H.-S. G. Chen

Bleomycin pharmacokinetics in man: II. Intracavitary administration

Disposition of bleomycin was studied in plasma and urine (14 patients) and ascites fluid (2 patients) after intraperitoneal (IP) and intrapleural (IPl) administration, by radioimmunoassay. Peak plasma bleomycin concentrations after 60 U/m2 in 12 patients ranged between 0.4 and 5.0 mU/ml. For those patients with creatinine clearances greater than 50 ml/min the composite terminal phase bleomycin plasma half-lives (±SD) for three ‘IPl’ and six ‘IP’ patients were 3.4±0.3 and 5.3±0.4 h, respectively. The composite IP plasma half-life was significantly longer than the IPl hal-life (P<0.001) and previously reported IV half-life (t1/2=4.0 ±0.6 h) (P<0.01). In patients with normal renal function, bleomycin excretion during the first 24 h was in most cases lower following intracavitary (IC) than following IV administration (21.7%±8.6% vs. 44.8%±12.6%, respectively) (P<0.005). Comparison of bleomycin plasma concentration time products normalized for dose and half-life for IV and IC administration allowed an estimate that about 45% of the IC bleomycin dosage is absorbed into the systemic circulation. When calculating the total systemic exposure to bleomycin for a patient we suggest using the sum of the IV dose and one-half of the IC dose.

Bleomycin pharmacokinetics in man. I. Intravenous administration.

SummaryDisposition of bleomycin was studied in plasma and urine (14 patients) and ascites fluid (2 patients) after intraperitoneal (IP) and intrapleural (IPl) administration, by radioimmunoassay. Peak plasma bleomycin concentrations after 60 U/m2 in 12 patients ranged between 0.4 and 5.0 mU/ml. For those patients with creatinine clearances greater than 50 ml/min the composite terminal phase bleomycin plasma half-lives (±SD) for three ‘IPl’ and six ‘IP’ patients were 3.4±0.3 and 5.3±0.4 h, respectively. The composite IP plasma half-life was significantly longer than the IPl hal-life (P<0.001) and previously reported IV half-life (t1/2=4.0 ±0.6 h) (P<0.01). In patients with normal renal function, bleomycin excretion during the first 24 h was in most cases lower following intracavitary (IC) than following IV administration (21.7%±8.6% vs. 44.8%±12.6%, respectively) (P<0.005). Comparison of bleomycin plasma concentration time products normalized for dose and half-life for IV and IC administration allowed an estimate that about 45% of the IC bleomycin dosage is absorbed into the systemic circulation. When calculating the total systemic exposure to bleomycin for a patient we suggest using the sum of the IV dose and one-half of the IC dose.SummaryBleomycin plasma decay kinetics and urinary excretion were studied in nine patients after IV bolus injections of 13.7 to 19.9 U/M2. Radio-immunoassay was used to measure bleomycin in plasma and urine samples. The resulting plasma concentration versus time data for each patient and the combined data obtained from all patients were fitted to a multiexponential equation using a nonlinear regression computer program. Pharmacokinetic parameters derived from the mean of all individual patient parameters and the composite of all plasma decay data were similar. Bleomycin initial and terminal plasma half-lives and volume of distribution for all plasma decay data from eight patients with normal serum creatinies were 24.4±4.0 min, 237.5±8.5 min, and 17.3±1.5 L/M2, respectively. Mean 24-h urinary excretion accounted for 44.8±12.6% of the dose in seven patients who had normal serum creatinine values and complete urine collections. The total body clearance and renal clearance in these seven patients averaged 50.5±4.1 ml/min/M2 and 23.0±1.9 ml/min/M2, respectively. One patient with a serum creatinine of 1.5 mg% (normal 0.7 to 1.3 mg%) who was given 15.6 U/M2 had a terminal plasma halflife of 624 min, a volume of distribution of 36.3 L/M2, and 24-h urinary excretion of 11.6% of the dose. We conclude that bleomycin after intravenous bolus injection has a relatively short terminal phase plasma halflife and relatively large urinary elimination.

