Intrahepatic and intravenous administration of adriamycin--a comparative pharmacokinetic study in patients with malignant liver tumours

The pharmacokinetics of adriamycin in patients with malignant tumours of the liver were studied after peripheral intravenous treatment and after regional administration of the drug either by the arterial route or by the portal vein, with or without hepatic artery ligation. The plasma concentration of adriamycin after intravenous as well as after intrahepatic administration followed a three-compartment open model. The results in the present study confirm previous reports of a large inter-individual variation of the pharmacokinetics of adriamycin. After intravenous administration the individual variations in AUC/mg/m2 and Cp,max/mg/m2 (dose normalized area under plasma concentration time curve and dose normalized maximum plasma concentration, respectively) were more than 5-fold. The area under the plasma concentration time curve (AUC) was on the average 1.5 times higher after the peripheral intravenous administration than after intrahepatic administration. The reduction of maximum plasma concentration (Cp,max) of adriamycin after intrahepatic administration was even more pronounced than the reduction in AUC (mean value Cp,max iv/Cp,max ihep = 1.7). The plasma concentration of adriamycinol did not exceed 20 ng/ml. The AUC values of adriamycinol were 20% (median value) of the AUC values of adriamycin, indicating the importance of adriamycinol in the adriamycin therapy.     

Intrahepatic and intravenous administration of adriamycin—A Comparative pharmacokinetic study in patients with malignant liver tumours

The pharmacokinetics of adriamycin in patients with malignant tumours of the liver were studied after peripheral intravenous treatment and after regional administration of the drug either by the arterial route or by the portal vein, with or without hepatic artery ligation. The plasma concentration of adriamycin after intravenous as well as after intrahepatic administration followed a three-compartment open model. The results in the present study confirm previous reports of a large inter-individual variation of the pharmacokinetics of adriamycin. After intravenous administration the individual variations in AUC/mg/m² andC _p,max/mg/m² (dose normalized area under plasma concentration time curve and dose normalized maximum plasma concentration, respectively) were more than 5-fold. The area under the plasma concentration time curve (AUC) was on the average 1.5 times higher after the peripheral intravenous administration than after intrahepatic administration. The reduction of maximum plasma concentration (C _p,max) of adriamycin after intrahepatic administration was even more pronounced than the reduction in AUC (mean valueC _p,max iv/C _p,max ihep=1.7). The plasma concentration of adriamycinol did not exceed 20 ng/ml. The AUC values of adriamycinol were 20% (median value) of the AUC values of adriamycin, indicating the importance of adriamycinol in the adriamycin therapy.     

Pharmacokinetics of 4' epi-adriamycin after morning and afternoon intravenous administration

The chronopharmacokinetics of 4' epi-adriamycin (Epi) have been studied in ten patients with gynecological malignancies. The drug (45 mg m-2) was administered as a short time (5.0 min) intravenous infusion at 7 a.m. and 7 p.m., in a randomized cross-over design. The pharmacokinetics of Epi were evaluated according to the statistical moment theory. Morning and afternoon dosing of Epi was not bioequivalent. The area under the plasma concentration-time curve (AUC), the maximum plasma concentration (Cmax), mean residence time (MRT) and the terminal half-life time (t1/2) could differ by more than 35% after morning and afternoon dosing. The inter-individual variation of AUC and Cp,max were larger after morning dosing than after afternoon dosing (P less than 0.04). The morning dose of Epi resulted in higher values of AUC in seven of the ten treated patients as compared to the afternoon dose. The terminal half-life times were shorter in eight of the patients after the morning dose.     

A pharmacokinetic study of adriamycin and 4′epi-adriamycin after simultaneous intra-arterial liver administration

The plasma pharmacokinetics of adriamycin and 4′epi-adriamycin were studied in patients with malignant tumors of the liver after simultaneous regional administration of equal amounts of the two anthracyclines by the arterial route. The use of a highly selective liquid chromatographic analytical method permitted quantification of plasma concentrations of the two drugs as well as their corresponding 13-hydroxy metabolites. The plasma concentrations of each drug followed a three-compartment open model. On average the area under the plasma concentration time curve (AUC) and the maximum plasma concentration (C _max) were 2.1 and 1.7 times larger for adriamycin than for 4′epi-adriamycin, respectively. 4′Epi-adriamycin was eliminated faster than adriamycin, the terminal half-life time being on the average 1.5 times higher for adriamycin. These findings are in agreement with what has previously been observed after intravenous administration. The plasma concentrations of the 13-hydroxy metabolites did not exceed 30 ng ml^?1. The AUC values of these metabolites were on average 20% of the AUC values of the intact drugs.     

