Ixazomib is the world's first oral proteasome inhibitor. Specific usage and dosage must be strictly followed as directed by your doctor.
How to Use Ixazomib
1. Standard Dosing Regimen
Ixazomib must be used in combination with lenalidomide and dexamethasone to form the IRd regimen. A standard treatment cycle is 28 days, with the following specific dosage instructions:
(1) Ixazomib: The recommended starting dose is 4 mg, taken orally once on days 1, 8, and 15 of each cycle.
(2) Lenalidomide: 25 mg orally daily from days 1 to 21.
(3) Dexamethasone: 40 mg orally once daily on days 1, 8, 15, and 22.
2. Key Points for Medication
(1) Timing of Administration: Take on an empty stomach at least 1 hour before a meal or at least 2 hours after a meal to ensure drug absorption.
(2) Administration: Swallow the whole capsule with warm water. Do not chew, crush, or open the capsule. Avoid contact between the capsule contents and skin or mucous membranes.
(3) Management of Missed Dose or Vomiting: If a dose is missed, take it only ≥72 hours after the next dose. If vomiting occurs after taking the medication, no additional dose is needed; take the next dose as scheduled.
Adverse Reactions of Ixazomib
Common adverse reactions (≥20%) of ixazomib combination therapy include thrombocytopenia, neutropenia, diarrhea, constipation, peripheral neuropathy, nausea, peripheral edema, rash, vomiting, and bronchitis.
1. Hematologic Toxicity
(1) Thrombocytopenia: Very common (85%), with a grade 3-4 incidence rate of up to 30%. Platelet troughs often occur on days 14-21 of each cycle. Platelet counts should be monitored at least monthly, with more frequent monitoring recommended for the first three cycles. Discontinue use or adjust the dose according to severity, and administer platelet transfusions if necessary.
(2) Neutropenia: Also common (74%), with a grade 3-4 incidence rate of 34%. Management includes discontinuing the medication, considering granulocyte colony-stimulating factor (G-CSF), and dose adjustment.
2. Non-hematologic toxicities
(1) Gastrointestinal toxicities: Diarrhea (52%), constipation (35%), nausea (32%), and vomiting (26%) are relatively common. Supportive treatment can be provided with pre-treatment or the use of antidiarrheal and antiemetic drugs; dose adjustment is necessary in severe cases.
(2) Peripheral neuropathy: Primarily manifested as sensory neuropathy (24%), mostly grade 1-2. Patient symptoms need to be monitored, and dose discontinuation or reduction should be considered if new or worsening lesions occur.
(3) Skin rash: Occurrence rate of 27%. For grade 2 or 3 rashes, lenalidomide or ixazomib should be discontinued and the dose reduced; in cases of severe skin reactions such as Stevens-Johnson syndrome or toxic epidermal necrolysis, permanent discontinuation of the medication is necessary.
(4) Other Important Adverse Reactions: These include peripheral edema, hepatotoxicity (requiring regular monitoring of liver enzymes), and, although rare, serious thrombotic microangiopathy. If suspected, the drug should be discontinued immediately and the patient evaluated.
Pharmacokinetics of Ixazomib
1. Absorption and Distribution
(1) Absorption: The median time to peak absorption after oral administration is 1 hour, with an absolute bioavailability of 58%. High-fat foods significantly reduce exposure (AUC decreases by 28%), therefore it must be taken on an empty stomach.
(2) Distribution: Plasma protein binding is as high as 99%, and the apparent volume of distribution is large (543 L), indicating its widespread distribution in tissues.
2. Metabolism and Excretion
(1) Metabolism: Ixazomib is extensively metabolized by various CYP450 enzymes (including 3A4, 1A2, 2B6, etc.) and non-CYP enzymes, with no single dominant metabolic pathway.
(2) Excretion: Approximately 62% of the radioactive dose is excreted in the urine, and 22% in the feces. Very little of the unchanged drug is excreted in the urine (<3.5%), and the terminal half-life is approximately 9.5 days.
