Applies to sulfamethoxazole / trimethoprim: intravenous solution, oral suspension, oral tablet
The most common side effects have included nausea, vomiting, anorexia, rash, and urticaria. Side effects generally are more common and more severe in patients with AIDS.
The most frequently reported serious adverse reactions in elderly patients have included severe skin reactions, generalized bone marrow suppression, a specific decrease in platelets (with or without purpura), and hyperkalemia.
Sulfonamides have rarely been associated with fatal reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias.
Adverse reactions to sulfamethoxazole-trimethoprim occur in 50% to 100% of patients with AIDS, compared to approximately 14% in those without AIDS receiving treatment for Pneumocystis jiroveci pneumonia. Up to 57% of AIDS patients treated with sulfamethoxazole-trimethoprim require a change in therapy due to adverse effects.
Dermatologic side effects were usually due to hypersensitivity to the sulfamethoxazole component.
A few cases of acute febrile neutrophilic dermatosis (Sweet's syndrome), characterized by abrupt onset of painful erythematous plaques or nodules and a fever greater than 38 degrees Celsius, have been reported.
Rare (less than 0.1%): Acute febrile neutrophilic dermatosis (Sweet's syndrome), acute patchy exanthematous pustulosis (at least 1 case)
Frequency not reported: Mild erythroderma, severe exfoliative dermatitis, Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme, exfoliative dermatitis, generalized skin eruptions, photosensitivity, phototoxicity, pruritus, urticaria, rash
Frequency not reported: Nausea, vomiting/emesis, diarrhea, stomatitis, glossitis, abdominal pain, anorexia, pseudomembranous colitis, Clostridium difficile associated diarrhea, pancreatitis
Frequency not reported: Anaphylaxis, allergic myocarditis, angioedema, Henoch-Schonlein purpura, serum sickness-like syndrome, generalized allergic reactions, fixed drug eruption, hypersensitivity reactions (including cholestatic jaundice, interstitial nephritis, liver failure, renal failure, pancytopenia, hypotension, pulmonary edema, elevated serum transaminases)
A case of fixed drug eruption due to polysensitivity (sulfamethoxazole-trimethoprim and tenoxicam) and reactivation of previous (10 years earlier) sulfamethoxazole-trimethoprim-associated fixed drug eruption lesions has been reported.
Hypersensitivity reactions may be more likely in patients with HIV infection, with opportunistic infections, or patients who are slow acetylators.
Hypotension, pulmonary edema, and elevated serum transaminases have been reported following sulfamethoxazole-trimethoprim administration to HIV-infected patients.
Hypersensitivity reactions in some cases have included cholestatic jaundice, interstitial nephritis, liver failure, renal failure, and pancytopenia.
A 48-year-old male developed liver failure, renal failure requiring hemodialysis, and pancytopenia requiring blood transfusions after 10 days of treatment with sulfamethoxazole-trimethoprim for pyelonephritis. This was believed to be a hypersensitivity reaction. He was a slow acetylator phenotype and had concurrently taken acetaminophen and diclofenac; the acetaminophen may have contributed to the reaction by inhibiting NAT2.
Frequency not reported: Agranulocytosis, aplastic anemia, thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia
Postmarketing reports: Thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura
Because trimethoprim inhibits a step in folate synthesis, patients that are likely to have preexisting folate deficiencies (e.g., alcoholics, malnourished patients, patients on phenytoin or antifolate metabolites, and those with chronic hemolysis) are at risk of developing megaloblastic anemia during sulfamethoxazole-trimethoprim therapy. Folate replenishment reverses this effect.
Methemoglobinemia occurred twice in an HIV-infected patient who inadvertently received sulfamethoxazole-trimethoprim a second time after the first course was discontinued due to development of methemoglobinemia.
Rare (less than 0.1%): Higher-level gait disorder (at least 1 case)
Frequency not reported: Aseptic meningitis, convulsions, peripheral neuritis, ataxia, vertigo, tinnitus, headache, dizziness, tremors, lightheadedness, coma, seizures, multifocal myoclonus, bilateral asterixis, exacerbation of posthypoxic action myoclonus
Exacerbation of posthypoxic action myoclonus occurred in a patient with non-Hodgkin's lymphoma who was receiving high-dose intravenous sulfamethoxazole-trimethoprim (115 mg/kg/day) for suspected Pneumocystis pneumonia.
HIV-infected patients receiving high-dose intravenous sulfamethoxazole-trimethoprim appear to have a greater incidence of tremors. The tremors generally appear several days after initiating therapy and resolve several days after discontinuation or dose reduction.
