Aminophylline for Dogs

Aminophylline is a methylxanthine drug, a soluble salt of theophylline, theophylline ethylenediamine. It has 79 percent of theophylline's potency on a mg-for-mg basis (100 mg aminophylline equivalent to 79 mg theophylline). The principal use of aminophylline is as a bronchodilator to provide symptomatic relief from reversible obstructive airway disease (like asthma in people and in cats, bronchitis in dogs).

The pharmacodynamic effects of aminophylline are to relax smooth muscle of the airways and pulmonary vasculature, stimulate the CNS, induce diuresis, increase gastric acid secretion, reduce lower esophageal sphincter pressure, and inhibit uterine contractions. Its mechanism of action was formerly thought to be due to phosphodiesterase inhibition, increasing cAMP; however, it is now thought to work by either inhibiting intracellular adenosine, stimulation of endogenous catecholamine release, antagonism of prostaglandins, mobilization of intracellular Ca++, or through a -adrenergic agonist mechanism. It is readily absorbed from the gastrointestinal tract after ingestion and distributes principally into non-fatty tissues. Aminophylline is 85 to 90 percent metabolized by the liver and is excreted via the kidneys.

In the United States, aminophylline is a prescription drug.

This drug has not been specifically approved and labeled for use in animals by the Food and Drug Administration. It can be prescribed legally by veterinarians as an extra-label drug.BRAND NAMES AND OTHER NAMES

This drug is registered for use in humans only.Human formulations: Various generic preparations exist. Manufacturers include Abbott, Balan, Bioline, Roxane, Searle and URL.Veterinary formulations: NoneUSES OF AMINOPHYLLINE

Aminophylline is used for bronchodilation in the treatment of bronchitis and asthma (cats). It is also used in the symptomatic relief of pulmonary edema. Aminophylline has been used as a CNS stimulant (analeptic function) such as in the treatment of apnea in neonates and as a cardiac stimulant in heart failure.PRECAUTIONS AND SIDE EFFECTS

Aminophylline should not be used in animals with known hypersensitivity or allergy to the drug. Liver disease will reduce clearance and prolong effects so aminophylline should be used with caution in animals with hepatic dysfunction. Aminophylline should be used with caution when cardiac disease or cardiac arrhythmias are present, though dogs do not seem to be susceptible to aminophylline's arrhythmogenic effects.

High doses of aminophylline may cause toxicity. Toxic signs include ventricular dysrhythmias, restlessness and convulsions.DRUG INTERACTIONS

Injectable aminophylline is compatible with all IV solutions except those containing 10 percent fructose or invert sugar solutions.

Ketoconazole, rifampin, and loop diuretics are some drugs that may reduce the plasma level of aminophylline. Calcium channel blockers, cimetidine, corticosteroids, and ephedrine are some drugs that may increase plasma aminophylline levels.

The CNS effects of benzodiazepines and aminophylline oppose each other. Because of this, aminophylline can be used to reverse excessive sedation resulting from benzodiazepines.

B-adrenergic agents are synergistic with aminophylline and aminophylline may augment the arrhythmogenicity of certain anesthetic agents, like halothane. Coadministration of aminophylline and ketamine potentiates ketamine's seizurogenic effects.

Aminophylline will, to some extent, antagonize the anesthetic effects of propofol.HOW AMINOPHYLLINE IS SUPPLIED

Aminophylline is available in 100 mg and 200 mg immediate release tablets and a 105 mg/5 ml oral liquid. Injectable aminophylline is available in a 250 mg/10 ml concentration. In addition, aminophylline is available as 250 mg and 500 mg suppositories.DOSING INFORMATION

In dogs, aminophylline is dosed at 6 to 11 mg/kg PO, IM, or IV every 8 hours. Be aware that the IM injection is painful.

In cats, aminophylline is dosed at 5 mg/kg PO every 8 to 12 hours.REFERENCES

Drug Facts and Comparisons, 57th Edition. 2003, pp 734-8

Boothe DM. Anticonvulsants drugs and analeptic agents. In Adams HR (editor), Veterinary Pharmacology and Therapeutics, 8th Edition. 2001, pp 376-7

Hamlin RL, Sally JL: Lack of arrhythmogenicity of aminophylline in dogs. J Vet Pharmacol Therap. 1993, 16:15-22

Plumb, DC. Veterinary Drug Handbook, 4th Edition. Pharma Vet Publishing, White Bear Lake, MN. 1995.

Veterinarians frequently prescribe aminophylline for dogs suffering from asthma or bronchitis even though it is not currently approved by the FDA for use in animals. Aminophylline belongs to a class of drugs called bronchodilators, used to relax the smooth muscle wall in the airway and allowing unrestricted air passage.Dosage for Dogs

Aminophylline is available by prescription for dogs. It is available in tablets, oral liquid, injection and suppository form. Typical dosage is 3 to 5 mg per pound every 8 hours.Side Effects of Aminophylline for Dogs

A dog on aminophylline can experience side effects such as vomiting, diarrhea, anxiety or nervousness, insomnia, or increased hunger, thirst and urination. Side effects may subside with continued therapy or may require dosage adjustments.

