Interaction of dexrazoxane with red blood cells and hemoglobin alters pharmacokinetics of doxorubicin

Purpose: The mechanism of the cardioprotective action of dexrazoxane against doxorubicin cardiotoxicity is not fully understood. It has been suggested that its hydrolysis product, ICRF-198, chelates and removes free iron and iron associated with doxorubicin-iron complex and, therefore, prevents the formation of free radical, lipid peroxidation and cardiotoxicity. Dexrazoxane is also known to inhibit topoisomerase II, to prevent the inactivation of cytochrome c oxidase by Fe³⁺-doxorubicin and to increase the levels of transferrin receptor (trf-rec) mRNA and cellular iron uptake. This sequestration of iron and its effect on cellular iron homeostasis may also contribute to its protective effect against doxorubicin cardiotoxicity. The present project was designed to investigate the interaction of dexrazoxane with hemoglobin and red blood cells and the subsequent effect on the pharmacokinetics and toxicodynamics of doxorubicin. Methods: In an in vitro investigation the binding of doxorubicin (0.5–25 μg/ml) to red blood cells, erythrocyte ghosts and hemoglobin in the presence of dexrazoxane was evaluated. In an in vivo study female Sprague Dawley rats were pretreated with 100 mg/kg of dexrazoxane by intravenous injection 1 h before the injection of ¹⁴C-doxorubicin (specific activity 0.4 μCi/mg, 10 mg/kg). The time-course of doxorubicin associated with blood cells and plasma was evaluated with simultaneous characterization of doxorubicin and its metabolites in the bile and urine. The serum concentration of endothelin was measured as a biomarker of cardiotoxicity in separate groups of animals. Results: The in vitro data indicated that dexrazoxane inhibited the binding of DOX to red blood cells in a concentration-dependent manner. At 1 μg/ml it reduced the binding of doxorubicin to red blood cells by about 30% and at 100 μg/ml by about 60%. It had no effect on the association of doxorubicin with erythrocyte ghosts. The investigation of binding of doxorubicin to hemoglobin revealed the existence of two distinct binding sites and dexrazoxane reduced the association constant of doxorubicin with the low-affinity and high-capacity class of binding sites significantly. The pharmacokinetic analysis showed that pretreatment with dexrazoxane (100 mg/kg) reduced the area under plasma concentration-time curve of doxorubicin, its mean residence time and plasma clearance significantly. Similar reductions were also shown with the pharmacokinetic analysis of doxorubicin associated with blood cells. The biliary and urinary elimination of unchanged doxorubicin increased significantly. The pretreatment reduced the serum concentration of endothelin from about 20 ng/ml to about 12 ng/ml. The per cent of this reduction was proportional to the reduction in the AUC of blood cells. Conclusion: The cardioprotective effect of dexrazoxane is due, in part, to its interaction with hemoglobin and red blood cells and this interaction modifies the pharmacokinetics of DOX. Received: 29 July 1999 / Accepted: 11 February 2000     

Cardioprotection by dexrazoxane in rats treated with doxorubicin and paclitaxel

Purpose: Results of several clinical studies suggest that the combination of doxorubicin (DOX) and paclitaxel (PTX) is highly active against solid tumors. Both drugs are known to cause adverse cardiac effects, cardiomyopathy in the case of DOX and acute changes in cardiac rhythm in the case of PTX. It has been suggested that the addition of dexrazoxane (DZR) to this regimen may reduce the risk of cardiotoxicity. A model of chronic cardiomyopathy in the rat was used to determine whether DZR was tolerated and cardioprotective in a DOX+PTX combination. Methods: Male rats were treated once weekly for 7 weeks with one of the following vehicle and/or drug sequences: Group A, M/6 sodium lactate/saline/Cremophor EL (CEL); Group B, lactate/DOX/CEL; Group C, DZR/DOX/CEL; Group D, lactate/DOX/PTX; and Group E, DZR/DOX/PTX. DZR and DOX or their respective vehicles were given i.v. whilst PTX or CEL were given i.p. DZR, DOX and PTX were administered at 16 mg/kg, 0.8 mg/kg and 2.4 mg/kg, respectively, doses which caused minimal noncardiac toxicities. The hearts were examined histologically 5 weeks following the last treatment. Results: There were no deaths and no signs of overt toxicity during the 12 weeks of study. There was a significant decrease (P < 0.01) in white blood cell count in rats treated with DZR+DOX, DOX+PTX or DZR+ DOX+PTX but not in those given DOX alone. Liver and kidney weights were increased in rats given DOX (P < 0.05) but not in those given DZR+DOX. PTX had no effect on the DOX-induced liver and kidney changes and did not interfere with the protective effect of DZR on the kidney. The severity and extent of cardiomyopathy expressed as the mean total score (MTS) for each treatment group, was similar for DOX and DOX+PTX (4.6 and 4.2, respectively). DZR provided significant cardioprotection (P < 0.01) when added to either DOX (MTS 2.0) or to DOX+PTX (MTS 2.1). Conclusions: The results suggest that PTX does not exacerbate the chronic cardiomyopathy caused by DOX and when added to the DOX+PTX combination, DZR retains its protective activity against DOX-induced cardiotoxicity without increasing noncardiac toxicity. Received: 7 October 1998 / Accepted: 3 December 1998     

