Answer: An over-the-counter medication (OTC) can generally be purchased from the pharmacy without a prescription. One often assumes because there is no requirement for direct physician supervision, the medication is safe. While many items purchased OTC started as prescription items, there is no guarantee they are safe, especially when used in combination with other medications and in people who may have compromised kidney function. Drugs can interact with each other regardless of whether or not a prescription is required.

When a medication is shifted from prescription to OTC, the patient must assume a vital role in understanding how this medication is to be taken. The patient must prepare an accurate list of each medication, the name, brand name, dose, frequency, date started, date stopped, and name of the prescribing doctor – or whether it’s OTC. Click here to get a helpful form. It is not really possible to memorize the vast list of medications, or to keep straight the generic name or brand name. Luckily, there are resources, especially on the Internet. Click here or click here.

Many drugs are eliminated by the kidneys, and when kidney function worsens, toxic drug metabolites may accumulate. Likewise, drug elimination often involves liver enzymes in the Cytochrome P450 family (often called CYP). When drugs share the same CYP enzyme system (isoform) for their elimination toxins may accumulate, and some may cause serious heart disturbances known as arrhythmias. Click here for a list of well-referenced medications grouped by CYP liver enzyme isoform. Since patients with kidney disease often have secondary illnesses, such as diabetes or hypertension, they are on several medications, making a drug interaction more likely.

Many people now order medications online or buy them at a supermarket, but for those purchasing OTCs from the local pharmacy, asking the pharmacist is a simple matter. Although Internet resources are easily accessible, the physician is the best resource. Each patient should consult the physician when contemplating the use of OTC medications, regardless of where purchased.

Each medication has two names – brand and generic. For instance, the brand name for the generic “ibuprofen” is “Motrin.” By knowing both the generic and brand name, and by listing each and every pill one intends to swallow, the common mistake of duplicating medications can be avoided. Listing each pill to be taken helps check references for drug interactions. These maxims hold for all medications taken, be they OTC or prescription.

This article details seven OTC medications and a brief review of how these may interact with other medications commonly prescribed to patients with chronic kidney disease (CKD), heart disease and diabetes. Though by no means comprehensive in itself, this short list gives the reader an opportunity to see how Internet resources can be used in finding clinically relevant material about common drug interactions. All the information used in preparation for this discussion is readily available on the Internet:

1. Aspirin – Although originally developed to reduce pain and fever, aspirin is largely used today to prevent cardiovascular disease and stroke because of its ability to coat platelets and prevent clots. It can cause stomach injury and even gastrointestinal bleeding. It may interact with several medications: blood thinners (coumadin), oral antidiabetic agents, captopril, Lasix (furosemide), antihypertensives such as Cardizem (diltiazem), potassium sparing diuretics (Aldactone (spironolactone)) and other arthritis medications such as the non-steroidal anti-inflammatory drugs (NSAIDS).

2. NSAIDS¹ – Motrin (ibuprofen) and Aleve (naproxen) – NSAIDS relieve musculoskeletal pain by reducing some of the inflammatory chemicals (prostaglandins) that cause it. They may worsen kidney disease by causing an allergic reaction known as interstitial nephritis, and also decrease the blood flow inside the kidneys. NSAIDS can cause a relapse of heart failure² and can contribute to the accumulation of potassium (hyperkalemia), a mineral eliminated by the kidney that must be kept in balance for the body to function. Since antihypertensive medications such as the beta blockers (labetalol and metoprolol), angiotensin receptor blockers (irbesartan and losartan), converting enzyme inhibitors (lisinopril, enalopril and captopril) and potassium sparing diuretics (spironolactone) all cause hyperkalemia, the combined use of any of these medications in kidney disease must be monitored. Adding Motrin or Aleve may worsen hyperkalemia and bring on symptoms. Since hyperkalemia can be life threatening, it is imperative for patients taking medications similar to the above to speak first with their physician when contemplating a NSAID.

