March 29, 2017
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Side Effects


The following serious adverse reactions are discussed in greater detail in other sections of the prescribing information:

Clinical Trials

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

The data below reflect exposure to Elitek in 265 pediatric and 82 adult patients enrolled in one active-controlled trial (Study 1), two uncontrolled trials (Studies 2 and 3), and an uncontrolled safety trial (n=82). Additional data were obtained from an expanded access program of 356 patients, for whom data collection was limited to serious adverse reactions. Among these 703 patients 63% were male, the median age was 10 years (range 10 days to 88 years), 73% were Caucasian, 9% African, 4% Asian, and 14% other/unknown.

Among the 347 patients for whom all adverse reactions regardless of severity were assessed, the most frequently observed adverse reactions (incidence ≥ 10%) were vomiting (50%), fever (46%), nausea (27%), headache (26%), abdominal pain (20%), constipation (20%), diarrhea (20%), mucositis (15%), and rash (13%). In Study 1, an active control study, the following adverse reactions occurred more frequently in Elitek-treated subjects than allopurinol-treated subjects: vomiting, fever, nausea, diarrhea, and headache. Although the incidence of rash was similar in the two arms, severe rash was reported only in one Elitek-treated patient.

Further studies, including one-active controlled study (Study 4) and four supportive studies, have been conducted in adult patients. In these studies, Elitek was administered to a total of 434 adult patients [58% male, 42% female; median age 56 years (range 18 years to 89 years); 52% Caucasian, 7% African, 14% Asian, 28% other/unknown].

Of these 434 patients, 275 adult patients with leukemia, lymphoma, or solid tumor malignancies at risk for hyperuricemia and tumor lysis syndrome (TLS) were randomized in an open label trial receiving either Elitek alone, Elitek in combination with allopurinol, or allopurinol alone (Study 4).

A drug-related adverse reaction in Study 4 of any grade was experienced in 4.3% of Elitek-treated patients, 5.4% of Elitek/allopurinol-treated patients, and 1.1% of allopurinol-treated patients.

Table 1 presents the per patient incidence of adverse reactions by study arm in Study 4.

Table 1 : per patient incidence of selected adverse reactions by study arm in Study 4

Adverse Reaction* Elitek
Elitek / Allopurinol
All Grades % Grades 3,4 % All Grades % Grades 3,4 % All Grades % Grades 3,4 %
Nausea 57.6 1.1 60.9 1.1 54.9 2.2
Peripheral edema 50 2.2 43.5 3.3 42.9 6.6
Vomiting 38 1.1 37 0 30.8 1.1
Anxiety 23.9 3.3 17.4 0 17.6 0
Abdominal pain 21.7 3.3 33.7 4.3 25.3 2.2
Hypophosphatemia 17.4 4.3 22.8 6.5 16.5 6.6
Hyperbilirubinemia 16.3 3.3 14.1 2.2 7.7 4.4
Pharyngolaryngeal pain 14.1 1.1 20.7 0 9.9 0
Sepsis 12 5.4 7.6 6.5 4.4 4.4
Fluid overload 12 0 6.5 0 3.3 1.1
Increased alanine aminotransferase 10.9 3.3 27.2 4.3 17.6 2.2
Hyperphosphatemia 9.8 0 15.2 0 8.8 1.1
*Events were reported and graded according to NCI-CTC version 3.0 and presented as preferred terms MedDRA version 10.1.
*Overall incidence ≥ 10% in any Elitek arm and the difference between any Elitek arm versus the allopurinol arm ≥ 5%.

Hypersensitivity reactions occurred in 4.3% of Elitek-treated patients and 1.1% of Elitek/allopurinol-treated patients in Study 4. Clinical manifestations of hypersensitivity included arthralgia, injection site irritation, peripheral edema, and rash.

The following serious adverse reactions occurred at a difference in incidence of ≥ 2% in patients receiving Elitek compared to patients receiving allopurinol in randomized studies (Study 1 and Study 4): pulmonary hemorrhage, respiratory failure, supraventricular arrhythmias, ischemic coronary artery disorders, and abdominal and gastrointestinal infections.

The incidence of anaphylaxis, hemolysis, and methemoglobinemia was less than 1% of the 887 Elitek-treated patients entered on these clinical trials.


As with all therapeutic proteins, there is potential for immunogenicity. Elitek can elicit anti-product antibodies that bind to rasburicase and in some instances inhibit the activity of rasburicase in vitro [see BOXED WARNING, WARNINGS AND PRECAUTIONS].

In clinical trials of pediatric patients with hematologic malignancies, 24/218 patients tested (11%) developed antibodies by day 28 following Elitek administration as assessed by qualitative ELISA.

Using quasi-quantitative immunoassays in rasburicase na´ve adult patients with hematological malignancies, 47/260 (18%) patients were positive for anti-rasburicase immunoglobulin G (IgG), 21/260 (8%) patients were positive for anti-rasburicase neutralizing IgG, and 16/260 (6%) patients were positive for anti-rasburicase immunoglobulin E (IgE) from day 14 to 24 months after 5 daily doses of Elitek.

The incidence of antibody responses detected is highly dependent on the sensitivity and specificity of the assay, which have not been fully evaluated. Additionally, the observed incidence of antibody positivity in an assay may be influenced by several factors, including serum sampling, timing and methodology, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies to Elitek with the incidence of antibodies to other products may be misleading.

Post-marketing Experience

The following adverse reactions have been identified from clinical trials and/or post-marketing surveillance. Because they are reported from a population of unknown size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Central nervous system disorders: convulsion, muscle contractions involuntary

Immune system disorders: Cases of anaphylaxis with potential fatal outcome have been reported.

Read the Elitek (rasburicase) Side Effects Center for a complete guide to possible side effects


Laboratory Test Interference

At room temperature, Elitek causes enzymatic degradation of the uric acid in blood/plasma/serum samples potentially resulting in spuriously low plasma uric acid assay readings. The following special sample handling procedure must be followed to avoid ex vivo uric acid degradation.

Uric acid must be analyzed in plasma. Blood must be collected into pre-chilled tubes containing heparin anticoagulant. Immediately immerse plasma samples for uric acid measurement in an ice water bath. Plasma samples must be prepared by centrifugation in a pre-cooled centrifuge (4°C). Finally, the plasma must be maintained in an ice water bath and analyzed for uric acid within four hours of collection [see BOXED WARNING].

Rasburicase does not metabolize allopurinol, cytarabine, methylprednisolone, methotrexate, 6-mercaptopurine, thioguanine, etoposide, daunorubicin, cyclophosphamide or vincristine in vitro. No metabolic-based drug interactions are therefore anticipated with these agents in patients.

This monograph has been modified to include the generic and brand name in many instances.

Last reviewed on RxList: 6/28/2016

Side Effects

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