Phase I study of oral CP-4126, a gemcitabine derivative, in patients with advanced solid tumors.

CP-4126 is a gemcitabine (2',2'-difluorodeoxycytidine; dFdC) 5' elaidic acid ester. The purpose of this dose-escalating study was to assess safety, pharmacokinetics (PK) and preliminary antitumor activity of the oral formulation and to determine the recommended dose (RD) for phase II studies. The study had a two-step design: a non-randomized dose-escalating step I with oral CP-4126 alone, followed by a randomized, cross-over step II that compared oral CP-4126 with dFdC i.v.. CP-4126 was given on days 1,8,15 in a 4-week schedule with increasing doses until the RD was established. 26 patients with different solid tumours were enrolled in step I at seven dose levels (100-3,000 mg/day). The most frequent drug-related AEs were fatigue and dysgeusia, the majority being grade 1-2. One patient experienced a dose limiting toxicity after one dose of CP-4126 at 1,300 mg/day (ASAT grade 3). PK of CP-4126 could not be determined. The metabolites dFdC and dFdU obeyed dose-dependent pharmacokinetics. Exposures to dFdC were about ten-fold lower compared to exposures after comparable doses of dFdC i.v.. Nine patients reached stable disease as best response, whereby in one patient with vaginal carcinoma a 25 % reduction of tumor volume was reached. This study demonstrates that CP-4126 can be safely administered orally to patients up to 3,000 mg/day in a d1,8,15 q4w schedule with a tolerable safety profile. CP-4126 acts as a prodrug for dFdC when given orally, but because of the poor absorption and the rapid pre-systemic metabolism the study was terminated early and no RD could be determined.

In vivo stability and excretion of gadodiamide (GdDTPA-BMA), a hydrophilic gadolinium complex used as a contrast enhancing agent for magnetic resonance imaging.

The stability and excretion of [14C]-gadodiamide (GdDTPA-BMA) was studied in male rats after i.v. injection of 0.3 mmol/kg [14C]-GdDTPA-BMA (Gd-diethylenetriaminepentaacetic-acid-bis-methylamide) formulated as gadodiamide injection (OMNISCAN, Nycomed Imaging AS, Oslo, Norway). Samples of blood and urine obtained within 60 min and 6 h postdosing, respectively, were analyzed for radiolabeled compounds. Analysis of GdDTPA-BMA in high and low molecular weight fractions of serum indicated no protein binding. HPLC analyses of urine samples obtained 0-2 h, 2-4 h and 4-6 h after injection revealed no detectable amounts of biotransformation products of GdDTPA-BMA. Serum samples obtained 30 min and 60 min after injection contained 9-13 microM of an unidentified compound which had a retention time different from all conceivable metabolites of gadodiamide. A similar concentration of this unknown compound was found in spiked predose serum samples. The total amount of the unknown compound in serum was less than 1% of the injected dose of [14C]-gadodiamide injection. It is concluded that gadodiamide, when administered i.v. as gadodiamide injection at a dosage of 0.3 mmol/kg, is stable in vivo and that the very major part of the dose (> 99%) is excreted in urine as an unchanged complex.

Metabolism of levomepromazine in man.

The phenothiazine drug, levomepromazine (LM), is used in the treatment of psychiatric disorders and as an analgesic. A single 50 or 100 mg dose of LM was given to healthy male volunteers, and urine samples were collected for 24 h. The urine was treated with beta-glucuronidase, purified by solid-phase extraction, and analyzed on a GC-MS system for identification of LM metabolites. Mass spectra suggesting 14 different LM metabolites were obtained from the samples. Our of these, 13 spectra could be ascribed to specific metabolites, 5 of which have not previously been identified. All these 5 metabolites were hydroxylated at the phenothiazine nucleus. Although the applied method did not determine the positions of hydroxyl groups on phenothiazine nuclei. 3 of the 5 metabolites were identified as O-desmethyl 3-hydroxy LM, O-desmethyl 7-hydroxy LM, and N,O-didesmethyl 7-hydroxy LM, based on their chromatographic properties. In addition two metabolites, one being hydroxylated on the phenothiazine nucleus, and one being O-demethylated and hydroxylated on the nucleus, were found. It is suggested that these were 8-hydroxy LM and O-desmethyl 8-hydroxy LM. The concentrations of 3-hydroxy LM (free+conjugated) appeared to be much higher than the concentrations of any other metabolite in the samples.

