cold : Antihistamines, Decongestants, and Cold Remedies

Antihistamines
Histamine is an important body chemical that (or this, or whatever) is responsible for the congestion, sneezing, and runny nose that a patient suffers with an allergic attack or an infection. Antihistamine drugs block the action of histamine, therefore reducing the allergy symptoms. For the best result, antihistamines should be taken before allergic symptoms get well established.

The most annoying side effect that antihistamines produce is drowsiness. Though desirable at bedtime, it is a nuisance to many people who need to use antihistamines in the daytime. To some people, it is even hazardous. These drugs are not recommended for daytime use for people who may be driving an automobile or operating equipment that could be dangerous. Newer non-sedating antihistamines, available by prescription only, do not have this effect. The first few doses cause the most sleepiness; subsequent doses are usually less troublesome.

Typical antihistamines include Allegra®, Benadryl®, Chlor-Trimetron,®, Claritin®, Clarinex®, Teldrin®, Zyrtec,® etc.

Decongestants, on the other hand, cause constriction or tightening of the blood vessels in those membranes, which then forces much of the blood out of the membranes so that they shrink, and the air passages open up again.

Decongestants are chemically related to adrenalin, the natural decongestant, which is also a type of stimulant. Therefore, the side effect of decongestants is a jittery or nervous feeling. They can cause difficulty in going to sleep, and they can elevate blood pressure and pulse rate. Decongestants should not be used by a patient who has an irregular heart rhythm (pulse), high blood pressure, heart disease, or glaucoma. Some patients taking decongestants experience difficulty with urination. Furthermore, decongestants are often used as ingredients in diet pills. To avoid excessively stimulating effects, patients taking diet pills should not take decongestants.

Typical decongestants are phenylephrine (Neo-Synephrine®*), and pseudoephedrine (Sudafed®, etc.)

* May be available over–the–counter without a prescription. Read labels carefully, and use only as directed.

Combination Remedies
Theoretically, if the side effects could be properly balanced, the sleepiness sometimes caused by antihistamines could be cancelled by the stimulation of decongestants. Numerous combinations of antihistamines with decongestants are available: Actifed,®* Allegra-D,® Chlor-Trimeton D,®* Claritin D,® Contac,®* Co-Pyronil 2,®* Deconamine,® Demazin,®* Dimetapp,®* Drixoral,®* Isoclor,®* Nolamine,® Novafed A,® Ornade,® Sudafed Plus,® Tavist D,®* Triaminic,®* and Trinalin,® to name just a few.

A patient may find one preparation quite helpful for several months or years but may need to switch to another one when the first loses its effectiveness. Since no one reacts exactly the same as another to the side effects of these drugs, a patient may wish to try his own ideas on adjusting the dosages. One might take the antihistamine only at night and take the decongestant alone in the daytime. Or take them together, increasing the dosage of antihistamine at night (while decreasing the decongestant dose) and then doing the opposite for daytime use.

Nose Sprays
The types of nose sprays that maybe can be purchased without a prescription usually contain decongestants for direct application to nasal membranes. They can give prompt relief from congestion by constricting blood vessels. However, direct application creates a stronger stimulation than decongestants taken by mouth. It also impairs the circulation in the nose, which after a few hours, stimulates the vessels to expand to improve the blood flow again. This results in a "bounce-back" effect. The congestion recurs. If the patient uses the spray again, it starts the cycle again. Spray–decongestion– rebound–and more congestion.

In infants, this rebound rhinitis can develop in two days, whereas in adults, it often takes several more days to become established. An infant taken off the drops for 12 to 24 hours is cured, but well-established cases in adults often require more than a simple "cold turkey" withdrawal. They need decongestants by mouth, sometimes corticosteroids, and possibly (in patients who continuously have used the sprays for months and years) a surgical procedure to the inside of the nose. For this reason, the labels on these types of nose sprays contain the warning "Do not use this product for more than three days." Nose sprays should be reserved for emergency and short term use.

