Disposition kinetics in dogs of diethyldithiocarbamate, a metabolite of disulfiram

A disulfiram/copper gluconate co-loaded bi-layered long-term drug delivery system for intraperitoneal treatment of peritoneal carcinomatosis

To develop a long-term drug delivery system for the treatment of primary and metastatic peritoneal carcinoma (PC) by intraperitoneal (IP) injection, a disulfiram (DSF)/copper gluconate (Cu-Glu)-co-loaded bi-layered poly (lactic acid-coglycolic acid) (PLGA) microspheres (Ms) - thermosensitive hydrogel system (DSF-Ms-Cu-Glu-Gel) was established. Rate and mechanisms of drug release from DSF-Ms-Cu-Glu-Gel were explored. The anti-tumor effects of DSF-Ms-Cu-Glu-Gel by IP injection were evaluated using H22 xenograft tumor model mice. The accumulative release of DSF from Ms on the 10th day was 83.79% without burst release. When Ms were dispersed into B-Gel, burst release at 24 h decreased to 14.63%. The results showed that bis (diethyldithiocarbamate)-copper (Cu(DDC)2) was formed in DSF-Ms-Cu-Glu-Gel and slowly released from B-Gel. In a pharmacodynamic study, the mount of tumor nodes and ascitic fluid decreased in the DSF-Ms-Cu-Glu-Gel group. This was because: (1) DSF-Ms-Cu-Glu-Gel system co-loaded DSF and Cu-Glu, and physically isolated DSF and Cu-Glu before injection to protect DSF; (2) space and water were provided for the formation of Cu(DDC)2; (3) could provide an effective drug concentration in the abdominal cavity for a long time; (4) both DSF and Cu(DDC)2 were effective anti-tumor drugs, and the formation of Cu(DDC)2 occurred in the abdominal cavity, which further enhanced the anti-tumor activity. Thus, the DSF-Ms-Cu-Glu-Gel system can be potentially used for the IP treatment of PC in the future.

A novel UPLC-ESI-MS/MS method for the quantitation of disulfiram, its role in stabilized plasma and its application

Disulfiram (DSF) has been used to treat alcoholism for many years and it has been suggested to play a key role in combatting many kinds of tumors. However, disulfiram has complex pharmacokinetics and is rapidly eliminated which limits its use as a tumor treatment. Therefore, a rapid and sensitive analytical method based on ultra performance liquid chromatography coupled to electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) was developed and validated for the determination of disulfiram in rat plasma. Blood samples were pre-stabilized with a stabilizing agent and then plasma was obtained and subjected to solid phase extraction (SPE), and chromatographed on a Phenomenex Kinetex(®) XB C18 column with gradient elution using a mobile phase consisting of acetonitrile-water (containing 0.1% formic acid and 1mM ammonium acetate) at a flow rate of 0.2mL/min for 3min. Multiple reactions monitoring in positive mode was carried out with disulfiram at 296.95/115.94 and diphenhydramine (internal standard, IS) at 256.14/167.02 over a linear range from 0.6 to 1200ng/mL. The extraction recovery of disulfiram for different concentrations ranged from 75.7% to 78.3%. The intra- and inter-day precision was less than 8.93% and 12.39%, respectively, and the accuracy was within ±7.75%. The validated method was successfully applied to a pharmacokinetic study of disulfiram in rat plasma after oral administration of a dose of 180mg/kg.

Determination of the binding parameters of drug to protein by equilibrium dialysis/piezoelectric quartz crystal sensor

A novel method, equilibrium dialysis/piezoelectric quartz crystal sensor, applied to determine the binding parameters of diethyldithiocarbamate to human plasma protein is proposed. Based on the investigation of the equilibrium reaction for the binding of drug to protein, the related theoretical equations for this binding were derived. By monitoring the frequency responses of a copper-plated piezoelectric quartz crystal sensor to drug in and out of a dialysis membrane after equilibrium, the binding parameters were determined, i.e., 0.375 micromol g(-1) for beta(p), 6.496 microM for K(dp), 141.99 L mmol(-1) for K(p), and 0.043 for N. These values were in good agreement with reference values. It was found that this method may have application for studying the characteristics of the interaction between other drugs and proteins.

