This non-randomized study reports pharmaco-clinical data on 5-FU administered by the widely used 5-day continuous infusion schedule to 42 patients with metastatic colorectal cancer; 5-FU was given by hepatic intra-arterial route (h.i.a.) at doses ranging from 800 to 1,450 mg/m2, and by a systemic intravenous route (i.v.) at doses ranging from 650 to 1,300 mg/m2. 5-FU blood levels were available for a total of 179 cycles. Toxicity was dose-dependent during h.i.a. cycles but not during i.v. cycles. For h.i.a. cycles, 1,000 mg/m2/day represented the threshold dose for tolerance. The individual total cycle drug concentration-time product might predict toxicity for both i.v. and h.i.a. cycle when the threshold is set at 30,000 ng/ml.hr. These data may be of practical value for improving the therapeutic index of 5-day continuous treatment by 5-FU given by i.v. or h.i.a. routes.

Centre Antoine Lacassagne, 36 voie Romaine, 06054 Nice Cedex, France Summary Recent biochemical and pharmacological findings concerning tamoxifen (TMX) have proven that both the unchanged drug and the main metabolites, N-desmethyltamoxifen (NDT) and 4-hydroxytamoxifen (4 OHT) are biologically active. An HPLC method based on on-line post-column UV irradiation with fluorescence detection is described. Optimized conditions allowed complete and rapid separation of TMX 40HT, NDT and two other recently reported metabolites, Y and Z. This method was applied to plasma and cytosol drug and metabolite analyses. In plasma, from the moment of initial drug administration until the steady state (after 1 month or more of continuous oral TMX treatment), the values of NDT to TMX ratios were completely reversed: 22 to 215 in mean %, P<0.01. The presence of metabolites Y and Z is significant. 40HT, hardly detectable at the first dose, was measured at the steady state with high interpatient variability. It is hypothesized that metabolite evolution with time may be due to auto-induction of drug metabolism. In cytosols, which were all obtained during continuous TMX treatment, the ratios between TMX and metabolites were comparable to those observed in plasma, but with greater interpatient variability. Metabolite Y was not detectable in cytosols. This variability was not linked to the levels of cytosolic oestradiol receptors before initiation of treatment.

Eighteen patients with liver metastasis or locoregional recurrence of colon carcinoma received locoregional treatment by continuous 5-day infusions of 5-FU. 5-FU blood levels were measured by HPLC every day of the cycle at 8 am and 5 pm for a total of 87 cycles. Twelve patients were given the drug by an intra-arterial hepatic (i.a.h.) route, 3 by the portal vein (i.p.v.) and 3 by an intra-arterial pelvic (i.a.p.) route. These three routes were compared in respect of their relative pre-systemic drug uptake and the effect of dose escalation. Both the i.a.h. and i.p.v. routes, but not the i.a.p. route, resulted in a significant reduction in AUC 0-105 h compared to the i.v. route at the same dose range. Increasing the dose led to a modification in circulating 5-FU levels proportional to the dose for the i.v. and i.a.p. routes. By contrast, for the i.a.h. and i.p.v. routes, systemic drug delivery was significantly elevated, out of proportion with the dose, indicating a saturable process. For the i.a.h. route, increasing the 5-FU dose from 780 to 1000 mg m-2 day-1 caused a drop in hepatic extraction from 0.93 (0.90-0.95) to 0.44 (0.21-0.66). Liver saturation mechanisms were also evidenced by a mean increase of 2.6 times for the circulating drug level during the second part of the cycle as compared to the first part (P less than 0.001). The evolution of 5-FU AUC 0-105 h as a function of the dose was exponential (r = 0.75, P less than 0.001). Local extraction consecutive to i.a.p. was non-existent, implying that this route of drug administration has no potential advantage over classical i.v. infusion.

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