• Zinc lozenges shorten the duration of symptoms from the common cold, such as a cough and runny nose, in adults but not in children.
• The lozenges must be taken frequently, starting as soon as symptoms are noticed (within 24 hours of the onset).
• Adverse side effects of short-term use of zinc are an unpleasant taste and nausea: for longer use, side effects are unknown.
• Patients and their physicians can decide whether the benefit of a shorter cold outweighs the inconvenience of frequent doses and the unpleasant taste of the lozenges.
• No preventive treatment or ultimate cure for the common cold is available.

Initially introduced in the early 1980's, zinc lozenges are being used by increasing numbers of people when they have colds. With the arrival of the current winter season, the lozenges once again have attracted the public's attention. In addition, the public's interest has been heightened by a recent settlement between a maker of the lozenges and the Federal Trade Commission (FTC) regarding the claims for zinc as a treatment for the cold.

Good food sources of zinc include meats, liver, seafood (especially oysters), and eggs. Zinc also is found in whole-grain products such as whole wheat or rye bread, oatmeal, and whole corn. However, its effectiveness (or bioavailability) is less in these food sources. Bioavailability refers to the absorption of an element from the intestine into the blood stream so that it is available to participate in necessary biological functions in the tissues of the body. The type of food eaten can affect the bioavailability of zinc. For example, phytate (which is found in certain cereal proteins) and dietary fiber can reduce the absorption of zinc, and thereby decrease the bioavailability of zinc. An additional source of this essential mineral is multivitamin pills, which usually contain 100% of the RDA for zinc.

Five of the randomized clinical trials, which were done in adults, determined that zinc was effective in treating the common cold if the lozenges were started within 24 hours of the onset of cold symptoms. In one study, the lozenges reduced the severity of symptoms (assessed by using a scoring system). In the other four studies, the duration of symptoms was decreased by 3 to 4 days. In all of these trials, the lozenges contained 13.3 to 23.7 mg of elemental zinc and the patients took the lozenges once every 2 hours while awake.

In another study, the treatments with zinc or the placebo were begun before the volunteer subjects were purposely injected with a cold virus. The treatments were also continued afterwards. This is the only study to evaluate the effectiveness of zinc lozenges in preventing colds. The subjects in the zinc and placebo groups came down with about the same number of colds. The zinc lozenges therefore failed to prevent colds. However, and as experienced in the other trials, the severity of cold symptoms was significantly less in the group taking the zinc than in those taking the placebo.

In five other randomized, controlled trials in adults, there was no reported benefit of zinc in treating the common cold. A close examination of each of these trials, however, revealed one or more possible explanations for the lack of benefit. In some of these trials, the dose of zinc may have been too low. For example, in one trial, each lozenge contained only 4.5 mg of zinc. In four of these trials, compounds such as citric acid, tartaric acid, mannitol, and sorbitol, which were added to improve the flavor of the zinc lozenge, may have impaired the bioavailability of the zinc. These added compounds can form chemical bonds with zinc, thereby making the ingested zinc unavailable for its therapeutic effect.

The only study done in children and adolescents showed no value of zinc lozenges in treating the common cold. This was a large, randomized, controlled trial that was well-executed. The conclusion, therefore, is that either the 10 mg of elemental zinc used in this study may have been too low to relieve cold symptoms in children or the beneficial effects of zinc on the severity and duration of colds are limited to adults.

As for using higher doses of zinc, taking 300 mg of elemental zinc daily for six weeks impairs the body's immune responses. This would theoretically increase a person's susceptibility to infections. To consume that much elemental zinc daily from zinc lozenges alone, a person would have to take more than 22 lozenges per day (each containing 13.3 mg), which is almost double the maximum recommended dose. High doses of zinc also are associated with decreased levels of high-density lipoprotein cholesterol (the "good" cholesterol) in the blood, which could be another undesirable effect.

Adverse interactions between zinc lozenges and other drugs have not been reported to date. However, citric acid, which is found in oranges, grapefruits, and lemons, can inactivate zinc salts. While vitamin C has been reported to increase the absorption of iron, a similar effect on zinc has not been seen.