Dose escalation of cyclophosphamide in patients with breast cancer: consequences for pharmacokinetics and metabolism.

1997 ◽  
Vol 15 (5) ◽  
pp. 1885-1896 ◽  
Author(s):  
D Busse ◽  
F W Busch ◽  
F Bohnenstengel ◽  
M Eichelbaum ◽  
P Fischer ◽  
...  

PURPOSE The alkylating anticancer agent cyclophosphamide (CP) is a prodrug that undergoes a complex metabolism in humans producing both active and inactive metabolites. In parallel, unchanged CP is excreted via the kidneys. The aim of this study was to investigate the influence of dose escalation on CP pharmacokinetics and relative contribution of activating and inactivating elimination pathways. PATIENTS AND METHODS Pharmacokinetics of CP were assessed in 12 patients with high-risk primary breast cancer who received an adjuvant chemotherapy regimen that included four courses of conventional-dose CP (500 mg/m2 over 1 hour every 3 weeks) followed by one final course of high-dose CP (100 mg/kg over 1 hour). Plasma concentrations of CP were analyzed by high-performance liquid chromatography (HPLC), 24-hour urinary concentrations of CP, and its inactive metabolites (carboxyphosphamide, dechloroethylcyclophosphamide [dechlorethylCP], ketocyclophosphamide [ketoCP]) were determined by 31-phosphorus-nuclear magnetic resonance (31P-NMR)-spectroscopy. RESULTS There was no difference in dose-corrected area under the concentration-time curve (AUC) (216 v 223 [mumol.h/[mL.g]), elimination half-life (4.8 v 4.8 hours), systemic clearance (79 v 77 mL/min) and volume of distribution (0.49 v 0.45 L/kg) of CP between conventional- and high-dose therapy, respectively. However, during high-dose chemotherapy, we observed a significant increase in the renal clearance of CP (15 v 23 mL/min; P < .01) and in the formation clearance of carboxyphosphamide (7 v 12 mL/min; P < .05) and dechloroethylCP (3.2 v 4.2 mL/min; P < .05), whereas metabolic clearance to ketoCP remained unchanged (1.3 v 1.2 mL/min). Consequently, metabolic clearance to the remaining (reactive) metabolites decreased from 52 to 38 mL/min (P < .001). The relative contribution of the different elimination pathways to overall clearance of CP demonstrated wide interindividual variability. CONCLUSION Overall pharmacokinetics of CP are apparently not affected during eightfold dose escalation. However, there is a shift in the relative contribution of different clearances to systemic CP clearance in favor of inactivating elimination pathways, thereby indicating saturation of bioactivating enzymes during dose escalation. Besides individual enzyme capacity, hydration and concomitant medication with dexamethasone modulated CP disposition.

1999 ◽  
Vol 90 (4) ◽  
pp. 988-992 ◽  
Author(s):  
Auke Dirk van der Meer ◽  
Anton G. L. Burm ◽  
Rudolf Stienstra ◽  
Jack W. van Kleef ◽  
Arie A. Vletter ◽  
...  

Background Prilocaine exists in two stereoisomeric configurations, the enantiomers S(+)- and R(-)-prilocaine. The drug is clinically used as the racemate. This study examined the pharmacokinetics of the enantiomers after intravenous administration of the racemate. Methods Ten healthy male volunteers received 200 mg racemic prilocaine as a 10-min intravenous infusion. Blood samples were collected for 8 h after the start of the infusion. Plasma concentrations were measured by stereoselective high-performance liquid chromatography (HPLC). Unbound fractions of the enantiomers in blank blood samples, spiked with racemic prilocaine, were determined using equilibrium dialysis. Results The unbound fraction of R(-)-prilocaine (mean +/- SD, 70%+/-8%) was smaller (P &lt; 0.05) than that of S(+)-prilocaine (73%+/-5%). The total plasma clearance of R(-)-prilocaine (2.57+/-0.46 l/min) was larger (P &lt; 0.0001) than that of S(+)-prilocaine (1.91+/-0.30 l/min). The steady-state volume of distribution of R(-)-prilocaine (279+/-94 l) did not differ from that of S(+)-prilocaine (291+/-93 l). The terminal half-life of R(-)-prilocaine (87+/-27 min) was shorter (P &lt; 0.05) than that of S(+)-prilocaine (124+/-64 min), as was the mean residence time of R(-)-prilocaine (108+/-30 min) compared with S(+)-prilocaine (155+/-59 min; P &lt; 0.005). Conclusions The pharmacokinetics of prilocaine are enantioselective. The difference in clearance is most likely a result of a difference in intrinsic metabolic clearance. The difference in the pharmacokinetics of the enantiomers of prilocaine does not seem to be clinically relevant.