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.     

A pharmacokinetic study of adriamycin and 4'epi-adriamycin after simultaneous intra-arterial liver administration

The plasma pharmacokinetics of adriamycin and 4'epi-adriamycin were studied in patients with malignant tumors of the liver after simultaneous regional administration of equal amounts of the two anthracyclines by the arterial route. The use of a highly selective liquid chromatographic analytical method permitted quantification of plasma concentrations of the two drugs as well as their corresponding 13-hydroxy metabolites. The plasma concentrations of each drug followed a three-compartment open model. On average the area under the plasma concentration time curve (AUC) and the maximum plasma concentration (Cmax) were 2.1 and 1.7 times larger for adriamycin than for 4'epi-adriamycin, respectively. 4'Epi-adriamycin was eliminated faster than adriamycin, the terminal half-life time being on the average 1.5 times higher for adriamycin. These findings are in agreement with what has previously been observed after intravenous administration. The plasma concentrations of the 13-hydroxy metabolites did not exceed 30 ng ml-1. The AUC values of these metabolites were on average 20% of the AUC values of the intact drugs.     

Pharmacokinetics and Central Haemodynamic Effects of Doxorubicin and 4'Epi-Doxorubicin in the Pig

The relationship between the cardiotoxicity and the haemodynamics/ pharmacokinetics of clinical concentrations of doxorubi-cin and 4'epi-doxorubicin was studied. Twelve pigs were randomized to receive i.v. infusions of either drug of 50 mg/m^z over 3.0 min. Aortic, pulmonary arterial, coronary sinus and central venous plasma concentrations of the agents were determined until 180 min after the infusion. the V5 ECG, left ventricular dP/dT, aortic, pulmonary arterial and right atrial pressures were recorded continuously, cardiac output and coronary sinus blood flow were recorded intermittently. No haemodynamic changes were recorded after administration of either drug. Pharmacokinetic data indicated myocardial extraction, followed by myocardial release of both drugs. This release was higher after administration of 4'epi-doxorubicin than after doxorubicin, within the range 2-4 min and 20-40 min after the infusion. the tendency of greater myocardial release of 4'epi-doxorubicin may explain its lower cardiotoxicity.     

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.     

Electrochemical treatment of cancer. III: Plasma pharmacokinetics of adriamycin after intraneoplastic administration

Plasma pharmacokinetics of Adriamycin (doxorubicin) has been studied after intraneoplastic administration during electrochemical treatment to patients with lung cancer that is noncurable with radiotherapy, surgery, or chemotherapy. Intraneoplastic administration of Adriamycin via the anode resulted in a dramatic change of the pharmacokinetic pattern in plasma as compared with what has been previously observed after intravenous administration. A fivefold reduction of the area under the plasma concentration time curve and a 25-fold reduction of the maximum plasma concentration was observed.     

Pharmacokinetic study of intralesional cisplatin for the treatment of hepatocellular carcinoma.

BACKGROUND: In the current study the authors examined the pharmacokinetics of direct intralesional injection of cisplatin/epinephrine/bovine collagen gel in patients with hepatocellular carcinoma and cirrhosis. METHODS: Six patients with cirrhosis and unresectable hepatocellular carcinoma received a direct intralesional injection (range, 6.7-26.7 mg) into their tumors under ultrasonographic guidance. The authors determined the total cisplatin (Pt) concentration in the plasma and urine and nonprotein-bound free Pt in plasma ultrafiltrate using flameless atomic absorption spectrometry. Data from individual patients were analyzed to calculate the pharmacokinetic parameters via a noncompartmental method for constant infusion. To demonstrate that the changes in pharmacokinetics are not related to the underlying cirrhosis, a similar methodology was applied to measure the pharmacokinetic parameters of four similar patients who were treated with cisplatin, 75 mg/m(2), as a 1-hour intravenous infusion. RESULTS: The time to attain maximum concentration of total Pt after intralesional injection was dose-dependent and ranged from 2-13 hours. The concentration-time curve was biphasic in nature. The initial half-life of total Pt in patients who received an intralesional injection varied with the cisplatin dose. The initial half-life for cisplatin doses < 15 mg was approximately 9 hours and the initial half-life at higher cisplatin doses (> 15 mg) was approximately 25 hours. The area under the curve (AUC) was dose-dependent with values ranging from 38-150 microm/mL x hour. Pharmacokinetic parameters for free Pt (ultrafiltrate) were significantly different. The time to attain maximum concentration (t-max) and terminal half-life were shorter and the average AUC was approximately 100-fold lower than total Pt. After the intravenous infusion of cisplatin, the t-max for total and free Pt was 1.3 hours and 1.1 hours, respectively. The terminal half-life and average AUC for total Pt was 194 hours and 247 microg/mL per hour, respectively, and its corresponding parameters for free Pt after intravenous infusion were much lower, similar to the findings for the intralesional injection. CONCLUSIONS: The prolonged t-max and initial half-life noted with the intralesional injection of cisplatin/epinephrine/collagen gel are consistent with its proclaimed ability to retain cisplatin at the tumor and delay its release in systemic circulation. The kinetics of intralesional cisplatin injection also suggest local sequestration of the drug in the injected site. Parameters of intravenous cisplatin infusion in cirrhotic patients are similar to those of patients from the historic control group.     