Effect of levomepromazine and metabolites on debrisoquine hydroxylation in the rat.

The influence of the major metabolites of the phenothiazine derivative, levomepromazine (methotrimeprazine), on hydroxylation of debrisoquine was examined in male Sprague-Dawley rats. The metabolic ratio of debrisoquine/4-hydroxy debrisoquine was first determined in rats after oral administration of 10 mg/kg of debrisoquine. Then the same dose of debrisoquine was co-administered with various doses of levomepromazine or one of its metabolites. Levomepromazine and its sulphoxidated, N-demethylated and O-demethylated metabolites caused highly significant and dose-dependent increases in the debrisoquine metabolic ratio. 3-Hydroxy levomepromazine had no significant effect on the metabolism of debrisoquine. This indicates that the non-hydroxylated metabolites of levomepromazine have relatively high affinities for the cytochrome P450 enzyme which converts debrisoquine to 4-hydroxy debrisoquine in the rat. Such metabolites may therefore be responsible for a considerable part of the inhibitory effect of debrisoquine hydroxylation previously reported in patients treated with phenothiazine neuroleptics.

Preclinical safety assessment and pharmacokinetics of gadodiamide injection, a new magnetic resonance imaging contrast agent.

In a wide range of preclinical studies of gadodiamide injection (Omniscan, Sanofi Winthrop, New York, NY, and Nycomed AS, Oslo, Norway), the pharmacokinetics of the compound have been delineated and its safety demonstrated. The pharmacokinetic behavior of gadodiamide was consistent with its extracellular distribution. Its half-life in rats, rabbits, and monkeys was short, 18, 38, and 75 minutes, respectively. Gadodiamide was shown to be excreted rapidly, primarily through the kidneys. In rats, 94% of the administered dose was excreted in the urine within the first 24 hours after administration. Approximately 1% to 4% appeared in the feces during the same period. Gadodiamide injection has been shown to have a remarkably low acute lethal toxicity, superior to that of gadopentetate dimeglumine injection (Magnevist, Berlex Laboratories, Wayne, NJ, and Schering AG, Berlin, Germany) or gadoterate meglumine (Dotarem, Laboratoire Guerbet, Aulnay-Sous-Bois, France). In comparison with gadopentetate dimeglumine injection, gadodiamide injection had fewer effects on cardiovascular and hemodynamic function after rapid intravenous injection in anesthetized dogs and, in vitro at high concentrations, on erythrocyte fragility and arterial wall tension. The lesser effects might be attributable, at least in part, to the lower osmolality of gadodiamide injection, although it remains to be seen whether this will translate into any advantage for gadodiamide injection at the lower doses used for imaging procedures in patients. Similar to all known intravenously administered diagnostic imaging agents, gadodiamide injection produces vacuolization of the proximal tubular cells in the kidney, without any change in renal function. However, the single-dose threshold for this effect is greater than 0.5 mmol/kg in the rat; even after a dose of 10 mmol/kg, the vacuolization was only "moderate" in degree and was shown to have regressed partially during the 7 days after administration. In monkeys, administration of 0.25 mmol/kg daily for 28 days had no effect on the kidney, thus providing reassurance of the wide margin of safety for any effect of this compound on the kidney. Although intended for single administration in patients, gadodiamide injection has been studied extensively in a range of subchronic studies in rats and monkeys. The compound was well tolerated in monkeys even when administered at doses up to 1.25 mmol/kg daily for 28 consecutive days. In rats, significant toxicity occurred only at high doses, particularly in male animals, and the pattern of toxicity (involving the stomach, testes, and skin) suggested a disturbance of zinc metabolism. Gadodiamide injection produced no significant irritation when administered by a variety of intravascular and extravascular routes.