The cardioprotector monoHER does not interfere with the pharmacokinetics or the metabolism of the cardiotoxic agent doxorubicin in mice

PURPOSE: Monohydroxyethylrutoside (monoHER) has proved to be a good protector against doxorubicin-induced cardiotoxicity without interfering with the antitumor effect of doxorubicin. The aim of the present study was to determine whether there is a pharmacokinetic interaction between monoHER and doxorubicin which may be involved in monoHER cardioprotection. METHODS: Mice were treated with monoHER (500 mg x kg(-1) i.v.) alone, monoHER 5 min after doxorubicin (10 mg x kg(-1) i.v.), doxorubicin alone and doxorubicin 5 min after monoHER. The levels of monoHER and doxorubicin(ol) in plasma and heart tissue were measured by HPLC 24 h and 48 h after monoHER and doxorubicin administration, respectively. RESULTS: The areas under the concentration-time curves (AUCs) of monoHER and doxorubicin(ol) were not affected by the coadministered drug. No changes were observed in pharmacokinetic parameters such as initial and final half-lives, mean residence time, clearance and volume of distribution of monoHER and doxorubicin(ol) after single or combined administration. CONCLUSION: The cardioprotection of monoHER in mice is not caused by a pharmacokinetic interaction between monoHER and doxorubicin.     

Comparative pharmacokinetics of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes

The comparative pharmacokinetics of free doxorubicin and doxorubicin entrapped in cardiolipin liposomes was evaluated in rats at a dose of 6 mg/kg i.v. Doxorubicin was entrapped in cardiolipin liposomes by using 11.2 mumol of drug, 5.6 mumol of cardiolipin, 28.5 mumol of phosphatidylcholine, 19.5 mumol of cholesterol, and 11.1 mumol of stearylamine. The peak plasma concentration with free doxorubicin at 5 min was 1.7 micrograms/ml which was reduced to 0.3 micrograms/ml by 1 h. With cardiolipin liposomes, the peak plasma concentration of doxorubicin achieved at 5 min was 20.9 micrograms/ml. The plasma levels of doxorubicin decreased gradually and by 1 h the drug concentration in plasma was 10 micrograms/ml. The plasma levels of free doxorubicin and doxorubicin entrapped in liposomes were fitted to a 3-compartment computer model. The terminal half-life with free doxorubicin in plasma was 17.3 h whereas it was 69.3 h with drug entrapped in liposomes. The area under the plasma concentration curve with liposomal doxorubicin was 81.4 micrograms X h X ml-1 compared to 1.95 micrograms X h X ml-1 observed with free doxorubicin. The steady state volume of distribution with free doxorubicin was about 23-fold higher than liposomal doxorubicin. The terminal half-life with free doxorubicin in cardiac tissue was 17.9 h compared to 12.6 h with drug encapsulated in liposomes. The terminal half-lives in liver and spleen following administration of liposomal doxorubicin were 15- and 2.3-fold higher, respectively, compared to free drug; furthermore, the concentration X time values of liposomal doxorubicin in liver were 26-fold higher and in spleen 6-fold higher than the free drug. Free doxorubicin and doxorubicin entrapped in liposomes demonstrated 17 and 20% excretion in bile of the injected dose, respectively, in rats. The present studies demonstrate that liposomal encapsulation of doxorubicin significantly alters its pharmacokinetics in plasma and tissues compared to free drug.     

