Carboplatin

Carboplatin is a second-generation platinum-based antineoplastic agent widely used in veterinary oncology. It is primarily utilized for the treatment of various carcinomas and sarcomas, most notably as an adjunctive therapy for **canine osteosarcoma** following amputation. **Clinical Pearls & Advantages:** * **Feline Safety:** Unlike its predecessor cisplatin (which causes fatal pulmonary edema in cats—often remembered by the mnemonic *"cisplatin splats cats"*), carboplatin is relatively safe and routinely used in feline patients. * **Reduced Toxicity:** Carboplatin is generally considered the "kinder, gentler" platinum agent. It exhibits significantly less nephrotoxicity and emetogenic (vomiting) potential compared to cisplatin, eliminating the need for aggressive pre- and post-treatment IV fluid diuresis. * **Versatility:** Beyond systemic IV administration, it has shown promise in intracavitary (pleural effusion), intra-arterial, and intralesional (equine sarcoids, feline nasal planum carcinomas) applications.

กลไกการออกฤทธิ์: Carboplatin acts as a **bifunctional alkylating agent**. * **Cellular Entry & Activation:** Once inside the cell, the drug undergoes aquation (water molecules replace the cyclobutanedicarboxylate leaving group), forming highly reactive, positively charged platinum complexes. * **DNA Crosslinking:** These active complexes bind covalently to nucleophilic sites on DNA (primarily the N7 position of guanine and adenine). * **Inhibition:** This binding creates **intra-strand and inter-strand crosslinks** in the DNA double helix, physically obstructing DNA polymerases and RNA polymerases. * **Apoptosis:** The resulting DNA damage inhibits DNA replication, RNA transcription, and protein synthesis, ultimately triggering apoptosis (programmed cell death). > **Note:** Carboplatin is **cell-cycle nonspecific**, meaning it can damage cells during any phase of the cell cycle, though cells are most vulnerable during the G1 and S phases.

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