What causes a metallic taste in an adult patient with a history of gastroesophageal reflux disease (GERD) and sinus infections, who is taking medications such as antibiotics, antihistamines, or decongestants?

Metallic Taste: Causes and Clinical Approach

In an adult patient with GERD and sinus infections taking antibiotics, antihistamines, or decongestants, the metallic taste is most likely medication-induced (particularly from antibiotics like metronidazole) or caused by gastroesophageal reflux reaching the nasopharynx, and you should systematically evaluate medications first, then pursue GERD treatment if medication adjustment doesn't resolve symptoms. 1, 2

Medication-Induced Causes

Antibiotics

• Metronidazole causes a "sharp, unpleasant metallic taste" as one of its most common adverse reactions, occurring frequently enough that the FDA label specifically mentions it as "not unusual." 2
• Ethionamide (used for tuberculosis) commonly causes metallic taste along with profound gastrointestinal effects including nausea and vomiting. 1
• The metallic taste from antibiotics typically resolves after discontinuation, though recovery may take weeks to months depending on the agent. 3

Antihistamines and Decongestants

• These medications cause dry mouth (xerostomia), which alters taste perception and contributes to dysgeusia rather than directly causing metallic taste. 1
• The mechanism is indirect—reduced saliva flow changes the oral environment and taste receptor function. 1

Other Medications to Consider

• Phenylbutazone, oxyphedrine, carbamazepine, chlormezanone/paracetamol combinations, and baclofen can cause partial or complete loss of taste, with recovery taking weeks to months after discontinuation. 3
• Eszopiclone (sleep medication) shows 15.2-26.1% incidence of metallic taste with a +0.07 risk difference versus placebo. 1

GERD-Related Mechanisms

Direct Acid Contact Pathway

• Gastric acid refluxes through the lower esophageal sphincter into the distal esophagus, continues proximally through the upper esophageal sphincter into the pharynx, and can reach the nasopharynx where direct acid contact alters taste perception. 1, 4
• This mechanism has been objectively documented using dual-pH probe monitoring with probes placed simultaneously in the distal esophagus and nasopharynx. 4
• In adults with chronic sinusitis refractory to conventional therapy, 64% had documented gastroesophagopharyngeal reflux using 3-site ambulatory pH monitoring, compared to only 18% of healthy controls. 1, 4

Critical Clinical Pitfall

• Up to 75% of patients with reflux-related extraesophageal manifestations lack typical symptoms such as heartburn or regurgitation, making the GERD connection less obvious. 1, 5
• Patients may present only with chronic sore throat, throat clearing, globus sensation, or altered taste without any gastrointestinal complaints. 1, 5

Diagnostic Algorithm

Step 1: Medication Review

• Immediately review all current medications, prioritizing antibiotics (especially metronidazole), antihistamines, and decongestants. 1, 2
• If metronidazole or other high-risk medications are identified, consider discontinuation or substitution if clinically appropriate. 2
• Document timeline: did metallic taste begin after medication initiation? 2

Step 2: GERD Assessment

• Assess for GERD symptoms including heartburn, regurgitation, dysphagia, or relief with antacids, though absence does not rule out GERD as a contributor. 1, 5
• Look for symptoms suggesting esophageal involvement: heartburn, regurgitation, dysphagia, odynophagia, or relief with antisecretory agents. 1
• Specifically ask about chronic sore throat, throat clearing, or globus sensation even without gastrointestinal complaints. 1, 5

Step 3: Empiric PPI Trial (If GERD Suspected)

• Initiate a 4-8 week trial of PPI therapy for typical GERD symptoms, but extraesophageal manifestations (including taste alterations) typically require 8-12 weeks minimum for adequate response. 1, 5
• High-dose PPI therapy may be required for extraesophageal symptoms. 5
• The American College of Gastroenterology recommends this empiric approach if GERD symptoms are present. 5

Step 4: Objective Testing (If PPI Trial Fails)

• If one PPI trial fails (up to 12 weeks), pursue objective testing with pH-impedance monitoring off PPI rather than trying additional empiric PPI trials, as further empiric therapy is low yield. 1
• Do not continue empiric PPI therapy beyond 12 weeks without objective testing, as 50-60% of patients with extraesophageal manifestations will not have GERD. 1
• Prolonged wireless pH monitoring off medication (96-hour preferred) is required to confirm nasopharyngeal reflux and establish causation. 1, 4

Step 5: Upper Endoscopy Indications

• Consider upper endoscopy if symptoms include dysphagia, odynophagia, gastrointestinal bleeding, unexplained iron deficiency anemia, weight loss, or recurrent vomiting. 1
• No single diagnostic tool conclusively identifies reflux as the cause; diagnosis requires integrating symptoms, endoscopy findings, reflux monitoring results, and treatment response. 1

Multidisciplinary Approach

• A multidisciplinary approach with communication between gastroenterology, otolaryngology, and allergy/immunology produces the best outcomes for suspected extraesophageal reflux patients. 1, 4
• Many conditions mimic extraesophageal reflux, requiring coordinated evaluation. 4
• After one failed PPI trial, referral to gastroenterology for objective testing is indicated. 4

Rare Causes to Consider

• Copper overload from foreign bodies (e.g., copper-containing objects in the gastric wall) can cause chronic metallic taste, though this is extraordinarily rare. 6
• Zinc metabolism alterations have been suggested as a possible mechanism for metallic taste with certain medications. 7
• Cancer patients receiving chemotherapy, targeted therapy, or concomitant radiotherapy experience metallic taste in 34% of those with taste changes (46% overall prevalence of taste changes). 8