Comparative studies on the pharmacokinetics of hydrophilic prolinedithiocarbamate, sarcosinedithiocarbamate and the less hydrophilic diethyldithiocarbamate

The pharmacokinetics of the antitoxic and anticarcinogenic compounds diethyldithiocarbamate, prolinedithiocarbamate and sarcosinedithiocarbamate were compared in rats. The bioavailability, the distribution in the organism, the oxidation to thiuramdisulfides, the cleavage to CS2 and the excretion in urine and bile were investigated. The results showed different behaviour of the three compounds. The more toxic diethyldithiocarbamate had a short in vivo half-life, was oxidized to tetraethylthiuramdisulfide in blood, and was metabolized to high yields of CS2 in 24 h. In contrast, prolinedithiocarbamate was more stable in vivo, was found predominantly in the urinary tract and was excreted in urine. The differences could not be explained by the presence of the carboxy group in the latter dithiocarbamate, since sarcosinedithiocarbamate, which also contains a carboxy group, behaved like diethyldithiocarbamate.

Chelation in metal intoxication. XXXIV. Mixed ligand chelation in lead poisoning

The effectiveness of alpha-mercapto-beta-(2-furyl)acrylic acid (MFA) and N-benzyl-N-dithiocarboxy-D-glucamine (NaB), used in combination, in the mobilization and excretion of lead was investigated in rats. Male Wistar rats received 10 mg Pb/kg as lead acetate intragastrically daily for 6 weeks. The lead-exposed rats were treated with either MFA or NaB or both 200 mumol/kg i.p., each, daily for 3 days. Both chelating agents provoked significant urinary and faecal excretion and lowered the soft-organ lead burden. However, combined therapy did not elicit any additive or synergistic response.

Cisplatin rescue therapy: experience with sodium thiosulfate, WR2721, and diethyldithiocarbamate

Cisplatin has a steep dose response curve for both antitumor and adverse effects. Therapeutic strategies aimed at reducing toxicity and allowing dose escalation of intravenous cisplatin, such as administration in hypertonic saline and pharmacokinetically based dosing schedules, have been partially successful in reducing nephrotoxicity and bone marrow suppression. However, new dose-limiting toxicities consisting of peripheral neuropathy and ototoxicity have emerged, which continue to restrict potential use of high dose cisplatin therapy. Intraperitoneal administration of high dose cisplatin also offers the potential of markedly increased local drug exposure if systemic toxicity can be avoided. Proposed chemoprotective agents, including sodium thiosulfate, WR2721, and diethyldithiocarbamate (DDTC) are being extensively examined as "rescue agents" for either regional or systemic administration of cisplatin. Although each agent offers unique advantages to be considered in developing successful rescue therapy, many questions remain regarding molecular and pharmacokinetic interactions with cisplatin, appropriate dosing schedules, and effects on antineoplastic activity. We present a review of current investigations of chemoprotectors for prevention of cisplatin-related toxicities.

The rate of the in vivo dithiocarbamate-induced mobilization of hepatic and renal cadmium deposits

The dithiocarbamate-induced removal of aged cadmium from intracellular sites in the kidneys and liver of mice has been followed as a function of time. The processes are quite rapid with the entire course of the cadmium-removal process being completed in 60-90 min. An examination of the rates at which a dithiocarbamate removes cadmium from hepatic and renal deposits in vivo and from metallothionein in vitro, suggests strongly that the processes are similar. A common mechanism is proposed for both processes which involves the direct attack by the dithiocarbamate on cadmium ion incorporated into metallothionein. Such a mechanism is consistent with the similarities in rates and the degree of overall mobilization of cadmium by the same dithiocarbamate both in vitro and in vivo. The administration of 1 mmol/kg of sodium N-(4-methoxybenzyl)-D-glucamine dithiocarbamate (MeOBDCG) to cadmium-loaded mice leads to a reduction of in vivo renal and hepatic cadmium levels of 45% and 30%, respectively, over a period of only 1 h. Previously the incubation of metallothionein in vitro in the presence of 1 mmol/l of MeOBDCG was found to lead to the reduction of the cadmium content of metallothionein of approximately 60% over a period of 1 h. The administration of higher doses of this compound (2 mmol/kg and 4 mmol/kg) to cadmium-loaded mice led to an even more rapid and more extensive removal of cadmium from both the liver and the kidney. The major factors which limit the ability of dithiocarbamates to mobilize cadmium from in vivo sites appear to be molecular structural features which hinder or prevent the access of the dithiocarbamates to the intracellular sites at which the majority of aged cadmium deposits are held.

