therapeutic insights
Effect and Side Effect
A review of the OTC allergy/sinus/cold medications
By Bobby Christensen, O.D., F.A.A.O.

Over the counter (OTC) medications do not always equate to "safer than" prescription medications. OTC antihistamines and decongestants are prime examples of medications that often have more side effects than their prescription brethren.

There are hundreds of combinations of antihistamines and decongestants available on grocery and pharmacy shelves. The large selection makes it difficult -- for doctors, pharmacists, and especially for patients -- to match the appropriate medication to the condition. We need a basic understanding of how these drugs work both individually and in different combinations. We must give careful consideration to the possible side effects as well.

Fortunately, most of the products can be categorized into basic allergy/sinus classifications.

Diphenhydramine

Diphenhydramine (Benadryl) is an antihistamine most often used for acute allergic reactions. The doctor of optometry would likely use it for acute allergic reactions with chemosis involving the conjunctiva and/or lids. Its rapid action reduces edema and itching. Usually we only need to pre-scribe diphenhydramine for one to three days to achieve the desired results. It can also suppress cough, treat motion sickness and induce sleep.

Diphenhydramine is marketed under about twenty brand names. For prescription purposes, it's easier to just remember "Benadryl." It's an FDA category B drug, which means it's unlikely to cause harm to an unborn fetus. But it is passed to a baby in breast milk and may cause harm.

Probably the most significant side effects of Benadryl are drowsiness and the sedation induced when used in combination with specific other drugs. Driving or operating machinery can be quite dangerous -- that might include operating a phoropter!

Alcohol combined with most medications can lead to serious complications and/or sedation. It not only increases the risk of liver damage, but also multiplies the sedation or depression of the central nervous system. This also applies to tranquilizers and antidepressant medications such as Valium, Prozac and Zoloft.

Other side effects include dryness, difficulty urinating (men), increased IOP, increased blood pressure and erratic blood sugar control for diabetics.

Chlorpheniramine & pseudoephedrine

Chlorpheniramine is an antihistamine most often used for chronic allergy and sinus problems. Pseudoephedrine is a decongestant used to dry the sinus and nasal mucosa; dry eye patients may require extra lubrication or temporary plugs while taking this combination.

Chlorpheniramine/pseudoephedrine is typically prescribed for four to seven days for chronic allergic conjunctivitis; it's usually used in conjunction with topical ophthalmic mast cell stabilizers/antihistamines.

The combination comes in approximately 40 brands, including Chlor-Trimeton Allergy Decongestant or Sudafed Plus. It's an FDA category B drug and passes to breast milk.

Side effects include increased IOP, increased blood pressure, drowsiness, enlarged prostate, blurred vision and excitation in children. It shouldn't be pre-scribed if the patient is taking MAOI inhibitors. Alcohol, tranquilizers and anti-depressants are a dangerous mix with any of these OTC antihistamine/decongestant remedies.

This combination causes less drowsiness than Benadryl, but more than the prescription drugs Claritin, Allegra and Zyrtec.

Guaifenesin & phenylpropanolamine

Guaifenesin decreases the viscosity of the mucous and promotes drainage from the respiratory system (expectorant). Phenylpropanolamine is a decongestant that makes this combination appear to be a contra- diction: The expectorant liquifies the mucous and the decongestant dries the mucous, but it works well in combination.

Entex LA is probably the most commonly known brand name and there are about 15 others. It's an FDA category C drug, meaning that it isn't known if it causes injury to the fetus. It isn't known if the drugs are excreted in breast milk.

Phenylpropanolamine is a sympathomimetic much like the other decongestants and thus demands cautious use in patients having hypertension, diabetes, heart disease, glaucoma or prostate problems.

This combination wouldn't often be used for eye conditions; one of the few scenarios I can think of would be a patient with sinus headache and eye ache due to congestion; Entex LA could be prescribed for four to seven days to reduce the sinus pressure.

Acetaminophen, dipenhydramine & pseudoephedrine

Acetaminophen (APAP or Tylenol) is a pain reliever and fever reducer. It's widely used -- everyone is aware of the Tylenol brand. Acetaminophen is available in combination with many other products such as aspirin and caffeine, expectorants, cough suppressants, decongestants and antihistamines. Acetaminophen is also combined with schedule drugs such as codeine and hydrocodone. It's easy on the stomach and safe when taken in moderation.

Liver damage is a common side effect when higher doses are taken. Taking acetaminophen and drinking alcohol can also cause severe liver damage. The maximum amount of acetaminophen for a healthy patient with no alcohol intake is 4000 mg per day. Never take more than 2000 mg per day if three or more alcoholic drinks are consumed per day. Both drugs are fighting for the same liver enzymes to break down and eliminate the chemicals from the body.

Dipenhydramine is the antihistamine and pseudoephedrine is the decongestant. The same side effects listed earlier can occur with these medications, particularly drowsiness. Remember that liver damage is an additional concern.

Acetaminophen/dipenhydramine/pseudoephedrine is an FDA category C drug and should not be taken by mothers who are breast feeding. There are eight brands containing this combination of drugs, including Benadryl Allergy Sinus.

This OTC combo would most often be prescribed for the patient with a cold. It would be prescribed for three to seven days corresponding with the predicted remaining duration of the viral infection.

Some final thoughts

The prescription anti-histamines are safer to use than the OTC medications. In most cases it would be wiser to prescribe one of these medications vs. the OTC medications if the patient needs an antihistamine. If you prescribe the "D" formulation of the prescription medications, the side effects of decongestants must be considered, i.e. Claritin D, Allegra D.

Of greater importance is being informed about them when patients ask questions about what can be used with their glaucoma or diabetes medication. And I personally want to know the safety profile of these OTC drugs so that my family or I can make a safe decision when selecting a medication late Saturday night for achy muscles, watering eyes and runny nose. Hey, I want to keep my liver for a few more years.

Dr. Christensen has a partnership practice in Midwest City, Okla. He's a diplomate in the Cornea and Contact Lens Section of the American Academy of Optometry. He's also a member of National Academies of Practice.