Effect of a low-protein diet on doxorubicin pharmacokinetics in the rabbit

Summary Malnutrition involving protein deficiency, which commonly occurs in cancer patients receiving anthracycline treatment, is considered to be a risk factor for the development of cardiotoxicity. Protein deficiency has been shown to impair the metabolism of drugs such as theophylline and acetaminophen. If protein deficiency also impairs anthracycline metabolism, it could explain at least in part the enchanced anthracycline toxicity associated with malnutrition. We tested this idea by determining the effect of a low- protein, isocaloric diet on doxorubicin pharmacokinetics in rabbits. The animals were randomized into two groups for 8–12 weeks. Rabbits in group 1 received a low-protein (5%), isocaloric diet, whereas those in group 2 received a normal-protein (15%) diet. Both groups (group 1,n=15; group 2,n=14) were given 5 mg/kg doxorubicin by i.v. bolus. After doxorubicin injection, blood samples were obtained over the next 52 h for the measurement of doxorubicin and doxorubicinol plasma concentrations by high-performance liquid chromatography (HPLC) with fluorometric detection. The low-protein diet significantly decreased doxorubicin clearance (48±3 vs 59±4 ml min^–1 kg^–1;P<0.05), prolonged the terminal climination half-life (28±2 vs 22±2 h;P<0.05), and increased the area under the plasma concentration/time curve extrapolated to infinity (1722±122 vs 1405±71 ng h ml^–1;P<0.05) as compared with the values determined for rabbits fed the standard rabbit chow (15% protein). The volume of distribution for doxorubicin was not altered by the low-protein diet. In addition, in rabbits fed the the low-portein diet, the terminal elimination half-life of the alcohol metabolite, doxorubicinol was prolonged (52±5 vs 40±2 h;P<0.05). Thus, a low-protein diet causes a reduction in the ability of rabbits to eliminate doxorubicin and possibly its alcohol metabolite doxorubicinol. If a similar alteration in anthracycline pharmacokinetics occurs in malnourished cancer patients, this phenomenon may contribute to their increased risk of developing cardiotoxicity associated with anthracycline therapy.Supported by the Department of Veterans Affairs and the American Heart Foundation     

坎地沙坦联合小剂量卡维地洛或右丙亚胺对乳腺癌患者使用蒽环类化疗药物过程中的心脏保护作用对比研究

目的 对比研究坎地沙坦联合小剂量卡维地洛或右丙亚胺对乳腺癌患者使用蒽环类化疗药物过程中的心脏保护作用.方法 对104例乳腺癌患者的临床资料进行回顾性研究,按照不同治疗方式将患者分为试验组与对照组,每组52例.对照组患者在化疗方案中加用右丙亚胺;试验组患者在化疗方案中加用坎地沙坦联合小剂量卡维地洛.比较两组患者在治疗前以及治疗4、8个周期后心电图变化、肌钙蛋白水平、心肌重构指标以及不良反应发生情况.结果 化疗8个周期后,试验组患者QRS波群电压下降、心律失常、ST-T异常发生率明显低于对照组(P﹤0.01).化疗前两组患者LVEF、LVEDD及BNP比较,差异无统计学意义(P﹥0.05);化疗4、8个周期后,试验组患者LVEF下降程度低于对照组,LVEDD、BNP上升程度低于对照组(P﹤0.01).两组患者化疗4个周期后肌钙蛋白异常情况发生率比较,差异无统计学意义(P﹥0.05),化疗过程中两组患者未发生明显的肌钙蛋白异常情况(P﹥0.05).两组患者不良反应发生率比较,差异无统计学意义(P﹥0.05).结论 坎地沙坦联合小剂量卡维地洛能降低蒽环类化疗药物对癌症患者的心脏不良反应,且不良反应较轻,可在乳腺癌化疗患者中推广使用.     

