Doctor, Should I take Antihistamines?

Insight into decongestants and cold remedies

Drugs for stuffy nose, sinus trouble, congestion, and the common cold constitute the largest segment of the over-the-counter market for America's pharmaceutical industry. When used wisely, they provide welcome relief for at least some of the discomforts that affect almost everyone occasionally and that affect many people chronically. Drugs in these categories are useful for relief of symptoms from allergies, upper respiratory infections (i.e., sinusitus, colds, flu), and vasomotor rhinitis (a chronic stuffy nose caused by such unrelated conditions as emotional stress, thyroid disease, pregnancy, and others). These drugs do not cure the allergies, infections, etc.; they only relieve the symptoms, thereby making the patient more comfortable.

Histamine is an important body chemical that 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 Benadryl,®* Chlor-Trimetron,®* Claritin,® Dimetane,®* Allegra,® PBZ,®* Polaramine,® Tavist,®* Teldrin,® Zyrtec,® etc.

Congestion in the nose, sinuses, and chest is due to swollen, expanded, or dilated blood vessels in the membranes of the nose and air passages. These membranes have an abundant supply of blood vessels with a great capacity for expansion (swelling and congestion). Histamine stimulates these blood vessels to expand as described previously.

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®*), phenylpropanolamine (Dura-Vent,® Entex,®), and pseudoephedrine (Novafed,®* Sudafed,®* etc.)

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

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-Trimetron 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.

Decongestants and/or antihistamines are the principal ingredients in "cold" remedies, but drying agents, aspirin (or aspirin substitutes) and cough suppressants may also be added. The patient should choose the remedy with ingredients best suited to combat his own symptoms. If the label does not clearly state the ingredients and their functions, the consumer should ask the pharmacist to explain them.

The types of nose sprays that 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.

(The above description and advice does not apply to the type of prescription anti-allergy nose sprays that may be ordered by your physician.)

© 2004 AAO-HNS/AAO-HNSF