Author(s):  
Ajay K. Ola ◽  
Harpal S. Sandhu ◽  
Vinod K. Dumka ◽  
Bibhuti Ranjan

Pharmacokinetics and urinary excretion of an intravenous dose of 5 mg.kg–1 ofloxacin were investigated in water buffalo calves. Plasma concentrations of ofloxacin were determined by high-performance liquid chromatography. Ofloxacin was rapidly distributed from the central to the peripheral compartment as evidenced by a short distribution half-life (0.09 h ± 0.003 h) and high K12 (4.7 h–1 ± 0.1 h–1), and was detected in plasma for 8 h. The large volume of distribution (2.48 L.kg–1 ± 0.18 L.kg–1) obtained in this study indicated high distribution of ofloxacin in water buffalo calves. The elimination half-life, the area under the plasma drug concentration–time curve and total body clearance were 2.11 h ± 0.13 h, 6.20 µg.mL—1 ± 0.23 µg.mL—1.h and 0.81 mL.kg–1.h–1 ± 0.03 mL.kg–1.h–1, respectively. About 18.7% of administered drug was bound to plasma proteins and approximately 32.5% of the administered dose was recovered in urine within 48 h. The results of the study indicated a favourable pharmacokinetic profile of ofloxacin in water buffalo calves, which suggests that ofloxacin may be effective against urinary pathogens in this species.


2020 ◽  
Vol 68 (1) ◽  
pp. 65-70 ◽  
Author(s):  
Duygu Durna Corum ◽  
Orhan Corum ◽  
Ramazan Yildiz ◽  
Hatice Eser Faki ◽  
Merve Ider ◽  
...  

AbstractThe pharmacokinetics of levofloxacin (4 mg/kg), administered both alone and in combination with tolfenamic acid (2 mg/kg) and flunixin meglumine (2.2 mg/kg), was established after intravenous administration in sheep. Plasma levofloxacin concentrations were assayed by high-performance liquid chromatography and analysed according to the two-compartment open model. Following the administration of levofloxacin alone, the mean distribution half-life, elimination half-life, total clearance, volume of distribution at steady state and area under the plasma concentration–time curve were 0.20 h, 1.82 h, 0.39 L/h/kg, 0.96 L/kg and 10.40 h × µg/mL, respectively. Tolfenamic acid and flunixin meglumine caused a slow elimination and increased plasma concentrations of levofloxacin in combination administration. Levofloxacin, with an alteration in the dosage regimen, can be used effectively with tolfenamic acid and flunixin meglumine for the therapy of infections and inflammatory conditions in sheep.


1995 ◽  
Vol 13 (11) ◽  
pp. 2835-2841 ◽  
Author(s):  
S Kaul ◽  
L N Igwemezie ◽  
D J Stewart ◽  
S Z Fields ◽  
M Kosty ◽  
...  