Doxorubicin pharmacokinetics after intravenous and intraperitoneal administration in the nude mouse

Summary The pharmacokinetics of doxorubicin in nude mice have been investigated following intravenous and intraperitoneal administration of single doses of 12 mg/kg. The areas under the concentration curves of doxorubicin in kidney, heart, and striated muscle following intraperitoneal administration were approximately half the areas following intravenous injection, whereas plasma and liver showed nearly identical concentrations after a distribution phase of 2 h. Only minor differences in pharmacokinetics were found between nude and normal mice.     

The plasma and cerebrospinal fluid pharmacokinetics of erlotinib and its active metabolite (OSI-420) after intravenous administration of erlotinib in non-human primates

PURPOSE: Erlotinib hydrochloride is a small molecule inhibitor of epidermal growth factor receptor (EGFR). EGFR is over-expressed in primary brain tumors and solid tumors that metastasize to the central nervous system. We evaluated the plasma and cerebrospinal fluid (CSF) pharmacokinetics of erlotinib and its active metabolite OSI-420 after an intravenous (IV) dose in a non-human primate model. METHODS: Erlotinib was administered as a 1 h IV infusion to four adult rhesus monkeys. Serial blood and CSF samples were drawn over 48 h and erlotinib and OSI-420 were quantified with an HPLC/tandem mass spectroscopic assay. Pharmacokinetic parameters were estimated using non-compartmental and compartmental methods. CSF penetration was calculated from the AUC(CSF):AUC(plasma). RESULTS: Erlotinib disappearance from plasma after a short IV infusion was biexponential with a mean terminal half-life of 5.2 h and a mean clearance of 128 ml/min per m(2). OSI-420 exposure (AUC) in plasma was 30% (range 12-59%) of erlotinib, and OSI-420 clearance was more than 5-fold higher than erlotinib. Erlotinib and OSI-420 were detectable in CSF. The CSF penetration (AUC(CSF):AUC(plasma)) of erlotinib and OSI-420 was <5% relative to total plasma concentration, but CSF drug exposure was approximately 30% of plasma free drug exposure, which was calculated from published plasma protein binding values. The IV administration of erlotinib was well tolerated. CONCLUSIONS: Erlotinib and its active metabolite OSI-420 are measurable in CSF after an IV dose. The drug exposure (AUC) in the CSF is limited relative to total plasma concentrations but is substantial relative the free drug exposure in plasma.     

Pharmacokinetic study of temozolomide on a daily-for-5-days schedule in Japanese patients with relapsed malignant gliomas: first study in Asians

