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Bismuth subsalicylate / metronidazole / tetracycline Side Effects

For the Consumer

Applies to bismuth subsalicylate / metronidazole / tetracycline: oral capsule, oral tablet, oral tablet chewable

Along with its needed effects, bismuth subsalicylate / metronidazole / tetracycline may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking bismuth subsalicylate / metronidazole / tetracycline:

More common
  • Abdominal or stomach pain
  • bloody or black, tarry stools
  • diarrhea
  • nausea
Less common
  • Burning, prickling, or tingling sensations
  • dizziness
  • vomiting
  • Bloody vomit
  • convulsions (seizures)
  • fainting
  • heart attack
  • irritation of the mouth or tongue
  • joint pain and swelling
  • sensitivity of the skin to sunlight
  • skin rash
  • trouble with swallowing

Get emergency help immediately if any of the following symptoms of overdose occur while taking bismuth subsalicylate / metronidazole / tetracycline:

Symptoms of overdose
  • Clumsiness or unsteadiness
  • confusion
  • continuing ringing or buzzing in ears
  • fast heartbeat
  • fast or deep breathing
  • fever
  • pain, numbness, or tingling in the arms, legs, hands, or feet
  • unusual tiredness
  • vomiting

Some side effects of bismuth subsalicylate / metronidazole / tetracycline may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common or rare
  • Burning or itching around the anus
  • constipation
  • general feeling of discomfort or illness
  • loss of appetite
  • nervousness
  • trouble sleeping

For Healthcare Professionals

Applies to bismuth subsalicylate / metronidazole / tetracycline: oral kit


The most commonly reported side effects included nausea, abdominal pain, and diarrhea.[Ref]


Very common (10% or more): Nausea (up to 12%)
Common (1% to 10%): Abdominal pain, anal discomfort, constipation, diarrhea, duodenal ulcer, dyspepsia, flatulence, gastrointestinal hemorrhage, melena, stool abnormality/darkening/black stools, tongue discoloration/darkening, vomiting
Frequency not reported: Dry mouth, dysphagia, eructation, gastrointestinal monilia, glossitis, intestinal obstruction, rectal hemorrhage, stomatitis, tooth disorder

Frequency not reported: Abdominal pain, constipation, candida overgrowth, diarrhea, dry mouth, furry tongue, glossitis, nausea, pancreatitis, stomatitis, vomiting

Frequency not reported: Anogenital region inflammatory lesions/inflammatory lesions with Candida overgrowth, black hairy tongue, diarrhea, dysphagia, enterocolitis, esophagitis, esophageal ulceration, glossitis, nausea, vomiting[Ref]

Nervous system

Common (1% to 10%): Dizziness, dysgeusia/taste perversion/metallic taste, headache, paresthesia
Frequency not reported: Cerebral ischemia, somnolence, syncope

Frequency not reported: Aseptic meningitis, ataxia, convulsive seizures, dizziness, dysarthria, encephalopathy, headache, incoordination, metallic taste, peripheral neuropathy, syncope, vertigo

Frequency not reported: Intracranial hypertension, pseudotumor cerebri[Ref]


Common (1% to 10%): Asthenia, pain
Frequency not reported: Infection, malaise

Frequency not reported: Fever, weakness

Frequency not reported: Tinnitus[Ref]


Common (1% to 10%): Sinusitis, upper respiratory infection
Frequency not reported: Rhinitis

Frequency not reported: Nasal congestion[Ref]


Common (1% to 10%): Insomnia
Frequency not reported: Nervousness

Frequency not reported: Confusion, decreased libido, depression, insomnia, irritability[Ref]


Common (1% to 10%): Anorexia

Frequency not reported: Anorexia

Frequency not reported: Anorexia[Ref]


Frequency not reported: Acne, ecchymosis, photosensitivity reaction, pruritus, rash

Frequency not reported: Erythematous rash, pruritus, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria

Frequency not reported: Drug rash with eosinophilia and systemic symptoms (DRESS) syndrome, erythema multiforme, exfoliative dermatitis, Henoch-Schonlein purpura, maculopapular/erythematous rash, nail discoloration, onycholysis, photosensitivity, Stevens-Johnson syndrome, systemic lupus erythematosus exacerbation, toxic epidermal necrolysis, urticaria[Ref]


Frequency not reported: Chest pain, hypertension, myocardial infarction

Frequency not reported: T-wave flattening, flushing

Frequency not reported: Pericarditis[Ref]


Frequency not reported: Arthritis, rheumatoid arthritis, tendonitis

Frequency not reported: Joint pain

Frequency not reported: Myasthenic syndrome[Ref]


Frequency not reported: ALT increase, AST increase

Frequency not reported: Hepatotoxicity, liver failure[Ref]


Frequency not reported: Urinary tract infection

Frequency not reported: Darkened urine, dyspareunia, dysuria, incontinence, proctitis, sense of pelvic pressure, vaginal/vulvar dryness[Ref]


Frequency not reported: Flu syndrome

Frequency not reported: Serum sickness-like reaction[Ref]


Frequency not reported: Conjunctivitis

Frequency not reported: Optic neuropathy[Ref]


Frequency not reported: Neoplasm[Ref]


Frequency not reported: Reversible neutropenia/leukopenia, reversible thrombocytopenia

Frequency not reported: Eosinophilia, hemolytic anemia, neutropenia, thrombocytopenia, thrombocytopenic purpura


Frequency not reported: Cystitis

Frequency not reported: Increased blood urea nitrogen


Frequency not reported: Anaphylaxis, angioedema[Ref]


1. "Product Information. Helidac (bismuth subsalicylate/metronidazole/TCN)." Prometheus Inc, San Diego, CA.

Some side effects of bismuth subsalicylate / metronidazole / tetracycline may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.