Mechanistic aspects of the dithiocarbamate-induced mobilization of cadmium

The examination of some of the species involved in the in vivo processes in which dithiocarbamates mobilize cadmium from its intracellular deposits indicates that several competing reactions occur. Rates of hydrolytic decomposition of a series of dithiocarbamates capable of mobilizing cadmium in vivo have been determined, and the solubility behavior and nuclear magnetic resonance (NMR) spectra of their cadmium complexes have been examined. Some of the dithiocarbamates most effective in this mobilization process are shown to undergo slow conversion to oxazolidine-2-thiones in the presence of cadmium. All of the cadmium complexes involved in the mobilization process are shown to undergo rapid ligand exchange. While dissociative mechanisms based on the turnover of metallothionein are inconsistent with the experimental data, at least two associative mechanisms are possible. These involve attack on the metallothionein by the dithiocarbamate itself or by a compound derived from it by known metabolic processes.

Optimal dithiocarbamate structure for immunomodulator action

While the commercially available sodium diethyldithiocarbamate (DEDTC) has been used by several groups in the treatment of AIDS patients, chemical evidence suggests that other dithiocarbamates which are more stable at pH 7.4 might prove to be quite superior for this purpose. Of these other compounds, sodium pyrrolidinedithiocarbamate (PDTC) and sodium di-n-propyldithiocarbamate (DPDTC) which have much longer half lives at pH 7.4, are expected to exhibit similar lipophilicity to DEDTC but superior stability towards hydrolysis. They can be expected to be superior to DEDTC, especially for oral administration.

Diethyldithiocarbamic acid-methyl ester: a metabolite of disulfiram and its alcohol sensitizing properties in the disulfiram-ethanol reaction

Diethyldithiocarbamic-acid-methyl ester (DDTC-Me) is a major metabolite of disulfiram. When given to rats, DDTC-Me was found to inhibit the liver mitochondrial low Km aldehyde dehydrogenase (ALDH) without having any effect on the high Km isoenzyme. Inhibition of low Km ALDH by DDTC-Me in vivo exhibited a dose-response relationship, with inhibition of ALDH from 11% to 90% found when DDTC-Me was administered in a dose range from 1.8 to 158 mg/kg, IP. After a single dose of DDTC-Me (41.2 mg/kg, IP), the low Km ALDH was inhibited for 168 hours suggesting an irreversible enzyme inhibition. After an ethanol challenge to DDTC-Me-treated rats, a decrease in mean arterial pressure (MAP) and increase in heart rate was observed. Decreases in MAP occurred almost immediately after ethanol challenge and remained low throughout a four hour post-ethanol period. These results suggest that in vivo administration of DDTC-Me can cause an alcohol-sensitizing reaction, and that DDTC-Me actually may be the metabolite of disulfiram which produces the disulfiram-ethanol reaction. It is proposed the reaction be more correctly identified as the DDTC-Me-Ethanol Reaction or D-MER.

Chelating-agent suppression of cadmium-induced hepatotoxicity

The administration of sodium N-methyl-N-dithiocarboxy-D-glucamine (NaG) at 500 mg/kg, i.p., or sodium calcium diethylenetriaminepentaacetic acid (DTPA) at 632.5 mg/kg, i.p., reduces the serum enzyme levels characteristic of hepatic damage following the intravenous administration of cadmium chloride (3.5 mg CdCl2.2.5H2O/kg). Some effect on serum enzyme levels was found even when the interval between administration of cadmium chloride and that of the antagonist was as great as 4 h. The enzymes examined included aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), alanine aminotransferase (SGPT), and alkaline phosphatase (AP). A histopathological examination of the livers of such animals also reveals the presence of a significant protective action.

A review of metabolite kinetics

The importance of metabolites as active and toxic entities in drug therapy evokes the need for an examination of metabolite kinetics after drug administration. In the present review, emphasis is placed on single-compartmental characteristics for a drug and its primary metabolites under linear kinetic conditions. The determination of the first-order elimination rate constants for drug and metabolite are also detailed. For any ith primary metabolite mi formed solely in liver, kinetic parameters with respect to primary metabolite formation under first-order conditions require a comparison of the areas under the metabolite concentration-time curve after drug and preformed metabolite administrations. These area ratios hold regardless of the number of noneliminating compartments for the drug and metabolite. These parameters include fmi and gmi, the fractions of total body clearance that respectively furnishes mi to the general circulation and forms mi, and hmi, the fraction of hepatic clearance responsible for the formation of mi. Moreover, the fraction of dose dmi converted to form mi is defined with respect to the route of drug administration. The inherent assumption of these estimates, however, requires that the extent of sequential elimination of the generated mi be identical to the extent of metabolism of preformed mi. Discrepancies have been found, and may be attributed mostly to the uneven distribution of drug-metabolizing activities as well as to the presence of diffusional barriers. Other linear systems that involve mi formation from multiple organs are briefly described.