Precautions:

Caution should be used when giving aminophylline to dogs with seizure disorders. Medications used to treat seizures can lessen the effectiveness of this drug.Animals with hypothyroidism, liver or kidney disease or congestive heart failure should use aminophylline with caution as it can cause problems with these conditions.Aminophylline should not be given to dogs that are pregnant or nursing or to dogs who are allergic to this class of medication.Although not approved by the FDA for use in dogs, aminophylline can be used with care in the treatment of canine asthma and bronchitis. As with other prescription medications, dosing instructions should be followed carefully.

Treating Congestive Heart Failure in Dogs With Vetmedin

Read more: Treating Congestive Heart Failure in Dogs With VetmedinDespite a diagnosis of congestive heart failure, dogs can live long happy lives. Today's medications aid heart health for years. With dietary changes and prescription medications like Vetmedin, your dog can remain energetic and comfortable.Understanding Congestive Heart FailureWith congestive heart failure, dogs' lungs and chest cavity retain fluids because the heart is not pumping as effectively. Congestive heart failure is common in large breeds like Great Danes and Mastiffs, but all breeds can be susceptible to this disease. In most cases of congestive heart failure, dogs usually have an underlying disease or genetic predisposition.Keep Watch for Common SymptomsIn cases of congestive heart failure, dogs show clear symptoms. These common signs include:

CoughingDifficulty breathingDizzy spellsSudden fatigueWeight loss

Some congestive heart failure dogs will be actively playing and suddenly drop to the ground wheezing and unable to catch his/her breath. If this happens, seek veterinary care immediately.Vetmedin for Congestive Heart FailureWhen treating congestive heart failure, dogs respond well to the cost-effective heart medication known as Vetmedin. Vetmedin works to expand the heart's blood vessels allowing blood to travel properly throughout the body.

Once your pet is taking Vetmedin, you should see improvements in seven days.

Read more: Treating Congestive Heart Failure in Dogs With VetmedinDog Congestive Heart Failure Prognosis

Dog congestive heart failure occurs when fluid builds up in your dog's chest cavity and compresses his heart. It usually happens as a result of structural abnormalities in the heart muscle. Here's what you should know about canine congestive heart failure.Causes of Congestive Heart Failure in Dogs

There are a number of factors that can contribute to congestive heart failure in dogs. If your dog is born with congenital heart defects, that can contribute to congestive heart failure. Heartworm infestation can contribute to congestive heart failure, as can arrhythmia. Other causes of canine congestive heart failure include:

CardiomyopathyDegeneration of the valves of the heartPericardium diseases affecting the membrane around the heart

Dogs of any age, breed or gender can develop congestive heart failure. However, the large and giant breeds, which are also prone to dilated cardiomyopathy, are especially prone to congestive heart failure as a result of their condition.

Congestive heart failure usually occurs in older dogs, over the age of eight years. Younger dogs may develop this condition, though it's usually a result of birth defects in these animals. Symptoms of Congestive Heart Failure in Dogs

Congestive heart failure causes your dog to experience chronic fatigue, since it reduces the amount of blood being pumped through his body. He may accumulate fluid in his lungs, chest cavity and abdomen. Symptoms of congestive heart failure include labored breathing, coughing, shortness of breath, fatigue and weight loss.Diagnosing Congestive Heart Failure in Dogs

Your vet will perform a complete physical exam and take your dog's medical history, if he doesn't already have it. He may need to take X-rays, EKGs and ultrasounds to determine the extent of the damage to your dog's organs. Blood pressure measurements will give your vet an idea of how well your dog's heart is functioning at the time of the exam.Treating Canine Congestive Heart Failure

Your dog may require hospitalization, especially if his heart failure is advanced. Your vet will administer diuretic drugs to help your dog excrete any accumulated fluid from his chest, lungs or abdomen. Nitroglycerin and enzyme inhibitors can help improve your dog's heart function.

Your dog will need to go on a new, low sodium diet. Your vet may recommend dietary supplements. Your dog will also need to restrict himself to gentle exercise, since congestive heart failure can make him get tired very easily. Follow your vet's instructions and administer all medications as directed.Congestive Heart Failure Prognosis for Dogs

Your dog won't show many symptoms until his congestive heart failure becomes advanced. By this time, it's generally too late for treatment to make any significant impact on your dog's health. While beta blockers and other drugs can help to slow the progression of many canine heart conditions, by the time your dog starts showing symptoms, his heart may be too damaged and drugs may not extend his life. Most dogs with congestive heart failure die within six months to a year of diagnosis.