Human pharmacokinetics of iodixanol.

The pharmacokinetic properties of the x-ray contrast medium, iodixanol, a new nonionic dimer, were investigated in a phase I study including 40 healthy male volunteers. Iodixanol (300 mg I/mL) was administered intravenously (i.v.) at four dose levels--0.3, 0.6, 0.9, and 1.2 g iodine (I)/kg body weight--and saline was given as a control. 51Cr-EDTA was given concomitantly with iodixanol at all dose levels to study renal excretion of iodixanol. Mean half-lives were 26 and 131 minutes in the distribution and elimination phase, respectively. Apparent volume of distribution was 0.28 1/kg body weight, indicating distribution to extracellular fluid only. Within 24 hours after injection, 97% of the dose was excreted unmetabolized in the urine via glomerular filtration. The excretion in feces was 1.2% of the dose. The parameters calculated were independent of the given dose. The pharmacokinetics of iodixanol are comparable with those reported for other intravascular contrast media.

High-performance liquid chromatographic determination of levomepromazine (methotrimeprazine) and its main metabolites in serum and urine.

A new analytical method has been developed for simultaneous quantitation of levomepromazine and its five main metabolites in serum and urine. The method uses C-2 bonded phase extraction and reversed-phase high-performance liquid chromatography, based on ion-pair formation with dodecyl sulfate. The detection limits were 15 nM for levomepromazine and N-desmethyl levomepromazine, 28 nM for levomepromazine sulfoxide, and 56 nM for 3-hydroxylevomepromazine. 7-hydroxylevomepromazine, and O-desmethyllevomepromazine in serum, and lower in urine. The method was applied to measure steady-state serum and urine concentrations of levomepromazine and metabolites in five psychiatric patients. The concentrations of levomepromazine sulfoxide and N-desmethyllevomepromazine were generally higher than the concentrations of levomepromazine. The hydroxylated and O-demethylated metabolites were also found in higher concentrations than levomepromazine, but mainly as conjugates.

Negative gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles at 0.02 Tesla.

Gastrointestinal contrast enhancement and image distortion induced by superparamagnetic particles were evaluated in vitro and in rabbits at 0.02 Tesla. Test tubes containing 0.01-1.0 mg particles/ml were imaged in an oil or water bath in order to demonstrate the concentration-dependent signal void and image distortion in vitro at several pulse sequences. The lowest concentration of particles tested clearly decreased the signal intensity. Image distortion was observed when the concentration exceeded 0.07 mg/ml and was more pronounced on the T2-weighted images. The in vitro T2 relaxation time decreased from 122 ms to 56 ms with an increase in the particle concentration from 0.01 to 0.06 mg/ml. A loss of the GI-tract signal was observed in rabbits after the administration of 1 mg particles/kg, given as a 0.03 mg/ml suspension. At a dose of 20 mg/kg (0.6 mg/ml suspension) significant image distortion was observed.

Muscarinic cholinergic and histamine H1 receptor binding of phenothiazine drug metabolites.

In vitro binding affinities of chlorpromazine, fluphenazine, levomepromazine, perphenazine and some of their metabolites for dopamine D2 receptors, alpha 1- and alpha 2 adrenoceptors in rat brain were previously reported from our laboratories. The present study reports the in vitro binding affinities of the same compounds for muscarinic cholinergic receptors and for histamine H1 receptors in rat brain, using 3H-quinuclidinyl benzilate and 3H-mepyramine as radioligands. Chlorpromazine, levomepromazine, and their metabolites had 5-30 times higher binding affinities for muscarinic cholinergic receptors than fluphenazine, perphenazine and their metabolites. Levomepromazine was the most potent and fluphenazine the least potent of the four drugs in histamine H1 receptor binding. 7-Hydroxy levomepromazine, 3-hydroxy levomepromazine and 7-hydroxy fluphenazine had only 10% of the potency of the parent drug in histamine H1 receptor binding, while the 7-hydroxy-metabolites of chlorpromazine and perphenazine had about 75% of the potency of the parent drug in this binding system. Their histamine H1 receptor binding affinities indicate that metabolites may contribute to the sedative effects of chlorpromazine and levomepromazine.

