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SIDE EFFECTS
The most common adverse effects are gastrointestinal
disturbances (nausea, vomiting, anorexia) and allergic skin reactions
(such as rash and urticaria). FATALITIES ASSOCIATED WITH THE ADMINISTRATION
OF SULFONAMIDES, ALTHOUGH RARE, HAVE OCCURRED DUE TO SEVERE REACTIONS,
INCLUDING STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS,
FULMINANT HEPATIC NECROSIS, AGRANULOCYTOSIS, APLASTIC ANEMIA AND
OTHER BLOOD DYSCRASIAS AND HYPERSENSITIVITY OF THE RESPIRATORY TRACTS
(SEE WARNINGS). Additional Information for IV Infusion: Local reaction,
pain, and slight irritation on IV administration are infrequent.
Thrombophelbitis has rarely been observed.
Hematologic: Agranulocytosis, aplastic anemia,
thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic
anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia.
Allergic Reactions: Stevens-Johnson syndrome,
toxic epidermal necrolysis, anaphylaxis, allergic myocarditis, erythema
multiforme, exfoliative dermatitis, angioedema, drug fever, chills,
Henoch-Schoenlein purpura, serum sickness-like syndrome, generalized
allergic reactions, generalized skin eruptions, photosensitivity,
conjunctival and scleral injection, pruritus, urticaria, and rash.
In addition, periarteritis nodosa and systemic lupus erythematosus
have been reported.
Gastrointestinal: Hepatitis, including cholestatic
jaundice and hepatic necrosis, elevation of serum transaminase and
bilirubin, pseudomembranous enterocolitis, pancreatitis, stomatitis,
glossitis, nausea, emesis, abdominal pain, diarrhea, anorexia.
Genitourinary: Renal failure, interstitial nephritis,
BUN and serum creatinine elevation, toxic nephrosis with oliguria
and anuria, and crystalluria.
Metabolic: Hyperkalemia, hyponatremia.
Neurologic: Aseptic meningitis, convulsions, peripheral
neuritis, ataxia, vertigo, tinnitus, headache.
Psychiatric: Hallucinations, depression, apathy,
nervousness.
Endocrine: The sulfonamides bear certain chemical
similarities to some goitrogens, diuretics (acetazolamide and the
thiazides), and oral hypoglycemic agents. Cross-sensitivity may
exist with these agents. Diuresis and hypoglycemia have occurred
rarely in patients receiving sulfonamides.
Musculoskeletal: Arthralgia and myalgia.
Respiratory System: Cough, shortness of breath,
and pulmonary infiltrates (see WARNINGS).
Miscellaneous: Weakness, fatigue, insomnia.
DRUG INTERACTIONS
In elderly patients concurrently receiving certain diuretics, primarily
thiazides, an increased incidence of thrombocytopenia with purpura
has been reported.
It has been reported that sulfamethoxazole; trimethoprim may prolong
the prothrombin time in patients who are receiving the anticoagulant
warfarin. This interaction should be kept in mind when sulfamethoxazole;
trimethoprim is given to patients already on anticoagulant therapy,
and the coagulation time should be reassessed.
Sulfamethoxazole; trimethoprim may inhibit the hepatic metabolism
of phenytoin. Sulfamethoxazole; trimethoprim, given at a common
clinical dosage, increased the phenytoin half-life by 39% and decreased
the phenytoin metabolic clearance rate by 27%. When administering
these drugs concurrently, one should be alert for possible excessive
phenytoin effect.
Sulfonamides can also displace methotrexate from plasma protein
binding sites, thus increasing free methotrexate concentrations.
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