Physiologically based pharmacokinetic models for anticancer drugs

SummaryThe rationale and history of the development of physiologically based pharmacokinetic models are briefly reviewed in this paper. The methods of model construction and the previous application of this type of model to anticancer drugs are discussed.Future research should be focused on the following areas: (1) interspecies scaling, (2) the effects of disease states on the pharmacokinetics of anticancer drugs, and (3) the applications of pharmocokinetics to the studies of growth behavior of cancer cells. The ultimate goal will be to utilize this basic information to design an optimal dosage regimen and treatment schedule for the safe and effective cancer chemotherapy of each individual patient.

Clinical Correlations of Drug Sensitivity in the Human Tumor Stem Cell Assay

We have applied an in vitro soft-agar tumor-colony assay (which is now applicable to a variety of human cancers) to measurement of in vitro sensitivity to drugs and prediction of clinical response to cancer chemotherapy. The assay predicts drug resistance with 96% accuracy and sensitivity (in healthy pretreated patients) with 62% accuracy. On a pharmacokinetic basis the zone in vitro sensitivity for any given drug was only 5%-10% of the clinical concentration-time product (Cxt) achievable. This suggests that intratumoral drug concentrations in vivo may be lower than those in the plasma, and/or that > 2 log kills of tumor stem cells (not measurable in the assay) are required for clinical response. Serial in vitro studies showed that acquisition of drug resistance is a common clinical phenomenon which can be directly detected and quantitated in vitro.

The limited role of corticosteroids in ameliorating experimental doxorubicin skin toxicity in the mouse.

SummaryLocal skin necrosis is a serious complication of doxorubicin (Adriamycin) infiltration in man. Intradermal (ID) doxorubicin injection was used in the mouse to create skin lesions, after wich a number of local corticosteroid interventions were studied. The most effective local antidote was low-dose (2.5 mg) hydrocortisone (HC), but only against the low-dose doxorubicin challege (0.05 mg). Other andidotes with lesser effectiveness included dexamethasone-sodium bicarbonate and an intermediate dose of HC (6.25 mg). Larger doses of ID HC did not prevent local doxorubicin toxicity and were inherently toxic to the skin. Systemic corticosteroids were similarly ineffective. The superiority of the low ID HC dose, the ineffectiveness of additions (sodium bicarbonate, topical HC cream), and the resistance of the high-dose doxorubicin ID challenge (0.5 mg) suggests a limited role for corticosteroids in the management of experimental doxorubicin skin toxicity.

Experimental model of doxorubicin extravasation in the mouse

Doxorubicin (Adriamycin), a widely used antitumor agent, can occasionally cause severe and protracted local tissue damage if inadvertently extravasated during intravenous injection. An animal model was developed in adult BALB/c mice to experimentally duplicate such human skin toxicity, Intradermal (ID) doxorubicin injections of 0.5, 0.05 and 0.005 mg (per 0.05 ml) provided reproducible, dose-related skin lesions, quantitated with daily measurement of perpendicular diameters of induration, erythema, and ulceration. Maximal lesions developed rapidly (within 3-5 days) and slowly resolved over 30-40 days. There were dose-related increments in peak toxicity levels, total toxicity, and the duration of damage for each parameter (0.5 > 0.05 > 0.005 mg). Subcutaneous (ie, subpannicular) injections, and ID saline control injections did not cause local skin toxicity. A local intervention with ID hydrocortisone (2.5 mg) substantially reduced erythema and induration, and eliminated ulceration only in animals receiving the lower dose (0.05 mg) doxorubicin challenge (p < 0.05). This direct skin toxicity method is compared to reported animal skin toxicity models, and the intervention results are discussed in reference to current toxicity observations in man.

