Bactrim Side Effects

Generic name: sulfamethoxazole / trimethoprim

Medically reviewed by Drugs.com. Last updated on Sep 5, 2023.

Note: This document provides detailed information about Bactrim Side Effects associated with sulfamethoxazole / trimethoprim. Some dosage forms listed on this page may not apply specifically to the brand name Bactrim.

Applies to sulfamethoxazole / trimethoprim: oral suspension, oral tablet.

Other dosage forms:

• intravenous solution

Serious side effects of Bactrim

Along with its needed effects, sulfamethoxazole / trimethoprim 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 sulfamethoxazole / trimethoprim:

More common side effects

• black, tarry stools
• blistering, peeling, or loosening of the skin
• changes in skin color
• chest pain or tightness
• chills
• clay-colored stools
• cough or hoarseness
• dark urine
• diarrhea
• dizziness
• fever
• general feeling of tiredness or weakness
• headache
• itching, skin rash
• joint or muscle pain
• light-colored stools
• loss of appetite
• lower back or side pain
• nausea
• pain, tenderness, or swelling of the foot or leg
• painful or difficult urination
• pale skin
• red skin lesions, often with a purple center
• red, irritated eyes
• sore throat
• sores, ulcers, or white spots in the mouth or on the lips
• stomach pain
• swollen or painful glands
• trouble breathing
• unpleasant breath odor
• unusual bleeding or bruising
• vomiting of blood
• yellow eyes or skin

Incidence not known

• back, leg, or stomach pains
• bleeding gums
• blindness or vision changes
• bloating
• blood in the urine or stools
• bluish-colored lips, fingernails, or palms
• burning, crawling, itching, numbness, painful, prickling, "pins and needles", or tingling feelings
• burning of the face or mouth
• cloudy urine
• clumsiness or unsteadiness
• confusion
• constipation
• continuing ringing or buzzing or other unexplained noise in the ears
• cracks in the skin
• decreased frequency or amount of urine
• difficulty with swallowing
• fainting spells
• fast, pounding, or irregular heartbeat or pulse
• general body swelling
• general feeling of discomfort or illness
• hair loss
• hearing loss
• hives
• increased thirst
• indigestion
• large, flat, blue, or purplish patches in the skin
• large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
• loss of heat from the body
• muscle or joint pain
• nosebleeds
• not able to pass urine
• numbness or tingling in the hands, feet, or lips
• pain or burning while urinating
• pinpoint red spots on the skin
• puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• raised red swellings on the skin, the buttocks, legs, or ankles
• redness of the white part of the eyes
• redness, swelling, or soreness of the tongue
• seizures
• soreness of the muscles
• stiff neck or back
• stomach tenderness
• swelling of the face, hands, legs, and feet
• unsteadiness, trembling, or other problems with muscle control or coordination
• weakness in the hands or feet
• weakness or heaviness of the legs
• weight gain or loss

Other side effects of Bactrim

Some side effects of sulfamethoxazole / trimethoprim 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:

More common side effects

• passing of gas

Incidence not known

• discouragement
• feeling of constant movement of self or surroundings
• feeling sad or empty
• increased sensitivity of the skin to sunlight
• lack of feeling or emotion
• loss of interest or pleasure
• muscle pain, stiffness, cramps, or spasms
• nervousness
• redness or other discoloration of the skin
• seeing, hearing, or feeling things that are not there
• sensation of spinning
• severe sunburn
• trouble concentrating
• trouble sleeping
• uncaring
• weight loss

For healthcare professionals

Applies to sulfamethoxazole / trimethoprim: intravenous solution, oral suspension, oral tablet.

General adverse events

The most common side effects were gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (e.g., rash, urticaria).

Effects associated with Pneumocystis jirovecii pneumonia management have included severe hypersensitivity reactions, rash, pyrexia, neutropenia, thrombocytopenia, elevated liver enzymes, hyperkalemia, hyponatremia, and rhabdomyolysis; such effects were very rare.

Although rare, fatalities associated with sulfonamide use have occurred due to severe reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, other blood dyscrasias, and respiratory hypersensitivity.^[Ref]

Metabolic

• Very common (10% or more): Hyperkalemia
• Frequency not reported: Anorexia, hypoglycemia, hyponatremia, decreased appetite
• Postmarketing reports: Metabolic acidosis^[Ref]

Hypoglycemia has been reported in patients using sulfonamides.^[Ref]

Gastrointestinal

• Common (1% to 10%): Nausea, diarrhea
• Uncommon (0.1% to 1%): Vomiting
• Frequency not reported: Glossitis, stomatitis, pseudomembranous enterocolitis, pancreatitis, emesis, abdominal pain, pseudomembranous colitis, Clostridium difficile-associated diarrhea, constipation, sore mouth^[Ref]

Nervous system

• Common (1% to 10%): Headache
• Frequency not reported: Aseptic meningitis, convulsions/seizures, peripheral neuritis/neuropathy, ataxia, dizziness, vertigo, tinnitus, tremor, other neurological manifestations (e.g., ataxia, ankle clonus, apathy), lethargy, paresthesia, syncope^[Ref]

Aseptic meningitis was rapidly reversible when this drug was stopped but recurred in several cases upon re-exposure to either this combination drug or to trimethoprim alone.

