What causes a metallic taste and how is it treated?

Metallic Taste: Causes and Treatment

Metallic taste is most commonly caused by medications (particularly metronidazole, clindamycin, lithium, and sleep medications like zopiclone), and treatment depends on identifying and addressing the underlying cause—either by discontinuing the offending agent when possible, treating copper deficiency if present, or using alpha-lipoic acid (200-600 mg daily) for idiopathic cases associated with burning mouth syndrome. 1, 2, 3

Primary Medication Causes

The most frequent culprits are:

• Metronidazole: Causes "a sharp, unpleasant metallic taste" that is "not unusual" according to FDA labeling, occurring commonly enough to be listed as an expected adverse effect rather than a rare one 3

• Sleep medications: Zopiclone and eszopiclone cause bitter/metallic taste in 7-26% of patients, representing their most common adverse effect with a risk difference of +0.07 compared to placebo 2

• Clindamycin: FDA labeling reports "an unpleasant or metallic taste" after oral administration 4

• Lithium: Can cause metallic taste as a miscellaneous reaction unrelated to dosage 5

• Ethionamide: Commonly causes profound metallic taste along with nausea and vomiting, though symptoms may improve if taken with food or at bedtime 2

Metabolic and Nutritional Causes

Copper deficiency should be considered, particularly in specific at-risk populations:

• Patients post-bariatric surgery or after abdominal surgeries excluding the duodenum 6
• Those with neuropathy of unclear etiology 6
• Patients on long-term parenteral nutrition 6
• Those fed by jejunostomy tubes 6

Diagnostic approach for copper deficiency:

• Measure plasma copper simultaneously with CRP 6
• With levels <12 μmol/L and CRP >20 mg/L, deficiency is likely and copper administration should be considered 6
• With levels <8 μmol/L (with or without elevated CRP), repletion is indicated 6

Oral and Implant-Related Causes

Metal hypersensitivity from dental or orthopedic implants can cause metallic taste:

• Nickel, aluminum, vanadium, and titanium in implants can trigger local and systemic symptoms including metallic taste 2
• Fretting corrosion from orthopedic implants (micromotion as little as 100 μm) can release metal ions causing hypersensitivity reactions 7
• Contact dermatitis from nickel in ear piercings is common, affecting about 10% of women with pierced ears 6

Age-Related Factors

In older adults, metallic taste results from:

• Alterations in olfaction and gustatory sensation from healthy aging 2
• Changes in muscles of mastication and lower salivary flow rates 2
• Polypharmacy, as many medications consumed by older adults contribute to taste disturbances 2

Cancer Treatment-Related

Cancer patients have high rates of metallic taste:

• Overall prevalence of 29% (95% CI [0.21; 0.39]) in cancer patients 8
• Occurs with chemotherapy, concomitant radiotherapy, and targeted therapy 9
• Women experience metallic taste more often than men 9
• 46% of cancer patients report taste changes, with 34% of those reporting metallic taste specifically 9

Treatment Approach

First-Line Treatment

For idiopathic metallic taste or burning mouth syndrome:

• Alpha-lipoic acid 200-600 mg daily in divided doses 1

Alternative Treatments

For burning mouth syndrome with metallic taste:

• Benzydamine hydrochloride rinse every 3 hours, particularly before eating 1
• Magic mouthwash containing viscous lidocaine 2% (15 mL per application) 1
• Clobetasol propionate 0.05% mixed with Orabase applied directly to affected areas 1

Copper Deficiency Treatment

When copper deficiency is confirmed:

• Oral copper administration first in chronic conditions 6
• Copper 4-8 mg/day for deficiency repletion 6

For Wilson's disease-related metallic taste:

• Trientine 750-1500 mg/day in divided doses 1
• Zinc (dosage based on elemental zinc) to interfere with copper uptake 1
• Monitor 24-hour urinary copper excretion to assess treatment adequacy 1

Supportive Measures

• White soft paraffin ointment to lips every 2-4 hours 1
• Warm saline mouthwashes daily for oral hygiene 1

Clinical Pitfalls

Medication review is critical: Always systematically review all medications, as metallic taste is an adverse effect of numerous drugs beyond those listed above 2. The mechanism remains unclear but may involve alteration in zinc metabolism 10, 11.

Don't overlook zinc deficiency: While zinc supplementation has been studied for taste disorders, the relationship between serum zinc concentration and taste disorders has been discussed extensively, and zinc deficiency may manifest as taste alterations 11.

Consider multiple mechanisms: Metallic sensation is a complex flavor involving taste, smell, and chemesthetic sensations from multiple chemosensory systems (TRPV1, T1R3, TRPA1, and T2R7 receptors), not just taste alone 12.