Comparison of the protective effects of amifostine and dexrazoxane against the toxicity of doxorubicin in spontaneously hypertensive rats

Purpose: To compare the protective effects of amifostine and dexrazoxane against the chronic toxicity induced by doxorubicin in spontaneously hypertensive rats (SHR). Methods: The animals were pretreated with amifostine (200 mg/kg, i.p.), dexrazoxane (25 mg/kg, i.p.) or saline 30 min before the administration of doxorubicin (1 mg/kg, i.v.), once-weekly for 12 weeks. Control animals received similar amounts of amifostine or saline. The SHR underwent necropsy examination 1 week after the last dosing, and cardiac, renal, and gastrointestinal lesions were graded semiquantitatively. Results: Amifostine and dexrazoxane provided equal degrees of protection against the renal toxicity of doxorubicin. However, dexrazoxane was more cardioprotective than amifostine, and prevented the mortality induced by doxorubicin. This mortality was not decreased by pretreatment with amifostine. The loss of body weight caused by doxorubicin was actually worsened by coadministration of amifostine. Conclusions: Compared to dexrazoxane, amifostine provided a comparable degree of protection against the nephrotoxicity of doxorubicin, but was less cardioprotective and did not prevent the mortality and loss of body weight produced by doxorubicin. These differences may be related to the fact that amifostine may act as a scavenger of reactive oxygen species, whereas dexrazoxane may prevent their formation. Received: 20 May 1999 / Accepted: 14 October 1999     

Effect of phenytoin on the pharmacokinetics of doxorubicin and doxorubicinol in the rabbit

Summary Doxorubicin is metabolized extensively to doxorubicinol by the ubiquitous aldoketoreductase enzymes. The extent of conversion to this alcohol metabolite is important since doxorubicinol may be the major contributor to cardiotoxicity. Aldoketoreductases are inhibited in vitro by phenytoin. The present study was conducted to examine the effect of phenytoin on doxorubicin pharmacokinetics. Doxorubicin single-dose pharmacokinetic studies were performed in 10 New Zealand White rabbits after pretreatment with phenytoin or phenytoin vehicle (control) infusions in crossover fashion with 4–6 weeks between studies. Infusions were commenced 16 h before and during the course of the doxorubicin pharmacokinetic studies. Phenytoin infusion was guided by plasma phenytoin estimation to maintain total plasma concentrations between 20 and 30 g/ml. Following doxorubicin 5 mg/kg by i.v. bolus, blood samples were obtained at intervals over 32 h. Plasma doxorubicin and doxorubicinol concentrations were measured by HPLC. The mean plasma phenytoin concentrations ranged from 17.4 to 33.9 g/ml. Phenytoin infusion did not alter doxorubicin pharmacokinetics. The elimination half-life and volume of distribution were almost identical to control. Clearance of doxorubicin during phenytoin administration (60.9±5.8 ml/min per kg, mean±SE) was similar to that during vehicle infusion (67.5±5.4 ml/min per kg). Phenytoin administration was associated with a significant decrease in doxorubicinol elimination half-life from 41.0±4.8 to 25.6±2.8 h. The area under the plasma concentration/time curve (AUC) for doxorubicinol decreased significantly from 666.8±100.4 to 491.5±65.7 n.h.ml^-1. These data suggest that phenytoin at clinically relevant concentrations does not alter the conversion of doxorubicin to doxorubicinol in the rabbit. The reduction in the AUC for doxorubicinol caused by phenytoin appears to be due to an increased rate of doxorubicinol elimination. Phenytoin or similar agents may have the effect of modifying doxorubicinol plasma concentrations by induction of doxorubicinol metabolism rather than by inhibition of aldoketoreductase enzymes.     

Factors affecting the pharmacokinetics of pegylated liposomal doxorubicin in patients

Purpose  

There is significant inter-patient variability in the pharmacokinetics of pegylated liposomal doxorubicin (PLD). Identification of factors affecting the pharmacokinetics of PLD would enable personalization of therapy. We previously reported that age, gender, body composition, and monocytes affect the clearance of other liposomal agents. Therefore, we evaluated how these factors affect the pharmacokinetics of PLD.     

