Therapeutic & Toxic Potential of Over-the-Counter Agents

Drugs are divided by law into two classes: those restricted to sale by prescription only and those for which directions for safe use by the public can be written. The latter category constitutes the nonprescription or over-the-counter (OTC) drugs. It is apparent that many OTC drugs are no more than “me too” products advertised to the public in ways that suggest significant differences between them. For example, there are over 100 different systemic analgesic products, almost all of which contain aspirin, acetaminophen, nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, or a combination of these agents as primary ingredients. They are made different from one another by the addition of questionable ingredients such as caffeine or antihistamines; by brand names chosen to suggest a specific use or strength(“women’s,” “migraine,” “arthritis,” “maximum”); or by special dosage formulations (enteric-coated tablets, geltabs, liquids, orally disintegrating strips and tablets, sustained-release products, powders). There is a price attached to all of these features, and in most cases a less expensive generic product can be equally effective. It is probably safe to assume that the public is generally overwhelmed and confused by the wide array of products presented and will probably use those that are most heavily advertised.

There are three reasons why it is essential for clinicians to be familiar with the OTC class of products: First, many OTC medications are effective in treating common ailments, and it is important to be able to help the patient select a safe, effective product. Second, many of the active ingredients contained in OTC drugs may worsen existing medical conditions or interact with prescription medications. Finally, the misuse or abuse of OTC products may actually produce significant medical complications. Phenylpropanolamine, for example, a sympathomimetic previously found in many cold, allergy, and weight control products, was withdrawn from market based on reports that the drug increased the risk of hemorrhagic stroke. Dextromethorphan, an antitussive found in many cough and cold preparations, has been increasingly abused in high doses (eg, > 5–10 times the recommended antitussive dose) by adolescents as a hallucinogen. Although severe complications associated with dextromethorphan as a single agent in overdose are uncommon, many dextromethorphan-containing products are formulated with other ingredients (acetaminophen, antihistamines and sympathomimetics) that can be fatal in overdose.

The next tables list examples of OTC products that may be used effectively to treat common medical problems. The selection of one ingredient over another may be important in patients with certain medical conditions or in patients taking other medications. The recommendations listed in the tables are based on the efficacy of the ingredients and on the following principles: 1. Select the product that is simplest in formulation with regard to ingredients and dosage form. In general, single- ingredient products are preferred. Although some combination products contain effective doses of all ingredients, others contain therapeutic doses of some ingredients and subtherapeutic doses of others. Furthermore, there may be differing durations of action among the ingredients, and there is always a possibility that the clinician or patient is unaware of the presence of certain active ingredients in the product. Acetaminophen, for example, is in many cough and cold preparations; a patient unaware of this may take separate doses of analgesic in addition to that contained in the cold preparation, potentially leading to hepatotoxicity.

2. Select a product that contains a therapeutically effective dose. 3 2. Select a product that contains a therapeutically effective dose. 3. Consumers and providers should carefully read the “Drug Facts” label to determine which ingredients are appropriate based on the patient’s symptoms, underlying health conditions, and whatever is known about the medications the patient is already taking. This is critical because many products with the same brand name contain different ingredients that are labeled for different uses. For example, multiple laxative products(with different active ingredients) carry the Dulcolax name including Dulcolax Balance (polyethylene glycol), DulcolaxLaxative (bisacodyl), and Dulcolax Stool Softener (docusate sodium). This marketing practice of “extending a brand name” across product lines, while legal, is confusing and can lead to medication errors. 4. Recommend a generic product if one is available. 5. Be wary of advertising claims of specific superiority over similar products. 6. For children, the dose, dosage form, and palatability of the product are prime considerations.

These agents should be avoided or used cautiously by type 1 diabetics and patients with hypertension, angina, or hyperthyroidism. Aspirin should not be used in children and adolescents for viral infections (with or without fever) because of an increased risk of Reye’s syndrome. Aspirin and other NSAIDs should be avoided by individuals with active peptic ulcer disease, certain platelet disorders, and patients taking oral anticoagulants. Cimetidine, an H2 -receptor antagonist, is a well-known inhibitor of hepatic drug metabolism and can increase the blood levels and toxicity of drugs such as phenytoin, theophylline, and warfarin.

Overuse or misuse of OTC products may induce significant medical problems. A prime example is rebound congestion from the regular use of decongestant nasal sprays for more than 3 days. The improper and long-term use of some antacids (eg, aluminum hydroxide) may cause constipation and even impaction in elderly people, as well as hypophosphatemia. Laxative abuse can result in abdominal cramping and fluid and electrolyte disturbances. Insomnia, nervousness, and restlessness can result from the use of sympathomimetics or caffeine hidden in many OTC products The long-term use of some analgesics containing large amounts of caffeine may produce rebound headaches, and long-term use of analgesics has been associated with interstitial nephritis. OTC products containing aspirin, other salicylates, acetaminophen, ibuprofen, or naproxen may increase the risk of hepatotoxicity and gastrointestinal hemorrhage in individuals who consume three or more alcoholic drinks daily.