The methylxanthines class includes dyphylline (known under various trade names); oxtriphylline (Choledyl); theophylline (known under numerous trade names); and theophyl­line ethylenediamine or Aminophyllin and aminophylline. Except for dyphylline, all are converted in the body to theophylline.

In the United States, theophylline is the mainstay of therapy for asthma. The most common form of the drug is aminophylline, which comes in tablet, liquid, or suppository form. The oral form is usually preferred. Aminophylline suppositories should be avoided because of their erratic absorption. The breakdown and excretion of theophylline differs considerably from one patient to another; one patient may take an amount of theophylline five or ten times greater than another pa­tient’s dose. Theophylline is usually prescribed on a twenty-four-hour schedule, although longer-acting theophylline preparations are being marketed that allow a dosage rate of every eight to twelve hours. Many patients continue to take a dosage based on a six-hour sched­ule. The physician ascertains the patient’s proper dose by obtaining a blood theophylline determination. As is true of any medication, theophylline has potential side effects; nervousness is the most com­mon, but nausea, vomiting, and headache may also occur. These symptoms are often the first sign of too much theophylline. An over­dose can even provoke convulsions. The way theophylline is metab­olized—hence, its level in the blood—can change in certain circum­stances, for example, when a patient has heart failure or liver disease, develops prolonged fever, smokes cigarettes, or takes certain anti­biotics. Some diets can also affect theophylline metabolism. Theo­phylline is one of the most common ingredients in combination asthma medicines such as Tedral and Marax. Occasionally, a physician may prescribe one of these combination products, but in general it is dif­ficult to custom-make a product, that is, proportion ingredients for a particular individual. The side effects that accompany some combina­tion products may not be caused by theophylline but by another in­gredient. Because one medication sometimes interacts with another, a particular medication can either lessen or increase the effect of the other. Caffeine (found in coffee) and theobromine (commonly found in tea) react similarly to theophylline. The doctor should know whether the patient is a heavy coffee, tea, or cola drinker, since high consumption of these beverages can increase the effect of theophyl­line. The patient should also tell the physician exactly what medica­tions he or she is taking, even when the physician forgets to ask, or when there is a change in the rate of consumption or in the patient’s condition. Vitamin pills and laxatives should not be forgotten, espe­cially if the patient is taking large amounts of them. Another side effect that can occur with theophylline (or with almost any other bronchodilator medication taken orally) involves the point at which the esophagus joins the stomach. A valvelike muscle there connects the two and prevents any material in the stomach from backing up into the esophagus. Theophylline relaxes this muscle so that regurgi­tation of stomach contents into the esophagus occurs, resulting in a condition popularly known as heartburn. These symptoms are easily treated with an antacid to help neutralize food contents in the stom ach. Other measures, such as raising the head of the bed or lying at a particular angle, sometimes help prevent this backward flow or reflux.

Hypogammaglobulinemia occurs when there is a decreased level of gamma globulin in the blood. It may be due to failure in the gamma globulin-producing cells (B lympho­cytes) or to greater losses through the kidneys, the gastrointestinal tract, or skin. The disease may also be secondary to other diseases that damage the gamma globulin-producing cells. Hyposensitization Hyposensitization is a method of treating allergies in which series of small doses of the substance that causes an allergy are administered in increasingly large concentrations, in the hope of increasing a person’s immunity to the substance. The method is also known as densensitization or immunotherapy. See also immunotherapy.

(egg-free, gluten-free, milk-free, wheat-free) 6 squares semisweet chocolate 2 tablespoons milk-free margarine Heat chocolate and milk-free margarine over hot water until chocolate is partially melted. Remove from hot water and stir rapidly until ingredi­ents are well blended and mixture is thick. Using a teaspoon, cover the inside surface of 10 large paper baking cups with a thin layer of mixture. Set in muffin pans; chill until hard. Fill with ice cream or pudding. Chill in refrigerator before peeling off paper.

