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Naloxone Hydrochloride



nal-oks′one hye-droe-klor′ide


Trade and other names: Narcan and Trexonil


Functional classification: Opioid antagonist



Pharmacology and Mechanism of Action


Opiate antagonist. Naloxone competes for opiate receptors and displaces opioid drugs from these receptors, thus reversing their effects. Naloxone is capable of antagonizing all opiate receptors.



Indications and Clinical Uses


Naloxone is used to reverse the effects of opiate agonists on receptors. Naloxone should be used to reverse overdoses or toxicity. It will reverse effects of morphine, oxymorphone, butorphanol, hydromorphone, and other opioids. It is less effective for reversing buprenorphine and may be titrated in gradually to achieve the optimum amount of reversal. At very low doses (one fifth of the dose needed to fully reverse opiates) it has been used to treat opioid-induced side effects such as vomiting, nausea, and dysphoria. A formulation for wildlife use (Trexonil) is more concentrated and used to reverse tranquilization in wild animals. Naloxone may have some temporary benefit for behavior modification (e.g., to suppress compulsive disorders) but the effects are short-lived. For example, in horses, it will temporarily decrease crib biting, but the duration of action is short.



Precautionary Information



Adverse Reactions and Side Effects


Tachycardia and hypertension have been reported in people. In animals, reversal of opioid may precipitate a severe reaction that includes high blood pressure, excitement, pain, tachycardia, and cardiac arrhythmias.



Contraindications and Precautions


Administration to an animal that is experiencing pain will precipitate extreme reactions because of blockade of endogenous opioids.



Drug Interactions


Naloxone will reverse the action of other opioid drugs.



Instructions for Use


Administration may have to be individualized based on response in each patient. Naloxone’s duration of action is short in animals (60 minutes) and it may have to be readministered. Start at the low end of the dosage rate and increase the dose to effect. Higher doses may be needed to reverse drugs that are mixed agonists/antagonists such as butorphanol or buprenorphine, compared to reversing drugs that are pure agonists. Low doses may be used to reduced opioid-induced dysphoria in animals. For this use, start with 0.04 mg/mL solution and administer increments of 1 mL every 30 seconds until vocalization or signs of dysphoria stop. A dose of 0.01 mg/kg IV has been given for this purpose without losing analgesic effects.


A dose of 1 mL (0.4 mg) will reverse 1.5 mg oxymorphone, 15 mg morphine, 100 mg meperidine, and 0.4 mg fentanyl.



Patient Monitoring and Laboratory Tests


Naloxone is used to reverse opioid analgesic drugs. When opioids are reversed in some animals, serious reactions may occur. In some patients, changes in blood pressure, tachycardia, and discomfort may result.



Formulations Available


Naloxone is available in injectable vials with preservatives in 0.4 or 1 mg/mL, without preservatives in 0.02 mg (20 mcg), 0.4 mg or 1 mg per mL, and as Trexonil in 50 mg/mL.



Stability and Storage


When used IV, it may be diluted in other fluids. For intravenous infusion, it may be added to sodium chloride or 5% dextrose. After dilution it should be used within 24 hours. Do not mix with other drugs or solutions that are alkaline. Store in a tightly sealed container, protected from light, and at room temperature.



Small Animal Dosage



Dogs and Cats



• 0.01-0.04 mg/kg IV, IM, or SQ, as needed to reverse opiate.

• Low dose to partially reverse dysphoric reaction: Administer 1 mL every 30 seconds (0.04 mg/mL solution) as needed.


Large Animal Dosage



Horses



• 0.02-0.04 mg/kg IV (duration of effect is only 20 minutes).


Regulatory Information


No withdrawal times are established. It is anticipated that naloxone is cleared rapidly after administration. Because of low risk of residues, short (24-48 hour) withdrawal times are suggested.


RCI Classification: 3



Naltrexone



nal-treks′one


Trade and other names: Trexan, Vivitrol


Functional classification: Opioid antagonist



Pharmacology and Mechanism of Action


Opiate antagonist. Naltrexone competes for opiate receptors and displaces opioid drugs from these receptors, thus reversing their effects. It is capable of antagonizing all opiate receptors. Its action is similar to naloxone except that it is longer-acting and administered orally. A related drug that does not have central-acting effects is methylnaltrexone (used to treat intestinal ileus). For humans, there is a long-acting injection formulated in microspheres that persists for 1 month after a single injection. The long-acting form has not been used in animals.



Indications and Clinical Uses


Naltrexone is used in people for treatment of opiate dependence and alcoholism. In animals some obsessive-compulsive disorders are believed to be mediated by endogenous opioids. It has been used successfully for treatment of some obsessive-compulsive behavioral disorders, such as tail chasing in dogs, acral lick granuloma in dogs, and crib biting in horses. The effect for each of these disorders is short-lived.



