Medicament Allergies - part 3

Anesthetics and insulin

Painkillers and various anesthetics cause allergic and toxic reactions fairly frequently. Some opiates, for example, may cause direct histamine release. If you have ever developed a rash or any kind of adverse reaction to a painkiller, sedative, or anesthetic, you should report this to your doctor. Possibly you should avoid medicaments of the same type that caused you a problem. Often another class of medicaments can be substituted.

Symptoms such as weakness, changes in heartbeat, and fainting when local anesthetics are injected are not usually due to allergy but rather to the stress of the experience. But if there is doubt as to the cause, and you want to know if you are in any danger using local anesthetics, skin testing can indicate whether an allergy exists. If the skin tests are negative, then gradually increasing doses of the medicament are injected to be certain that tolerance is good.

Anaphylaxis and other severe allergic reactions can occur during the administration of general anesthesia. This is manifested during surgery by a sudden calamitous drop in blood pressure and even cardiac arrest. Other allergic stigmata such as hives and rash are not always present. This type of reaction can be confused with many other nonallergic reactions during surgery. It is essential to establish when an allergic reaction has occurred because it will occur again and can be prevented by appropriate premedication. This is a very important point, and patients who have had this type of reaction during general anesthesia should discuss it with their own physicians. In some cases, the reaction may be due to latex allergy, and it is important to identify the cause.

Insulin allergy can be highly problematic to diabetic patients who need this substance to maintain health. There are various methods of coping, which should be reviewed with a physician specializing in diabetes.

Chymopapain and streptokinase

Papain and chymopapain, derived from the papaya tree, are enzymes used in a variety of products from meat tenderizer to toothpaste. Chymopapain is useful in treating herniated disks. Unfortunately, it also causes anaphylaxis in about 1 of every 100 persons treated. It is believed that exposure to meat tenderizer and certain grass pollen may predispose people to react badly to chymopapain.

Typically, patients are tested for chymopapain sensitivity by both an in vitro (laboratory) blood test and a skin test before the chymopapain is injected into the disk, but these tests are not always reliable.

Streptokinase, another enzyme, dissolves blood clots and is used to treat circulatory-system disorders, such as heart attacks and phlebitis. Unfortunately, many people are allergic to it and develop anaphylaxis.

X-ray dyes

X-ray dyes, also called radiographic contrast media, are often used prior to certain CAT scans, myelograms, angiography, kidney X rays, and so on. The dye helps the radiologist see the organ being studied. But the intravenous injection results in allergy like reactions in 1 of 15 cases, in dangerous reactions in 1 of 50 cases, and in death in 1 in 40,000.

If you have ever had an allergy like reaction to an X-ray dye, this must be noted in your medical records. Be sure to mention the reaction to any doctor contemplating such diagnostic testing. There are new dyes to which you may be less sensitive but which are not used routinely because they are expensive. One of these newer dyes, however, should be used if you have had any previous reaction, no matter how mild, to X-ray contrast media. Also, pretreatment with antihistamines and corticosteroids is very helpful in preventing or damping a reaction. Severe reactions are less common when, as in a myelogram or barium enema, the dye is not injected into a vein.

It was formerly thought that a history of shellfish allergy was a predictor of reactivity to these dyes, but this is not so. However, a history of hay fever or asthma does increase the risk slightly.

Prevention of dangerous medicament reactions

Other antibiotics and painkillers, too, may cause anaphylactic reactions. Chymopapain can be dangerous. The single most important thing that you can do to prevent an overwhelming anaphylactic medicament reaction is to stay within reach of medical help for a half hour to forty-five minutes after having an injection of a medicament, especially penicillin.

Oral doses of a medicament are much less likely to cause a severe reaction than injected doses. Delayed reactions are usually milder than those that arise in the first half hour or so. But this does not mean that you should ignore symptoms associated with an oral dose of medicine, whether they occur soon after the medicine is ingested or are delayed.

If you have found that you have a medicament allergy, it is important that you mention this to your doctor before trying a new medication. It is wise to learn which other common medicaments belong to the family of medicaments to which you are allergic. You should avoid that whole family of medicaments.

When a doctor prescribes a new medicament, always remind her or him of your allergy. Unfortunately a doctor may have forgotten your allergy or, worse, failed to have taken your earlier report seriously. Another prudent safeguard is to check with your pharmacist as to whether a prescribed medicament is related to the medicament or class of medicament that previously caused you difficulty.

To avoid delayed but nevertheless serious manifestations of medicament allergy, it is important to notice and remember any and all reactions that you may have had to a medicament in the past. A remembered rash or fever that cleared up suddenly when you stopped taking the medicament may be helpful in diagnosing a troublesome reaction in the present. Alert your doctor to any possible sensitivity before starting a course of treatment. Ask that the information be included in your medical records.

Diagnosis and treatment of medicament allergy

Diagnosis of medicament allergy is often uncertain, and treatment is usually simple avoidance. This avoidance, by the way, can also be helpful in the diagnosis. If the medicament is withdrawn and the symptoms disappear relatively promptly, the chances are that the cause of the trouble was some sort of allergy. Elevated levels of eosinophils in the blood, together with other signs of allergy, such as a rash, indicate that an allergic process is present. But an increased number of eosinophils by itself is rarely enough reason to diagnose medicament allergy.

Skin tests for medicament allergy are imprecise and can be dangerous. Nevertheless, they may be undertaken, always under a physician's supervision, when it is important to determine whether an allergy really is present. This situation arises most often in the case of patients who need treatment for certain infections, such as staph infections, or for a herniated disk, or for some other condition for which there is really only one medicament of choice.

Skin testing for penicillin sensitivity, while risky, is of value in that it reveals the sensitivity in most (but not all) instances in which a sensitivity does exist. Skin testing is also fairly reliable for sensitivity to insulin, chymopapain, and local anesthetics.

If a medicament-sensitive patient must have the medicament in question, a program of desensitization may be undertaken under controlled conditions (preferably in an intensive care unit). Penicillin and insulin are the medicaments for which desensitization is most often attempted, frequently with good results.

The treatment of symptoms of medicament allergy is usually with antihistamines and corticosteroids, if necessary. Often just stopping the medicament is sufficient.

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