Phenothiazine drug metabolites: dopamine D2 receptor, alpha 1- and alpha 2-adrenoceptor binding.

The in vitro binding affinities of levomepromazine, chlorpromazine, fluphenazine, perphenazine and methoxypromazine and their main metabolites to dopamine D2 receptors, alpha 1- and alpha 2-adrenoceptors in rat brain, were examined using [3H]spiperone, [3H]WB 4101 and [3H]yohimbine binding. All compounds had 10-500 times lower affinities to alpha 2-adrenoceptors than to dopamine D2 receptors and alpha 1-adrenoceptors. Ring-hydroxylated and N-demethylated metabolites had relative potencies for dopamine D2 receptor and alpha 1-adrenoceptor binding ranging from 20 to 70%, compared to that of the parent drugs. The ring sulphoxides of levomepromazine, chlorpromazine and perphenazine, except dextro levomepromazine sulphoxide, were virtually inactive in all binding systems. The results indicate that the metabolites having the highest binding affinities for dopamine D2 receptor and alpha 1-adrenoceptor binding may contribute significantly to the therapeutic effect and side-effects of the drugs, and should be measured together with the parent drugs in blood level-effect studies.

Phenothiazine drugs and metabolites: molecular conformation and dopaminergic, alpha adrenergic and muscarinic cholinergic receptor binding.

The solid state molecular structures of methoxypromazine and N-monodesmethyl chlorpromazine sulphoxide were determined by X-ray crystallography, as an extension of previous studies on the molecular structures of chlorpromazine sulphoxide and methotrimeprazine sulphoxide. The binding affinities of phenothiazine drugs and metabolites with known crystal structures to dopaminergic, alpha adrenergic and muscarinic cholinergic receptors in rat brain were examined using radio-ligand binding techniques. Comparison of their solid state molecular structures and potencies in neurotransmitter receptor binding reveals that these compounds exist in two different conformations: One, associated with low biological activity, has an angle between the planes of the two aryl rings in the range of 155-160 degrees, and a torsion angle of -80 to -84 degrees around the N(10)-C bond of the side-chain, calculated from the substituted benzene ring. In the other conformation, which is found in the biologically active derivatives, the angle between the planes of the two aryl rings is in the range of 134-145 degrees, and the torsion angle around the N(10)-C bond of the side-chain is in the range of 64-69 degrees or 129-144 degrees. The "active" and "inactive" conformations thus have the side-chain on opposite sides of the ring system.

Resin haemoperfusion in levomepromazine poisoning: evaluation of effect on plasma drug and metabolite levels.

Plasma levels of levomepromazine and two of its major metabolites N-desmethyl-levomepromazine and levomepromazine sulphoxide were studied in two poisoned patients treated with resin haemoperfusion at a constant blood flow of 200 ml/min. The mean haemoperfusion clearance of levomepromazine, N-desmethyl-levomepromazine and levomepromazine sulphoxide was 114, 123 and 151 ml/min, respectively, in patient no. 1, and 153, 148 and 184 ml/min, respectively, in patient no. 2. Patient no. 2 had also ingested amitriptyline, and the mean haemoperfusion clearance of amitriptyline and its metabolite nortriptyline was 183 and 183 ml/min respectively. Haemoperfusion did not seem to alter the elimination profile of levomepromazine or the two metabolites in either patient. We conclude that haemoperfusion is of little value in removing levomepromazine, N-desmethyl-levomepromazine or levomepromazine sulphoxide from the body. This is probably due to the large apparent volume of distribution and the high intrinsic hepatic metabolic clearance of these compounds.

Effects of low dose propranolol after coronary bypass surgery.

