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Racemethionine



rah-see’meth-eye’oh-neen


Trade and Other Names: Uroeze, Methio-Form, and generic brands and Pedameth, Uracid, and generic brands (human preparations)


Functional Classification: Acidifier



Pharmacology and Mechanism of Action


Urinary acidifier. Methionine lowers urinary pH. Racemethionine also has been used to protect against acetaminophen overdose in people by restoring hepatic concentrations of glutathione.



Indications and Clinical Uses


It is used as a urinary acidifier. In people it also is used to treat dermatitis caused by urinary incontinence (reduces urine ammonia).



Precautionary Information



Adverse Reactions and Side Effects


Adverse effects have not been reported.



Contraindications and Precautions


Do not use in animals with metabolic acidosis. Do not use in young cats. Do not use in animals with hepatic disease.



Drug Interactions


No drug interactions have been reported in animals.



Instructions for Use


Use for acetaminophen toxicity has been replaced by acetylcysteine.



Patient Monitoring and Laboratory Tests


Monitor CBC and hepatic enzymes if used to treat toxicity.



Formulations


Racemethionine is available in 500-mg tablets, 75-mg/5-mL pediatric oral solution, 200-mg capsules, and powders to add to an animal’s food.



Stability and Storage


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



Small Animal Dosage



Dogs



• 150-300 mg/kg/day PO.


Cats



• 1-1.5 g per cat PO (added to food each day).


Large Animal Dosage


No doses have been reported for large animals.



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).



Ramipril



ram’ih-pril


Trade and Other Names: Vasotop


Functional Classification: Vasodilator, angiotensin-converting enzyme (ACE) inhibitor



Pharmacology and Mechanism of Action


Like other ACE inhibitors, ramipril inhibits conversion of angiotensin I to angiotensin II. Angiotensin II is a potent vasoconstrictor and will stimulate sympathetic stimulation, renal hypertension, and synthesis of aldosterone. The ability of aldosterone to cause sodium and water retention contributes to congestion. Ramipril, like other ACE inhibitors, will cause vasodilation and decrease aldosterone-induced congestion. ACE inhibitors also contribute to vasodilation by increasing concentrations of some vasodilating kinins and prostaglandins. There is evidence for a cardioprotective effect when used to treat dogs with heart disease caused by cardiomyopathy or valvular disease.



Indications and Clinical Uses


Ramipril is used to treat hypertension and congestive heart failure (CHF). It has not been studied as much as other ACE inhibitors in animals (e.g., enalapril or benazepril), but it is expected to have similar pharmacodynamic effects. It has been primarily used in dogs. It has also been used safely in cats to control hypertension but has not been effective for treating hypertrophic cardiomyopathy.



Precautionary Information



Adverse Reactions and Side Effects


It has not been used as often as other drugs in this class; therefore, a full range of potential adverse effects has not been reported. Ramipril was well tolerated in clinical studies in dogs.



Contraindications and Precautions


Studies performed in experimental dogs indicated that dose adjustments are not necessary when administering ramipril in dogs with impaired renal function. Discontinue use of ACE inhibitors in pregnant animals; they cross the placenta and have caused fetal malformations and death of the fetus.



Drug Interactions


Use cautiously with other hypotensive drugs and diuretics. Nonsteroidal anti-inflammatory drugs (NSAIDs) may decrease vasodilating effects.



Instructions for Use


Clinical efficacy has been demonstrated in dogs with dilated cardiomyopathy. Other drugs used for treatment of heart failure may be used concurrently. Dogs also may receive pimobendan, digoxin and/or furosemide with ramipril.



Patient Monitoring and Laboratory Tests


Monitor patients carefully to avoid hypotension. With all ACE inhibitors, monitor electrolytes and renal function 3-7 days after initiating therapy and periodically thereafter.



Formulations


Ramipril is available in 1.25-, 2.5-, 5-, and 10-mg capsules.



Stability and Storage


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



Small Animal Dosage



Dogs



• 0.125-0.25 mg/kg daily PO.


Cats



• 0.125 mg/kg, q24h, PO.


Large Animal Dosage


No doses have been reported for large animals.



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).



Ranitidine Hydrochloride



rah-nit’ih-deen hye-droe-klor’ide


Trade and Other Names: Zantac


Functional Classification: Antiulcer agent



Pharmacology and Mechanism of Action


Histamine2 antagonist (H2 blocker). Ranitidine, like other H2 blockers, suppresses histamine stimulation of gastric parietal cell to decrease gastric acid secretion. Ranitidine will increase stomach pH. Ranitidine is longer acting and 4 to 10 times more potent than cimetidine. The half-life of ranitidine is longer than cimetidine, which results in decreased frequency of administration for ranitidine. When adjusting doses, ranitidine hydrochloride is 89% ranitidine.



