Pharmacokinetics of VM 26 given intrapericardially or intravenously in patients with malignant pericardial effusion

Three patients with lung cancer (1 SCLC, 2 NSCLC) and pericardial malignant effusion received 100 mg/m2 Teniposide (VM 26) i.v. and, 1 week later, 50 mg/m2 intrapericardially. Plasma, pericardial, and urine levels of the drug were measured in all patients after the two treatments by a HPLC assay. After intrapericardial administration, a high VM 26 concentration was found in the pericardial cavity and slow systemic drug absorption was observed. Since the drug AUC after intrapericardial administration was approximately 15-21 times that after i.v. administration, it could be that this treatment is more effective against neoplastic deposits localized in the pericardium. Even though this small series does not permit conclusions to be drawn on the efficacy of VM 26 given intrapericardially, the lack of local toxicity, minimal systemic toxicity, and the response observed in two out of three patients given intrapericardial VM 26 suggest that further investigation should be carried out on this method of VM 26 administration.

Inhibitory and inducing effects of denzimol on carbamazepine metabolism in the rat

In vivo and in vitro alterations in carbamazepine (CBZ) metabolism and the extent of enzyme induction of the hepatic cytochrome P-450 system after chronic oral denzimol to rats were evaluated. No effect on drug-metabolizing enzymes was detected for this new anticonvulsant drug at a dose of 15 mg/kg, which is just above the anticonvulsive dose. At higher doses (60 mg/kg) denzimol significantly raised the hepatic cytochrome P-450 content, enhanced CBZ clearance and tend to shorten its elimination t1/2 and that of its active metabolite. These results, combined with those of a previous study showing impairment of CBZ metabolism after single doses of denzimol, suggest that the drug may have either inductive or inhibitory effects on microsomal mixed-function oxidase activity in the rat, depending on the dose and schedule of treatment.

Comparative bioavailability of aspirin from buffered, enteric-coated and plain preparations

The bioavailability and pharmacokinetics of acetylsalicylic acid were studied in 6 volunteers, under a cross-over design, using plain compressed aspirin, two buffered preparations and an enteric-coated tablet. Absorption, calculated from urinary excretion, was complete for all the formulations. The buffered forms gave higher peak concentrations and AUC for acetylsalicylic acid than the other forms. Absorption from the enteric-coated tablet was the slowest. Acetylsalicylic acid was not measurable in plasma (less than 0.1 micrograms/ml) at any time in 3 subjects after plain and in 2 after enteric-coated aspirin. Acetylsalicylic acid was no longer measurable in plasma after 4 hours, irrespective of the preparation given.

Pharmacokinetics of etoposide in patients with abnormal renal and hepatic function

Etoposide (VP16) pharmacokinetics was investigated in three groups of cancer patients: a control group of 18 patients with renal and hepatic function tests in the normal range; a group of 8 patients with renal insufficiency; and a group of 15 patients with abnormal hepatic function. In the control group plasma clearance (Clp), volume of distribution (Vd), and elimination half-life (t1/2 beta) of VP16 were, respectively, 22.8 +/- 1.0 (SE) ml/min/m2, 11.4 +/- 0.8 liters/m2, and 5.6 +/- 0.4 h. In patients with renal insufficiency Clp was 12.8 +/- 1.1 ml/min/m2, Vd was 20.8 +/- 4.9 liters/m2, and t1/2 beta was 19.2 +/- 4.7 h. A statistically significant correlation (P = 0.0000001) was found between VP16 Clp and creatinine clearance. In 12 of 15 patients with abnormal liver tests Clp, Vd, and t1/2 beta were, respectively, 27.9 +/- 2.7 ml/min/m2, 12.4 +/- 1.5 liters/m2, and 5.4 +/- 0.6 h and are thus similar to those of the control group. In the other three cases with abnormal liver function VP16 plasma levels were very low. In these cases VP16 t1/2 beta values were similar (5.1, 4.4, and 5.1 h) whereas Clp values (320, 87, and 96 ml/min/m2) and Vd values (142, 33, and 42 liters/m2) were much larger than in controls. These results suggest that VP16 doses should be reduced in patients with renal function impairment but not necessarily in patients with liver impairment. The high VP16 Vd and Clp values found in a subset of patients with liver impairment require further elucidation.

