Direct delivery of platinum-based antineoplastics to the central nervous system: a toxicity and ultrastructural study.

Platinum drugs are playing an increasingly major role in cancer treatment, but systemic administration of these agents has resulted in significant toxicity. To examine the effects of cisplatin and two newer agents, iproplatin and carboplatin, we injected the agents directly into the cerebrospinal fluid of rats and found that neurotoxic reactions resulted from doses of cisplatin (10 nmol) much lower than those of iproplatin (40 nmol) or carboplatin (80 nmol). Moreover, central nervous system tissue appeared to be less adversely affected by direct exposure to carboplatin since chronic toxicity was not observed in any of the animals receiving carboplatin until a lethal dose was reached. Furthermore, only the animals receiving cisplatin showed histologic damage in their spinal cords, and ultrastructural studies confirmed that while significant abnormalities were observed in the spinal cords of rats receiving 40 nmol cisplatin, no architectural changes were detected in the spinal cords of animals receiving 240 nmol carboplatin. We conclude that platinum drugs can be delivered intrathecally to achieve a much greater concentration of active drug than can be achieved by intravenous administration and that carboplatin appears to be the most suitable platinum-based drug for use in systems delivering drugs directly to the brain and spinal cord.