右丙亚胺对表柔比星诱导乳腺癌细胞凋亡影响的研究

目的:探讨右丙亚胺(DEX)对表柔比星(EPI)诱导乳腺癌细胞凋亡的影响。方法:分别以不同浓度EPI作用于MCF-7、MDA-MB-231和BT474 3种乳腺癌细胞系24h,用MTT法检测抑制率,选择EPI最佳实验浓度;应用1.0μg/mL EPI与1.0、10和20μg/mL DEX分别及联合作用于3种乳腺癌细胞系,用MTT法检测抑制率,用流式细胞术检测细胞凋亡。结果:1.0μg/mL EPI组3种乳腺癌细胞的抑制率分别为(48.72±0.34)%、(64.40±2.63)%和(58.57±2.23)%,1.0μg/mL EPI联合1.0μg/mL DEX组3种细胞的抑制率分别为(46.44±1.35)%、(65.20±0.21)%和(57.52±2.31)%,1.0μg/mL EPI联合10μg/mL DEX组3种细胞抑制率分别为(47.57±2.20)%、(61.70±1.08)%和(59.54±1.26)%,1.0μg/mL EPI联合20μg/mL DEX组3种细胞抑制率分别为(43.85±1.19)%、(60.80±0.62)%和(58.25±3.50)%,EPI和DEX两药联合组(EPI∶DEX=1∶1和1∶10)与EPI组3种乳腺癌细胞系的抑制率比较差异无统计学意义,P>0.05;两者浓度为1∶20时对3种乳腺癌细胞系的增殖影响差异有统计学意义,P<0.05。流式细胞术检测1.0μg/mL EPI组3种乳腺癌细胞凋亡率分别为8.54%、11.25%和10.78%,EPI∶DEX=1∶10组3种乳腺癌细胞凋亡率分别为8.74%、11.85%和10.49%,两组细胞凋亡率差异无统计学意义,P>0.05。结论:心脏保护剂量的DEX并不影响EPI诱导的乳腺癌细胞凋亡效果。     

The influence of ranitidine on the pharmacokinetics and toxicity of doxorubicin in rabbits

Summary The influence of ranitidine on the pharmacokinetics and toxicity of doxorubicin was studied in six female New Zealand white rabbits. Plasma pharmacokinetic data were first obtained from rabbits given 3 mg/kg doxorubicin. After 1 month, the same rabbits were treated with ranitidine, 2.5 mg/kg or 25 mg/kg, before and during doxorubicin administration. The plasma doxorubicin assays to determine pharmacokinetic parameters were repeated. Drug toxicity was evaluated using complete blood counts, and hepatic function was measured using a ¹⁴C-aminopyrine breath test. High-dose ranitidine increased the total exposure to doxorubicin (area under the curve of doxorubicin alone =1.44±0.88 M·h/ml vs 4.49±2.35 M·hr/ml for doxorubicin given with high-dose ranitidine; P=0.06). Low-dose ranitidine did not alter doxorubicin pharmacokinetics. Exposure to doxorubicinol was altered by either high-dose or low-dose ranitidine. ¹⁴C-Aminopyrine half-life was altered by a raniditine dose of 25 mg/kg (aminopyrine half-life after placebo control =97±6 min as against aminopyrine half-life after ranitidine =121±7 min; mean±SEM; P<0.02). Low-dose ranitidine did not exacerbate doxorubicin-induced myelosuppression. High-dose ranitidine enhanced doxorubicin-induced erythroid suppression while sparing the myeloid series. At cytochrome P-450-inhibitory doses, ranitidine's effects upon doxorubicin plasma pharmacokinetics are similar to those previously seen with cimetidine. These changes did not appear to alter drug detoxification and are not related to microsomal inhibition of doxorubicin detoxification. Low doses of ranitidine do not alter doxorubicin plasma pharmacokinetics or toxicity in rabbits.Grant support: Glaxo Inc., Veterans Administration, NIH BRSG RR-05424, NIH Grant RR-00095, Clinical Research Center. American Cancer Society Institutional Grant IN25V     

Topoisomerase IIbeta mediated DNA double-strand breaks: implications in doxorubicin cardiotoxicity and prevention by dexrazoxane