Comparison of metabolism and activity of an aryldimethyltriazene and an aryldiethyltriazene

The antitumoral activity and metabolism of 1-(4-acetylphenyl)-3,3-dimethyltriazene [pAc-(CH3)2] and 1-(4-acetylphenyl)-3,3-diethyltriazene [pAc-(C2H5)2] were studied in mice. pAc-(CH3)2 showed significant antitumoral activity against M5076 ovarian reticular cell sarcoma, L1210 leukemia, EL 4 lymphoma in mice, but not against Lewis lung carcinoma. pAc-(C2H5)2 was inactive in all these murine tumors and was much more toxic than pAc-(CH3)2. pAc-(CH3)2 and pAc-(C2H5)2 were rapidly metabolized in vitro and in vivo to their respective monoalkyltriazenes and to 4-aminoacetophenone (pAc-NH2). In vitro, 79% of the dimethyltriazene was metabolized to its monomethyl analogue, but only 27% of the diethyltriazene was metabolized to the monoethyltriazene. The monoalkytriazenes were almost completely biotransformed to pAc-NH2 by a 9000 g liver fraction. The metabolic pattern in the in vitro study was comparable to that found in vivo.

Ionization constants and partition coefficients of 1-arylpiperazine derivatives

The ionization constant (pKa) and liposolubilities (log P) of fourteen 1-arylpiperazines were determined by n-octanol/buffer partition. pKa varied little across the entire series. Log P values ranged from less than 1 to about 2 for the highly lipophilic derivatives of the preset series. The results are discussed in relation to the extent to which these derivatives, known to be centrally active, may enter the brain.

Kinetic and pharmacological studies on estazolam in mice and man

After i.v. and oral doses of estazolam (5 mg/kg) to mice, the drug was rapidly cleared with a beta half-life (t1/2 beta) of 0.7 h. The active metabolite, 1-oxo-estazolam, was present in traces in mouse plasma and brain. Its elimination t1/2 (beta), determined after i.v. injection of 1-oxo-estazolam (5 mg/kg) to mice, was similar to that of the parent drug in both plasma and brain. After a single oral dose of estazolam (4 mg) to four human volunteers the drug was rapidly absorbed and reached maximum plasma concentrations in one to three hours. Elimination t1/2 of estazolam in humans was 19 h. The metabolite was undetectable in human plasma after either single or multiple doses of estazolam. These results, together with the finding that 1-oxo-estazolam was less effective than estazolam, in terms of ED50 and brain concentrations necessary to antagonize leptazol convulsions and disrupt rota-rod performance in mice, indicate that the metabolite does not contribute significantly to the pharmacological effects of its parent drug.

Pharmacokinetics of teniposide in patients with ovarian cancer

Pharmacokinetics of teniposide (VM26) after each of three doses were investigated by high-performance liquid chromatographic assay in eight patients with ovarian cancer with normal liver and renal functions. Treatment consisted of a first dose of 100 mg/m2 iv as a 1-hour infusion (Day 1), a second dose of 150 mg/m2 iv as a 1-hour infusion (Day 8), and a third dose of 150 mg/m2 as an approximately 1-day infusion (Day 22). Disappearance of VM26 from plasma followed a biexponential decay pattern. The mean terminal half-life (+/- SE) was 6.9 +/- 0.9 hours after the first dose, 6.1 +/- 0.7 hours after the second dose, and 9.7 +/- 1.4 hours after the third dose. VM26 levels in ascites were lower than those in plasma in the first hours after drug administration, but by 24 hours they were similar or slightly higher. Urinary elimination of VM26 as unchanged drug amounted to less than 10% of the dose.