Background Temozolomide (TMZ) is widely used in Europe and the United States. For the safe use of TMZ in the Japanese, as representative of Asians, the pharmacokinetics of TMZ was investigated in Japanese patients and compared to that in Caucasians. Methods The pharmacokinetics and safety of TMZ following oral administration of 150 and 200 mg/m² per day for the first 5 days of a 28-day treatment cycle were investigated in six Japanese patients with relapsed gliomas. Results The time-to-maximum plasma concentration (tmax) of TMZ was about 1 h and the elimination half-life of terminal excretion phase (t_1/2λz) was about 2 h. A dose-dependent increase was observed in maximum plasma concentration (Cmax) and AUC, while values for t_1/2λz, apparent total body clearance (CL/F), and apparent distribution volume (Vz/F) were independent of dose. After administration for 5 days, changes in pharmacokinetics and accumulation were not observed. The plasma 5-(3-methyl)1-triazen-1-yl-imidazole-4-carboxamide (MTIC) concentration changed in parallel with the TMZ plasma concentration, and the Cmax and AUC of MTIC were about 2% of those of TMZ. The pharmacokinetic parameters of TMZ and MTIC in Japanese patients in this study were comparable to those previously determined in Caucasian subjects. Adverse events occurred in all patients, but toxicities were mostly mild or moderate, and continuation of administration was possible by adjusting the dose and by delaying the start of the next treatment cycle. Conclusion The pharmacokinetic and safety profile of TMZ in Japanese patients was comparable to that in Caucasians. The treatment regimen used in Europe and the United States will be suitable for Asian patients, including Japanese.     

Influence of schedule of administration on methotrexate penetration in brain tumours

The influence of the administration schedule (intravenous (i.v.) bolus versus i.v. infusion) on the pharmacokinetics of methotrexate (MTX) in plasma and extracellular fluid (ECF) of a brain C6-glioma was investigated in rats. MTX concentrations were determined by high performance liquid chromatography (HPLC)-ultraviolet radiation (UV). MTX (50 mg/kg) was administered by i.v. bolus or i.v. infusion (4 h). Concentration-time profiles were fitted to a two-compartment open model. Maximum MTX concentrations ranged between 178 and 294 microgram/ml (i.v. bolus), and between 11 and 24 microgram/ml (i.v. infusion) in plasma. MTX rapidly entered the tumour tissue although its concentrations in the ECF were much lower than those observed in plasma for both modes of administration. In spite of an important interindividual variability, AUC(ECF) was approximately 5-fold higher and mean MTX penetration in tumour ECF (AUC(ECF)/AUC(Plasma)) was approximately 3-fold higher after i.v. bolus than after i.v. infusion administration. These results indicate that i.v. bolus administration schedules promote MTX delivery in brain tumour tissue.     

Lattice intrahepatic doxorubicin with and without in-flow occlusion: a pharmacokinetic study of direct liver injection.

AIM: To assess possible improvements in drug delivery to unresectable liver tumours we investigated the pharmacokinetics of intrahepatic doxorubicin in the dog liver with and without inflow occlusion. METHODS: Using a lattice template, doxorubicin was injected into 16 sites (over a 9 cm2 area) in each of three lobes of the liver for a total of 48 sites. The total doses of doxorubicin used were 4.8 mg and 96 mg (0.1 and 2 mg/site). Dogs with intravenous and intra-arterial delivery of the same total doses of doxorubicin were used as controls. Experiments using intrahepatic injection were performed with and without a 30 min occlusion of the hepatic artery, common bile duct and portal vein (inflow occlusion). The studies with vascular stasis were performed to determine if drug clearance from the injection sites and their plasma levels were reduced. Also, it was observed that blood and drug loss along the needle tract was reduced when inflow occlusion was used. Plasma and liver samples were harvested over a 90-min period and analysed by high pressure liquid chromatography (HPLC). RESULTS: In plasma mean peak levels and mean area under the curve (AUC) were significantly lower with intrahepatic doxorubicin (P<0.05) than with intravenous or intra-atrial delivery. In the liver AUCintrahepatic/AUCintravenous ratios were 3.45 and 3.6 with 4.8 mg and 96 mg of doxorubicin respectively. The AUCintrahepatic/AUCintraarterial ratios were 1.97 and 1.65 respectively. The liver extraction ratio (AUCliver/AUCplasma) after intravenous administration with 4.8 mg and 96 mg of doxorubicin was 31.9 with both doses of doxorubicin. The corresponding extraction ratios were 107.6 and 51 for intra-arterial administration and 425.2 and 237.7 for intrahepatic administration for the two doses of doxorubicin. Intrahepatic injection with inflow occlusion minimized the leakage back along the needle-tracts. The liver visibly retained the injected drug more completely. However, there was a decrease in systemic clearance resulting in a reduction of the pharmacological advantage. CONCLUSION: These results indicate that lattice-intrahepatic administration of doxorubicin into the liver using a lattice template was associated with a significant increase in local and decrease in systemic exposure as compared to intravenous or intra-arterial administration of the same doses. Simultaneous occlusion of arterial and portal venous inflow was not shown to improve regional drug delivery. These pharmacokinetic studies may constitute a basis for palliative treatment of liver tumours by lattice intralesional injection when these cancers are found to be unresectable at the time of exploratory surgery.     

