Helidac Side Effects

Generic name: bismuth subsalicylate / metronidazole / tetracycline

Medically reviewed by Drugs.com. Last updated on May 24, 2025.

Note: This document provides detailed information about Helidac Side Effects associated with bismuth subsalicylate / metronidazole / tetracycline. Some dosage forms listed on this page may not apply specifically to the brand name Helidac.

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

Precautions

It is very important that your doctor check your progress at regular visits to make sure this medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

Do not use this medicine if you are also using methoxyflurane (Penthrane®) or have used disulfiram (Antabuse®) in the last 2 weeks. Do not drink alcohol and other products containing propylene glycol while you are using this medicine and for at least 3 days after your last dose.

If your condition does not improve or if it becomes worse, check with your doctor.

Using this medicine while you are pregnant, especially during the second and later part of a pregnancy, can harm your unborn baby. Birth control pills may not work as well to prevent pregnancy when used with this medicine. Use an effective form of birth control (eg, condoms, spermicide) to keep from getting pregnant. If you think you have become pregnant while using this medicine, tell your doctor right away.

Metronidazole may cause some people to become dizzy, clumsy, or trouble seeing clearly.

Children or teenagers who have or who are recovering from chickenpox or influenza should not use this medicines unless directed by the child's doctor. If nausea or vomiting occurs after using this medicine, check with the child's doctor right away.

Tetracycline may cause your skin to be more sensitive to sunlight than it is normally. Exposure to sunlight, even for brief periods of time, may cause a skin rash, itching, redness or other discoloration of the skin, or a severe sunburn. When you begin taking tetracycline:

• Stay out of direct sunlight, especially between the hours of 10:00 a.m. and 3:00 p.m., if possible.
• Wear protective clothing, including a hat. Also, wear sunglasses.
• Apply a sunblock product that has a skin protection factor (SPF) of at least 15. Some patients may require a product with a higher SPF, especially if they have a fair complexion. If you have any questions about this, check with your doctor.
• Apply a sunblock lipstick that has an SPF of at least 15 to protect your lips.
• Do not use a sunlamp or tanning bed or booth.

You may still be more sensitive to sunlight or sunlamps for 2 weeks to several months or more after stopping tetracycline. If you have a severe reaction, check with your doctor.

Bismuth subsalicylate may cause your tongue to become a darker color or even black. It may also make your stools (bowel movements) black. This is only temporary and will not hurt you. Your tongue and stools will go back to normal when you stop using this medicine. Ask your doctor about this if you have any concerns.

Check with your doctor right away if you start to have a stiff neck, drowsiness, fever, severe headache, nausea, vomiting, painful eye movements, or eye sensitivity to light. These could be symptoms of a serious condition called aseptic meningitis.

Check with your doctor right away if you are having burning, numbness, tingling, or painful sensations in the arms, hands, legs, or feet. These could be symptoms of a condition called peripheral neuropathy.

This medicine lowers the number of some types of blood cells in your body. Because of this, you may bleed or get infections more easily. Avoid people who are sick. Wash your hands often. Stay away from rough sports or other situations where you could be bruised, cut, or injured. Brush and floss your teeth gently. Be careful when using sharp objects, including razors and fingernail clippers.

Serious skin reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and drug reaction with eosinophilia and systemic symptoms (DRESS) can occur with this medicine. Check with your doctor right away if you have black, tarry stools, blistering, peeling, or loosening of the skin, chest pain, chills, cough, diarrhea, fever, itching, joint or muscle pain, painful or difficult urination, red irritated eyes, red skin lesions, severe acne or skin rash, sore throat, sores or ulcers on the skin, swollen glands, unusual bleeding or bruising, or unusual tiredness or weakness while you are using this medicine.

This medicine may cause serious allergic reactions. Check with your doctor right away if you have feeling of warmth, itching, redness of the face, neck, arms and occasionally, upper chest, or redness of the skin.

Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests (eg, x-rays).

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or non-prescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Serious side effects of Helidac

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:

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

Symptoms of overdose

• blue lips, fingernails, or skin
• burning, numbness, tingling, or painful sensations
• continuing ringing or buzzing or other unexplained noise in the ears
• coughing that sometimes produces a pink frothy sputum
• difficult, noisy, fast, or deep breathing
• hearing loss
• increased sweating
• irregular, fast or slow, or shallow breathing
• loss of consciousness
• pale skin
• seizures
• shakiness and unsteady walk
• slow heartbeat
• swelling in the legs and ankles
• unsteadiness, trembling, or other problems with muscle control or coordination
• weakness in the arms, hands, legs, or feet

Other side effects of Helidac

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:

See also:

For healthcare professionals

Applies to bismuth subsalicylate / metronidazole / tetracycline: oral kit.

General adverse events

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

Gastrointestinal

• 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

Metronidazole:

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

Tetracycline:

• 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

Metronidazole:

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

Tetracycline:

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

Other

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

Metronidazole:

• Frequency not reported: Fever, weakness

Tetracycline:

• Frequency not reported: Tinnitus^[Ref]

Respiratory

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

Metronidazole:

• Frequency not reported: Nasal congestion^[Ref]

Psychiatric

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

Metronidazole:

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

Metabolic

• Common (1% to 10%): Anorexia

Metronidazole:

• Frequency not reported: Anorexia

Tetracycline:

• Frequency not reported: Anorexia^[Ref]

Dermatologic

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

Metronidazole:

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

Tetracycline:

• 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]

Cardiovascular

• Frequency not reported: Chest pain, hypertension, myocardial infarction

Metronidazole:

• Frequency not reported: T-wave flattening, flushing

Tetracycline:

• Frequency not reported: Pericarditis^[Ref]

Musculoskeletal

• Frequency not reported: Arthritis, rheumatoid arthritis, tendonitis

Metronidazole:

• Frequency not reported: Joint pain

Tetracycline:

• Frequency not reported: Myasthenic syndrome^[Ref]

Genitourinary

• Frequency not reported: Urinary tract infection

Metronidazole:

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

Hepatic

• Frequency not reported: ALT increase, AST increase

Tetracycline:

• Frequency not reported: Hepatotoxicity, liver failure^[Ref]

Immunologic

• Frequency not reported: Flu syndrome

Tetracycline:

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

Ocular

• Frequency not reported: Conjunctivitis

Metronidazole:

• Frequency not reported: Optic neuropathy^[Ref]

Oncologic

• Frequency not reported: Neoplasm^[Ref]

Hematologic

Metronidazole:

• Frequency not reported: Reversible neutropenia/leukopenia, reversible thrombocytopenia

Tetracycline:

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

Renal

Metronidazole:

• Frequency not reported: Cystitis

Tetracycline:

• Frequency not reported: Increased blood urea nitrogen

Hypersensitivity

Tetracycline:

• Frequency not reported: Anaphylaxis, angioedema^[Ref]

Further information

Helidac side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer