MEDICATIONS AND PERFORMANCE – MCZ
MEDICATIONS AND PERFORMANCE
For a drug to have an effect, it must enter the body and be delivered to the site at which it will act. Drugs can be taken into the body by many different means. They can be ingested orally and then absorbed into
the body through the lining of the stomach or the small intestine. They can be injected under the skin, where they diffuse slowly into the blood stream, or intramuscular, where they are more quickly taken
up by blood vessels. Drugs can also be injected directly into a blood vessel (usually a vein) or directly into the target tissue (for example, a joint). Some drugs can be absorbed directly through the skin. Carrier
agents such as dimethylsulfoxide (DMSO) can also be used to carry a drug rapidly across the skin and into the blood stream.
As a general rule, drugs given orally are slower to reach effective levels within the blood stream because they must first dissolve before being absorbed. However, effective levels are maintained in the blood for a long time after oral administration. At the other end of the spectrum, drugs that are administered intravenously reach effective levels immediately, but the levels are not maintained as long because the drug is rapidly removed from the blood by the liver and kidneys. Subcutaneous and intramuscular administration have intermediate absorption and clearance times. Once in the body, the drug is delivered by the blood stream to the site at which it will act. The location of action is determined by small molecules on the surfaces of cells called receptors. The drug attaches to the receptors and is drawn into the cell. Receptors are generally very specific — they will only permit certain drugs into the cell. If there are receptors for a certain drug in many tissues in the body, then that drug will have widespread effects throughout the body. On the other hand, if there are receptors for a certain drug in only one location in the body, then that drug will have a localized effect in that organ only. For example, insulin acts on virtually every cell in the body, whereas a tranquilizer acts predominantly on cells in the brain. Side effects occur when a drug has effects on tissues other than the target tissue. For example, antihistamines are commonly used by people suffering from allergies to decrease nasal secretions. However, cells in the brain also have receptors for antihistamines, and their effect on the brain is to cause drowsiness. Side effects are somewhat like weeds in a garden. They are doing the right thing but in the wrong place.
Because the percentage of cells that have receptors for a drug is usually small, only a small fraction of most drugs actually reaches cells with receptors and has an effect. The rest of the drug is eventually eliminated. Individual animals vary in their absorption and utilization of drugs, so drug dosages should always be considered on an individual basis. The amount of a drug recommended for one animal should never be used on another animal without first consulting a veterinarian. Once inside the cell, the drug has a biochemical effect on cellular processes. The drug may have a direct effect, such as blocking the ability of nerves to feel pain, or it may set in motion a series of biochemical events that ultimately produce the desired effects.
Once a drug has had its effect, it does not remain in its active form but is changed to an inactive form so that it can be excreted by the body. There are two major organs that are involved in the elimination of drugs: the liver and the kidneys. The liver is responsible for changing, or detoxifying, many drugs. Liver cells contain enzymes which metabolize many different biochemical substances, producing nontoxic metabolites that are then excreted in the urine. Excretion of these metabolites by the kidneys is the reason that samples of urine are taken for drug testing.
ADVERSE DRUG REACTIONS
The suggested doses for drugs are just that — suggested doses. These doses have been arrived at by testing a wide variety of dogs of different sizes and breeds. However, they are not always right for every dog. Just as in humans, dogs have individual resistances and sensitivities to drugs. There are many reasons why a drug may have a different effect in one animal than another (Table 1). Doses for drugs are usually given in relationship to body weight. A very obese dog, however, may weigh twice what its normal body weight should be, but the extra weight consists almost entirely of fat. If the drug is not soluble in fat, the nonfat portion of
that dog’s body may be exposed to twice the amount of drug because the drug was administered on the basis of body weight alone. If, on the other hand, the drug is absorbed by fat, it may be difficult to achieve and maintain effective levels of the drug in an obese dog because the excess fat absorbs the drug.
The incidence of adverse drug reactions is much greater in very young and in very old dogs. The tissues of dogs less than 30 days old may not have all of the biochemical components needed to metabolize a drug. Older dogs may have developed a hypersensitivity to a drug or may have organ dysfunction, such as liver failure, which can reduce the amount of drug metabolized by the body and increase the likelihood of toxic effects. Pregnant animals may be more sensitive to some drugs because alterations in body weight and circulation may affect tissue distribution of the drug. Animals with inhalant allergies seem to be more susceptible
to adverse drug reactions.