Pharmacokinetics of bronchial artery infusion of mitomycin in patients with non-small cell lung cancer

The pharmacokinetics of bronchial artery infusion of 20 mg (11.4–14.0 mg/m²) mitomycin was studied in 14 patients with non-small cell lung cancer (NSCLC). The mean elimination half-life was 34.3 min (range 6–72), and the area under the plasma concentration-time curve (AUC) was 166 ng h/ml (39–312). The mean maximum plasma drug concentration (C_max) was 178 ng/ml (12–540) and back-extrapolated plasma drug concentration was 308 ng/ml (17–1423). The mean volume of distribution in the one-compartment model was 0.183 l/kg (0.010–0.887) and the rate constant for unchanged drug appearing in the urine was 1.91/min (0.57–7.27). There was considerable variation among individuals with respect to the pharmacokinetics of mitomycin, and the mean C_max and AUC were lower than those reported after intravenous administration.     

Pharmacokinetic comparison of 120-hour infusion versus hyperfractionated oral administration of idarubicin

The aim of this study was to compare the pharmacokinetics of idarubicin (IDA) and its active metabolite idarubicinol (IDOL) after chronic oral and continuous intravenous (i.v.) IDA administration in order to establish the oral doses needed to reach the i.v. equiactive plasma drug exposure. The pharmacokinetic profile of IDA and IDOL was investigated in 23 patients receiving 12 mg/m2 IDA by 120-h i.v. infusion (2.4 mg/m2/day) combined with cyclophosphamide, etoposide and prednisone in comparison to 28 patients receiving oral IDA doses ranging from 2 to 10 mg/day for 21 days in a phase I study. We found that IDA AUC24h/dose/m2 was 4.7-fold greater during i.v. than oral administration, whereas IDOL AUC24h/dose/m2 was only about 2-fold higher after i.v. administration. The metabolic ratio between IDOL AUC24h and IDA AUC24h in plasma was about 3-fold higher after oral administration. Based on these results we were able to estimate that equiactive plasma drug exposure was reached with an approximately 2.5-fold greater oral dose/m2 of IDA than the corresponding i.v. dose.     

Influence of high-dose ketoconazole on the pharmacokinetics of docetaxel

OBJECTIVE: The pharmacokinetics (PK) of docetaxel are characterized by large inter-individual variability in systemic drug exposure (AUC) and drug clearance. The PK variability is thought to be largely related to differences in the catalytic function of CYP3A, involved in docetaxel metabolism and elimination. As variability in efficacy and toxicity is associated with variability in docetaxel AUC and clearance, reducing inter-individual PK variability may help improve the risk-benefit ratio of docetaxel therapy. We investigated if high-dose ketoconazole, a potent CYP3A inhibitor, could result in a uniform reduction of docetaxel clearance and reduce the inter-individual variability in docetaxel AUC and clearance. METHODS: Seven patients were treated in a randomized-cross over design with intravenous docetaxel (100 mg/m(2)) followed 3 weeks later by docetaxel (15 mg/m(2)) given in combination with orally administered ketoconazole (400 mg 3 times daily, up to 47 hours after docetaxel infusion) or vice versa. Docetaxel plasma concentration-time data were described by a three-compartment PK model. Ketoconazole plasma concentration-time data were described by a one-compartment PK model. RESULTS: Docetaxel clearance was reduced by 50% (P = .018) from 32.8 +/- 13.7 L/hr to 16.5 +/- 8.15 L/hr upon ketoconazole coadministration, albeit with large inter-individual variability (fractional change in clearance, range 0.31 - 0.66). In the presence of ketoconazole, inter-individual variability in clearance and AUC, expressed as coefficient of variation, was increased from 41.6 to 49.5% and from 28.0 to 35.1%, respectively, and not, as we had hypothesized, reduced. CONCLUSION: Inhibition of CYP3A by concomitant high-dose ketoconazole administration does not result in a uniform reduction of docetaxel clearance and does not reduce the inter-individual variability in docetaxel AUC or clearance. This approach is unsuitable as method to achieve a uniform docetaxel PK profile.     

