Comparative aspects of disulfiram and its metabolites in the disulfiram-ethanol reaction in the rat

In Vitro Activities of Dithiocarbamate Derivatives against Echinococcus multilocularis Metacestode Vesicles

The metacestode stage of the fox tapeworm Echinococcus multilocularis causes the severe zoonotic disease alveolar echinococcosis. New treatment options are urgently needed. Disulfiram and dithiocarbamates were previously shown to exhibit activity against the trematode Schistosoma mansoni. As both parasites belong to the platyhelminths, here we investigated whether these compounds were also active against E. multilocularis metacestode vesicles in vitro. We used an in vitro drug-screening cascade for the identification of novel compounds against E. multilocularis metacestode vesicles with disulfiram and 51 dithiocarbamates. Five compounds showed activity against E. multilocularis metacestode vesicles after five days of drug incubation in a damage marker release assay. Structure-activity relationship analyses revealed that a S-2-hydroxy-5-nitro benzyl moiety was necessary for anti-echinococcal activity, as derivatives without this group had no effect on E. multilocularis metacestode vesicles. The five active compounds were further tested for potential cytotoxicity in mammalian cells. For two compounds with low toxicity (Schl-32.315 and Schl-33.652), IC50 values in metacestode vesicles and IC50 values in germinal layer cells were calculated. The compounds were not highly active on isolated GL cells with IC50 values of 27.0 ± 4.2 µM for Schl-32.315 and 24.7 ± 11.5 µM for Schl-33.652, respectively. Against metacestode vesicles, Schl-32.315 was not very active either with an IC50 value of 41.6 ± 3.2 µM, while Schl-33.652 showed a low IC50 of 4.3 ± 1 µM and should be further investigated in the future for its activity against alveolar echinococcosis.

Recent Advances in Repurposing Disulfiram and Disulfiram Derivatives as Copper-Dependent Anticancer Agents

Copper (Cu) plays a pivotal role in cancer progression by acting as a co-factor that regulates the activity of many enzymes and structural proteins in cancer cells. Therefore, Cu-based complexes have been investigated as novel anticancer metallodrugs and are considered as a complementary strategy for currently used platinum agents with undesirable general toxicity. Due to the high failure rate and increased cost of new drugs, there is a global drive towards the repositioning of known drugs for cancer treatment in recent years. Disulfiram (DSF) is a first-line antialcoholism drug used in clinics for more than 65 yr. In combination with Cu, it has shown great potential as an anticancer drug by targeting a wide range of cancers. The reaction between DSF and Cu ions forms a copper diethyldithiocarbamate complex (Cu(DDC)₂ also known as CuET) which is the active, potent anticancer ingredient through inhibition of NF-κB and ubiquitin-proteasome system as well as alteration of the intracellular reactive oxygen species (ROS). Importantly, DSF/Cu inhibits several molecular targets related to drug resistance, stemness, angiogenesis and metastasis and is thus considered as a novel strategy for overcoming tumour recurrence and relapse in patients. Despite its excellent anticancer efficacy, DSF has proven unsuccessful in several cancer clinical trials. This is likely due to the poor stability, rapid metabolism and/or short plasma half-life of the currently used oral version of DSF and the inability to form Cu(DDC)₂ at relevant concentrations in tumour tissues. Here, we summarize the scientific rationale, molecular targets, and mechanisms of action of DSF/Cu in cancer cells and the outcomes of oral DSF ± Cu in cancer clinical trials. We will focus on the novel insights on harnessing the immune system and hypoxic microenvironment using DSF/Cu complex and discuss the emerging delivery strategies that can overcome the shortcomings of DSF-based anticancer therapies and provide opportunities for translation of DSF/Cu or its Cu(DDC)₂ complex into cancer therapeutics.

N-acetyl-S-(N,N-diethylcarbamoyl) cysteine in rat nucleus accumbens, medial prefrontal cortex, and in rat and human plasma after disulfiram administration

