EpistemisInhibitors of microtubules and nuclear enzymes
Drugs directed against the cytoskeletal scaffolding of microtubules or topological DNA replication during cell mitosis.
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Paclitaxel Taxol, Abraxane (albumin-bound)Pharmacological Group: Mitotic spindle inhibitor antineoplastic agent, taxane group.
Mechanism of Action: Unlike vinca alkaloids, paclitaxel specifically binds to the beta subunit of tubulin and hyperstably promotes the assembly of microtubules, blocking their physiological cellular depolymerization. This alters the dynamic balance of the mitotic spindle, preventing chromosome segregation during anaphase, irreversibly arresting the cell cycle in the G2/M mitotic phase and activating the mitochondrial apoptosis cascade preferentially in tumor cells.
| Routes and Directions | Critical Pharmacokinetics | Main Adverse Effects |
|---|---|---|
| Approved: First-line and advanced metastatic ovarian cancer; first-line and adjuvant breast cancer (in combination with anthracyclines); non-small cell lung cancer (with cisplatin); AIDS-related Kaposi sarcoma. | Via: IV (slow infusion over 3 or 24 hours). Distribution: Very broad and does not penetrate the CNS. Metabolism: Mainly hepatic through the enzymes CYP2C8 (forming 6-alpha-hydroxypaclitaxel) and CYP3A4. t1/2: Triphasic; average terminal 13 to 52 hours. Elimination: Biliary/Fecal (70%); unchanged kidney (7%). | Acute hypersensitivity (severe): Dyspnea, severe hypotension, angioedema, urticaria (mediated by Cremophor EL solvent in conventional formulation). Myelosuppression: Severe dose-dependent neutropenia. Sensory peripheral neuropathy: Bilateral stocking-and-glove paresthesias, chronic distal neuropathic pain. Complete alopecia. fast. |
Perla Clínica: Mandatory Premedication and Benefits of Abraxane
The conventional formulation of paclitaxel requires dilution in a highly allergenic lipophilic excipient, polyoxyethylated castor oil (Cremophor EL), a frequent inducer of anaphylactic shock due to mast cell degranulation. Systematic premedication with corticosteroids (dexamethasone 20 mg PO/IV 12 and 6 hours before), H1 antihistamines (diphenhydramine) and H2 inhibitors (ranitidine/famotidine) is required. The version of paclitaxel bound to human albumin nanoparticles (Abraxane) avoids the use of Cremophor EL, eliminating the need for steroid premedication and achieving greater intratumoral transport through gp60 receptor-mediated endothelial transcytosis.
Dosage and Adjustment for Toxicity
Usual Dose (Taxol): 135-175 mg/m² IV administered as a 3-hour infusion every 21 days.
Adjustment by Counts: Discontinue or defer if absolute neutrophil count is less than 1500/mm3 or platelets are less than 100,000/mm3. In case of persistent moderate sensory neuropathy, reduce the dose by 20% in successive cycles.
Epistemis is educational review material. It is not a medical device, does not diagnose or prescribe treatment, and does not replace formal medical training, current clinical guidelines, or professional clinical judgment.
- System
- Immunology, Oncology and Toxicology
- Cluster
- Basic Oncology