PURPOSE To assess the pharmacokinetics and bioequivalence of etoposide following intravenous (i.v.) administration of etoposide phosphate (Etopophos; Bristol-Myers Squibb, Princeton, NJ), a prodrug of etoposide, and VePesid (Bristol-Myers Squibb). PATIENTS AND METHODS Forty-nine solid tumor patients were randomized to receive Etopophos or VePesid on day 1 of a day-1,3,5 schedule of treatment. The alternate drug was given on day 3 and repeated on day 5. The dose, 150 mg/m2 of etoposide equivalent, was administered by constant rate infusion over 3.5 hours. The plasma concentrations of etoposide phosphate and etoposide were determined using validated high-performance liquid chromatography (HPLC) assays. Pharmacokinetic parameters were calculated by a noncompartmental method. Etopophos was considered to be bioequivalent to VePesid if the 90% confidence limits for the differences in mean maximum concentration (Cmax) and AUCinf of etoposide were contained within 80% to 125% for the long-transformed data. RESULTS Forty-one patients were assessable for pharmacokinetics and bioequivalence assessment. Following i.v. administration, etoposide phosphate was rapidly and extensively converted to etoposide in systemic circulation, resulting in insufficient data to estimate its pharmacokinetics. The mean bioavailability of etoposide from Etopophos, relative to VePesid, was 103% (90% confidence interval, 99% to 106%) based on Cmax, and 107% (90 confidence interval, 105% to 110%) based on area under the concentration versus time curve from zero to infinity (AUCinf) values. Mean terminal elimination half-life (t1/2), steady-state volume of distribution (Vss), and total systemic clearance (CL) values of etoposide were approximately 7 hours, 7 L/m2, and 17 mL/min/m2 after Etopophos and VePesid treatments, respectively. The main toxicity observed was myelosuppression, characterized by leukopenia and neutropenia. CONCLUSION With respect to plasma levels of etoposide, i.v. Etopophos is bioequivalent to i.v. VePesid.


1992 ◽  
Vol 10 (10) ◽  
pp. 1635-1642 ◽  
Author(s):  
B L Lum ◽  
S Kaubisch ◽  
A M Yahanda ◽  
K M Adler ◽  
L Jew ◽  
...  

PURPOSE To determine the effects of high-dose cyclosporine (CsA) infusion on the pharmacokinetics of etoposide in patients with cancer. PATIENTS AND METHODS Sixteen patients were administered 20 paired courses of etoposide and CsA/etoposide. Etoposide was administered daily for three days, alone or with CsA, which was delivered by a loading dose and 3-day infusion. Etoposide was measured by high-performance liquid chromatography (HPLC) and serum CsA by nonspecific immunoassay. Etoposide pharmacokinetics included area under the concentration-time curve (AUC), total and renal clearance (CL), half-life (T1/2), and volume of distribution at steady state (Vss). RESULTS CsA concentrations more than 2,000 ng/mL produced an increase in etoposide AUC of 80% (P less than .001), a 38% decrease in total CL (P < .01), a > twofold increase in T1/2 (P < .01), and a 46% larger Vss (P = .01) compared with etoposide alone. CsA levels ranged from 297 to 5,073 ng/mL. Higher CsA levels (< 2,000 ng/mL v > 2,000 ng/mL) resulted in greater changes in etoposide kinetics: Vss (1.4% v 46%) and T1/2 (40% v 108%). CsA produced a 38% decrease in renal and a 52% decrease in nonrenal CL of etoposide. Etoposide with CsA levels > 2,000 ng/mL produced a lower WBC count nadir (900/mm3 v 1,600/mm3) compared with baseline etoposide cycles. CONCLUSIONS High-dose CsA produces significant increases in etoposide systemic exposure and leukopenia. These pharmacokinetic changes are consistent with inhibition by CsA of the multidrug transporter P-glycoprotein in normal tissues. Etoposide doses should be reduced by 50% when used with high-dose CsA in patients with normal renal and liver function. Alterations in the disposition of other multidrug resistance (MDR)-related drugs should be expected to occur with modulation of P-glycoprotein function in clinical trials.


2012 ◽  
Vol 56 (10) ◽  
pp. 5076-5081 ◽  
Author(s):  
Keith A. Rodvold ◽  
Mark H. Gotfried ◽  
J. Gordon Still ◽  
Kay Clark ◽  
Prabhavathi Fernandes