Disulfiram (DSF), a treatment for alcohol use disorders, has shown some clinical effectiveness in treating addiction to cocaine, nicotine, and pathological gambling. The mechanism of action of DSF for treating these addictions is unclear but it is unlikely to involve the inhibition of liver aldehyde dehydrogenase (ALDH2). DSF is a pro-drug and forms a number of metabolites, one of which is N-acetyl-S-(N,N-diethylcarbamoyl) cysteine (DETC-NAC). Here we describe a LCMS/MS method on a QQQ type instrument to quantify DETC-NAC in plasma and intracellular fluid from mammalian brain. An internal standard, the N,N-di-isopropylcarbamoyl homolog (MIM: 291>128) is easily separable from DETC-NAC (MIM: 263>100) on C18 RP media with a methanol gradient. The method's linear range is 0.5-500 nM from plasma and dialysate salt solution with all precisions better than 10% RSD. DETC-NAC and internal standards were recovered at better than 95% from all matrices, perchloric acid precipitation (plasma) or formic acid addition (salt) and is stable in plasma or salt at low pH for up to 24 h. Stability is observed through three freeze-thaw cycles per day for 7 days. No HPLC peak area matrix effect was greater than 10%. A human plasma sample from a prior analysis for S-(N,N-diethylcarbamoyl) glutathione (CARB) was found to have DETC NAC as well. In other human plasma samples from 62.5 mg/d and 250 mg/d dosing, CARB concentration peaks at 0.3 and 4 nM at 3 h followed by DETC-NAC peaks of 11 and 70 nM 2 h later. Employing microdialysis sampling, DETC-NAC levels in the nucleus accumbens (NAc), medial prefrontal cortex (mPFC), and plasma of rats treated with DSF reached 1.1, 2.5 and 80 nM at 6h. The correlation between the appearance and long duration of DETC-NAC concentration in rat brain and the persistence of DSF-induced changes in neurotransmitters observed by Faiman et al. (Neuropharmacology, 2013, 75C, 95-105) is discussed.

S-(N, N-diethylcarbamoyl)glutathione (carbamathione), a disulfiram metabolite and its effect on nucleus accumbens and prefrontal cortex dopamine, GABA, and glutamate: a microdialysis study

Disulfiram (DSF), used for the treatment of alcohol use disorders (AUDs) for over six decades, most recently has shown promise for treating cocaine dependence. Although DSF's mechanism of action in alcohol abuse is due to the inhibition of liver mitochondrial aldehyde dehydrogenase (ALDH2), its mechanism of action in the treatment of cocaine dependence is unknown. DSF is a pro-drug, forming a number of metabolites each with discrete pharmacological actions. One metabolite formed during DSF bioactivation is S-(N, N-diethylcarbamoyl) glutathione (carbamathione) (carb). We previously showed that carb affects glutamate binding. In the present studies, we employed microdialysis techniques to investigate the effect of carb administration on dopamine (DA), GABA, and glutamate (Glu) in the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), two brain regions implicated in substance abuse dependence. The effect of DSF on DA, GABA, and Glu in the NAc also was determined. Both studies were carried out in male rats. Carb (20, 50, 200 mg/kg i v) in a dose-dependent manner increased DA, decreased GABA, and had a biphasic effect on Glu, first increasing and then decreasing Glu in both the NAc and mPFC. These changes all occurred concurrently. After carb administration, NAc and mPFC carb, as well as carb in plasma, were rapidly eliminated with a half-life for each approximately 4 min, while the changes in DA, GABA, and GLu in the NAc and mPFC persisted for approximately two hours. The maximal increase in carb (Cmax) in the NAc and mPFC after carb administration was dose-dependent, as was the area under the curve (AUC). DSF (200 mg/kg i p) also increased DA, decreased GABA, and had a biphasic effect on Glu in the NAc similar to that observed in the NAc after carb administration. When the cytochrome P450 inhibitor N-benzylimidazole (NBI) (20 mg/kg i p) was administered before DSF dosing, no carb could be detected in the NAc and plasma and also no changes in NAc DA, GABA, and GLu occurred. Changes in these neurotransmitters occurred only if carb was formed from DSF. When NBI was administered prior to dosing with carb, the increase in DA, decrease in GABA, and biphasic effect on GLu was similar to that seen after dosing with carb only. The i p or i v administration of carb showed similar changes in DA, GABA, and GLu, except the time to reach Cmax for DA as well as the changes in GABA, and GLu after i p administration occurred later. The elimination half-life of carb and the area under the curve (AUC) were similar after both routes of administration. It is concluded that carb must be formed from DSF before any changes in DA, GABA, and GLu in the NAc and mPFC are observed. DSF and carb, when administered to rats, co-release DA, GABA, and GLu. Carb, once formed can cross the blood brain barrier and enter the brain. Although inhibition of liver ALDH2 is the accepted mechanism for DSF's action in treating AUDs, the concurrent changes in DA, GABA, and GLu in the NAc and mPFC after DSF administration suggest that changes in these neurotransmitters as a potential mechanism of action not only for AUDs, but also for cocaine dependence cannot be excluded.