Allergic disease usually appears during childhood. Although it is clear that inherited genetic factors largely determine who will be allergic, little is known about the modulating influence of the genetic code. Current research suggests that viral infections may act as triggers, contributing to a predisposition to allergy in an individual. Perhaps exposure to antigens passed across the placenta, or ingested during the first month of life, influence the course an allergy takes. Researchers have uncovered evidence that suggests that avoidance of certain foods during the early months of life can decrease the in­cidence of respiratory allergy years later. In addition to the allergic diseases already mentioned, allergic children seem to experience a specific complication of allergic rhinitis known as Eustachian tube dysfunction. This complication occurs because swollen allergic membranes in the nose and throat impede the normal functioning of the Eustachian tubes, which equal­ize pressure between the middle ear and the outside world. When the tubes do not function properly, fluid can build up in the middle ears, resulting in recurrent ear infection or hearing loss, or both. If medication and control of environmental allergens do not improve the situation sufficiently, artificial ventilating tubes made of poly­ethylene must be placed surgically in the tympanic membrane to equalize the pressure. Research in middle ear disease among allergic children is aimed at identifying the scope of the problem, as well as evaluating the various treatments using antihistamines, decongestants, and topical corticosteroids either individually or in combination.

For simplicity, pathological reactions with an immunologic basis are grouped according to four types, I through IV. Type I — immediate hypersensitivity. An immediate hypersensitivity (anaphylactic) reaction is mediated by the IgE antibody on mast cells and basophil leukocytes. An antigen interacting with cell-bound IgE antibodies causes the release of a group of substances known as mediators. These substances are most directly responsible for the major clinical manifestations of immediate hypersensitivity, the symp­toms of which usually begin within minutes after exposure to an antigen. When this type of reaction occurs in humans, it is called an allergic reaction, or allergy. Hay fever, some forms of asthma and hives (urticaria), anaphylactic shock, and some reactions that occur after insect stings or the ingestion of certain drugs or foods are ex­amples of IgE-mediated hypersensitivity reactions. It is well known that clinical manifestations of IgE-mediated reactions may persist for hours, days, or even weeks. When this occurs, additional pathological mechanisms must be invoked. Type II — cytotoxic reactions. Cytotoxic reactions are those in which an IgG antibody directed against a cell membrane component reacts with the component and, in so doing, activates the body’s com­plement system. The complement system consists of interacting pro­teins (some of which are enzymes) in series which, when activated, react in a cascade manner. The end product of this reaction is the destruction of the membrane of the cells or. the bacteria. The unto­ward reaction following a transfusion of incompatible blood is one example of an IgG antibody-mediated cytotoxic reaction. Type III — immune complexes. Type III reactions are those in which immune complexes form. That is, aggregates containing many molecules of antigen and antibody, mainly of the IgG and IgM classes, are formed. Immune complexes can become localized in small blood vessels, where they activate the complement system, producing local, acute inflammation. When an antigen is injected into the skin of a sensitized animal, an area of local swelling and erythema appears The complement system consists of a series of interacting enzymes which can be activated in either of two ways. In one, known as the classical pathway, the system is turned on when antibody reacts with an antigen such as a red blood cell (RBC), forming an immune complex. This com­plex binds CI, the first enzyme in the series, and the cascade reaction begins. In the alternate pathway, certain substances — such as the toxins (poisons) produced by bacteria — trigger the latter part of the cascade.
after one to two hours. This condition will peak in three to six hours; after that, it usually subsides. This is known as the Arthus reaction. Serum sickness is a more generalized immunopathology (vasculitis) caused by circulating immune complexes. Some reactions to drugs are mediated by the immune-complex mechanism. Type IV — delayed hypersensitivity. The tuberculin test is the clas­sic example of a type IV reaction. In this type, a local reaction occurs in the skin twenty-four to forty-eight hours after injection of tuber­culin in a person sensitive to tuberculin. This reaction is also known as a cell-mediated immune response. Sensitized T cells interact with antigen, proliferate, then secrete substances called lymphokines. Lym-phokines draw other cells, principally monocytes, from the blood to the site of the antigen. The local reaction, then, results from the in teraction of monocytes (which are transformed into macrophages] with the localized deposit of antigen. This reaction can produce im­munity in the case of an infectious agent, such as Mycobacterium, the cause of tuberculosis. Rejection of tissue or an organ transplant from one individual to another is also an example of cell-mediated re­action.