ABSTRACTThe steady-state concentrations of solithromycin in plasma were compared with concomitant concentrations in epithelial lining fluid (ELF) and alveolar macrophages (AM) obtained from intrapulmonary samples during bronchoscopy and bronchoalveolar lavage (BAL) in 30 healthy adult subjects. Subjects received oral solithromycin at 400 mg once daily for five consecutive days. Bronchoscopy and BAL were carried out once in each subject at either 3, 6, 9, 12, or 24 h after the last administered dose of solithromycin. Drug concentrations in plasma, ELF, and AM were assayed by a high-performance liquid chromatography-tandem mass spectrometry method. Solithromycin was concentrated extensively in ELF (range of mean [± standard deviation] concentrations, 1.02 ± 0.83 to 7.58 ± 6.69 mg/liter) and AM (25.9 ± 20.3 to 101.7 ± 52.6 mg/liter) in comparison with simultaneous plasma concentrations (0.086 ± 0.070 to 0.730 ± 0.692 mg/liter). The values for the area under the concentration-time curve from 0 to 24 h (AUC0–24values) based on mean and median ELF concentrations were 80.3 and 63.2 mg · h/liter, respectively. The ratio of ELF to plasma concentrations based on the mean and median AUC0–24values were 10.3 and 10.0, respectively. The AUC0–24values based on mean and median concentrations in AM were 1,498 and 1,282 mg · h/L, respectively. The ratio of AM to plasma concentrations based on the mean and median AUC0–24values were 193 and 202, respectively. Once-daily oral dosing of solithromycin at 400 mg produced steady-state concentrations that were significantly (P< 0.05) higher in ELF (2.4 to 28.6 times) and AM (44 to 515 times) than simultaneous plasma concentrations throughout the 24-h period after 5 days of solithromycin administration.


1994 ◽  
Vol 12 (9) ◽  
pp. 1902-1909 ◽  
Author(s):  
D R Budman ◽  
L N Igwemezie ◽  
S Kaul ◽  
J Behr ◽  
S Lichtman ◽  
...  

PURPOSE To determine the toxicities, maximum-tolerated dose (MTD), and pharmacology of etoposide phosphate, a water-soluble etoposide derivative, administered as a 5-minute intravenous infusion on a schedule of days 1, 3, and 5 repeated every 21 days. PATIENTS AND METHODS Thirty-six solid tumor patients with a mean age of 63 years, performance status of 0 to 1, WBC count > or = 4,000/microL, and platelet count > or = 100,000/microL, with normal hepatic and renal function were studied. Doses evaluated in etoposide equivalents were 50, 75, 100, 125, 150, 175, and 200 mg/m2/d. Etoposide in plasma and urine and etoposide phosphate in plasma were measured by high-performance liquid chromatography (HPLC). Eleven of 36 patients were treated with concentrated etoposide phosphate at 150 mg/m2/d. RESULTS Grade I/II nausea, vomiting, alopecia, and fatigue were common. Leukopenia (mainly neutropenia) occurred at doses greater than 75 mg/m2, with the nadir occurring between days 15 and 19 posttreatment. All effects were reversible. Hypotension, bronchospasm, and allergic reactions were not observed in the first 25 patients. The MTD due to leukopenia was determined to be between 175 and 200 mg/m2/d. In 11 patients treated with concentrated etoposide phosphate, no local phlebitis was noted, but two patients did develop allergic phenomena. The conversion of etoposide phosphate to etoposide was not saturated in the dosages studied. Etoposide phosphate had peak plasma concentrations at 5 minutes, with a terminal half-life (t1/2) of 7 minutes. Etoposide reached peak concentrations at 7 to 8 minutes, with a t1/2 of 6 to 9 hours. Both etoposide phosphate and etoposide demonstrated dose-related linear increases in maximum plasma concentration (Cmax) and area under the curve (AUC). CONCLUSION Etoposide phosphate displays excellent patient tolerance in conventional dosages when administered as a 5-minute intravenous bolus. The suggested phase II dose is 150 mg/m2 on days 1, 3, and 5. The ability to administer etoposide phosphate as a concentrated, rapid infusion may prove of value both in the outpatient clinic and in high-dose regimens.