Anxiogenic and stress-inducing effects of peripherally administered acetaldehyde in mice: similarities with the disulfiram-ethanol reaction

Peripheral accumulation of acetaldehyde, the first metabolite of ethanol, produces autonomic responses in humans called "flushing". The aversive characteristics of flushing observed in some populations with an isoform of aldehyde dehydrogenase (ALDH2) less active, are the basis for treating alcoholics with disulfiram, an ALDH inhibitor. Although ethanol and centrally formed acetaldehyde have anxiolytic effects, peripheral accumulation of acetaldehyde may be aversive in part because it is anxiogenic.

OBJECTIVES

We investigated the effect of direct administration of acetaldehyde on behavioral measures of anxiety and on hormonal markers of stress in mice. The impact of disulfiram on the anxiolytic actions of ethanol was evaluated. Acetate (a metabolite of acetaldehyde) was also studied.

METHODS

CD1 male mice received acetaldehyde (0, 25, 50, 75 or 100 mg/kg) at different time intervals and were assessed in the elevated plus maze and in the dark-light box. Corticosterone release after acetaldehyde administration was also assessed. Additional experiments evaluated the impact of disulfiram on the anxiolytic effect of ethanol (0 or 1 mg/kg), and the effect of acetate on the plus maze.

RESULTS

Direct administration of acetaldehyde (100 mg/kg) had an anxiogenic effect at 1, 11 or 26 min after IP administration. Acetaldehyde was ten times more potent than ethanol at inducing corticosterone release. Disulfiram did not affect behavior on its own, but blocked the anxiolytic effect of ethanol at doses of 30 and 60 mg/kg, and had an anxiogenic effect at the highest dose (90 mg/kg) when co-administered with ethanol. Acetate did not affect any of the anxiety parameters.

CONCLUSIONS

Peripheral administration or accumulation of acetaldehyde produces anxiogenic effects and induces endocrine stress responses. This effect is not mediated by its metabolite acetate.

Acetate causes alcohol hangover headache in rats

BACKGROUND

The mechanism of veisalgia cephalgia or hangover headache is unknown. Despite a lack of mechanistic studies, there are a number of theories positing congeners, dehydration, or the ethanol metabolite acetaldehyde as causes of hangover headache.

METHODS

We used a chronic headache model to examine how pure ethanol produces increased sensitivity for nociceptive behaviors in normally hydrated rats.

RESULTS

Ethanol initially decreased sensitivity to mechanical stimuli on the face (analgesia), followed 4 to 6 hours later by inflammatory pain. Inhibiting alcohol dehydrogenase extended the analgesia whereas inhibiting aldehyde dehydrogenase decreased analgesia. Neither treatment had nociceptive effects. Direct administration of acetate increased nociceptive behaviors suggesting that acetate, not acetaldehyde, accumulation results in hangover-like hypersensitivity in our model. Since adenosine accumulation is a result of acetate formation, we administered an adenosine antagonist that blocked hypersensitivity.

DISCUSSION

Our study shows that acetate contributes to hangover headache. These findings provide insight into the mechanism of hangover headache and the mechanism of headache induction.

LC-MS/MS method for the determination of carbamathione in human plasma

Liquid chromatography-tandem mass spectrometry methodology is described for the determination of S-(N,N-diethylcarbamoyl)glutathione (carbamathione) in human plasma samples. Sample preparation consisted of a straightforward perchloric acid medicated protein precipitation, with the resulting supernatant containing the carbamathione (recovery ~98%). For optimized chromatography/mass spec detection a carbamathione analog, S-(N,N-di-i-propylcarbamoyl)glutathione, was synthesized and used as the internal standard. Carbamathione was found to be stable over the pH 1-8 region over the timeframe necessary for the various operations of the analytical method. Separation was accomplished via reversed-phase gradient elution chromatography with analyte elution and re-equilibration accomplished within 8 min. Calibration was established and validated over the concentration range of 0.5-50 nM, which is adequate to support clinical investigations. Intra- and inter-day accuracy and precision determined and found to be <4% and <10%, respectively. The methodology was utilized to demonstrate the carbamathione plasma-time profile of a human volunteer dosed with disulfiram (250 mg/d). Interestingly, an unknown but apparently related metabolite was observed with each human plasma sample analyzed.

Disulfiram effects on responses to intravenous cocaine administration

Disulfiram has been studied as a treatment for cocaine dependence. We report results of a randomized, double-blind, placebo-controlled, within-subject study to examine the interaction of disulfiram with intravenous cocaine.

METHODS

Non-treatment-seeking, cocaine-dependent, volunteers participated in serial experiments in which they received disulfiram placebo, 62.5 or 250 mg/day on days 1-6. On days 4-6, participants received a morning disulfiram dose 2 h prior to a scheduled session in which they were administered intravenous cocaine placebo, 0.25 mg/kg (n=9) or 0.5 mg/kg (n=3) over 1 min. Blood, cardiovascular and subjective measures were collected. Seven days of washout occurred between disulfiram conditions.

