Oxaliplatin (Page 5 of 10)

8.6 Patients with Renal Impairment

The AUC of unbound platinum in plasma ultrafiltrate was increased in patients with renal impairment [see Clinical Pharmacology (12.3)]. No dose reduction is recommended for patients with mild (creatinine clearance 50 to 79 mL/min) or moderate (creatinine clearance 30 to 49 mL/min) renal impairment, calculated by Cockcroft-Gault equation. Reduce the dose of oxaliplatin for injection in patients with severe renal impairment (creatinine clearance less than 30 mL/min) [see Dosage and Administration (2.3)].

10 OVERDOSAGE

The maximum dose of oxaliplatin that has been administered in a single infusion is 825 mg. Several cases of overdoses have been reported with oxaliplatin for injection. Adverse reactions observed following an overdosage were grade 4 thrombocytopenia (less than 25,000/mm3) without bleeding, anemia, sensory neuropathy (including paresthesia, dysesthesia, laryngospasm and facial muscle spasms), gastrointestinal disorders (including nausea, vomiting, stomatitis, flatulence, abdomen enlarged and grade 4 intestinal obstruction), grade 4 dehydration, dyspnea, wheezing, chest pain, respiratory failure, severe bradycardia and death.

Closely monitor patients suspected of receiving an overdose, including for the adverse reactions described above and administer appropriate supportive treatment.

11 DESCRIPTION

Oxaliplatin is a platinum-based drug with the molecular formula C8 H14 N2 O4 Pt and the chemical name of cis -[(1 R , 2 R)-1, 2-cyclohexanediamine-N ,N’ ] [oxalato (2-)-O ,O’ ] platinum. Oxaliplatin is an organoplatinum complex in which the platinum atom is complexed with 1,2-diaminocyclohaxane (DACH) and with an oxalate ligand as a leaving group.

structure
(click image for full-size original)

The molecular weight is 397.3. Oxaliplatin is slightly soluble in water at 6 mg/mL, very slightly soluble in methanol, and practically insoluble in ethanol and acetone.

Oxaliplatin for Injection, USP is for intravenous use. It is supplied in vials containing 50 mg or 100 mg of oxaliplatin as a sterile, preservative-free lyophilized powder for reconstitution. Lactose monohydrate is present as an inactive ingredient at 450 mg and 900 mg in the 50 mg and 100 mg dosage strengths, respectively.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Oxaliplatin undergoes nonenzymatic conversion in physiologic solutions to active derivatives via displacement of the labile oxalate ligand. Several transient reactive species are formed, including monoaquo and diaquo DACH platinum, which covalently bind with macromolecules. Both inter- and intrastrand Pt-DNA crosslinks are formed. Crosslinks are formed between the N7 positions of two adjacent guanines (GG), adjacent adenine-guanines (AG), and guanines separated by an intervening nucleotide (GNG). These crosslinks inhibit DNA replication and transcription. Cytotoxicity is cell-cycle nonspecific.

In vivo studies have shown antitumor activity of oxaliplatin against colon carcinoma. In combination with fluorouracil, oxaliplatin exhibits in vitro and in vivo antiproliferative activity greater than either compound alone in several tumor models (HT29 [colon], GR [mammary], and L1210 [leukemia]).

12.2 Pharmacodynamics

A pharmacodynamic relationship between platinum ultrafiltrate levels and clinical safety and effectiveness has not been established.

12.3 Pharmacokinetics

The reactive oxaliplatin derivatives are present as a fraction of the unbound platinum in plasma ultrafiltrate. After a single 2-hour intravenous infusion of oxaliplatin for injection at a dose of 85 mg/m2 , pharmacokinetic parameters expressed as ultrafiltrable platinum were Cmax of 0.814 mcg/mL and volume of distribution of 440 L.

Interpatient and intrapatient variability in ultrafiltrable platinum exposure (AUC0-48hr ) assessed over 3 cycles was 23% and 6%, respectively.

Distribution

At the end of a 2-hour infusion of oxaliplatin for injection, approximately 15% of the administered platinum is present in the systemic circulation. The remaining 85% is rapidly distributed into tissues or eliminated in the urine. The decline of ultrafiltrable platinum levels following oxaliplatin for injection administration is triphasic, including two distribution phases (t1/2α ; 0.43 hours and t1/2β ; 16.8 hours).