Indications and Clinical Uses


Ranitidine is used to treat ulcers and gastritis. It does not produce as much of a sustained increase in stomach pH as proton pump inhibitors (omeprazole). Ranitidine (6.6 mg/kg PO) in foals suppressed acid for 6 hours, but omeprazole suppressed acid for 22 hours at 4 mg/kg. It is used to prevent nonsteroidal anti-inflammatory drug (NSAID)–induced ulcers in animals, although efficacy has not been demonstrated for this effect. In horses, ranitidine did not improve healing of ulcers induced by NSAIDs, and it was not as effective as omeprazole for treating ulcers. Ranitidine may stimulate stomach emptying and colon motility via anticholinesterase action. In horses, the effect on gastric emptying is minimal.



Precautionary Information



Adverse Reactions and Side Effects


Adverse effects are usually seen only with decreased renal clearance. In people, CNS signs may occur with high doses. Ranitidine may have fewer effects on endocrine function and drug interactions compared to cimetidine.



Contraindications and Precautions


Fewer drug interactions are possible with ranitidine compared to cimetidine because ranitidine does not inhibit cytochrome P450 enzymes.



Drug Interactions


Ranitidine and other H2-receptor blockers block secretion of stomach acid. Therefore, they will interfere with oral absorption of drugs dependent on acidity, such as ketoconazole, itraconazole, and iron supplements. Unlike cimetidine, ranitidine is not known to inhibit microsomal P450 enzymes.



Instructions for Use


Pharmacokinetic information in dogs suggests that ranitidine may be administered less often than cimetidine to achieve continuous suppression of stomach acid secretion. Use in horses and foals is based on experimental studies and pharmacokinetic data.



Patient Monitoring and Laboratory Tests


No specific monitoring is necessary.



Formulations


Ranitidine is available in 75-, 150-, and 300-mg tablets; 50- and 300-mg capsules; and 25-mg/mL injection. Some forms are available over the counter (OTC).



Stability and Storage


Store in a tightly sealed container, protected from light, and at room temperature. Ranitidine hydrochloride is soluble in water. Tablets have been crushed and mixed with water and syrup and were stable for 7 days. Protect from freezing.



Small Animal Dosage



Dogs



• 2 mg/kg q8h IV or PO.


Cats



• 2.5 mg/kg q12h IV, or 3.5 mg/kg q12h PO.


Large Animal Dosage



Horses



• 2.2-6.6 mg/kg q6-8h PO. The higher dose (6.6 mg/kg) is more effective at suppressing stomach acid.

• 2 mg/kg q6-8h IV.


Calves



• 50 mg/kg q8h PO in milk-fed calves.


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: 5



Remifentanil Hydrochloride



Rem-i-fen’ ta-nil


Trade and Other Names: Ultiva


Functional Classification: Anesthetic, analgesic, opioid



Pharmacology and Mechanism of Action


Remifentanil is a potent opioid similar in potency and activity to fentanyl. Like fentanyl, remifentanil has activity primarily at the mu-opiate receptor. The difference between remifentanil and other opioids is that it has an ultrashort action. The rapid onset and peak effect and short duration of action are attributed to its unique disposition. Remifentanil is quickly metabolized by hydrolysis of the propanoic acid–methyl ester by blood and tissue esterases. Therefore it is rapidly metabolized in the blood, does not depend on liver metabolism, and can be used safely in patients with liver or kidney disease. It also is rapidly delivered to tissues with an octanol:water partition coefficient of 17.9 at pH 7.3. However, it does not accumulate in tissues or blood even after prolonged IV infusions. Because of the rapid metabolism and quick equilibration between plasma and tissues, remifentanil has a fast onset of activity after IV injection. The half-life in dogs is approximately 3-6 minutes and does not change with increasing doses. Recovery occurs rapidly (within 5 to 10 minutes), and when using constant rate infusions, new steady-state concentrations can be achieved within 5 to 10 minutes after changes in infusion rate. Because of rapid equilibration with tissues, it can be easily titrated to the desired depth of anesthesia/analgesia by changing the continuous infusion rate or by administering an IV bolus injection.



Indications and Clinical Uses


Remifentanil is used as an anesthetic agent, often in combination with other agents. Because of its rapid metabolism and short half-life, it should be administered via constant rate infusion (CRI) to maintain a balanced anesthetic effect. It is used for induction and maintenance of anesthesia. It can be administered with other drugs, including inhalant anesthetics, alpha-2 agonists, sedatives, and tranquilizers. Because it does not require hepatic metabolism or renal elimination, it can be administered safely to patients that have liver or kidney disease. Remifentanil use in dogs is limited to a few studies and case reports. Doses in animals have been extrapolated from humans (human starting dose is 0.1 mcg/kg/min CRI). Remifentanil has been infused safely in cats, and over a wide range of doses (0.06-16 mcg/kg/min) IV it did not affect isoflurane MAC.

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

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