RESULTS

Following active disulfiram treatments and cocaine 0.25 mg/kg administration, plasma cocaine AUC (0-480 min) was increased (p=0.003 and 0.001) and cocaine clearance decreased (p<0.001). Disulfiram treatments also decreased cocaine clearance for the 0.5 mg/kg cocaine dose (p=0.002 and<0.001). Neither disulfiram dose with cocaine altered cardiovascular responses relative to cocaine alone. Following cocaine 0.25 mg/kg, 'any high' (p=0.021 and 0.019), 'cocaine high' (p=0.017 and 0.018) and 'rush' (p=0.013 and 0.047) significantly decreased with either disulfiram dose.

CONCLUSIONS

Disulfiram decreased cocaine clearance without toxicity. Cocaine 'high' and 'rush' were diminished. Disulfiram may be a promising pharmacotherapy in selected cocaine dependent individuals.

Disulfiram metabolites permanently inactivate the human multidrug resistance P-glycoprotein

The human multidrug resistance P-glycoprotein (P-gp) uses ATP to transport a wide variety of structurally unrelated cytotoxic compounds out of the cell. The relatively high expression of P-gp in organs such as the intestine, kidney, blood-brain/testes barrier and in some tumor cells can compromise chemotherapy treatments for patients with cancer or AIDS/HIV. It has been difficult to inhibit P-gp during chemotherapy with noncovalent inhibitors because the relatively high levels of inhibitors have severe side effects. An alternative approach to inhibit P-gp would be to covalently modify cysteine residues within the NBDs. In this study, we tested whether metabolites of disulfiram, a drug currently used to treat chronic alcoholism, could inhibit P-gp. We show that the disulfiram metabolites, S-methyl N,N-diethylthiocarbamate sulfoxide and S-methyl N,N-diethylthiocarbamate sulfone inhibited the verapamil-stimulated ATPase activity of P-gp with IC50 values (concentrations that result in 50% inhibition of activity) of 9 and 4.8 microM, respectively. Similarly, S-methyl N,N-diethylthiocarbamate sulfoxide and S-methyl N,N-diethylthiocarbamate sulfone inhibited the activity of aldehyde dehydrogenase with IC50 values of 3.2 and 1.7 microM, respectively. Inhibition of P-gp by the metabolites was not reversed by addition of the reducing compound, dithiothreitol. We then determined which endogenous cysteine residue was responsible for inhibiting P-gp activity after exposure to the disulfiram metabolites. Treatment of P-gp mutants containing a single cysteine residue showed that inactivation was primarily due to modification of Cys1074 in NBD2. These results indicate that metabolites of disulfiram can covalently inactivate P-gp. Covalent modification of drug transporters could be a useful approach for inhibiting their activities during chemotherapy.

The effect of cyanamide and 4-methylpyrazole on the ethanol-induced locomotor activity in mice

To assess the role of cyanamide and 4-methylpyrazole (4-MP) in mediating ethanol-induced locomotor activity in mice, they were pretreated with cyanamide (12.5, 25, or 50 g/kg) prior to one ethanol injection (2.4 g/kg) and showed significantly depressed locomotor activity compared with control groups. Cyanamide (25 mg/kg) also cancelled out the biphasic action of ethanol (0, 0.8, 1.6, 2.4, 3.2, or 4 g/kg) on locomotor activity. The action of cyanamide and 4-MP in combined administration was also tested. Our data show that pretreatment with 4-MP alone does not change the spontaneous or ethanol-induced locomotor activity. Conversely, when mice were pretreated with cyanamide and 4-MP, the depressive effect of cyanamide on the locomotor activity induced by ethanol disappeared, and the locomotor activity rose to levels similar to those of the control group, recovering the biphasic ethanol effect. These effects cannot be attributed to peripheral elevated blood acetaldehyde levels, as pretreatment with 4-MP prevents accumulation of acetaldehyde. These data might suggest some influence of brain catalase and aldehyde dehydrogenase (ALDH) on the effects of ethanol.

