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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