Doxorubicin is among the most effective and widely used anticancer drugs in the clinic. However, cardiotoxicity is one of the life-threatening side effects of doxorubicin-based therapy. Dexrazoxane (Zinecard, also known as ICRF-187) has been used in the clinic as a cardioprotectant against doxorubicin cardiotoxicity. The molecular basis for doxorubicin cardiotoxicity and the cardioprotective effect of dexrazoxane, however, is not fully understood. In the present study, we showed that dexrazoxane specifically abolished the DNA damage signal gamma-H2AX induced by doxorubicin, but not camptothecin or hydrogen peroxide, in H9C2 cardiomyocytes. Doxorubicin-induced DNA damage was also specifically abolished by the proteasome inhibitors bortezomib and MG132 and much reduced in top2beta(-/-) mouse embryonic fibroblasts (MEF) compared with TOP2beta(+/+) MEFs, suggesting the involvement of proteasome and DNA topoisomerase IIbeta (Top2beta). Furthermore, in addition to antagonizing Top2 cleavage complex formation, dexrazoxane also induced rapid degradation of Top2beta, which paralleled the reduction of doxorubicin-induced DNA damage. Together, our results suggest that dexrazoxane antagonizes doxorubicin-induced DNA damage through its interference with Top2beta, which could implicate Top2beta in doxorubicin cardiotoxicity. The specific involvement of proteasome and Top2beta in doxorubicin-induced DNA damage is consistent with a model in which proteasomal processing of doxorubicin-induced Top2beta-DNA covalent complexes exposes the Top2beta-concealed DNA double-strand breaks.     

Treatment of experimental extravasation of amrubicin, liposomal doxorubicin, and mitoxantrone with dexrazoxane

Purpose  

Dexrazoxane is an established treatment option in extravasation of the classic anthracyclines such as doxorubicin, epirubicin, and daunorubicin. However, it is not known whether the protection against the devastating tissue injuries extends into extravasation with new types of anthracyclines, the anthracenediones, or the liposomal pegylated anthracycline formulations. We therefore tested the antidotal efficacy of dexrazoxane against extravasation of amrubicin, mitoxantrone, and liposomal pegylated doxorubicin in mice.     

Population pharmacokinetics of doxorubicin: A systematic review

Because of the high interindividual pharmacokinetic variability, several population pharmacokinetic (PopPK) models of doxorubicin (DOX) were developed to characterize factors influencing such variability. However, significant predictors for DOX pharmacokinetics identified using PopPK models varied across studies. Thus, this review aims to summarize PopPK models of DOX and its metabolites (if any) as well as significant covariates influencing DOX (and its metabolites) pharmacokinetic variability. A systematic search from PubMed, CINAHL Complete, Science Direct, and SCOPUS databases identified 503 studies. Of these, 16 studies met the inclusion criteria and were included in this review. DOX pharmacokinetics was described with two- or three-compartment models. Most studies found a significant increase in DOX clearance with an increase in body surface area from the median value of 1.8 m². Moreover, this review identified that while a 10-year increase in patient age resulted in a decrease in DOX clearance in adults and the elderly, younger children had lower DOX clearance compared to older children. Further, low DOX exposure was observed in pregnant women, and thus dosage adjustment is required. Concerning model applicability, predictive performance assessment of these published models should be performed before implementing such models in clinical practice.     

The effects of cimetidine upon the plasma pharmacokinetics of doxorubicin in rabbits

Summary Cimetidine is an H₂ antagonist which inhibits cytochrome P-450 and reduces hepatic blood flow. To determine whether cimetidine interferes with the plasma pharmacokinetics of doxorubicin, we gave six female New Zealand rabbits doxorubicin 3 mg/kg, followed a month later by cimetidine 120 mg/kg every 12 h over 72 h and doxorubicin 3 mg/kg. Serial plasma specimens were obtained over 72 h and assayed for doxorubicin and its metabolites by high-performance liquid chromatography and fluorescence detection.Doxorubicin plasma pharmacokinetics were prolonged after cimetidine pretreatment [AUC 0.76±0.22 vs. 2.85±1.22 M×h, no pretreatment vs pretreatment (p=0.005), half-life=11.7±6.55 vs 28.0±8.16 h (P=0.0002), and clearance=0.129±0.036 vs 0.036±0.0111/min^-1 kg^-1 (P=0.0007)]. No significant differences were found between the AUCs for doxorubicinol, 7-deoxy doxorubicinol aglycone, or two unidentified nonpolar metabolites in nonpretreatment and pretreatment studies. Cimetidine increases and prolongs the plasma exposure to doxorubicin in rabbits. Doxorubicin metabolism does not appear to be affected by cimetidine.Grant Support Veterans Administration, NIH Grant RR-05424 and Clinical Research Center Grant RR-00095 American Cancer Society Institutional Grants #IN25V and IN24V, and JFCF #649     