An 82-year-old male developed higher-level gait disorder on day 37 of treatment, 2 days after his dosage was doubled to sulfamethoxazole 320 mg-trimethoprim 1600 mg orally twice a day. During this time, the patient also had nocturnal delirium. Sulfamethoxazole-trimethoprim was discontinued on day 48 and the patient's gait returned to normal and his nocturnal delirium resolved by day 51.
Frequency not reported: Renal failure, interstitial nephritis, elevated BUN and serum creatinine, toxic nephrosis with oliguria and anuria, tubular necrosis, crystalluria, aggravation of renal disease, azotemia, hyperkalemic renal tubular acidosis, overestimations of normal creatinine values
Trimethoprim inhibits renal tubular creatinine secretion, which can result in a significant decrease in creatinine clearance. These changes appear to be completely reversible upon discontinuation of therapy. Sulfamethoxazole may cause sulfa crystalluria, especially during low urine output states.
Interstitial nephritis and tubular necrosis may be due to hypersensitivity.
The propylene glycol vehicle in intravenous sulfamethoxazole-trimethoprim and lorazepam has also been implicated in the development of acute tubular necrosis in a patient.
Hyperkalemia has occurred with both standard and high-dose therapy. Reported cases have resolved upon discontinuation of the drug, although a few have required treatment with sodium polystyrene sulfonate. Up to 20% of patients with AIDS who are given sulfamethoxazole-trimethoprim for Pneumocystis pneumonia develop mild hyperkalemia.
Sulfamethoxazole-trimethoprim may interfere with creatinine determinations by the Jaffe alkaline picrate assay, resulting in overestimations of normal values.
Cholestatic hepatitis associated with sulfamethoxazole-trimethoprim therapy may present with other signs of hypersensitivity, such as rash, fever, and eosinophilia. Biopsy findings in patients with sulfamethoxazole-trimethoprim-associated cholestatic hepatitis have included hepatic necrosis, hepatocyte degeneration, hepatic granuloma, centrilobular congestion, and inflammatory infiltrates.
A 34-year-old female developed pancreatitis and hepatitis after inadvertently receiving sulfamethoxazole-trimethoprim for treatment of a urinary tract infection several years after experiencing a previous episode of sulfamethoxazole-trimethoprim-associated hepatitis.
Frequency not reported: Hepatitis (including cholestatic jaundice, hepatic necrosis), elevated serum transaminase, elevated bilirubin, elevated liver function tests, fulminant hepatic failure, hepatic and/or cholestatic lesions, hepatitis with simultaneous pancreatitis, hepatorenal failure, cholestatic liver disease with ductopenia
Rare (less than 0.1%): Hypoglycemia
Frequency not reported: Hyperkalemia, metabolic acidosis, hyponatremia, hypouricemia
Hyperkalemia may occur as a result of the blocking of sodium channels by trimethoprim, which causes a reduction of potassium excretion in the distal tubule.
High doses of intravenous sulfamethoxazole-trimethoprim appear to be associated with a greater incidence of metabolic acidosis.
Sulfonamides may induce hypoglycemia. However, the establishment of a causal relationship has been difficult in most cases of suspected sulfa-induced hypoglycemia because many of the affected patients had AIDS, may have had another viral infection, or were on other medications.
Hypouricemia has been associated with high-dose therapy.
Frequency not reported: Sepsis-like syndrome (hypotension, fever, rash, and pulmonary infiltrates), weakness, fatigue, drug fever, chills, facial edema
Frequency not reported: Hallucinations, depression, apathy, nervousness, insomnia, irritability, confusion, disorientation, catatonia, nocturnal delirium, exacerbation of panic attacks, acute psychoses
Isolated cases of rhabdomyolysis have been reported, primarily in patients with AIDS.
Rare (less than 0.1%): Rhabdomyolysis
Frequency not reported: Arthralgia, myalgia, periarteritis nodosa, systemic lupus erythematosus
Frequency not reported: Cough, shortness of breath, pulmonary infiltrates
Hypersensitivity reactions of the respiratory tract associated with sulfonamides have included cough, shortness of breath, and pulmonary infiltrates.
Diuresis has been reported rarely in patients receiving sulfonamides.
Significant reductions in male sperm counts have been reported after 1 month of therapy.
Rare (less than 0.1%): Diuresis
Frequency not reported: Decreased sperm counts
Rare (less than 0.1%): Local reaction, pain, slight irritation
Local reaction, pain, and slight irritation on intravenous administration have been reported infrequently.
Rare (less than 0.1%): Thrombophlebitis
Postmarketing reports: QT prolongation resulting in ventricular tachycardia and torsade de pointes
Rare (less than 0.1%): Goiter
Endocrine side effects associated with sulfonamides have rarely included goiter production.
Frequency not reported: Conjunctival and scleral injection