1993 ◽  
Vol 4 (3) ◽  
pp. 155-159 ◽  
Author(s):  
M. Qian ◽  
A. R. Swagler ◽  
M. Mehta ◽  
C.T. Vishwanathan ◽  
J. M. Gallo

The current investigation was conducted to determine if zidovudine (AZT) altered the pharmacokinetics of dideoxyinosine (ddl) in non-hurnan primates, an appropriate animal model for AZT and ddl pharmacokinetics in human. Each of nine animals received 20 mg kg−1 of ddl intravenously in the absence and presence of two different dosage regimens of AZT. For each combination regimen, AZT was administered as a combined i.v. bolus-constant rate infusion regimen for 30 min that produced AZT plasma concentrations of about 4 μg ml−1 in six animals (low dose group) and 11 μg ml−1 in three others (high dose group). Serial blood samples were collected, and pharmacokinetic parameters for ddl were calculated based on plasma ddl concentrations measured by HPLC techniques. The pharmacokinetics of ddl given alone in the first phase of the low ( n = 6) and high ( n = 6) dose AZT groups, resulted in a mean elimination half-life 1.54 and 1.9h, a mean total clearance of 0.62 and 0.731 h−1 kg−1, and a mean steady state volume of distribution of 1.02 and 0.891 kg−1, respectively. Following combined ddl and AZT administrations, in both the low and high dose AZT groups, plasma concentration-time profiles of ddl were similar for each monkey, and no statistical differences were observed in the pharmacokinetic parameters compared to those obtained when ddl was given alone. The fact that AZT does not alter the pharmacokinetics of ddl at the range of AZT dose studied provides a basis for rational dosage design for combined ddl and AZT treatments in HIV infection.


2006 ◽  
Vol 50 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Anne Schmitt-Hoffmann ◽  
Brigitte Roos ◽  
Markus Heep ◽  
Michael Schleimer ◽  
Erhard Weidekamm ◽  
...  

ABSTRACT BAL8557 is the water-soluble prodrug of a novel antifungal triazole, BAL4815. BAL4815 is active against a broad spectrum of major opportunistic and pathogenic fungi, including strains that are resistant to other azoles. Cohorts of healthy male subjects received single-ascending oral (p.o.) doses of BAL8557 that were equivalent to 100, 200, or 400 mg of BAL4815 or single-ascending, 1-h constant-rate intravenous (i.v.) infusions of BAL8557 which were equivalent to 50, 100, or 200 mg of BAL4815. In each cohort, six subjects were randomly assigned to receive active drug and two subjects were assigned to receive the placebo. All doses were well tolerated, and no severe or serious adverse events occurred. Maximum plasma concentrations of BAL4815 were observed 1.5 to 3 h after p.o. drug intake or at the end of the 1-h infusion. After both routes of administration, values for maximum drug concentration observed in plasma and area under the concentration-time curve increased slightly more than proportionally to the administered dose. Mean elimination half-lives were particularly long (56 to 77 h after p.o. administration and 76 to 104 h after i.v. administration). The volume of distribution was large (155 to 292 liters after p.o. administration and 304 to 494 liters after i.v. administration) and systemic clearance was low (1.9 to 2.8 liter/h after p.o. administration and 2.8 to 5.0 liter/h after i.v. administration). Urinary recovery of BAL4815 was less than 0.4% of the infused dose. Based on the exposure data, oral bioavailability of BAL4815 is assumed to be very high. The pharmacokinetics of BAL4815 are well suited to maintaining concentrations of BAL4815 for a long period of time in the body and to enabling an effective treatment of systemic mycoses.


1987 ◽  
Vol 15 (1) ◽  
pp. 7-14 ◽  
Author(s):  
D. R. Stanski

Pharmacokinetic concepts describe the relationship between drug dose and resulting plasma concentration. A drug's pharmacokinetic profile can be described by distribution and elimination half-lives, initial volume of distribution, steady-state distribution volume, and metabolic and distributional clearance. After initiating a fixed rate of drug infusion, four to five terminal elimination half-lives are required to reach a steady state of constant plasma concentration. If a loading dose is given, a steady state can be achieved more rapidly. The most rapid method of achieving a constant plasma concentration involves using a variable rate of drug infusion that adjusts for the metabolic clearance and distribution of the drug. Computer-driven infusion pumps can be used to rapidly achieve, then maintain, constant plasma concentrations of a drug.


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