GRANISETRON Drug Interactions: What You Need to Know

INTERACTIONS Granisetron does not induce or inhibit the cytochrome P-450 drug-metabolizing enzyme system in vitro . There have been no definitive drug-drug interaction studies to examine pharmacokinetic or pharmacodynamic interaction with other drugs; however, in humans, granisetron hydrochloride injection has been safely administered with drugs representing benzodiazepines, neuroleptics and anti-ulcer medications commonly prescribed with antiemetic treatments. Granisetron hydrochloride injection also does not appear to interact with emetogenic cancer chemotherapies. Because granisetron is metabolized by hepatic cytochrome P-450 drug-metabolizing enzymes, inducers or inhibitors of these enzymes may change the clearance and, hence, the half-life of granisetron. No specific interaction studies have been conducted in anesthetized patients. In addition, the activity of the cytochrome P-450 subfamily 3A4 (involved in the metabolism of some of the main narcotic analgesic agents) is not modified by granisetron hydrochloride in vitro . In in vitro human microsomal studies, ketoconazole inhibited ring oxidation of granisetron hydrochloride. However, the clinical significance of in vivo pharmacokinetic interactions with ketoconazole is not known. In a human pharmacokinetic study, hepatic enzyme induction with phenobarbital resulted in a 25% increase in total plasma clearance of intravenous granisetron hydrochloride. The clinical significance of this change is not known. QT prolongation has been reported with granisetron hydrochloride. Use of granisetron hydrochloride in patients concurrently treated with drugs known to prolong the QT interval and/or are arrhythmogenic may result in clinical consequences. Serotonin syndrome (including altered mental status, autonomic instability, and neuromuscular symptoms) has been described following the concomitant use of 5-HT 3 receptor antagonists and other serotonergic drugs, including selective serotonin reuptake inhibitors (SSRIs) and serotonin and noradrenaline reuptake inhibitors (SNRIs) [see Warnings and Precautions (5.4) ] . Granisetron hydrochloride injection has been administered safely with benzodiazepines, neuroleptics, and anti-ulcer medications. ( 7 ) Does not appear to interact with emetogenic cancer chemotherapies. ( 7 ) Inducers or inhibitors of CYP450 enzymes may change the clearance and therefore the half-life of granisetron. ( 7 ) Coadministration of granisetron hydrochloride injection with drugs known to prolong the QT interval and/or are arrhythmogenic may result in clinical consequences. ( 7 )

SUSTOL is contraindicated in patients with hypersensitivity to granisetron, any of the components of SUSTOL, or to any of the other 5-HT 3 receptor antagonists [see Warnings and Precautions ( 5.3 ), Description ( 11 )] . Hypersensitivity to granisetron, any of the components of SUSTOL, or to any of the other 5-HT 3 receptor antagonists. ( 4 , 5.3 )

AND PRECAUTIONS Injection site reactions (ISRs), including infection, bleeding, pain, nodules, swelling and induration: Monitor for ISRs following SUSTOL injection. Inform patients that some ISRs may occur 2 weeks or more after SUSTOL administration. In patients receiving antiplatelet agents or anticoagulants, consider the increased risk of bruising or severe hematoma prior to the use of SUSTOL. ( 5.1 ) Gastrointestinal disorders: Monitor for constipation and consider optimizing patients' current bowel regimens used for managing preexisting constipation. Also monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction. Instruct patients to seek immediate medical care if signs and symptoms of ileus occur. ( 5.2 ) Hypersensitivity reactions: Serious reactions have been reported and may occur up to 7 days or longer following SUSTOL administration and may have an extended course. If a reaction occurs, administer appropriate treatment and monitor until signs and symptoms resolve. ( 5.3 ) Serotonin syndrome: Reported with 5-HT receptor antagonists alone but particularly with concomitant use of serotonergic drugs. If such symptoms occur, discontinue SUSTOL and initiate supportive treatment. If concomitant use of SUSTOL with other serotonergic drugs is clinically warranted, patients should be made aware of a potential increased risk for serotonin syndrome. ( 5.4 , 7.1 )