Read more: Dog Congestive Heart Failure PrognosisACE Inhibitors for Congestive Heart Failure Treatment in Dogs

Read more: ACE Inhibitors for Congestive Heart Failure Treatment in Dogs

The medications used in canine congestive heart failure treatment are ACE inhibitors, diuretics and drugs such as digitalis. Supplements such as vitamin-B, taurine and coenzyme Q are also found to be beneficial.Congestive Heart Failure

As a dog ages, the muscles of the heart weaken and his heart fails to pump efficiently. There is an insufficient amount of blood pumped through the dogs body. To compensate for the insufficient blood supply, the heart beats faster resulting in more damage. This slowing of the heart leads to a condition known as congestive heart failure or CHF. The condition can also strike younger dogs and may be hereditary. CHF is fatal as there is still no known cure.Symptoms of Congestive Heart Failure

Symptoms of congestive heart failure in dogs include:

FatigueFainting after mild exerciseDiscoloration of the gums and tongues of a bluish colorPale colored gumsDecrease in physical activityCoughingLoss of appetiteRapid breathingAbdominal swellingLoss of weightImpaired function of the liver, lungs and kidneys Labored breathing

Treatment of Congestive Heart Failure in Dogs

You should feed your pet a low salt diet if he has been diagnosed with congestive heart failure. You will have to administer medications that improve heart function and reduce fluid accumulation in the lungs. Angiotensin Converting Enzyme (ACE) inhibitors inhibit the action of the enzyme Angiotensin. This enzyme causes the constriction of blood vessels and increases the pressure on the heart.

ACE inhibitors inhibit this action and allow the blood vessels to dilate allowing blood to flow easily through them and reducing the amount of work the heart has to do. These medications thus help reduce blood pressure and volume, ease the stress on the heart, and halt its deterioration.ACE Inhibitors

ACE inhibitors such as enalapril maleate, lisinopril and benazepril are sold under the brand name of Enacard, Prinivil and Fortekor respectively. ACE inhibitors have improved the clinical signs of canine congestive heart failure and increased the life expectancy of affected dogs. These drugs can be given on an empty stomach or with food.Side Effects of ACE Inhibitors

Side effects of ACE inhibitors include:

VomitingDiarrheaImpaired kidney functionIncrease in potassium levels in the bloodHypotension Abnormalities in blood and urine tests

Usual Dosage of ACE Inhibitors

If you have to administer enalapril to your pet, the usual dosage is 0.5 mg for every kilogram of body weight twice a day. Benazepril should be given only once daily and the recommended dosage is 0.25 to 0.5 mg for every kilogram of body weight. Dogs medicated with ACE inhibitors show decreased pulmonary edema (fluid in the lungs) and a lower class of heart failure.

It is possible for your pet to live a full life for many years even after being diagnosed with congestive heart failure if you administer the proper medications, monitor his diet, ensure he has no salt in his food and restrict his exercise to gentle exercise only. You should also ensure that he is regularly checked by the vet as a pet with CHF should be monitored regularly.

Read more: ACE Inhibitors for Congestive Heart Failure Treatment in DogsSystemic Therapy of Airway Disease-Adrenergic Agonists

The -adrenergic agonists have beneficial effects in the treatment of bronchoconstrictive respiratory tract diseases (see -Adrenergic Receptor Agonist DrugsTables). Bronchial smooth muscle is innervated by 2-adrenergic receptors. Stimulation of these receptors leads to increased activity of the enzyme adenylate cyclase, increased cAMP, and relaxation of bronchial smooth muscle. Stimulation of receptors on mast cells decreases the release of inflammatory mediators from mast cells, but other inflammatory cells are not suppressed. There is some evidence that -adrenergic receptor agonists increase mucociliary clearance in the respiratory tract.

-Adrenergic Receptor Agonist Drugs

Drug

Dosage

Epinephrine

Dogs: 0.050.5 mg, intratracheally or IV

Cats: 0.1 mg, IV or IM

Large animals: 0.1 mg/kg, IV, SC, or IM

Isoproterenol

Dogs: 0.10.2 mg, IM or SC, qid

Cats: 46 g, IM, every 30 min as needed

Horses: 0.4 g/kg, IV (diluted)

Terbutaline

Dogs, cats: 0.1 mg/kg, SC, every 4 hr, or 0.03 mg/kg, PO, tid

Horses: 0.0033 mg/kg, IV, or 0.20.6 mg/kg, PO, bid

Albuterol

Dogs: 0.05 mg/kg, PO, tid

Horses: 8 g/kg, PO, bid

Clenbuterol

Horses: 0.83.2 g/kg, PO, bid

Epinephrine (adrenaline) stimulates and receptors, resulting in pronounced vasopressive and cardiac effects in addition to bronchodilation. Epinephrine is reserved for emergency treatment of life-threatening bronchoconstriction (eg, anaphylaxis). The nonspecific stimulation of other receptors and its short duration of action make it unsuitable for longterm use. Epinephrine is available as a 1 mg/mL solution. Its onset of action is immediate, and the duration of effect is 13 hr.

Isoproterenol is a potent -receptor agonist. It is selective for receptors, but cardiac (1) effects make it unsuitable for longterm use. It is administered by inhalation or injection and has a short duration of action (