3. Sudafed (pseudoephedrine) – This decongestant may raise the blood pressure and should be used with caution in patients who have hypertension. It may also interfere with some medications used to treat diabetes by decreasing effectiveness.

4. Prilosec (omeprazole)³ - This product is now OTC and is very similar to Nexium (esomeprazole), the prescription item. Since it decreases acidity in the stomach, it may interfere with many oral medications, such as iron and ketoconazole, an antibiotic used to treat fungus infections. It may also interfere with the hepatic metabolism of coumadin.

5. St. John’s Wort⁴ – This is a natural health product that interacts with the liver enzyme family (Cytochrome P450 3A4,5,7) responsible for metabolizing a variety of medications used for hypertension (Norvasc (amlodipine), Cardizem (diltiazem)), hyperlipidemia (Lipitor (atorvastatin), Zocor (simvastatin)), infections (erythromycin, rifampin or the antifungal antibiotic, ketocolazole)), abdominal pain (Tagamet (cimetidine)), or allergies (chlorpheniramine). Any one of the medications mentioned in this category has the potential of interacting with another since they all involve the same enzyme. Even grapefruit juice may influence this enzyme. In some situations the enzyme can be blocked, or used beyond its capacity leading to a drug accumulation. Other drugs such as grapefruit juice and St. John’s Wort can induce the enzyme and decrease a drugs intended effectiveness. Since the results of both are serious, it is important that patients inquire about any medications that are metabolized by this CYP enzyme.

6. Tylenol (acetaminophen) – This very popular drug may cause liver failure if administered in excessive doses to people who regularly consume alcohol. It should also be taken with caution when using topical anesthetics, such as lidocaine. It may also increase the risk of nephrotoxicity when used in combination with NSAIDS.⁵

7. Zantac (ranitidine) and Pepcid (famotidine)⁶ – These products control stomach acid secretion and are particularly useful in treating heartburn and indigestion. Both are eliminated by the kidney and the dosage must be reduced in patients with kidney disease. They may decrease the absorption of other oral medications, such as iron salts and ketoconazole.

References:

1.    ADDIN EN.REFLIST Pham K, Hirschberg R. Global safety of coxibs and NSAIDs. Curr Top Med Chem 2005;5:465-473.

2.    Feenstra J, Heerdink ER, Grobbee DE, Stricker BH. Association of nonsteroidal anti-inflammatory drugs with first occurrence of heart failure and with relapsing heart failure: the Rotterdam Study. Arch Intern Med 2002;162:265-70.

3.    Huang JQ, Hunt RH. Pharmacological and pharmacodynamic essentials of H(2)-receptor antagonists and proton pump inhibitors for the practising physician. Best Pract Res Clin Gastroenterol 2001;15:355-370.

4.    Mills E, Wu P, Johnston BC, Gallicano K, Clarke M, Guyatt G. Natural health product-drug interactions: a systematic review of clinical trials. Ther Drug Monit 2005;27:549-557.

5.    Feinstein AR, Heinemann LA, Curhan GC, Delzell E, Deschepper PJ, Fox JM, Graf H, Luft FC, Michielsen P, Mihatsch MJ, Suissa S, Van Der Woude F, Willich S. Relationship between nonphenacetin combined analgesics and nephropathy: a review. Ad Hoc Committee of the International Study Group on Analgesics and Nephropathy. Kidney Int 2000;58:2259-2264.

6.    Fisher AA, Le Couteur DG. Nephrotoxicity and hepatotoxicity of histamine H2 receptor antagonists. Drug Saf 2001;24:39-57.

Answer provided by Stephen Z. Fadem, MD, FACP, FASN. Dr. Fadem serves as a vice president of the AAKP National Board of Directors and is a member of the AAKP Medical Advisory Board. He is a practicing nephrologist in Houston.

This article originally appeared in the March/April 2006 issue of Kidney Beginnings: The Magazine, Vol. 5, No. 1.

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