Finally, drug interactions can increase or decrease the effects of a drug in a given tissue. For example, a number of drugs, including glucocorticoids, anticonvulsants, aspirin, and phenylbutazone, can alter the level of administered thyroid hormone in the body. The incidence of adverse drug reactions increases exponentially when more than one drug is administered because of the potential for drug interactions. Adverse drug reactions may be manifested in dogs in a number of ways. One type of adverse drug reaction occurs when the dose of the drug is too high or alterations in availability expose the tissues to abnormally high levels, causing toxic effects. The signs of this type of drug reaction vary according to the particular drug involved. One of the most life threatening reactions is anaphylaxis. This is an acute systemic allergic reaction, that can lead to shock. A dog experiencing anaphylaxis has cardiovascular collapse: the heart rhythm may become irregular, and the blood pressure lowers suddenly. The dog may begin to pace and may pant heavily, and it may vomit and/or have diarrhea. It is essential that dogs experiencing anaphylaxis or an adverse drug reaction are provided with veterinary care immediately. The veterinarian will provide life support, enhance elimination of the drug, and if possible, administer an antidote or antagonist.
SIDE EFFECTS/TOXICITY OF SOME DRUGS
Because drugs circulate throughout the body, they may have effects other than those for which they were administered. Many of the antibacterial or anti-fungal agents can have toxic side effects. For example, tetracycline’s can discolor puppies’ teeth and slow bone development. For these reasons, their use is not recommended either in pregnant dogs or puppies. Gentamicin, a broad-spectrum antibiotic, can cause kidney damage; dogs taking this antibiotic longterm should be monitored for signs of early renal damage. If this occurs, the drug can be discontinued and the kidney given time to repair itself. Glucocorticoids cause increased drinking and urination and can increase the frequency and/ or severity of seizures in dogs with epilepsy. There are many drugs that act on the brain, causing drowsiness, weakness, and lethargy. Some are listed in Table 2. A number of medications can impair the scenting ability of dogs. Some of these include dimethylsulfoxide (DMSO), codeine and morphine (used in cough suppressants), amphetamines, and glucocorticoids. Because the administration of glucocorticoids can affect the scenting ability of some dogs, their use is avoided in drug and bomb detection dogs. Latent epilepsy (in an animal which has not yet had a seizure) may be unmasked during corticosteroid use. Animals that have von Willebrand’s Disease may be more prone to bleeding episodes when treated with non-steroidal anti-inflammatory drugs such as aspirin.
It is essential that you ask your veterinarian about possible side effects whenever she prescribes medications for your dog. The veterinarian may not be familiar with the athletic exercises your dog must perform and therefore may not realize that a side effect that may go unnoticed in a house pet can be a significant impediment in a performance dog. For example, veterinarians sometimes prescribe phenobarbital for a dog that has had a single seizure. The weakness and lethargy caused by this drug can impair a dog’s athletic performance. Therefore, it is prudent to first determine whether the dog will have more seizures and, if so, at what frequency, before instituting treatment with this drug. A note should be made in the dog’s health records of the possible side effects of prescribed drugs and the dog observed carefully for them.
DRUGS, PERFORMANCE, AND ETHICS
The dictionary defines ethics as “the moral principle by which a person is guided.” When applied to sports, this ideal would state that the athlete, and in the case of canine performance events, the coach/handler strives to succeed in the sport by his/her own unaided effort and does not seek an unfair advantage. There are two major factors in the attainment of success in athletic events, whether human or canine. First, the competitor must be capable of superior athletic ability. Secondly, the competitor must be trained and handled by a coach with forethought and knowledge. In both human sports and canine sports, people have tried to improve upon these two basic components by providing ergogenic (ergon = work; gennan = to produce) aids to enhance performance. The issue of performance-enhancing drugs has been investigated much more thoroughly in human athletics, where drugs and other ergogenic aids have been used for centuries. At the level of Olympic competition, where the stakes are highest, organizers have had to grapple with which drugs will be banned and which are acceptable for the athlete to use. The principles that guide their decisions are that the athlete should be allowed to take drugs which permit him or her to be healthy enough to train and compete (to cure, control, or comfort). However, the athlete should not be permitted to take drugs that may artificially enhance performance or increase the excretion of performance- enhancing drugs, thereby reducing the likelihood of detection. With this in mind, the International Olympic Committee has a long list of drugs that are banned.
These can be broadly classified into the following groups:
• stimulants (such as amphetamines and caffeine), sympathomimetic
drugs (those that mimic the effects of the
sympathetic nervous system), and narcotics (such as codeine
• depressants and tranquilizers
• anabolic steroids
• diuretics, which may be taken in an effort to increase the
excretion of illegal drugs in the urine.
