Bactrim side effects: What you should know

Bactrim and Bactrim DS can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Bactrim and Bactrim DS in clinical trials:

• nausea
• vomiting
• loss of appetite

Mild side effects can occur with Bactrim and Bactrim DS use. This list doesn’t include all possible mild side effects of the drugs. For more information, you can refer to Bactrim’s prescribing information.

Mild side effects that have been reported with Bactrim and Bactrim DS include:

• nausea
• vomiting
• skin rash or hives (raised, itchy rash)
• diarrhea
• loss of appetite
• abdominal pain
• ringing or buzzing in the ears
• headache
• low blood sugar
• skin sensitivity to sun or light

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Bactrim or Bactrim DS and want to tell the FDA about it, visit MedWatch.

Bactrim and Bactrim DS may cause serious side effects. The list below may not include all possible serious side effects of the drugs. For more information, you can refer to Bactrim’s prescribing information.

If you develop serious side effects while taking Bactrim or Bactrim DS, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

• diarrhea (associated with C. diff infection), which may include symptoms such as:
  • abdominal pain
  • frequent diarrhea
  • fever
• hyponatremia (low blood sodium levels), which may include symptoms such as:
  • fatigue
  • confusion
  • headache
• liver problems, which may include symptoms such as:
  • nausea and vomiting
  • dark-colored urine
  • jaundice (yellowing of the skin or the whites of the eyes)
• kidney problems, which may include symptoms such as:
  • fluid retention (swelling in the hands, arms, legs, or feet)
  • blood in the urine
  • changes in frequency of urination
• certain blood disorders, including thrombocytopenia (low platelet levels) and aplastic anemia (decrease in certain blood cell counts), which may include symptoms such as:
  • bruising or bleeding more easily than usual
  • lightheadedness
  • shortness of breath
  • fatigue
• severe skin reactions*
• high potassium levels*

* For more information about this side effect, see “Side effect specifics” below.

ALLERGIC REACTION

For some people, Bactrim and Bactrim DS tablets can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious. You can learn more about possible symptoms in this article.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Bactrim or Bactrim DS, your doctor may recommend taking a different medication instead.

Bactrim and Bactrim DS may cause several side effects. Here are some frequently asked questions about the drugs’ side effects and their answers.

Does Bactrim cause long-term side effects?

It’s possible, but long-term side effects of Bactrim or Bactrim DS are rare. Long-term side effects include those that may start at any time during treatment and those that don’t go away even after you stop taking the drug.

Long-term side effects reported in studies of Bactrim or Bactrim DS include:

• lung problems
• blood disorders, such as thrombocytopenia
• liver problems, such as hepatitis
• C. diff-associated diarrhea
• severe skin reactions (see “Side effect specifics” section for more information)

Talk with your doctor or pharmacist if you have questions about the long-term side effects of Bactrim or Bactrim DS.

How long do the side effects of Bactrim last?

How long side effects last depends on what side effects you experience, what condition is being treated, and how long you take Bactrim or Bactrim DS. Most of the side effects from Bactrim and Bactrim DS are temporary and will go away on their own within days to weeks or soon after you stop taking the drug.

Bactrim and Bactrim DS are commonly prescribed to treat urinary tract infections (UTIs) for up to 14 days. If you experience side effects such as nausea or diarrhea, they will go away soon after you stop taking the drug.

Doctors may sometimes prescribe Bactrim or Bactrim DS long term to prevent a UTI or another infection. If you use Bactrim or Bactrim DS long term, you may be likely to experience side effects such as blood disorders or C. diff-associated diarrhea. In some people, C. diff-associated diarrhea can occur more than 2 months after stopping Bactrim or Bactrim DS.

If you have side effects that are bothersome or don’t go away, talk with your doctor. They can recommend ways to manage any side effects you have or may suggest a different medication.

Is Bactrim safe for older adults?

Yes, it’s typically safe for older adults to take Bactrim or Bactrim DS. However, older adults (ages 65 years and older) have a higher risk of experiencing severe side effects of the drug, such as high potassium levels and severe skin reactions. People with kidney problems, liver problems, or folate deficiency may have an increased risk of side effects.

In general, older adults are more likely to take more medications or to take medications that can increase the risk or severity of side effects.

For example, certain diuretics (a type of medication often used to treat high blood pressure or fluid retention) can increase the risk of thrombocytopenia in older adults. Thrombocytopenia is a low level of platelets in the blood, which can lead to a higher chance of bruising or bleeding. Treatment with angiotensin converting enzyme (ACE) inhibitors can increase the risk of high blood potassium.

If you’re an older adult, your kidneys and liver may not work as well to clear drugs from your system. For this reason, your doctor may prescribe you a lower dosage. They will also monitor you more closely for side effects.

Talk with your doctor or pharmacist if you have questions about possible side effects while taking Bactrim or Bactrim DS.

Learn more about some of the side effects that Bactrim may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Bactrim.

Severe skin reactions

Bactrim and Bactrim DS can cause severe skin reactions in some people. This side effect was rare in the drugs’ clinical studies. These reactions may be serious or life threatening.

Severe skin reactions that can occur include Stevens-Johnson syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS syndrome), acute febrile neutrophilic dermatosis, and acute generalized erythematous pustulosis.

These conditions can cause a rash and other side effects that affect your whole body, such as:

• muscle aches
• sore throat
• skin rashes that may peel or blister
• swollen lymph nodes
• fever
• joint pain

What you can do

Talk with your doctor if you have a skin rash that is peeling or blistering or a skin rash along with any of the symptoms listed above, such as fever. Your doctor will likely have you stop taking the drug. If you feel that your symptoms are serious or life-threatening, call 911 or your local emergency number.

High potassium levels

Bactrim and Bactrim DS may cause high blood potassium levels in some people. This wasn’t commonly reported in the drugs’ clinical studies. High potassium levels occur more often in people who are taking high doses but can also occur at recommended doses.

Your risk of high potassium levels may be increased if you already have kidney problems or are taking certain medications that can increase your potassium level, such as an ACE inhibitor or spironolactone.

This side effect may not cause symptoms until your potassium level is very high. Severe high potassium levels may cause symptoms such as:

• muscle cramps or weakness
• shortness of breath
• irregular heart rate or heart palpitations
• fatigue

What you can do

Be sure to tell your doctor about all medications you are taking. If you’re at a higher risk of high potassium levels, your doctor may want to monitor your blood potassium levels more closely.

High potassium can be serious in some cases. Talk with your doctor right away if you experience any symptoms of high potassium levels. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Before taking Bactrim or Bactrim DS, discuss your health history with your doctor. Bactrim or Bactrim DS may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

• kidney problems
• liver problems
• folate deficiency
• porphyria
• thyroid problems
• high potassium level
• megaloblastic anemia
• glucose-6-phosphate dehydrogenase (G6PD) deficiency
• age of less than 2 months
• previous allergic reaction to sulfamethoxazole, trimethoprim, sulfonamides, or a similar drug
• pregnancy
• breastfeeding
• alcohol consumption

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.