Cabazitaxel

MECHANISM OF ACTION 

Cabazitaxel is a taxane chemotherapy drug that works by binding to microtubules and stabilizing them, preventing their normal breakdown. This blocks cell division by arresting cancer cells in the G2/M phase of the cell cycle and triggers apoptosis.

PHARMACOKINETICS

Absorption

Cabazitaxel is not orally absorbed and must be administered intravenously. After IV infusion, it rapidly distributes into the bloodstream and tissues. Because it bypasses the gastrointestinal tract, issues of oral absorption and bioavailability are not relevant for cabazitaxel.

Distribution

Cabazitaxel has a large volume of distribution (≈4,864 L), indicating it spreads extensively into body tissues. It is 89–92% bound to plasma proteins, mainly albumin, which affects how much drug is available to act on cancer cells.

Metabolism

Cabazitaxel is primarily metabolized in the liver by the cytochrome P450 enzymes CYP3A4 and, to a lesser extent, CYP2C8. It undergoes oxidation and other biotransformations to produce inactive metabolites, which are then eliminated mainly via the feces. Hepatic function significantly affects cabazitaxel metabolism and dosing considerations.

Excretion

Cabazitaxel is primarily excreted through the feces (≈76%), with only a small portion eliminated in the urine (≈3.7%). Most of the drug is excreted as metabolites, and only a minor amount is unchanged. This emphasizes the importance of liver function in its clearance.

PHARMACODYNAMICS

Cabazitaxel is a microtubule-stabilizing taxane that inhibits cell division by binding to β-tubulin, preventing microtubule depolymerization. This arrests cancer cells in the G2/M phase of the cell cycle and induces apoptosis. Its activity is notable against docetaxel-resistant prostate cancer cellsdue to poor recognition by P-glycoprotein efflux pumps, allowing it to remain effective where other taxanes fail.

ADMINISTRATION

Cabazitaxel is given IV at 25 mg/m² every 3 weeks for prostate cancer after docetaxel, usually with prednisone. Premedication with steroids and antihistamines helps prevent reactions, and patients are closely monitored for blood counts and organ function.

DOSAGE AND STRENGTH

Cabazitaxel is administered as an intravenous infusion at a recommended dose of 25 mg/m² every 3 weeks, usually in combination with oral prednisone 10 mg daily. Infusions are given over one hour, and patients may receive pre-medications such as antihistamines,corticosteroids, or antiemetics to reduce infusion-related reactions.

DRUG INTERACTIONS

Cabazitaxel is primarily metabolized by CYP3A4. Drugs that strongly inhibit CYP3A4 (e.g., ketoconazole, clarithromycin) can increase cabazitaxel levels, raising the risk of toxicity. Conversely, CYP3A4 inducers (e.g., rifampicin, phenytoin, carbamazepine) can reduce its effectiveness. Cabazitaxel may also interact with other myelosuppressive drugs, increasing the risk of neutropenia and infections.

FOOD INTERACTIONS

Cabazitaxel has no known significant food interactions because it is administered intravenously, bypassing the gastrointestinal tract. Patients can eat normally before and after infusion without affecting the drug’s effectiveness.

CONTRAINDICATIONS

Cabazitaxel is contraindicated in patients with a history of severe hypersensitivity to cabazitaxel or other taxanes. It should not be used in patients with baseline severe neutropenia or those with uncontrolled infections. Severe hepatic impairment is also a contraindication due to its metabolism in the liver.

SIDE EFFECTS

• Neutropenia, anemia, thrombocytopenia 
• Diarrhea, nausea, vomiting, constipation 
• Fatigue and weakness 
• Peripheral neuropathy (tingling/numbness in hands or feet)

OVER DOSE

1. life-threatening neutropenia

2.thrombocytopeni

3. diarrhea

4. nausea

5. Vomiting

TOXICITY

Cabazitaxel toxicity mainly includes severe neutropenia, anemia, thrombocytopenia, diarrhea, peripheral neuropathy, liver enzyme elevation, fatigue, and hypersensitivityreactions, requiring regular blood and liver function monitoring.