Precautionary Information



Adverse Reactions and Side Effects


Adverse effects have not been reported in animals. In people, it can precipitate opioid withdrawal signs.



Contraindications and Precautions


Do not administer to animals in pain, or it may elicit a severe reaction.



Drug Interactions


Naltrexone will reverse the action of other opioid drugs.



Instructions for Use


For acute treatment of opiate toxicity, use naloxone instead because it can be injected with a more rapid onset of effects. Treatment for obsessive-compulsive disorders (canine compulsive disorder) in animals has been reported with naltrexone. Relapse rates may be high.



Patient Monitoring and Laboratory Tests


Monitor heart rate in treated animals.



Formulations


Naltrexone is available in 50 mg tablets. Vivitrol for humans is an encapsulated microsphere that can be injected to produce a long-lasting effect (one injection per month) to treat substance dependence. One vial contains 380 mg in microspheres in a 4 mL injection for IM use.



Stability and Storage


Store in a tightly sealed container, protected from light, and at room temperature. Naltrexone is soluble in water. It has been mixed with juices and syrups to mask the bitter taste and was stable for 60-90 days.



Small Animal Dosage



Dogs



• For behavior problems: 2.2 mg/kg q12h PO.


Large Animal Dosage



Horses



• Crib biting: 0.04 mg/kg IV or SQ. (Because injectable formulations are not available, it must be compounded for this indication.) Duration of effect is 1-7 hours.

• For reversal of opiates: 100 mg/animal IV or SQ. (Because injectable formulations are not available, it must be compounded for this indication.)


Regulatory Information


Withdrawal times are not established for animals that produce food. In wild animals that are captured with opiates and administered naltrexone for reversal, a 45-day withdrawal time is suggested. For additional extralabel use withdrawal interval estimates, contact FARAD at 1-888-USFARAD (1-888-873-2723).


RCI Classification: 3



Nandrolone Decanoate



nan′droe-lone dek-ah-noe′ate


Trade and other names: Deca-Durabolin


Functional classification: Hormone, anabolic agent



Pharmacology and Mechanism of Action


Anabolic steroid. Nandrolone is a derivative of testosterone used as an anabolic agent. Anabolic agents are designed to maximize anabolic effects while minimizing androgenic action.



Indications and Clinical Uses


Anabolic agents have been used for reversing catabolic conditions, promoting weight gain, increasing muscling in animals, and stimulating erythropoiesis. There are no differences in efficacy among the anabolic steroids reported in animals.



Precautionary Information



Adverse Reactions and Side Effects


Adverse effects from anabolic steroids can be attributed to the pharmacologic action of these steroids. Increased masculine effects are common. There has been an increased incidence of some tumors in people. Some of the oral anabolic steroids that are 17 alpha-methylated (oxymetholone, stanozolol, and oxandrolone) are associated with hepatic toxicity.



Contraindications and Precautions


Use cautiously in patients with hepatic disease. Do not use in pregnant animals.



Drug Interactions


No drug interactions have been reported.



Instructions for Use


Results of clinical studies in animals have not been reported. Nandrolone use in animals (and doses) is based on experience in people or anecdotal experience in animals.



Patient Monitoring and Laboratory Tests


Monitor liver enzymes in treated patients.



Formulations


Nandrolone decanoate is available in 50-, 100-, and 200-mg/mL injection.



Stability and Storage


Store in a tightly sealed container, protected from light, and at room temperature. Stability of compounded formulations has not been evaluated.



Small Animal Dosage



Dogs



• 1-1.5 mg/kg/wk IM.


Cats



• 1 mg/kg/wk IM.


Large Animal Dosage



Horses



• 1 mg/kg q4wk IM.


Regulatory Information


Nandrolone is a Schedule III controlled drug.


Do not administer to animals intended for food.


RCI Classification: 4



Naproxen



nah-proks′en


Trade and other names: Naprosyn, Naxen, and Aleve (naproxen sodium)


Functional classification: Nonsteroidal anti-inflammatory drug (NSAID)



Pharmacology and Mechanism of Action


Naproxen and other NSAIDs have produced analgesic and anti-inflammatory effects by inhibiting the synthesis of prostaglandins. The enzyme inhibited by NSAIDs is the cyclo-oxygenase enzyme (COX). The COX enzyme exists in two isoforms: COX-1 and COX-2. COX-1 is primarily responsible for synthesis of prostaglandins important for maintaining a healthy GI tract, renal function, platelet function, and other normal functions. COX-2 is induced and responsible for synthesizing prostaglandins that are important mediators of pain, inflammation, and fever. However, there are overlapping functions of the mediators derived from these isoforms. Naproxen is a nonselective inhibitor of COX-1 and COX-2.



