Drug-Induced Metallic Taste: No Irony

JULY 10, 2015
Jeannette Y. Wick, RPh, MBA
An altered sense of taste can cause patients to self-manage in ways that are detrimental to their health.
Patients may report changes in taste, a condition known as dysgeusia, ranging from complete loss of taste to an altered or “funny” taste. Among patients receiving chemotherapy, 38% to 84% reported altered taste,1-3 and the results of another study show that as many as 11% of elderly patients who take multiple medications experience taste problems.4 Suspect drug-induced dysgeusia if the problem has temporal proximity to the start of a new drug. 

Patients may find 1 alteration especially repulsive: metallic taste. Metallic taste usually originates from the following causes5-9:
• Pregnancy (and accompanying hormonal changes)
• Compromised sense of smell
• Upper respiratory infection
• Underlying medical conditions (eg, diabetes, pernicious anemia, Sjögren’s syndrome, zinc deficiency, and Crohn’s disease)
• Trauma (eg, burns, lacerations, surgery [especially head and neck surgery], radiation)
• Medications—more than 300 drugs are associated with metallic taste

Taste, Smell, Texture, Temperature
Studying taste is a difficult task because taste is entwined with the sense of smell and changes with food texture and temperature. It is almost impossible to determine if patients have decreased sensitivity (a quantitative problem) or distorted perception (a qualitative problem).10 Although little research has been done to determine why specific taste distortions occur, research has provided several explanations (Table 110). Some common drugs are frequent culprits (Table 25,6,11-13).

When dysgeusia occurs, patients may change their eating habits to try to restore normal taste or they may discontinue the medication they believe is the cause of the problem without informing their health care team. Changes in taste can alter a patient’s life, causing adverse medical consequences,5,10,13 such as anorexia, malnutrition, food aversions, and/or unintentional weight loss or gain.

Management
The best approach to treating a metallic taste is prevention or correction of the underlying disorder. Because a zinc deficiency is a common but often overlooked cause, encourage patients and primary care providers to assess zinc levels.7,8 Warning patients in advance about medications likely to cause dysgeusia is helpful, as is assuring patients using certain agents for short-term treatment (ie, antibiotics) that this adverse effect will disappear once they discontinue the drug. If drug therapy is likely to be long term or the problem seems to be related to high doses, dose reduction may be a suitable option (Table 2).

Also consider keeping on hand a list of low-cost, simple interventions that patients can implement to combat dysgeusia, of which oral hygiene is one. Recommend frequent brushing and flossing to clear away trace minerals; this can be especially useful for patients with a heightened sense of taste or phenytoin- induced gingival hyperplasia. Warn against eating immediately after brushing, as toothpaste’s detergents can alter food taste.14 Recommend that patients tell their dentist about their dysgeusia at the next visit, since the condition may be related to dental fillings or a prosthesis.15 An especially effective remedy for patients who have dry mouth from dysgeusia is sugarfree mint gum or hard candies. These increase saliva production, which helps flush away the taste and/or smell.16

Next, discuss food preparation. Suggest adding acidic flavors (tomato, citrus) or strong spices or herbs. Cold or frozen food tends to taste better than warm food and may ameliorate the metallic taste, as well.10,17 Some patients taste their metal flatware, so recommend that those patients use plastic cutlery and glass cookware. Switching to alternative cooking materials directly prevents metal ion loss. This is especially useful if the sense of taste is heightened.10,17 Patients with drug-induced dysgeusia can rinse their mouths and gargle with salt and baking soda or brush with baking soda. Patients should mix a half teaspoon of salt and a half teaspoon of baking soda in 1 C of warm water and rinse (but not swallow).10

End Note
Humans use their sense of taste to evaluate food, select appetizing food, and identify food that has gone bad. Taste is a critical sense, even though some clinicians may consider it to be trivial, especially in patients who have comparatively serious health problems. Dysgeusia, specifically a metallic taste, can cause patients to self-manage in ways that are detrimental to their health (eg, by increasing salt or sugar intake). Therefore, if the cause of dysgeusia cannot be determined, referral to a multidisciplinary taste and smell center is recommended.


Ms. Wick is a visiting professor at the University of Connecticut School of Pharmacy.

References
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  2. Rehwaldt M, Wickham R, Purl S, et al. Self-care strategies to cope with taste changes after chemotherapy. Oncol Nurs Forum. 2009;36(2):E47-E56. doi: 10.1188/09.ONF. E47-E56.
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  17. Touger-Decker R, Mobley C, Epstein JB, eds. Diet and nutritional considerations for patients with head and neck cancer. In: Nutrition and Oral Medicine. New York: Springer; 2014:Appendix 2B.



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