Bismuth/Metronidazole/Tetracycline (Pylera) - Uses, Side Effects, and More

What are the most common side effects of bismuth/metronidazole/tetracycline?

The most common side effects of bismuth/metronidazole/tetracycline are listed below. Tell your health care provider if you have any of these side effects that bother you.

• Dark-colored or black stools (poop)
• Diarrhea
• Nausea
• Headache

There may be other side effects of bismuth/metronidazole/tetracycline that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of bismuth/metronidazole/tetracycline?

While less common, the most serious side effects of bismuth/metronidazole/tetracycline are described below, along with what to do if they happen.

Severe Allergic Reactions. Bismuth/metronidazole/tetracycline may cause allergic reactions, including a specific type of allergic reaction called DRESS. DRESS stands for Drug Reaction with Eosinophilia and Systemic Symptoms. It is also sometimes called multiorgan hypersensitivity. This is a reaction that can affect multiple parts of the body, including your liver, kidneys, and heart. Stop taking the medicine and get help right away if you have any of the following symptoms of this serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching, skin rash, or pale red bumps on the skin called hives
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain
• Dark-colored pee
• Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Severe Skin Reactions. Metronidazole may cause severe skin reactions, called Stevens-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP). These can lead to death if not treated. If you develop a rash or pus-filled pimples, stop taking metronidazole and immediately call your health care provider. Get emergency help right away if you have any of the following symptoms of a severe skin reaction.

• Painful red or purple skin that looks burnt and peels off
• Flat red rash or blisters on your skin, mouth, nose, and genitals
• Red, painful, watery eyes

Antibiotic-Associated Diarrhea. An overgrowth of germs called Clostridioides difficile, or “C. diff,” can happen in your gut with many types of antibiotics. This can cause a condition known as antibiotic-associated diarrhea and can happen even up to two months after stopping the antibiotic. Call your health care provider right away if you have any of the following symptoms of this condition.

• Watery diarrhea
• Diarrhea that does not go away
• Blood in your stool (poop)
• Severe stomach cramps
• Fever that starts after you start or finish the medicine

Nerve Problems. Nerves are the fibers that carry sensations from your body to the brain. Damage to these nerves, called peripheral neuropathy (including nerves in your eyes), may happen in people who are taking metronidazole. Stop taking this medicine and call your health care provider if you develop pain, burning, tingling, numbness, or weakness in your arms, hands, legs, or feet or if you have blurred or reduced vision or pain in your eyes.

Brain or Central Nervous System (CNS) Effects. Bismuth/metronidazole/tetracycline may rarely cause effects on the brain or central nervous system (CNS). These problems include meningitis (inflammation of the protective membranes around the brain and spinal cord), encephalopathy (a rare but potentially serious condition that affects the brain), and pseudotumor cerebri (a serious condition where the pressure around the brain increases). Stop taking this medicine and get help right away if you have any of the following symptoms.

• Trouble with balance or coordination
• Dizziness
• Nausea or vomiting
• Slurred or slow speech
• Confusion, memory problems, or difficulty concentrating
• Severe headache
• Stiff neck
• Vision changes
• Fever

Seizures. Some people who have taken metronidazole have reported having seizures. There are many different types of seizures and some of them are not easy to recognize. Stop taking this medicine and call your health care provider if you have any of the following signs that a seizure is happening or could happen.

• Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
• Stiffening of your arms and legs
• Feeling anxious, nervous, confused, or a sense of dread
• Feeling dizzy or lightheaded
• Falling or losing consciousness

Heart Rhythm Changes. Metronidazole may cause a rare dangerous heart rhythm problem called QT prolongation and torsade de pointes. Some people have a higher risk for this, including people who are older, have other people in their family who have had these conditions, have low potassium or magnesium, or who take some medicines for other heart rhythm problems. Tell your health care provider right away if you faint or have changes in your heart rate or rhythm, such as a fast or skipped heartbeat.

Sensitivity to Sunlight. Your skin may be very sensitive to light from the sun and devices that give off similar light, such as sunlamps and tanning beds, while you are taking certain medicines, including tetracycline. This is called photosensitivity. Exposing your skin to this kind of light, even for a short time, can cause your skin to be severely sunburned, blistered, or swollen. Stop taking this medicine and tell your health care provider right away if you have any of these symptoms. Avoid being in the sun or using sunlamps while taking this medicine. Use sunscreen and wear a hat and clothes that cover your skin if you must be in the sunlight.

Another Infection. Taking bismuth/metronidazole/tetracycline may lead to an infection with other types of germs, such as fungi. Call your health care provider if your infection does not get better or gets worse. 

Permanent Teeth Discoloration. Tetracycline can cause a permanent change in tooth color to yellow, gray, or brown. It may also affect the growth of tooth enamel (also called enamel hypoplasia). These side effects can happen during tooth development when this medicine is taken in the last half of pregnancy and in children up to age eight years. Tell your health care provider if you are or plan to become pregnant. If your child is taking tetracycline and is less than eight years old, call your health care provider right away.