noted within 4 to 6 hours after ingestion of a toxic dose and include depression, vorniting, anorexia and lethargy, tachypnea (caused by initial respiratory alkalosis), and hyperthermia. The vomitus may be blood-tinged from GI ulceration. CNS depression leads to muscle weakness and ataxia; coma and death can occur within I or more days. Gastrointestinal ulceration or perforation may be seen after the administration of repeated doses over several days' duration. Anemia, bone marrow depression, Heinz body formation (cats), and toxic hepatitis may occur.
Toxic signs may be seen at doses of Pepto-Bismol >7 mL/kg/day in dogs and cats. Two tablespoons of PeptoBismol contain the salicylate equivalent of one 5-grain aspirin tablet.
Treatment There is no specific antidote. The stomach should be emptied by induction of emesis or lavage if within <2 hours of ingestion though there are literature reports that gastric evacuation may be of value up to 12 hours after ingestion of enteric-coated aspirin preparations. Multiple-dose activated charcoal is warranted. Acid-base balance is corrected as needed; diuresis is instituted. Alkalinization of the urine with sodium bicarbonate can be done to hasten urinary excretion, though this requires intense monitoring and is difficult to achieve safely. Peritoneal dialysis allows direct removal of salicylic acid from serum. Gastric ulceration or perforation is treated as needed.
Sources Cooking, baking, candy, landscaping (with cacao shells), white chocolate (negligible amounts of theobromine), sweetened milk chocolate (1/10 the amount of theobromine as found in unsweetened chocolate, approximately 45 to 60 mg/oz), semisweet or dark chocolate contains 130 to 185 mg/oz. Unsweetened (baking) chocolate (450 mg/oz), cocoa powder (150 to 600 mg/oz); coffee, tea, soft drinks.
Mechanism of action Theobromine inhibits phosphodiesterase, which results in increased cAMP and release of catecholamines. Caffeine directly stimulates the myocardium and central nervous system. It also causes a competitive antagonism of cellular adenosine receptors. Increased muscle contractility is caused by increased entry of calcium and inhibition of sequestration by the sarcoplasmic reticulum (mechanism unknown). Benzodiazepine receptors in the brain are competitively antagonized.
A slight increase in blood pressure is seen. Bradycardia or more commonly tachycardia occurs, and myocardial dysrhythmias, especially ventricular premature beats, are possible. Central nervous system excitability, manifested as nervousness, excitement, tremors, seizures, and ultimately coma, are seen. Panting and urinary incontinence are also possible. Death occurs within 6 to 24 hours with acute exposure. With chronic ingestion (over several days), death may result from cardiac failure.
Tachycardia, tachypnea, hyperexcitability, tremors, seizures, premature ventricular beats. Dilatation of coronary, pulmonary, and systemic vessels may cause congestion or hemorrhage. The lethal dose for caffeine is 150 mg/kg for dogs, cats, and people.
Treatment No antidote exists; treatment is supportive. Emesis is used and may be effective even after several (4 to 6) hours have passed since ingestion; gastric lavage is useful if emesis is only partially productive or contraindicated. Activated charcoal is useful and can significantly decrease the half-life of theobromine. Diazepam is used to control tremors, anxiety, or seizures. Bradycardia is treated with atropine; tachycardias are treated with lidocaine, metoprolol, or propranolol. The urinary bladder should be catheterized to prevent reabsorption of theobromine through bladder mucosa. Fluids are given as part of supportive treatment.
HORMONES These are often found in homes to treat many different human problems, but for some reason, owners seem tempted to give these medications to their cats. Dosages for most all hormones are so radically different and require such specificity of diagnosis that one should be encouraged to resist any temptation to give a hormonal medication to a cat.
NONSTEROIDAL ANTIINFLAMMATORY DRUGS
Ibuprofen,(Motrin, Advil, Nuprin, Vick's DayQuil), phenylbutazone (Bute, Butazolidin), naproxen (Naprosyn, Aleve), indomethacin, piroxicam (Feldene).
Clinical signs Abdominal pain, lethargy, anemia, melena, and hematernesis are most commonly seen with GI irritation and ulceration. If perforation has occurred, clinical signs may include abdominal pain, perhaps a fluid wave, shock, injected sclera, brick-red mucous membranes, and tachycardia. Temperature may be elevated or depressed. Pulses may be bounding or weak and thready.
Clinical signs associated with acute renal failure include hyposthenuria or isosthenuria, renal tubular cell casts in the urine sediment, or glucosuria without hyperglycemia. Urine gammaglutamyltransferase (GGT) will be elevated. These early signs of acute renal failure will be followed by increasing BUN and creatinine, electrolyte disturbances, and possibly oliguria or more rarely polyuria. Occasionally, increased alanine aminotransferase (ALT) and alkaline phosphatase (ALP) may be seen
OVER-THE-COUNTER WORMERS are old drugs used decades ago. Most have toxicities not seen with today's modern and safer wormers prescribed by veterinarians. Many over-the-counter womers cause weakness, staggering, difficulty breathing, vomiting, tremors, seizures and death. Use ONLY wormers prescribed by your veterinarian after performing a fecal analysis to determine the appropriate wormer for the particular parasite, as different worms require different treatments.
PEPTO-BISOMOL Because this product contains salicylate which is similar to aspirin, toxicity and death can occur in cats.
PHOSPHATE ENEMA (FLEET) These enemas can cause serious electrolyte disturbances and cause death within an hour or two of administration.
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