In patients, plasma protein binding of platinum is irreversible and is greater than 90%. The main binding proteins are albumin and gamma-globulins.

Platinum also binds irreversibly and accumulates (approximately 2-fold) in erythrocytes, where it appears to have no relevant activity. No platinum accumulation was observed in plasma ultrafiltrate following 85 mg/m2 every two weeks.

Elimination

The decline of ultrafiltrable platinum concentrations from plasma is characterized by a long terminal elimination phase (t1/2 γ ; 392 hours).

Metabolism

Oxaliplatin undergoes rapid and extensive nonenzymatic biotransformation. There is no evidence of cytochrome P450-mediated metabolism in vitro.

Up to 17 platinum-containing derivatives have been observed in plasma ultrafiltrate samples from patients, including several cytotoxic species (monochloro DACH platinum, dichloro DACH platinum, and monoaquo and diaquo DACH platinum) and a number of noncytotoxic, conjugated species.

Excretion

The major route of platinum elimination is renal excretion. At five days after a single 2-hour infusion of oxaliplatin, urinary elimination accounted for about 54% of the platinum eliminated, with fecal excretion accounting for only about 2%. Platinum was cleared from plasma at a rate (10-17 L/h) that was similar to or exceeded the average human glomerular filtration rate (GFR; 7.5 L/h). The renal clearance of ultrafiltrable platinum is significantly correlated with GFR.

Special Populations

Sex

There was no significant effect of sex on the clearance of ultrafiltrable platinum.

Patients with renal impairment

Patients with normal function (CLcr greater than 80 mL/min) and patients with mild (CLcr=50-80 mL/min) and moderate (CLcr equal to 30-49 mL/min) renal impairment received oxaliplatin for injection 85 mg/m2 and those with severe (CLcr less than 30 mL/min) renal impairment received oxaliplatin for injection 65 mg/m2. Mean dose adjusted AUC of unbound platinum was 40%, 95%, and 342% higher for patients with mild, moderate, and severe renal impairment, respectively, compared to patients with normal renal function. Mean dose adjusted Cmax of unbound platinum appeared to be similar among the normal, mild and moderate renal function groups, but was 38% higher in the severe group than in the normal group [see Dosage and Administration (2.3)].

Drug Interaction Studies

No pharmacokinetic interaction between oxaliplatin for injection 85 mg/m2 and infusional fluorouracil has been observed in patients treated every 2 weeks, but increases of fluorouracil plasma concentrations by approximately 20% have been observed with doses of 130 mg/m2 of oxaliplatin for injection administered every 3 weeks.

In vitro platinum was not displaced from plasma proteins by the following medications: erythromycin, salicylate, sodium valproate, granisetron, and paclitaxel.

In vitro oxaliplatin does not inhibit human cytochrome P450 isoenzymes.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term animal studies have not been performed to evaluate the carcinogenic potential of oxaliplatin. Oxaliplatin was not mutagenic to bacteria (Ames test) but was mutagenic to mammalian cells in vitro(L5178Y mouse lymphoma assay). Oxaliplatin was clastogenic both in vitro (chromosome aberration in human lymphocytes) and in vivo (mouse bone marrow micronucleus assay).

In a fertility study, male rats were given oxaliplatin at 0, 0.5, 1, or 2 mg/kg/day for five days every 21 days for a total of three cycles prior to mating with females that received two cycles of oxaliplatin on the same schedule. A dose of 2 mg/kg/day (less than one-seventh the recommended human dose on a body surface area basis) did not affect pregnancy rate, but resulted in 97% postimplantation loss (increased early resorptions, decreased live fetuses, decreased live births) and delayed growth (decreased fetal weight).

Testicular damage, characterized by degeneration, hypoplasia, and atrophy, was observed in dogs administered oxaliplatin at 0.75 mg/kg/day (approximately one-sixth of the recommended human dose on a body surface area basis)x 5 days every 28 days for three cycles. A no effect level was not identified.

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