Tremor and other neurological manifestations (e.g., ataxia, ankle clonus, apathy) occurred during therapy with this drug in several patients with AIDS; although such effects have also been associated with the underlying disease process, these symptoms resolved within 2 to 3 days after stopping this drug.^[Ref]

Dermatologic

• Common (1% to 10%): Rash
• Frequency not reported: Diffuse rash, erythematous rash, maculopapular rash, morbilliform rash, pruritic rash, urticaria, photosensitivity, pruritus, exfoliative dermatitis, fixed drug eruption, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, Henoch-Schonlein purpura, drug reaction with eosinophilia and systemic symptoms (DRESS), generalized skin eruptions, purpura, angioedema, generalized pustular dermatosis, alopecia, allergic/hypersensitivity vasculitis resembling Henoch-Schonlein purpura, erythema nodosum, bullous dermatitis^[Ref]

Other

• Common (1% to 10%): Fungal/monilial overgrowth
• Frequency not reported: Drug fever, chills, weakness, fatigue, abnormal elevations in alkaline phosphatase, positive lupus erythematous phenomenon, moniliasis^[Ref]

Cardiovascular

• Frequency not reported: Thrombophlebitis, allergic myocarditis, polyarteritis/periarteritis nodosa
• Postmarketing reports: QT prolongation (resulting in ventricular tachycardia and torsade de pointes)^[Ref]

Hematologic

• Frequency not reported: Leucopenia, neutropenia, thrombocytopenia, bone marrow depression, agranulocytosis, aplastic anemia, hemolytic anemia, megaloblastic anemia, methemoglobinemia, hypoprothrombinemia, eosinophilia, hematological toxicity, hemolysis, pancytopenia, granulocytopenia
• Postmarketing reports: Thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura^[Ref]

Severe cases of thrombocytopenia that were fatal or life-threatening have been reported. Thrombocytopenia generally resolved within a week when this drug was discontinued.

Hemolysis has been reported in certain susceptible glucose-6-phosphate deficient patients.^[Ref]

Hepatic

• Frequency not reported: Hepatitis, cholestatic jaundice, hepatic necrosis, elevated serum transaminase, elevated bilirubin, hepatic changes, abnormal elevations in serum transaminase levels, jaundice, elevated liver enzymes, disturbance in liver enzymes^[Ref]

Cases of cholestatic jaundice and hepatic necrosis have been fatal.

Jaundice (generally mild and transient) has been reported rarely, often occurring in patients with history of infectious hepatitis.^[Ref]

Hypersensitivity

• Frequency not reported: Hypersensitivity, allergic skin reactions, anaphylaxis, serum sickness-like syndrome, generalized allergic reactions, anaphylactic/anaphylactoid reactions, severe hypersensitivity reactions (including associated with P jirovecii pneumonia), serum sickness^[Ref]

Local

• Frequency not reported: Local reaction, pain, slight/local irritation, inflammation^[Ref]

Local reaction, pain, and slight irritation were reported infrequently with IV administration.^[Ref]

Musculoskeletal

• Frequency not reported: Arthralgia, myalgia, rhabdomyolysis, systemic lupus erythematosus, muscle weakness^[Ref]

Rhabdomyolysis has been reported with this drug, primarily in patients with AIDS.^[Ref]

Ocular

• Frequency not reported: Uveitis, conjunctival and scleral injection/redness/edema, periorbital edema, corneal ring infiltrates, vision problems^[Ref]

Psychiatric

• Frequency not reported: Depression/mental depression, hallucinations, apathy, nervousness, insomnia, psychotic disorder, confusional state, agitation, anxiety, abnormal behavior, nightmares^[Ref]

Renal

• Frequency not reported: Renal impairment/failure, interstitial nephritis, tubulointerstitial nephritis and uveitis syndrome, elevated BUN, elevated serum creatinine, toxic nephrosis, renal tubular acidosis, nephrotoxicity, functional kidney changes, abnormal elevations in serum urea, abnormal elevations in serum creatinine, stone formation, tubular necrosis, aggravation of renal disease, azotemia, hyperkalemic renal tubular acidosis, overestimations of normal creatinine values^[Ref]

Nephrotoxicity has been reported in association with cyclosporine.^[Ref]

Genitourinary

• Frequency not reported: Oliguria, anuria, crystalluria, diuresis, dysuria, hematuria, urgency changes, abnormal elevations in urine protein levels^[Ref]

Diuresis has been reported in patients using sulfonamides.^[Ref]

Respiratory

• Frequency not reported: Cough, dyspnea/shortness of breath, pulmonary infiltrates/lung infiltration, epistaxis, eosinophilic/allergic alveolitis, wheezing^[Ref]

Cough, dyspnea, and lung infiltration have been early indicators of respiratory hypersensitivity which, while very rare, has been fatal.^[Ref]

Frequently asked questions

• What drugs should be avoided with a sulfa allergy?
• Does Bactrim cause headaches?
• Does Bactrim make you tired?
• How long does it take for a boil to heal while taking Bactrim?
• Can I drink alcohol when taking sulfamethoxazole / trimethoprim DS?
• What dose of co-trimoxazole is used in a patient with a UTI?

Further information

Bactrim 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.

Some side effects may not be reported. You may report them to the FDA.

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