Effect of thiocarbonyl compounds on alpha-naphthylisothiocyanate-induced hepatotoxicity and the urinary excretion of [35S]alpha-naphthylisothiocyanate in the rat

The effect of disulfiram (DSF), sodium diethyldithiocarbamate (DDTC), methyl diethyldithiocarbamate (Me-DDTC), and ethionamide on the hepatotoxic response of alpha-naphthylisothiocyanate (ANIT) was studied in the rat. The hyperbilirubinemic response of ANIT was significantly inhibited by ip or po DSF pretreatment. A more marked inhibition of toxicity occurred when DSF was given via ip injection. DDTC, Me-DDTC, and ethionamide significantly inhibited ANIT-induced hyperbilirubinemia. Me-DDTC is approximately three times more potent than DDTC as an inhibitor of toxicity. Approximately 16% of a dose of [35S]ANIT was excreted in the urine as inorganic sulfate 48 hr after dosing. Me-DDTC administered simultaneously with [35S]ANIT significantly reduced urinary [35S]sulfate excretion in the first 24 hr. Ethionamide reduced urinary [35S]sulfate excretion. Pretreatment with phenobarbital which stimulates toxicity in vivo increased urinary [35S]sulfate excretion 300% in the first 12 hr. Thus, this study shows that agents which sensitize or protect rats from the toxic effects of ANIT, correspondingly stimulate or inhibit the oxidative desulfuration of [35S]ANIT in vivo.

Inhibition of lipid peroxidation in spinal cord homogenates by various drugs

The extent and kinetic profiles of lipid peroxidation induced with Fe2+-ascorbic acid in a homogenate of spinal cord from greyhound dogs were ascertained by measurement of the formation of malondialdehyde (MDA) and chemiluminescence in the presence of four drugs. Changes in MDA and chemiluminescence were correlated as a function of the activator or inhibitors. The kinetic profiles of chemiluminescence which were observed for 25 min after addition of the activator and individual inhibitors were similar regardless of the type of inhibitor studied. The most effective inhibition was by disulfiram which was approximately 11 and 33 times more effective than two other inhibitors, propyl gallate and promethazine, respectively, and 11,000 times more effective than D-alpha-tocopherol.

Metabolite pharmacokinetics: the area under the curve of metabolite and the fractional rate of metabolism of a drug after different routes of administration for renally and hepatically cleared drugs and metabolites

A model comprised of four compartments, a central and liver compartment for a drug, and a central and liver compartment for a metabolite, is presented to describe the interrelationships between the area under the curve of the metabolite and physiological parameters after intravenous and intraportal administration of the drug. The model includes renal and hepatic eliminatory mechanisms for both drug and metabolite as long as the metabolite is formed only by the liver. It is found that when competing renal eliminatory pathways exist for a drug, the area under the curve for the metabolite will change according to the route of drug administration. Also, the fractional rate of metabolism of a drug to form the metabolite will be underestimated by the normal use of the ratio areas under the curve of the metabolite. Other properties of the model are also discussed.

Comparative pharmacokinetics of quinidine and its O-desmethyl metabolite in rabbits

The pharmacokinetics of quinidine and the O-desmethyl metabolite 6'-hydroxycinchonine were studied in rabbits. After intravenous bolus injections of equimolar doses, the blood concentration-time curves of each agent declined biexponentially, which was characteristic of a two-compartment open model. A significant difference between quinidine and 6'-hydroxycinchonine was observed for the following parameters: t1/2 alpha, beta, t1/w beta, k12, Vd beta, and the intercompartmental distribution ratio, k12/k21. The results showed that the distribution of the metabolite was slower than quinidine and suggested that it also was less extensive. The Vd beta value for 6'-hydroxycinchonine was approximately one-half of the value observed for quinidine, and its k12/k21 ration was about one-fourth of the quinidine value. The terminal half-lives for quinidine and the metabolite were 132.4 +/- 27.1 and 65.4 +/- 34.4 min, respectively. Total body clearance was similar for both compounds. The findings of this study could be explained by the greater polarity or greater water solubility of 6'-hydroxycinchonine. The limited data in humans coupled with the results of this investigation suggest that, although it is intrinsically active, the O-demethylated metabolite probably contributed little to the antiarrhythmic effects seen after quinidine administration in humans.