SUSTOL (Page 2 of 5)

5.4 Serotonin Syndrome

The development of serotonin syndrome has been reported with 5-HT3 receptor antagonists. Most reports have been associated with concomitant use of serotonergic drugs (e.g., selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), monoamine oxidase inhibitors, mirtazapine, fentanyl, lithium, tramadol, and intravenous methylene blue). Some of the reported cases were fatal. Serotonin syndrome occurring with overdose of another 5-HT3 receptor antagonist alone has also been reported. The majority of reports of serotonin syndrome related to 5-HT3 receptor antagonist use occurred in a post-anesthesia care unit or an infusion center.

Symptoms associated with serotonin syndrome may include the following combination of signs and symptoms: mental status changes (e.g., agitation, hallucinations, delirium, and coma), autonomic instability (e.g., tachycardia, labile blood pressure, dizziness, diaphoresis, flushing, hyperthermia), neuromuscular symptoms (e.g., tremor, rigidity, myoclonus, hyperreflexia, incoordination), seizures, with or without gastrointestinal symptoms (e.g., nausea, vomiting, diarrhea). Patients should be monitored for the emergence of serotonin syndrome, especially with concomitant use of SUSTOL and other serotonergic drugs. If symptoms of serotonin syndrome occur, discontinue SUSTOL and initiate supportive treatment. Patients should be informed of the increased risk of serotonin syndrome, especially if SUSTOL is used concomitantly with other serotonergic drugs [see Drug Interactions (7.1)].


The following clinically significant adverse reactions are described elsewhere in the labeling:

  • Injection Site Reactions [see Warnings and Precautions (5.1)]
  • Gastrointestinal Disorders [see Warnings and Precautions (5.2)]
  • Hypersensitivity Reactions [see Warnings and Precautions (5.3)]
  • Serotonin Syndrome [see Warnings and Precautions (5.4)]

6.1 Clinical Trials Experience

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 safety of a 10 mg subcutaneous dose of SUSTOL was evaluated in two double-blind, randomized, active-controlled studies, in which 210 patients (23%) received MEC and 467 patients (51%) received AC combination chemotherapy. The data described below reflect exposure to a single 10 mg dose of SUSTOL in 924 patients whose mean age was 56 years (range 19 to 91 years); 76% of patients were female; 70% of patients were Caucasian, 16% Asian, 10% Black, and 4% other races. Dexamethasone was co-administered with SUSTOL in Study 1 and Study 2 and an NK1 receptor antagonist was co-administered with SUSTOL in Study 2.

Table 1 lists the most common adverse reactions reported in at least 3% of patients following a single-dose of SUSTOL 10 mg in Study 1 and/or Study 2. Overall, injection site reactions (ISRs) were the most common group of adverse reactions in SUSTOL-treated patients. Specific types of ISRs reported by SUSTOL-treated patients are shown in Table 2.

Table 1. Adverse Reactions Occurring in at Least 3% of Patients Treated with SUSTOL 10 mg in Study 1 and/or Study 2
Study 1 Study 2
Adverse Reaction SUSTOL10 mgsubcutaneous(N=468)% Palonosetronhydrochloride0.25 mgintravenous(N=463)% SUSTOL10 mgsubcutaneous(N=456)% Ondansetron0.15 mg/kgintravenous(N=459)%
Rates of individual injection site reactions (ISRs) are shown in Table 2
The placebo subcutaneous injection for Study 1 was normal saline and for Study 2 was a SUSTOL-matched control consisting of the SUSTOL polymer vehicle without active drug.
Injection Site Reactions, any * 37 15 62 See footnote
Constipation 14 11 22 15
Fatigue 11 10 21 24
Headache 9 9 13 19
Diarrhea 8 7 9 8
Abdominal Pain 7 7 7 4
Insomnia 4 2 5 6
Dyspepsia 3 3 6 7
Dizziness 3 2 5 5
Asthenia 4 6 2 2
Gastroesophageal Reflux 1 1 5 4

Injection Site Reactions (ISRs)

Injection site reactions occurred in 37% (175/468) in Study 1, Cycle 1 only, and 62% (281/456) in Study 2 of SUSTOL-treated patients. The ISR manifestations included pain, erythema, mass/nodule, swelling/induration, and bleeding. The incidence of individual ISRs is shown in Table 2. Patients may have experienced one or more types of injection site reactions; a total of 213 of 924 patients had three or more.

ISR reporting procedures included both investigator- and patient-reported outcomes in Study 2, while Study 1 used only investigator reporting.

Table 2. Injection Site Adverse Reactions Following a Single 10 mg SUSTOL Dose
Injection Site Reaction Study 1Treatment Arm (Subcutaneous Injection) Study 2*, SUSTOL(N=456)%
SUSTOL(N=468)% Saline Control(N=463)%
Patient diary was used in Study 2 to collect ISR information daily.
The placebo subcutaneous injection for Study 2 was a SUSTOL-matched control consisting of the SUSTOL polymer vehicle without active drug. ISR data for this group are not shown.
Other includes injection site discoloration, vesicles, irritation, lipoma, paresthesia, pruritus, rash, reaction, scab, scar, and warmth.
Total Subjects with at least 1 ISR 37 15 62
Pain 3 1 20
Tenderness 4 1 27
Bruising/Hematoma 22 10 45
Bleeding 2 1 4
Erythema/Redness 11 3 17
Swelling/Induration 1 0 10
Mass/Nodule 11 1 18
Infection at injection site <1 0 1
Other 2 1 1

Less common adverse reactions reported in less than 3% of SUSTOL-treated patients in clinical trials are syncope, elevation of serum transaminase levels, pancreatitis, atrial fibrillation, somnolence, flushing, and hypersensitivity reactions (e.g., anaphylaxis, urticaria).

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