Antihistamines are used in treating various disorders of the stom­ach and intestines (the gastrointestinal tract) and of the nose and skin. They are particularly effective in the treatment of hay fever (allergic rhinitis) and other inflammations of the nose (vasomotor rhinitis and intrinsic rhinitis); of hives (urticaria); contact derma­titis; eczema; allergic rashes similar to measles; and allergic reactions in the stomach and intestines (gastrointestinal allergy). The itching associated with rashes such as eczema and contact dermatitis is de­creased, although the appearance of the rash often is not immediately altered. Antihistamines are also used to supplement the treatment of allergic reactions or reactions similar to those of allergies which in­volve more than one body system (for example, the lungs and the skin). These reactions are known medically as systemic allergic reac­tions or idiosyncratic reactions (reactions similar to systemic allergic reactions, but in which allergic mechanisms cannot be demonstrated). In general, antihistamines are not effective in treating asthma, al­though some asthma patients may benefit from treatment with these drugs. Representative Drugs The antihistamines used to treat allergic disorders are commonly divided into six classes, with the following chemical names: ethanola-mine, ethylenediamine, alkylamine, piperazine, and phenothiazine. The sixth class is a group of miscellaneous compounds. Drugs classi­fied as members of the first five classes are chemically related; those in class VI are not necessarily related chemically to each other, nor to members of the five other classes. The drugs in classes I through V have therapeutic properties similar to those of other drugs in the same class. Although patients vary in their responses to specific drugs, their reactions to various chemically related preparations are similar. Sometimes a patient develops a tolerance to an antihistamine drug, which renders the antihistamine ineffective for that patient. This phenomenon is usually dealt with by switching to a chemically un­related antihistamine, or by discontinuing an antihistamine for awhile, which removes the tolerance for that antihistamine. Class I antihistamines —the ethanolamines—are the most potent antihistamines in terms of therapeutic equivalents. This group in­cludes: bromodiphenhydramine; dimenhydrinate (Dramamine and Ambodryl); carbinoxamine (Clistin and Clistin R.A.); clemastine (Tavist); diphenhydramine (Baramine, Benadryl, and SK-Diphenhy-dyramine); diphenylpyraline (Diafen and Hispril); and doxylamine (Decapryn). Class II, the ethylenediamines, includes: methapyrilene (Histadyl) ; pyrilamine (Histalon, Neo-Antergan, Neo-Pyramine, and Nisaval); and tripelennamine (Pyribenzamine, Pbz, and Pbz-SR). Class III, the alkylamines, contains probably the most commonly prescribed antihistamines. Representative compounds are: bromphe­niramine (Dimetane and Dimetane Extentabs); chlorpheniramine (sold under numerous trade names); dexbrompheniramine (Disomer Chronotabs) ; dexchlorpheniramine (Polaramine and Polaramine Repetabs); dimethindine (Forhistal, Forhistal Lontabs, Triten, and Triten Tab-In); and triprolidine (Actidil). Some ethylenediamines and alkylamines are available without pre­scription. They are also available in many nonprescription, fixed-dose combinations marketed as compounds for the relief of colds, hay fever, and headaches. Class IV consists of piperazines and includes cyclizine (Marezine) and meclizine (Bonine). Drugs in this group, along with dimenhydri­nate in class I, are used primarily for treating motion sickness. Phenothiazines make up class V. Representative drugs are methdi-
lazine (Tacaryl), promethazine (Phenergan), and trimeprazine (Temaril). Phenothiazines are used principally as tranquilizers, al­though they also have antihistaminic properties, which make them useful in relieving rashes. Class VI, a group of miscellaneous compounds, includes the chem­ically related azatadine (Optimine) and cyproheptadine (Periactin). Both compounds inhibit the neurotransmitter serotonin, as well as histamine, and are used mostly to alleviate the itching common in skin disorders. Cyproheptadine may be helpful in treating hives caused by exposure to low temperatures (cold urticaria). The hydroxyzines (Atarax and Vistaril) are related most closely to the piperazines. Hydroxyzine, used primarily for treating allergic rashes, has recently been demonstrated as beneficial in the relief of hay fever in some patients; it is also useful as a tranquilizer. Many fixed-ratio combinations of two or more antihistamines, or of antihistamines plus decongestants, are widely used. Another group of antihistamines, the H2 antihistamines, have vastly different treatment properties. Cimetidine (known by the trade name Tagamet) is, however, the only member of this group approved by the Food and Drug Administration, having been approved for treating peptic ulcers but not allergic disorders. Some studies indicate that a combination of cimetidine and an antihistamine from one of the other groups may be more effective than other antihistamines alone in treating some cases of hives that last more than three months (chronic urticaria). Theoretically, cimetidine should not be used alone in the treatment of allergic disorders.