Determination of in vivo adducts of disulfiram with mitochondrial aldehyde dehydrogenase

Extensive use for disulfiram (DSF) has been found in the aversion therapy treatment of recovering alcoholics. Although it is known to irreversibly inhibit hepatic aldehyde dehydrogenase (ALDH), the specific mechanism of in vivo inhibition of the enzyme by the drug has not been determined yet. We have demonstrated in this report a novel, but simple and rapid method for structurally characterizing in vivo derived protein-drug adducts by linking on-line sample processing to HPLC-electrospray ionization mass spectrometry (HPLC-MS) and HPLC-tandem mass spectrometry (HPLC-MS/MS). Employing this approach, rats were administered DSF, and their liver mitochondria were isolated and solubilized. Both native and in vivo DSF-treated mitochondrial ALDH (mALDH) were purified in one step with an affinity cartridge. The in vivo DSF-treated mALDH showed 77% inhibition in enzyme activity as compared with that of the control. Subsequently, the control and DSF-inhibited mALDH were both subjected to HPLC-MS analyses. We were able to detect two adducts on DSF-inhibited mALDH, as indicated by the mass increases of approximately 71 and approximately 100 Da. To unequivocally determine the site and structure of these adducts, on-line pepsin digestion-HPLC-MS and HPLC-MS/MS were performed. We observed two new peptides at MH(+) = 973.7 and MH(+) = 1001.8 in the pepsin digestion of DSF-inhibited enzyme. These two peptides were subsequently subjected to HPLC-MS/MS for sequence determination. Both peptides possessed the sequence FNQGQC(301)C(302)C(303), derived from the enzyme active site region, and were modified at Cys(302) by N-ethylcarbamoyl (+71 Da) and N-diethylcarbamoyl (+99 Da) adducts. These findings indicated that N-dealkylation may be an important step in DSF metabolism, and that the inhibition of ALDH occurred by carbamoylation caused by one of the DSF metabolites, most likely S-methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO). Finally, there was no evidence of the presence of an intramolecule disulfide bridge modification on the peptide FNQGQCCC.

Effect of enzyme inhibitors on protein quaternary structure determined by on-line size exclusion chromatography-microelectrospray ionization mass spectrometry

Aldehyde dehydrogenases (ALDH) are a family of enzymes primarily involved in the oxidation of various aldehydes. Most ALDH enzymes derived from mammalian sources have been shown to exist as homotetramers, consisting of four identical subunits of approximately 54 kDa. The presence of the homotetramer appears to be necessary for enzyme activity. In this study, recombinant rat liver mitochondrial ALDH (rmALDH) was inhibited in vitro with four different inhibitors, namely, disulfiram (MW, 296.5), prunetin (MW, 284.3), benomyl (MW, 290.3), and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) (MW, 351.8). Subsequently, inhibited rmALDH was analyzed by a novel approach of on-line size exclusion chromatography-microelectrospray ionization-mass spectrometry (SEC-muESI-MS) to examine the noncovalent quaternary structural stability of the inhibited enzyme. Analysis of native rmALDH by SEC-muESI-MS revealed predominantly the homotetramer (Mr = approximately 217,457 Da, +/- 0.01%) with some in-source, skimmer-induced dissociation to afford monomer (Mr = approximately 54,360 Da, +/- 0.01%). Both disulfiram and prunetin inhibited rmALDH by >70% and >90%, respectively, but did not disrupt the quaternary structure of rmALDH. Furthermore, there was no detectable change within experimental error (+/- 0.01%) of the disulfiram or the prunetin homotetramers (Mr = approximately 217,448 Da and Mr = approximately 217,446 Da). This may possibly indicate that inhibition occurred via formation of intramolecular disulfide bond at the enzyme active site, or weak affinity noncovalent binding. In contrast, benomyl-inhibited rmALDH homotetramer (>90% inhibition) exhibited a Mr = approximately 217,650 Da (+/- 0.01%) corresponding to two butylcarbamoyl adducts on two of the four enzyme subunits. The skimmer-induced monomer afforded a mixture of unmodified rmALDH (Mr = approximately 54,365 Da, +/- 0.01%) and butylcarbamoylated enzyme (Mr = approximately 54,459 Da, +/- 0.01%). Finally, TPCK (>90% inhibition) modified all four subunits of rmALDH to give Mr = approximately 218,646 Da (+/- 0.01%). In all four cases while significant enzyme inhibition occurred, no destabilization of the quaternary complex was detected.

Role of disulfiram in the in vitro inhibition of rat liver mitochondrial aldehyde dehydrogenase