The use of performance-enhancing drugs has not been formally addressed to any extent by the bodies that govern canine performance events, except for the organizers of Greyhound races. The widespread use of performance- enhancing (or perceived performance-enhancing) drugs in dogs suggests that the issue should be addressed. When questioned regarding their policy on performance-enhancing drugs, the American Kennel Club refers to their rule that a dog should not have its appearance altered by artificial means. The broader interpretation of this rule is that a dog in competition should not receive performance-enhancing drugs since they would alter its appearance in performance events. On this basis, one could unequivocally state that a dog that has been given anabolic steroids should not be allowed to compete, nor should a dog that has been given amphetamines or caffeine to increase its energy level. However, on considering this issue further, it becomes less clear cut. For example, may an old, slightly arthritic dog be given aspirin to relieve pain when it is competing in a Veterans class? The strictest interpretation would argue that he should not.
Should a dog scheduled to be shown in conformation on Saturday that develops a small, localized skin infection on the stomach after being cut by brambles be given antibiotics to treat the infection? The strictest interpretation of the current guidelines suggests that the dog should not be given the antibiotic, or if it is, it should not compete. The absolute strictest interpretation would be that a dog that has been diagnosed as hypothyroid, and which will have to be treated with thyroid hormone for the rest of its life, should not compete again. Nor should a bitch compete that has been given Ovaban® or Cheque® to delay its heat cycle. Nor should any dog on medication to prevent seizures compete. Yet we know that they do. I would propose that canine athletic events use the same guidelines as the Olympics. This would mean that it would be permissible and ethical to administer drugs that cure, control, or comfort, but any drug that would give a dog an unfair advantage in performance would not be permitted. With the exception of diuretics, all classes of ergogenic drugs that are used in human athletes are being used in performance dogs. To that list might be added the following:
• drugs such as atropine and thyroid hormone that improve
(or are believed to improve) physical appearance,
• drugs to control heat cycles in the bitch
Stimulants are used to enhance a dog’s performance in athletic competition, but their use is not without consequences. Studies of people taking stimulants to enhance performance have shown that these drugs significantly increase the risk of hyperthermia (heat stroke) and, in large doses, may lead to disorientation, nervousness, and anxiety. Amphetamines and cocaine are addictive and can be fatal in people. Occasionally, cocaine is administered to dogs as a central nervous system stimulant. Dogs that have been treated with cocaine have increased muscular tone, a rapid heart rate, irregular heart rhythms, and an increased respiratory rate. If overdosed, the cardiovascular effects can be life-threatening, and there are no specific antidotes for cocaine intoxication.
Depressants are more commonly used in the conformation ring than in other performance events and may be used to tone down the nervousness of an animal, especially one that is not well socialized or that is hyperactive. There is probably little benefit to the use of tranquilizers in athletic events, in which speed and precision are needed, unless a dog is very hyperactive. If overdosed, these drugs can cause depression of the respiratory and cardiovascular systems and even death. Anabolic steroids were developed by scientists commissioned by Adolf Hitler, who wanted a drug to make the SS more aggressive. These drugs were also shown to have some effects in the healing of fractures and in the building up of muscle. The 1988 Olympics, in which the winner of the 100-meter race tested positive for anabolic steroids, revealed just how widespread their use is even by the most prominent athletes. In dogs, anabolic steroids are used to improve dogs’ muscular strength in performance events requiring speed and strength. In humans, there is serious doubt as to whether the anabolic steroids do actually increase growth. Although anabolic steroids help to increase muscle mass if used with a program of heavy weight training (particularly isotonic exercises, which, by the way, are difficult to accomplish in dogs), they actually result in a decrease in stature if used in young people because they cause premature closure of the growth plates of the bones.
These drugs also increase aggressiveness (unnecessary in any canine sport!) and prolonged use can cause testicular atrophy and irreversible sterility. In addition, they can cause enlargement of the prostate gland and can contribute to prostatic cancer, heart disease, and liver damage. Drugs to modify heat cycles are used by competitors in obedience, field trials, hunting tests, and other competitions in which females in heat are prohibited from competing. Trainers and handlers have observed that these drugs sometimes alter a bitch’s behavior (either depressing or increasing activity level) and have begun to use them with behavior alteration as a primary goal. These drugs, if used on a continuous basis, can cause permanent aberrations in the female’s heat cycle, possibly leading to infertility. Performance-modifying drugs are being administered to dogs in a variety of different performance events. But a little knowledge is a dangerous thing, and those administering these drugs are often not aware of the long-term problems they may be causing. I hope that a knowledge of some of the side effects of these drugs will give people cause to reconsider the value of their use. Unfortunately, to some people, winning is more important than the health of their dogs. The question of whether to administer performance-modifying drugs depends on an individual’s ethics — the moral principles by which a person is guided.