Only after critical appraisal should sulfasalazine delayed release tablets be given to patients with hepatic or renal damage or blood dyscrasias. Deaths associated with the administration of sulfasalazine have been reported from hypersensitivity reactions, agranulocytosis, aplastic anemia, other blood dyscrasias, renal and liver damage, irreversible neuromuscular and central nervous system changes, and fibrosing alveolitis. The presence of clinical signs such as sore throat, fever, pallor, purpura, or jaundice may be indications of serious blood disorders or hepatotoxicity. Complete blood counts, as well as urinalysis with careful microscopic examination, should be done frequently in patients receiving sulfasalazine delayed release tablets (see PRECAUTIONS, Laboratory Tests). Discontinue treatment with sulfasalazine while awaiting the results of blood tests. Oligospermia and infertility have been observed in men treated with sulfasalazine; however, withdrawal of the drug appears to reverse these effects.
Serious infections, including fatal sepsis and pneumonia, have been reported. Some infections were associated with agranulocytosis, neutropenia, or myelosuppression. Discontinue sulfasalazine delayed release tablets if a patient develops a serious infection. Closely monitor patients for the development of signs and symptoms of infection during and after treatment with sulfasalazine delayed release tablets. For a patient who develops a new infection during treatment with sulfasalazine delayed release tablets, perform a prompt and complete diagnostic workup for infection and myelosuppression. Caution should be exercised when considering the use of sulfasalazine in patients with a history of recurring or chronic infections or with underlying conditions or concomitant drugs which may predispose patients to infections.
Severe hypersensitivity reactions may include internal organ involvement, such as hepatitis, nephritis, myocarditis, mononucleosis-like syndrome (i.e., pseudomononucleosis), hematological abnormalities (including hematophagic histiocytosis), and/or pneumonitis including eosinophilic infiltration.
Serious skin reactions, some of them fatal, including exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis, have been reported in association with the use of sulfasalazine. Patients are at highest risk for these events early in therapy, with most events occurring within the first month of treatment. Sulfasalazine should be discontinued at the first appearance of skin rash, mucosal lesions, or any other sign of hypersensitivity.
Severe, life-threatening, systemic hypersensitivity reactions such as drug rash with eosinophilia and systemic symptoms have been reported in patients taking sulfasalazine. Early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident. If such signs or symptoms are present, the patient should be evaluated immediately. Sulfasalazine should be discontinued if an alternative etiology for the signs or symptoms cannot be established.
Sulfasalazine delayed release tablets should be given with caution to patients with severe allergy or bronchial asthma. Adequate fluid intake must be maintained in order to prevent crystalluria and stone formation. Patients with glucose-6-phosphate dehydrogenase deficiency should be observed closely for signs of hemolytic anemia. This reaction is frequently dose related. If toxic or hypersensitivity reactions occur, sulfasalazine delayed release tablets should be discontinued immediately.
Isolated instances have been reported when sulfasalazine delayed release tablets have passed undisintegrated. If this is observed, the administration of sulfasalazine delayed release tablets should be discontinued immediately.
Information For Patients
Patients should be informed of the possibility of adverse effects and of the need for careful medical supervision. The occurrence of sore throat, fever, pallor, purpura, or jaundice may indicate a serious blood disorder. Should any of these occur, the patient should seek medical advice.
Patients should be instructed to take sulfasalazine delayed release tablets in evenly divided doses, preferably after meals, and to swallow the tablets whole. Additionally, patients should be advised that sulfasalazine may produce an orange-yellow discoloration of the urine or skin.
Patients with ulcerative colitis should be made aware that ulcerative colitis rarely remits completely, and that the risk of relapse can be substantially reduced by continued administration of sulfasalazine delayed release tablets at a maintenance dosage.
Rheumatoid arthritis rarely remits. Therefore, continued administration of sulfasalazine delayed release tablets is indicated. Patients requiring sulfasalazine should follow up with their physicians to determine the need for continued administration.
Complete blood counts, including differential white cell count and liver function tests, should be performed before starting sulfasalazine delayed release tablets and every second week during the first three months of therapy. During the second three months, the same tests should be done once monthly and thereafter once every three months, and as clinically indicated. Urinalysis and an assessment of renal function should also be done periodically during treatment with sulfasalazine delayed release tablets.
The determination of serum sulfapyridine levels may be useful since concentrations greater than 50 µg/mL appear to be associated with an increased incidence of adverse reactions.
Reduced absorption of folic acid and digoxin have been reported when those agents were administered concomitantly with sulfasalazine.
When daily doses of sulfasalazine 2 g and weekly doses of methotrexate 7.5 mg were coadministered to 15 rheumatoid arthritis patients in a drug-drug interaction study, the pharmacokinetic disposition of the drugs was not altered.
Daily doses of sulfasalazine 2 g (maximum 3 g) and weekly doses of methotrexate 7.5 mg (maximum 15 mg) were administered alone or in combination to 310 rheumatoid arthritis patients in two controlled 52-week clinical studies. The overall toxicity profile of the combination revealed an increased incidence of gastrointestinal adverse events, especially nausea, when compared to the incidence associated with either drug administered alone.