Docetaxel: pharmacokinetics and tissue levels after intraperitoneal and intravenous administration in a rat model

PURPOSE: Docetaxel (Taxotere) has been shown to possess a broad spectrum of antitumor activity against various malignancies such as breast and lung cancers, but also against intraabdominal malignancies such as mesothelioma and ovarian cancer. For cancers occurring within the abdominal cavity, the advantage of intraperitoneal chemotherapy is the prolonged high drug concentration that can be achieved locally with low systemic toxicity. Using a rat model, this study was designed to compare the pharmacokinetics and tissue distribution of intraperitoneal versus intravenous docetaxel. METHODS: The study animals were comprised of 15 Sprague Dawley rats. They were randomized into three groups according to dose and route of administration (15 mg/kg intravenously, 15 mg/kg intraperitoneally, or 150 mg/kg intraperitoneally) and then given a single dose of docetaxel. Blood and peritoneal fluid were sampled using a standardized protocol for 90 min. At the end of the procedure the rats were killed and docetaxel concentrations in peritoneal fluid, plasma and selected tissue samples were determined by high-performance liquid chromatography (HPLC). RESULTS: When docetaxel was delivered at 15 mg/kg the area under the curve (AUC) of the peritoneal fluid was significantly higher with intraperitoneal administration (110.6 microg/ml.min) as compared to intravenous administration (0.043 microg/ml.min; P=0.0079). This represents more than a 2500-fold increase in exposure for tissues at peritoneal surfaces after intraperitoneal administration. Conversely, at the same dose the AUC of the plasma was significantly lower with intraperitoneal administration (0.11 microg/ml.min) as compared to intravenous administration (4.25 microg/ml.min; P=0.0079). The AUC ratio (AUC peritoneal fluid/AUC plasma) was 976 for intraperitoneal administration as opposed to 0.01 for intravenous delivery. The AUC ratio for intraperitoneal docetaxel at 150 mg/kg was 3004. There were significantly different concentrations in the heart and the abdominal wall ( P=0.0079) and in the stomach and colon ( P=0.0159) when intraperitoneal versus intravenous docetaxel were compared. CONCLUSIONS: The exposure of the peritoneal surface to docetaxel is significantly increased and the systemic exposure decreased with intraperitoneal docetaxel administration. Also, high concentrations of drug were observed in the abdominal wall and in the colon after intraperitoneal delivery. This experiment suggests the need for clinical studies to evaluate intraperitoneal administration of docetaxel in humans.     

Pharmacokinetic analysis of high-dose toremifene in combination with doxorubicin

Purpose: Toremifene (Fareston) is an orally administered triphenylethylene derivative with chemosensitizing activity in vitro in estrogen receptor-negative multidrug-resistant human breast cancer cells. The purpose of this study was to evaluate the effects of high-dose toremifene (600 mg/day for 5 days) on the plasma pharmacokinetics of doxorubicin in humans. The 600-mg dose had been previously established as the maximum tolerated dose in a phase I study of 35 patients. Methods: Doxorubicin was administered as an intravenous (i.v.) bolus over 15 min at a dose of 60 mg/m² to 11 patients in the absence of toremifene pretreatment to establish baseline doxorubicin pharmacokinetics. Six of these patients received 600 mg/day toremifene for 5 days 4 weeks later, followed by an i.v. bolus dose of doxorubicin (60 mg/m²) on day 5. During toremifene pretreatment, blood specimens (5 ml) were drawn at 0, 2, 4, and 24 h after dosing to assess peak levels. Following doxorubicin administration in each cycle, blood specimens were collected over a 72-h period for determination of the terminal half-life of elimination. Plasma concentrations of doxorubicin and toremifene were assessed by high-performance liquid chromatography (HPLC). Cumulative linear areas under the time-concentration curve (AUC) for doxorubicin were calculated using a noncompartmental model. Results: Prior to toremifene dosing, baseline doxorubicin pharmacokinetic studies showed an average terminal half-life of elimination of 40.04 ± 7.86 h in 4 patients, and an average AUC of 135 600 ± 67 600 μg/ml · h in 11 patients. In 4 of the patients receiving 600 mg/day toremifene for 5 days, the average terminal half-life of elimination was 38.12 ± 7.81 h, and the average AUC was 141 900 ± 62 900 μg/ml · h in 6 patients, i.e. a slight increase of 4.6%. No statistically significant change in the doxorubicin elimination kinetics with or without toremifene therapy was observed. Conclusions: Toremifene does not appear to interfere with the elimination kinetics of doxorubicin. Received: 1 July 1997 / Accepted: 16 December 1997