The alcohol aversion therapy drug disulfiram has been shown to inhibit hepatic aldehyde dehydrogenase (ALDH), one of the key enzymes involved in ethanol metabolism. It is believed by some that disulfiram could be one of the active inhibitors in vivo. However, the actual interaction between disulfiram and ALDH remains ambiguous. We report here that when disulfiram inhibited recombinant rat liver mitochondrial ALDH (rlmALDH) in vitro, no significant molecular mass increase was detected during the first 30 min as determined by on-line HPLC-electrospray ionization mass spectrometry (LC-MS). This indicated that the inhibition in vitro was not caused directly by covalent adduct formation on the enzyme. We subsequently subjected both control and disulfiram-inhibited rlmALDH to Glu-C proteolytic digestion. LC-MS analysis of the Glu-C digestion of disulfiram-inhibited enzyme revealed that one peptide of M(r) = 4821, which contained the putative active site of the enzyme, exhibited a mass decrease of 2 amu as compared with the same peptide found in the Glu-C digestion of the control (M(r) = 4823). We believe that the loss of 2 amu indicated that inhibition of rlmALDH in vitro was due to formation of an intramolecular disulfide bond between two of the three adjacent cysteines in the active site, possibly via a very rapid and unstable mixed disulfide interchange reaction. Further confirmation of the intramolecular disulfide bond formation came from the fact that by adding dithiothreitol (DTT) we were able to recover partial enzyme activity. In addition, the peptide of M(r) = 4821 observed in the Glu-C digestion of the disulfiram-treated ALDH reverted to M(r) = 4823 after treatment with DTT, which indicated that the disulfide bond was reduced. We, thereby, conclude that disulfiram inhibited rlmALDH by forming an intramolecular disulfide, possibly via a fast intermolecular disulfiram interchange reaction.

Glutathione carbamoylation with S-methyl N,N-diethylthiolcarbamate sulfoxide and sulfone. Mitochondrial low Km aldehyde dehydrogenase inhibition and implications for its alcohol-deterrent action

S-Methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) and sulfone (DETC-MeSO2) both inhibit rat liver low Km aldehyde dehydrogenase (ALDH2) in vitro and in vivo (Nagendra et al., Biochem Pharmacol 47: 1465-1467, 1994). DETC-MeSO has been shown to be a metabolite of disulfiram, but DETC-MeSO2 has not. Studies were carried out to further investigate the inhibition of ALDH2 by DETC-MeSO and DETC-MeSO2. In an in vitro system containing hydrogen peroxide and horseradish peroxidase, the rate of DETC-MeSO oxidation corresponded to the rate of DETC-MeSO2 formation. Carbamoylation of GSH by both DETC-MeSO and DETC-MeSO2 was observed in a rat liver S9 fraction. Carbamoylation of GSH was not observed in the presence of N-methylmaleimide. In in vitro studies, DETC-MeSO and DETC-MeSO2 were equipotent ALDH2 inhibitors when solubilized mitochondria were used, but DETC-MeSO was approximately four times more potent than DETC-MeSO2 in intact mitochondria. In studies with rats, the dose (i.p. or oral) required to inhibit 50% ALDH2 (ED50) was 3.5 mg/kg for DETC-MeSO and approximately 35 mg/kg for DETC-MeSO2, approximately a 10-fold difference. Furthermore, maximum ALDH2 inhibition occurred 1 hr after DET(-MeSO administration, whereas maximal ALDH2 inhibition occurred 8 hr after DETC-MeSO2 dosing. DETC-MeSO is, therefore, not only a more potent ALDH2 inhibitor than DETC-MeSO2 in vivo, but also in vitro when intact mitochondria are utilized. The in vitro results thus support the in vivo findings. Since oxidation of DETC-MeSO can occur both enzymatically and non-enzymatically, it is possible that DETC-MeSO2 is formed in vivo. DETC-MeSO2, however, is not as effective as DETC-MeSO in inhibiting ALDH2, probably because it has difficulty penetrating the mitochondrial membrane. Thus, even if DETC-MeSO2 is formed in vivo from DETC-MeSO, it is the metabolite DETC-MeSO that is most likely responsible for the inhibition of ALDH2 after disulfiram administration.

Inhibition of human mitochondrial aldehyde dehydrogenase by the disulfiram metabolite S-methyl-N,N-diethylthiocarbamoyl sulfoxide: structural characterization of the enzyme adduct by HPLC-tandem mass spectrometry

S-Methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO) is a known metabolite of the aversion therapy drug disulfiram (DSF). MeDTC-SO is also a potent inhibitor of human mitochondrial aldehyde dehydrogenase (hmALDH) with an IC50 of 1.5 microM. Inhibition of the enzyme by MeDTC-SO resulted in the addition of approximately 100 Da to the molecular mass of the intact protein, as determined by on-line HPLC-electrospray ionization MS (LC-MS). Dialysis of the inhibited protein did not reverse the inhibition, and the molecular mass of 54,533 Da (+/- 0.01%) remained unchanged, indicating that a covalent modification of the protein had occurred. Proteolytic digestion of hmALDH under basic conditions using trypsin at pH 7.8 revealed that the adduct was base labile. However, treating the adducted protein with endopeptidase-Glu-C at pH 3.7 produced a peptide adduct at MH+ = 4924, tentatively attributable to a carbamoylated peptide. This peptide contains three adjacent cysteines, one of which has been implicated as a key amino acid in the highly conserved active site region of ALDH. A pepsin digestion of hmALDH carried out at pH 3.7 and subsequent LC-MS analysis revealed an ion at MH2(2+) = 501.5, corresponding to the carbamoylated peptide FNQGQC1C2C3. This peptide contains the same adjacent active site cysteines. This latter peptide was subjected to LC-MS/MS, which enabled us to determine that the site of carbamoylation was at Cys2. The MS/MS product ion data also confirmed the presence of a carbamoyl group as the adduct species.