Drug/Laboratory Test Interactions
Several reports of possible interference with measurements, by liquid chromatography, of urinary normetanephrine causing a false-positive test result have been observed in patients exposed to sulfasalazine or its metabolite, mesalamine/mesalazine.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Two year oral carcinogenicity studies were conducted in male and female F344/N rats and B6C3F1 mice. Sulfasalazine was tested at 84 (496 mg/m2), 168 (991 mg/m2) and 337.5 (1991 mg/m2) mg/kg/day doses in rats. A statistically significant increase in the incidence of urinary bladder transitional cell papillomas was observed in male rats. In female rats, two (4%) of the 337.5 mg/kg rats had transitional cell papilloma of the kidney. The increased incidence of neoplasms in the urinary bladder and kidney of rats was also associated with an increase in the renal calculi formation and hyperplasia of transitional cell epithelium. For the mouse study, sulfasalazine was tested at 675 (2025 mg/m2), 1350 (4050 mg/m2) and 2700 (8100 mg/m2) mg/kg/day. The incidence of hepatocellular adenoma or carcinoma in male and female mice was significantly greater than the control at all doses tested.
Sulfasalazine did not show mutagenicity in the bacterial reverse mutation assay (Ames test) or in the L51784 mouse lymphoma cell assay at the HGPRT gene. However, sulfasalazine showed equivocal mutagenic response in the micronucleus assay of mouse and rat bone marrow and mouse peripheral RBC and in the sister chromatid exchange, chromosomal aberration, and micronucleus assays in lymphocytes obtained from humans.
Impairment of male fertility was observed in reproductive studies performed in rats at a dose of 800 mg/kg/day (4800 mg/m2). Oligospermia and infertility have been described in men treated with sulfasalazine. Withdrawal of the drug appears to reverse these effects.
There are no adequate and well-controlled studies of sulfasalazine in pregnant women. Reproduction studies have been performed in rats and rabbits at doses up to 6 times the human maintenance dose of 2 g/day based on body surface area and have revealed no evidence of impaired female fertility or harm to the fetus due to sulfasalazine. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
There have been case reports of neural tube defects (NTDs) in infants born to mothers who were exposed to sulfasalazine during pregnancy, but the role of sulfasalazine in these defects has not been established. However, oral sulfasalazine inhibits the absorption and metabolism of folic acid which may interfere with folic acid supplementation (see Drug Interactions) and diminish the effect of periconceptional folic acid supplementation that has been shown to decrease the risk of NTDs.
A national survey evaluated the outcome of pregnancies associated with inflammatory bowel disease (IBD). In 186 pregnancies in women treated with sulfasalazine alone or sulfasalazine and concomitant steroid therapy, the incidence of fetal morbidity and mortality was comparable both to that of 245 untreated IBD pregnancies, and to pregnancies in the general population.2
A study of 1455 pregnancies associated with exposure to sulfonamides including sulfasalazine, indicated that this group of drugs did not appear to be associated with fetal malformation.3 A review of the medical literature covering 1155 pregnancies in women with ulcerative colitis suggested that the outcome was similar to that expected in the general population.4
No clinical studies have been performed to evaluate the effect of sulfasalazine on the growth development and functional maturation of children whose mothers received the drug during pregnancy.
Sulfasalazine and its metabolite, sulfapyridine, pass through the placenta. Sulfasalazine and its metabolite are also present in human milk. In the newborn, sulfonamides compete with bilirubin for binding sites on the plasma proteins and may cause kernicterus. Although sulfapyridine has been shown to have poor bilirubin-displacing capacity, monitor the newborn for the potential for kernicterus.
A case of agranulocytosis has been reported in an infant whose mother was taking both sulfasalazine and prednisone throughout pregnancy.
Sulfonamides, including sulfasalazine, are present in human milk (see Pregnancy, Clinical Considerations). Insignificant amounts of sulfasalazine have been found in milk, whereas levels of the active metabolite sulfapyridine in milk are about 30 to 60 percent of those in the maternal serum. Caution should be exercised when sulfasalazine delayed release tablets are administered to a nursing mother.
There are reports with limited data of bloody stools or diarrhea in human milk fed infants of mothers taking sulfasalazine. In cases where the outcome was reported, bloody stools or diarrhea resolved in the infant after discontinuation of sulfasalazine in the mother or discontinuation of breastfeeding. Due to limited data, a causal relationship between sulfasalazine exposure and bloody stools or diarrhea cannot be confirmed or denied. Monitor human milk fed infants of mothers taking sulfasalazine for signs and symptoms of diarrhea and/or bloody stools.
The safety and effectiveness of sulfasalazine delayed release tablets in pediatric patients below the age of 2 years with ulcerative colitis have not been established.
The safety and effectiveness of sulfasalazine delayed release tablets for the treatment of the signs and symptoms of polyarticular-course juvenile rheumatoid arthritis in pediatric patients aged 6–16 years is supported by evidence from adequate and well-controlled studies in adult rheumatoid arthritis patients. The extrapolation from adults with rheumatoid arthritis to children with polyarticular-course juvenile rheumatoid arthritis is based on similarities in disease and response to therapy between these two patient populations. Published studies support the extrapolation of safety and effectiveness for sulfasalazine to polyarticular-course juvenile rheumatoid arthritis1,5 (see ADVERSE REACTIONS).
It has been reported that the frequency of adverse events in patients with systemic-course of juvenile arthritis is high.6 Use in children with systemic-course juvenile rheumatoid arthritis has frequently resulted in a serum sickness-like reaction.5 This reaction is often severe and presents as fever, nausea, vomiting, headache, rash, and abnormal liver function tests. Treatment of systemic-course juvenile rheumatoid arthritis with sulfasalazine is not recommended.