5.1 Injection Site Reactions (ISRs)

Infections

Infections at the injection site occurred in 0.4% (7 of 1814) of patients with cancer and 0.2% (1 of 412) of healthy subjects in clinical trials. Infections had a median onset of 9 days (range 7 to 16 days) following SUSTOL administration. One patient who was neutropenic at the time of the infection was hospitalized. All patients with infection were treated with antibiotics and had complete resolution. Bruising and/or hematomas Bruising and/or hematomas at the injection site occurred in 426 of 1131 (38%) patients treated with SUSTOL 10 mg with a median time to onset of 2 days. Bruising and/or hematomas with a delayed onset (onset 5 or more days following SUSTOL administration) were reported in 175 (15%) patients. Severe bruising or hematoma (e.g., greater than 4 cm bruise or hematoma) occurred in 3% of patients. Patients receiving concomitant anticoagulant and antiplatelet medications were at greater risk for severe injection site bruising and hematomas.

Bleeding

Bleeding at the injection site occurred in 70 of 1814 (4%) patients treated with SUSTOL. One patient required emergency management. Bleeding for longer than 5 days was reported in 23 (1%) patients. Pain and Tenderness In a clinical trial that collected information about injection site pain and tenderness from patient diaries, pain with or without tenderness at the injection site was reported by 91 of 456 (20%) of patients treated with SUSTOL 10 mg, and an additional 50 of 456 (11%) of patients reported tenderness without pain. Pain and/or tenderness severe enough to require taking pain medication, interfere with patient activity level, or cause significant discomfort at rest was reported in 2% of patients. Among all patients who reported pain and/or tenderness with SUSTOL 10 mg in clinical trials, the median duration was 5 days, and pain lasting longer than 7 days occurred in 6% of patients.

Nodules

Nodules at the injection site occurred in 203 of 1131 (18%) of patients treated with SUSTOL 10 mg. Nodules persisted for a median of 15 days and 73 patients (6%) had nodules with durations longer than 21 days. Management of ISRs Monitor patients for ISRs following SUSTOL injection. Some ISRs (infections, bruising, and hematoma) may occur up to 2 weeks or more after SUSTOL administration. In patients receiving antiplatelet agents or anticoagulants, consider the increased risk of bruising or severe hematoma prior to the use of SUSTOL. In patients with ongoing or unresolved ISRs, administer SUSTOL at a site away from areas affected by ISRs [see Dosage and Administration ( 2.1 )] .

5.2 Gastrointestinal Disorders Constipation In clinical trials, 224 of 1131 (20%) of patients treated with SUSTOL 10 mg reported constipation compared to 13% to 15% in the 5-HT 3 receptor antagonist control arms. Hospitalization due to constipation or fecal impaction was reported in 5 SUSTOL-treated patients (0.3%). Monitor patients for the development of constipation while receiving treatment with SUSTOL taking into consideration the extended-release properties of the SUSTOL polymer formulation over at least 5 to 7 days, particularly in patients receiving opioid medications. Consider optimizing bowel regimens in patients using SUSTOL.

Progressive

Ileus and Gastric Distention SUSTOL may mask a progressive ileus and/or gastric distention. This should be particularly considered before use of SUSTOL in patients who have had recent abdominal surgery. Monitor for decreased bowel activity, particularly in patients with risk factors for gastrointestinal obstruction.

5.3 Hypersensitivity Reactions Hypersensitivity reactions, including anaphylaxis, have been reported in granisetron-treated patients who have exhibited hypersensitivity to other 5-HT 3 receptor antagonists <span class="opacity-50 text-xs">[see Contraindications ( 4 )]</span> . Avoid SUSTOL in patients who have had hypersensitivity reactions to other 5-HT 3 receptor antagonists <span class="opacity-50 text-xs">[see Contraindications ( 4 )]</span> . Due to the extended-release properties of the SUSTOL polymer formulation, exposure to granisetron may continue for 5 to 7 days following administration. Hypersensitivity reactions may occur up to 7 days or longer following SUSTOL administration and may have an extended course. Inform patients of the signs and symptoms of anaphylaxis, and instruct them to seek immediate medical care should signs and symptoms occur. If hypersensitivity reactions occur, administer appropriate treatment and monitor patients until signs and symptoms resolve.

5.4 Serotonin Syndrome The development of serotonin syndrome has been reported with 5-HT 3 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-HT 3 receptor antagonist alone has also been reported. The majority of reports of serotonin syndrome related to 5-HT 3 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 <span class="opacity-50 text-xs">[see Drug Interactions ( 7.1 )]</span> .