Indications and Clinical Uses


Naproxen is approved for use in people and is popular for treating osteoarthritis. It has been used for treatment of musculoskeletal problems, such as myositis and osteoarthritis in dogs and horses. There are no veterinary formulations marketed. Its use has diminished because there are registered drugs approved for these indications for horses and dogs.



Precautionary Information



Adverse Reactions and Side Effects


Naproxen is a potent NSAID. Adverse effects attributed to GI toxicity are common to all NSAIDs. Naproxen has produced serious ulceration in dogs because elimination in dogs is many times slower than in people or horses. Renal injury caused by renal ischemia also is possible with repeated doses.



Contraindications and Precautions


Caution is advised when using the OTC formulation designed for people because the tablet size is much larger than the safe dose for dogs. Therefore, warn pet owners about administration to dogs without consulting a veterinarian first. Dosing rates for people are not appropriate for dogs. Do not administer to animals prone to GI ulcers. Do not administer with other ulcerogenic drugs, such as corticosteroids.



Drug Interactions


Do not administer with other NSAIDs or with corticosteroids. Corticosteroids have been shown to exacerbate the GI adverse effects. Some NSAIDs may interfere with the action of diuretic drugs and angiotensin-converting enzyme (ACE) inhibitors.



Instructions for Use


Results of clinical studies in animals have not been reported. Use in animals (and doses) is based on pharmacokinetic studies in experimental animals.



Patient Monitoring and Laboratory Tests


Monitor for signs of GI ulceration.



Formulations


Naproxen is available in 220-mg tablets (OTC). (A 220-mg dose of naproxen sodium is equivalent to 200 mg naproxen.) It is also available in 25-mg/mL oral suspension and 250-, 375-, and 500-mg tablets (prescription).



Stability and Storage


Store in a tightly sealed container, protected from light, and at room temperature. Naproxen is practically insoluble in water at low pH, but it increases at high pH. It is soluble in ethanol.



Small Animal Dosage



Dogs



• 5 mg/kg initially, then 2 mg/kg q48h PO.


Large Animal Dosage



Horses



• 10 mg/kg q12h PO.


Regulatory Information


Withdrawal times are not established for animals that produce food. For extralabel use withdrawal interval estimates, contact FARAD at 1-888-USFARAD (1-888-873-2723).


RCI Classification: 4



N-Butylscopolammonium Bromide (Butylscopolamine Bromide)



en-byoo-til-skoe-pahl′ah-moe-nee-um broe′mide


Trade and other names: Buscopan


Functional classification: Antispasmodic



Pharmacology and Mechanism of Action


Antispasmotic, antimuscarinic, anticholinergic drug. This is a quarternary ammonium compound derived from belladonna alkaloid. Butylscopolamine, like other antimuscarinic drugs, blocks cholinergic receptors and produces a parasympatholytic effect. It affects receptors throughout the body, but it is used more commonly for its GI effects. It effectively inhibits secretions and motility of the GI tract by blocking parasympathetic receptors. It has a short half-life (15-25 minutes) and short duration of action.



Indications and Clinical Uses


Butylscopolamine bromide is indicated for treating pain associated with spasmodic colic, flatulent colic, and intestinal impactions in horses. It is also used to relax the rectum and reduce intestinal strain to facilitate diagnostic rectal palpation.



Precautionary Information



Adverse Reactions and Side Effects


Adverse reactions from anticholinergic drugs are related to their blocking of acetylcholine receptors and producing a systemic parasympatholytic response. As expected with this class of drugs, animals will have increased heart rate, decreased secretions, dry mucous membranes, decreased GI tract motility, and dilated pupils. In target animal safety studies in which doses of 1, 3 and 5 times the approved dose and up to 10 times the dose were administered to horses, the clinical signs described previously were observed. However, at high doses there were no CBC or biochemical abnormalities or lesions identified at necropsy.



Contraindications and Precautions


N-butylscopolammonium bromide will decrease intestinal motility. Use cautiously in conditions where decreased motility will be a concern.



Drug Interactions


N-butylscopolammonium bromide is an anticholinergic drug and therefore will antagonize any other medications that are intended to produce a cholinergic response (e.g., metoclopramide).



Instructions for Use


Experience is limited to treating spasmodic colic, flatulent colic, and intestinal impactions in horses. There is no experience in other animals.



Patient Monitoring and Laboratory Tests


Monitor equine intestinal motility (gut sounds and fecal output) during treatment. Monitor heart rate in treated animals.



Formulations


N-butylscopolammonium is available in a 20-mg/mL solution.



Stability and Storage


Store in a tightly sealed container, protected from light, and at room temperature.



Small Animal Dosage


No dose is reported for small animals.



Large Animal Dosage



Horses



• 0.3 mg/kg, slowly IV as a single dose (1.5 mL per 100 kg).


Regulatory Information


Do not administer to animals intended for food.



Neomycin



nee-oh-mye′sin


Trade and other names: Biosol


Functional classification: Antibacterial

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on N

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