This study was performed to record the occurrence of clinically important supraventricular tachyarrhythmias (SVA) during the first eight days following coronary bypass surgery after preoperative withdrawal of various betablockers and to investigate whether low dose propranolol medication postoperatively could reduce the occurrence of such arrhythmias. Forty patients with stable angina pectoris were postoperatively randomly assigned to either a group (B) receiving low doses of propranolol or to a group (A) not receiving this medication. The number of patients having episodes of clinically important SVA was recorded. Two out of sixteen patients in the propranolol group had such episodes compared with nine out of twenty without postoperative betablockade (p = 0.07). Thus among patients treated with various betablockers which were withdrawn prior to coronary surgery, the occurrence of postoperative clinically important SVA could not be significantly reduced by postoperative low dose propranolol administration.

Effect of diethylether on the formation of paracetamol sulphate and glucuronide in isolated rat hepatocytes.

Diethylether has previously been shown to inhibit several pathways of drug metabolism, including conjugation of paracetamol in isolated rat hepatocytes. Since overall paracetamol conjugation consists of pathways of different subcellular localization (cytosolar sulphation and microsomal glucuronidation) the response of both pathways to diethylether was tested. The elimination of paracetamol (160 mumol/l, initial concentration) and the formation of paracetamol sulphate and glucuronide were measured (high-performance liquid chromatography) in suspensions of isolated rat hepatocytes from fasted and fed animals over 1 h in the absence and presence of diethylether (30 mmol/l). Approximately 90% of the paracetamol elimination was by sulphation and nearly 10% by glucuronidation both in the controls and in the presence of ether. The overall disposition of paracetamol and the formation of sulphate were both reduced by about 50% in the presence of ether compared to the controls while the formation of glucuronide was reduced by 70%. The results were not influenced by the nutritional state of the animals before sacrifice. It is concluded that the inhibitory effect of ether on total paracetamol metabolism was mainly caused by reduced sulphation. Since microsomal glucuronidation was also inhibited by ether, both cytosolar and microsomal enzyme systems were sensitive to diethylether.

Pharmacokinetics and first-pass metabolism of levomepromazine in the rat.

The time course of the blood concentrations of levomepromazine and its two major non-polar metabolites in man were studied in the rat after single oral and intraarterial doses of levomepromazine hydrochloride. The blood levels of N-monodesmethyl levomepromazine were on average 179% of the levomepromazine levels after oral doses, but only 15% of the levomepromazine levels after intraarterial doses. The blood levels of levomepromazine sulfoxide, relative to the levomepromazine levels, were also generally higher after oral doses than after parenteral doses, on average 65% and 25%, respectively. Large interindividual variations were observed in the blood levels of levomepromazine and in the systemic availability of the drug after oral doses. The distribution phase lasted for about 8 hrs, the mean apparent volume of distribution was 16.6 l/kg, and the total body clearance was on average 12.3 ml/min. It is concluded that the rat provides a suitable model for the kinetics of levomepromazine in man, and that the sulfoxide and N-monodesmethyl metabolites of the drug are mainly formed by first-pass metabolism after oral doses in the rat, either in the liver or in the gut.

A sensitive gas chromatographic assay for amitriptyline and nortriptyline in plasma.

A method for the quantitative determination of the tricyclic antidepressant drug amitriptyline (AT) and its active major metabolite, nortriptyline (NT), in plasma is described. The method involves a three-step extraction procedure, no derivatization, and a rapid run on a gas--liquid chromatograph equipped with a nitrogen detector. The standard curves were linear in the range of 25-1,000 ng/ml. The lower detection limit was 2-5 ng/ml for both drugs. The method is specific for AT and NT, with a recovery of AT and NT of 68 and 71%, respectively. The precision of the method, expressed as the coefficient of variation, was 10.7% for AT and 12.9% for NT within 25--1,000 ng/ml. The method has proven to be suitable for monitoring plasma levels of AT and NT in patients, and in animals during experimental studies on pharmacokinetics after therapeutic and toxic doses of NT.