Exercise can cause bronchospasm in asthmatic patients, particularly children. The changes that occur during an attack are the same as those in other types of asthma, but no immuno­logical mechanism has yet been demonstrated. It is thought that in­halation of cold, dry air may contribute to the onset of the condition. Exercise-induced asthma can be prevented by pretreatment with one of the various medications used in treating asthma. Cromolyn and inhaled bronchodilators are especially useful for this purpose.

who has suffered an anaphylactic reaction—whether to a food, insect sting, drug, or medical procedure—is susceptible to other attacks. Although an anaphylactic reaction may never recur, that person cannot be certain of always avoiding concealed food, a drug accidentally administered, a medical procedure, or the sudden sting of an insect. Once an anaphylactic reaction begins, the best treatment is an injection of epinephrine (Adrenalin) . The drug works within minutes, tightening the blood vessels to prevent serum from escaping, and thus preventing edema. The same action tends to maintain blood pressure while acting simultaneously to keep the airways open. The injection procedure is not difficult to learn. Before prescribing the self-medication of Adrenalin, a physician should demonstrate its proper use and allow the patient to practice the self-injection pro­cedure. First-aid kits containing epinephrine (the generic name for Adren­alin) are available in various forms. The Emergency Ana-Kit (manufactured by Hollister-Stier in Spokane, Washington) contains 1 preloaded syringe containing a 0.3-milliliter (5 milliliters equals 1 teaspoon) dose of epinephrine in a red plastic box 4Vi inches long, one and three-fourths inches wide, and an inch deep; four chewable doses of the antihistamine Chlorpheniramine (2 milligrams each) in a sealed, clear plastic wrap; two wrapped, isopropyl alcohol swabs, and a thin string-type tourniquet. The Insect Sting First Aid Kit, sold by Center Laboratories in Port Washington, New York, is a box approximately 6 by 2 г А by 1 inch and containing a prefilled syringe containing a 1:1,000 solution of epinephrine, an alcohol pad, a tourni­quet, antihistamine tablets of Chlorpheniramine (4 milligrams each), and 2 ephedrine-phenobarbital tablets. Some other manufacturers market prefilled syringes of epinephrine, which can be injected auto­matically (Epi. Pen. Center Laboratories). The needle is injected into the fatty tissue under the skin —not in a muscle, vein, or artery. The usual dose is 0.3 milliliter of a 1:1,000 solution of epinephrine. It is best to administer a smaller dose, preferably 0.2 milliliter, to patients under age seven, to those who weigh less than forty pounds, or to adults with heart irregulari­ties or coronary vessel disease. This step is followed by taking an antihistamine tablet. Among adults, 50 milligrams of Benadryl or 4 of Chlortrimeton (Chlor­pheniramine) is commonly used. Children under the age of seven should take half this dosage. If an anaphylactic reaction has not begun to subside within twenty minutes, the dose should be repeated. Epinephrine is also available in a metered, self-administered aerosol activated by hand while the user inhales. Such preparations as Medihalor-Epi, manufactured by Riker Laboratories in Northridge, California, are available without prescription. Although not a sub­stitute for injectable epinephrine in cases of anaphylaxis, Medihalor-Epi may be helpful as a backup treatment for the throat (laryngeal edema) or for bronchial swelling (asthma), either of which may occur alone or as a manifestation of anaphylaxis. Portable and virtually indestructible, these devices can be carried in automobiles, briefcases, handbags, and so on. The kits should be checked every month to make sure the clear epinephrine solution has not discolored (usually becoming amber). Such change, accelerated by sunlight, indicates decreased potency. The aerosol should be activated periodically to determine whether the valve opening is still free of dust. If it is not, cleaning with soapy water or ammonia will remove the dust. If an allergen —for example, food or medicine—causing the ana­phylaxis has been ingested, remove as much of the material as pos­sible by spitting or rinsing it out, making sure that you do not swallow. If necessary, vomiting can usually be induced by placing one or two fingers at the rear of the mouth. If the allergen has been injected into the arm, a tourniquet should be applied tightly between the site of the injection and the shoulder. Tourniquets are available in first-aid kits, or they can be purchased separately or improvised from shoestrings, cord, or large rubber bands. Tourniquets placed between the injection site and the heart will slow the absorption and circulation of such allergens as bee or wasp venom.

House-dust allergy is extremely common in the United States. Avoidance of dust, use of antihistamines, and desensitization injec­tions are the usual therapeutic approaches, with avoidance the most important. Your allergist can advise you about how to avoid house dust.