Determination of acetaldehyde in biological samples by gas chromatography with electron-capture detection

A simple specific assay was developed for the determination of acetaldehyde in biological samples. Acetaldehyde was derivatized to 2,4-dinitrophenylhydrazone, which was determined by gas chromatography with electron-capture detection. The use of this detection method is an important device to which no one drew notice. This procedure was very simple and so sensitive that as little as 500 fmol of acetaldehyde could be measured in aqueous solution. The calibration curve of acetaldehyde was linear at least up to 40 microM. Its recoveries from human plasma and rat liver homogenate were 96.5 and 95.7%, respectively.

Inhibition of aldehyde dehydrogenase by disulfiram and its metabolite methyl diethylthiocarbamoyl-sulfoxide

Disulfiram (DSF) is presently the only available drug used in the aversion therapy of recovering alcoholics. It acts by inhibiting aldehyde dehydrogenase (ALDH), leading to high blood levels of acetaldehyde. The in vitro inhibition of ALDH by DSF and its metabolites was systematically studied by combined enzyme inhibition assay with direct molecular weight determination of the same sample using electrospray ionization-mass spectrometry (ESI-MS). Enzyme activity was measured after incubating yeast ALDH (yALDH) with excess concentrations of DSF, methyl diethyldithiocarbamate (MeDDC) and methyl diethylthiocarbamoyl-sulfoxide (MeDTC-SO) and then subjected to analysis by ESI-MS. Addition of DSF resulted in complete enzyme inhibition; however, ESI-MS analysis demonstrated no discernible shift in molecular weight, indicating that no intermolecular adduct was formed with the protein. Treatment of yALDH with MeDTC-SO also completely abolished yALDH activity with a concomitant increase of + approximately 100 Da in the molecular mass of the enzyme. This indicated formation of a covalent carbamoyl protein adduct. Furthermore, the effects of dithiothreitol (DTT) were examined on samples of inhibited protein in vitro. At pH 7.5, DTT completely reversed inhibition after DSF treatment. yALDH inhibited by MeDTC-SO could not be recovered by DTT at pH 7.5, but at pH 9 the enzymic activity was fully restored and a mass loss of approximately 100 Da was noted. This observations are consistent with mechanisms where inhibition of yALDH by DSF in vitro involves oxidation of the active site, whereas MeDTC-SO forms a covalent adduct with the protein in vitro resulting in cessation of enzyme activity.

Effects of disulfiram on positron emission tomography and neuropsychological studies in severe chronic alcoholism

Disulfiram is an aldehyde dehydrogenase inhibitor that is widely used as an adjunctive agent in the treatment of patients with severe chronic alcoholism. Recent positron emission tomography (PET) studies of local cerebral metabolic rates for glucose (ICMRglc) and benzodiazepine receptor binding in alcoholic patients have shown regional cerebral abnormalities; however, some of the patients were studied while receiving disulfiram, which could influence the biochemical processes under investigation. In a retrospective investigation, we examined the influence of disulfiram administration on the results of PET studies of ICMRglc and benzodiazepine receptor binding and neuropsychological tests of cognition and executive function in patients with severe chronic alcoholism. [18F]Fluorodeoxyglucose was used to measure ICMRglc in 48 male patients, including 11 receiving and 37 not receiving disulfiram in therapeutic doses. [11C]Flumazenil was used to measure benzodiazepine receptor binding in 17 male patients, including 3 receiving and 14 not receiving disulfiram. All patients studied with FMZ were also examined with fluorodeoxyglucose. PET studies of ICMRglc revealed significantly decreased global values in the patients receiving disulfiram compared with those not receiving disulfiram. PET studies of benzodiazepine receptor binding revealed decreased flumazenil influx and distribution volume in patients receiving disulfiram. The neuropsychological tests demonstrated no differences between the two groups of subjects. The findings suggest that disulfiram may influence the results of PET studies of glucose metabolism and benzodiazepine receptor binding.

