Pharmacokinetic Study of Carboplatin Given on a 5‐Day Intravenous Schedule

We investigated whether carboplatin pharmacokinetics is altered when the drug is delivered daily over 5 days, compared to a single‐day infusion. Carboplatin was infused in 11 patients with lung cancer, who were randomly assigned to 2 groups. In the first group, the agent was administered on a conventional single‐day schedule in the first course and then on a 5‐day schedule in the second course. In the second group, the order was reversed (crossover design). The dose was calculated using Calvert's formula with 24 h creatinine clearance (Ccr, ml/min) as a substitute for glomerular filtration rate (GFR): carboplatin (mg) = AUC X (Ccr+25), where AUC denotes the area under the concentration versus time curve (mg ml(–1) min). No difference of carboplatin clearance between the single‐day and 5‐day schedule was observed (94.8± 19.9 versus 96.1+29.9 ml/min, P=0.818, paired t test). The formula systematically overestimated the carboplatin clearance; the ratio of estimated clearance/ observed clearance ranged from 1.01 to 1.58 (median 1.28; 95% confidence interval, 1.18 to 1.39). We concluded that the individual dosing strategy based on renal function can be applied with a 5‐day schedule as well as a single‐day schedule. Carboplatin is overdosed when Ccr is substituted for GFR in Calvert's formula.