Comparative kinetics of oral benz(a)anthracene, chrysene and triphenylene in rats: Study with hydrocarbon mixtures

Distribution and elimination of benz(a)anthracene (B(a)A) was compared in blood, liver, brain, parametrial adipose and mammary tissue of young female rats after oral administration of the polycyclic aromatic hydrocarbons (PAH) singly or in equimolar mixtures with chrysene (Ch) or triphenylene (Tr). The relative availability of B(a)A in tissues was not influenced by Ch or Tr in the mixture. However, the presence of B(a)A halved the relative availability of Tr and raised that of Ch. The relative availability of the three isomers decreased in the order Tr greater than B(a)A greater than Ch; this may be correlated to their solubility in water.

Pharmacokinetic study of VM26 given as a prolonged IV infusion to ovarian cancer patients

Plasma levels of VM26 were assayed by HPLC in six ovarian cancer patients with normal renal and liver function who received the drugs as an initial 1-h IV infusion of 80 mg/m2 followed by a 24-h IV infusion of 120 mg/m2. These doses and infusion rates were chosen on the basis of mean VM26 clearance values found in a previous study, with the aim of reaching plasma steady-state levels of approximately 6 micrograms/ml in a short time. Plasma steady-state levels of 4-10 micrograms/ml, close to those predicted theoretically, were in fact attained at 4-9 h during the second, slower infusion. Mean half-lives and clearance values were 8.6 +/- 1.1 h and 0.78 +/- 0.08 l/h/m2. Six percent of the VM26 dose was recovered as unchanged drug in the urines collected up to 24 h after the end of infusion. The glucuronide of VM26 aglycone (4'-demethylepipodophyllotoxin) was identified in the urine of all patients, in amounts corresponding to about 8% of the drug dose.

Amiodarone kinetics after single i.v. bolus and multiple dosing in healthy volunteers

We studied three healthy volunteers after a single i.v. bolus of amiodarone, during 1 month of chronic oral dosing and after the discontinuation of the drug. Blood concentrations of amiodarone declined rapidly in a bi-exponential fashion after i.v. bolus. The terminal half-life ranged from 10 to 17 h; after discontinuation of chronic treatment the terminal half-lives were 8-21 days. The i.v. data, the trough levels during multiple dosing and the washout phase could be simultaneously fitted using a triexponential equation. The subjects were carefully monitored for cardiac and thyroid function. One subject had to stop taking amiodarone because of profound bradycardia. A reduction of serum TT3 and FT3 concentrations and an increase of serum rT3 and FT4 was found.

Bioavailability of drugs with long elimination half-lives

Methods for estimating the bioavailability of drugs with long elimination half-lives are examined. Provided both absorption and disposition are linear a simple linear regression method is developed which can be used to calculate bioavailability in situations where only an incomplete estimate of the area under the curve (AUC) is available. The regression method and the traditional method of comparing the AUC following an oral dose to the AUC following an i.v. dose were applied to simulated data. It was found that the AUC ratio method works well as long as absorption is complete within the time over which the AUC is computed. The regression method is less precise than the AUC ratio method but is more accurate for drugs with long absorption half-lives. When applied to published data on a beta blocker the two methods produced comparable results. The bioavailability of amiodarone in three human subjects was calculated to be 0.20, 0.44 and 0.98 using the regression method with similar results from the ratio method. It is not possible to estimate the clearance of amiodarone from single dose data.

Pharmacokinetics of amiodarone in rats

We studied the kinetics of amiodarone in the rat. After an intravenous dose of 50 mg/kg, the time-course of the drug concentrations was assessed by high-pressure liquid chromatography in blood and tissues up to 16 h. The drug disappeared from the blood with an elimination half-life (t1/2beta) of 514 min and distributed extensively into tissues [apparent volume of distribution (Vd)= 29.51 L/kg]. Concentrations were highest in liver, kidney, and heart, and lowest at all times in the brain. The highest concentrations were found within 5-30 min of administration. Amiodarone accumulated extensively in adipose tissue and reached a fat/blood concentration ratio of about 1,000 at 16 h. Single-pass rat liver perfusion experiments gave an hepatic extraction ratio of 0.49 and an intrinsic clearance of 5.48 ml/min. Amiodarone disappearance in rat liver recirculation experiments was biexponential, with a half-life of 58 min.