Influence of the interval between the administration of doxorubicin and paclitaxel on the pharmacokinetics of these drugs in patients with locally advanced breast cancer

PURPOSE: Amsalog, a derivative of 9-aminoacridine, is an inhibitor of topoisomerase II. Early studies of intravenous amsalog administered either once weekly, or daily for 3 days repeated every 3 weeks, showed that myelosuppression is the dose-limiting toxicity (DLT). Phase II studies showed only limited activity in breast, head and neck, and non-small-cell lung cancer. The activity of other topoisomerase inhibitors is schedule-dependent. We therefore performed a phase I study to evaluate the use of amsalog on a more prolonged schedule. METHODS: A group of 19 patients with refractory malignancies were treated in six cohorts using 2-h infusions of amsalog daily for 5 days, repeated every 3 weeks. RESULTS: Myelosuppression was seen as DLT at 200 mg/m2 per day. Other toxicities included nausea and vomiting, fatigue, and, when administered via a peripheral venous line, severe phlebitis necessitating administration via an indwelling central venous catheter for doses greater than 100 mg/m2. Pharmacokinetic studies showed a linear relationship between Cmax and AUC, and dose. The terminal half-life was 2 h, consistent with previous studies. CONCLUSION: We conclude that amsalog can be safely given on a 5-day schedule every 3 weeks at doses up to 200 mg/m2. The dose recommended for further studies is 180 mg/m2 per day for 5 days repeated every 3 weeks. However, in view of the phlebitis, which necessitated the use of central venous catheters for administration, other routes of administration, for example oral formulations, should be explored.     

Comparative responsiveness and pharmacokinetics of doxorubicin in human tumor xenografts

The antineoplastic activity of the anthracyclin antibiotic doxorubicin (Adriamycin®) differs in its cytotoxic effectiveness against different types of human tumors. In the present study the effect of doxorubicin on the growth of two human lung carcinomas and one human mammary carcinoma transplanted into athymic mice was correlated with the pharmacokinetics of doxorubicin in the same tumors after intraperitoneal administration. Doxorubicin produced a greater inhibition of tumor growth in the lung carcinomas than in the mammary carcinoma. Furthermore, the pharmacokinetic characteristics of doxorubicin differed widely within the three human solid tumors. No apparent correlation was found to exist between the different tumor growth sensitivities to doxorubicin and the pharmacokinetic parameters of doxorubicin within the tumor tissue. It is suggested that the differences in the demontrated antitumor effectiveness of doxorubicin may be due to differences in the “intrinsic sensitivity” of the three human solid tumors.     

Effect of whole-body hyperthermia on lonidamine and doxorubicin pharmacokinetics and toxicity in dogs

Six cycles of the maximum tolerable intravenous doses of lonidamine (400 mg/m²) and doxorubicin (30 mg/m²) were administered to three normothermic dogs and three dogs undergoing whole-body hyperthermia (WBH) (42°C × 90 min), at 3-week intervals. Lonidamine pharmacokinetics was unaltered by WBH. WBH increased doxorubicin clearance 1·6-fold, however this trend was not statistically significant. WBH resulted in a 2·4-fold increase in the volume of distribution (V_dss) of doxorubicin relative to dogs treated under euthermic conditions (p < 0·001). This finding suggests tissue extraction of doxorubicin was increased by WBH. The specific tissues in which this occurred is unknown, but myelosuppression and cardiotoxicity were only minimally increased. Therefore, doxorubicin uptake in critical normal tissues was probably unaffected. The biochemical and haematologic toxicities observed 6 h and 1 week after each treatment did not appear to differ in character or severity from that reported in dogs receiving lonidamine ± WBH or doxorubicin ± WBH. These results suggest WBH did not decrease the maximum tolerable dose of doxorubicin when given with lonidamine, and that the antitumour activity of this combination should be assessed.