Antitumour activity and plasma kinetics of bleomycin by continuous and intermittent administration

We have studied the cytotoxicity of bleomycin (4--10 u/kg/day for 6 days) given by continuous i.p. infusion (using an osmotic minipump) compared to daily i.p. bolus administration, against P388 leukaemic spleen colony-forming-units(LCFU-S). Continuous i.p. bleomycin at 8 u/kg/day caused a 0.5 log greater reduction of LCFU-S than did an identical dose given by intermittent bolus administration. The infusion minipump provided constant bleomycin plasma levels of 0.62 +/- 0.03 mu/ml and a total plasma AUC (area under the plasma decay curve) of 89.0 mu.h/ml for 6 days at 8 u/kg/day. Intermittent bolus bleomycin at 8 u.kg/day had a terminal-phase plasma t1/2 of 15 min and a total 6-day plasma AUC of 90.8mu.h/ml. These pharmacokinetic data validate the osmotic minipump as a constant drug-delivery system, and suggest that the two administration schedules resulted in equal total bleomycin dosages. Although high peak bleomycin plasma levels (i.e. 32 mu/ml) were achieved with the intermittent bolus administration, continuous-infusion bleomycins greater inhibition of LCFU-S was probably related to the drugs schedule-dependent cell-killing characteristics. The results of this study provide further rationale for the continuing use of infusion bleomycin schedules in cancer patients.

Effect of renal dysfunction in dogs on the disposition and marrow toxicity of melphalan.

The effect of renal failure on melphalan pharmacology and toxicity has been poorly understood. Such information is of interest because melphalan is the most commonly used anticancer drug in the treatment of multiple myeloma, which is frequently associated with renal failure. We have studied the disposition and marrow toxicity of parenteral melphalan in dogs before and after induction of renal failure with subtotal nephrectomy. The surgical procedure decreased the creatinine clearance by an average of 62% (P = 0.001). The lowest neutrophil counts following i.v. melphalan (1 mg/kg) averaged 4.9 x 10(3)/mm3 pre-nephrectomy and 0.9 x 10(3)/mm3 post-nephrectomy, respectively (P = 0.002). The mean lowest recorded platelet counts after melphalan (1 mg/kg) were 115 x 10(3)/mm3 in the pre-nephrectomized dogs, and 9.7 x 10(3/mm3 in those who had been nephrectomized (P = 0.002). Following nephrectomy, i.v. melphalans terminal-phase plasma half-life and renal clearance were both raised (P = 0.02) to 75% over pre-nephrectomy values. These studies show that i.v. melphalan-induced myelosuppression is markedly increased and its plasma elimination and renal clearance significantly decreased in the presence of renal dysfunction in dogs. These data suggest that parenteral melphalans starting dose be decreased by at least 50% when used in myeloma patients with renal failure.

The Disposition of Intraperitoneal Bleomycin, Melphalan, and Vinblastine in Cancer Patients

We have studied the disposition of bleomycin, melphalan, or vinblastine after intraperitoneal (IP) instillation in 14 cancer patients. Although IP bleomycin had a somewhat longer terminal-phase plasma half-life than after intravenous (IV) administration (5.5 vs 4.0 h, respectively), its systemic absorption averaged only 44%-52% of the administered dose. IP melphalans mean terminal-phase half-life of 1.3 h was similar to that seen after IV drug administration. Melphalans systemic absorption form the IP space averaged only 39% of the administered dose. In contrast, vinblastine plasma levels remained elevated for longer than 24 h after IP instillation. Its use was associated with life-threatening adynamic ileus in two patients. Bleomycins and melphalans reduced systemic availability after IP dosing suggests that their dose could be increased safely by a factor of two over their standard IV doses.

In Vitro Phase II Trial of Vinca Alkaloids1

SummaryThe in vitro human tumor stem cell assay (HTSCA) has proven accurate in predicting clinical responses to a wide variety of anticancer drugs. A recent analysis of 344 clinical correlations of dr