Suppression of alcohol intake after administration of the Chinese herbal medicine, NPI-028, and its derivatives

The Chinese herbal medicine, NPI-028, has been used for centuries in China to counteract alcohol intoxication. The present study used a number of different experimental conditions to determine whether NPI-028 and its derivatives might selectively influence alcohol intake in rodents that naturally exhibit high alcohol intakes. It was determined that intraperitoneal (i.p.) injections of NPI-028 (0.5, 0.75, and 1.0 g/kg) suppressed alcohol intake by up to 30% in both alcohol-preferring P and Fawn-Hooded (FH) rats during a continuous access schedule. These injections did not significantly affect food or water intakes, nor did the highest dose of NPI-028 (1 g/kg) alter blood ethanol levels after an i.p. injection of 2.5 g/kg of ethanol. In P rats, it was found that NPI-028 was orally active with the dose of 1.5 g/kg having a greater effect on ethanol intake than the 1.0 g/kg dose; once again, food and water intakes were not significantly altered. In FH rats maintained on a limited access schedule (1 hr/day), alcohol intake was completely abolished by 1.5 g/kg of NPI-028. Chronic i.p. administration of NPI-028 (0.75 g/kg) for four consecutive days in FH rats maintained on a continuous access schedule did not lead to any diminution of its alcohol-suppressant effects. Thus, NPI-028 has significant effects on alcohol intake without much effect on water and food intake, and tolerance does not readily develop to these effects. The i.p. administration of a partially purified extract (NPI-031) of NPI-028, obtained by countercurrent chromatography, also dose-dependently suppressed ethanol intake in FH rats, but the highest dose 200 mg/kg) also significantly decreased food intake. Finally, the i.p. administration of puerarin (NPI-31G), an isoflavone isolated from NPI-031 by countercurrent chromatography, significantly reduced ethanol intake in FH rats without affecting food or water intake. Therefore, NPI-028 and one of its pure components, NPI-031G, selectively reduced ethanol intake in alcohol-preferring rats.

Inhibition of rat liver low Km aldehyde dehydrogenase by thiocarbamate herbicides. Occupational implications

S-Methyl N,N-diethylthiolcarbamate (DETC-Me) is a metabolite formed during the bioactivation of disulfiram. The formation of its corresponding sulfoxide, S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO), from DETC-Me is required for low Km mitochondrial aldehyde dehydrogenase (ALDH2, EC 1.2.1.3) inhibition. DETC-Me is similar in structure to thiocarbamate herbicides with the general structure R1R2NC(O)SR3. Representative herbicides studied were n-propyl, n-propylthiocarbamate ethyl ester (EPTC), molinate, vernolate, ethiolate and butylate. All of these thiocarbamate herbicides inhibited rat liver ALDH2 in vivo. The dose of these thiocarbamates that inhibited rat liver ALDH2 by 50% (ID50) when administered 8 hr before determination of ALDH2, was found to be 5.2, 3.1, 1.6, 12, and 174 mg/kg, respectively. These thiocarbamates were ineffective rat liver ALDH2 inhibitors in vitro, unless rat liver microsomes and an NADPH-generating system were added to the incubation. The respective thiocarbamate sulfoxides were formed when the thiocarbamates were incubated with liver microsomes and an NADPH-generating system. The thiocarbamate sulfoxides all inhibited rat liver ALDH2 in vitro. An equimolar dose of molinate and molinate sulfoxide inhibited rat liver ALDH2 in vivo to the same degree. Molinate-treated rats challenged with ethanol exhibited a disulfiram-like ethanol reaction. In conclusion, thiocarbamate herbicides inhibit ALDH2, probably due to the formation of their sulfoxide, and therefore have the potential to produce a disulfiram-like ethanol reaction in an unsuspecting population.

Role of retinal metabolism in methanol-induced retinal toxicity

Methanol is a toxicant that causes systemic and ocular toxicity after acute exposure. The folate-reduced (FR) rat is an excellent animal model that mimics characteristic human methanol toxic responses. The present study examines the role of the methanol metabolites formaldehyde and formate in the initiation of methanol-induced retinal toxicity. After a single oral dose of 3.0 g/kg methanol, blood methanol concentrations were not significantly different in FR rats compared with folate-sufficient (FS) (control) rats. However, FR rats treated with 3.0 g/kg methanol displayed elevated blood (14.6 mM) and vitreous humor (19.5 mM) formate levels and abnormal electroretinograms (loss of b-wave) 48 h postdose. FR rats pretreated with disulfiram (DSF) prior to 3.0 g/kg methanol treatment failed to display these symptoms. Formaldehyde was not detected in blood or vitreous humor with or without DSF treatment, suggesting that formate is the toxic metabolite in methanol-induced retinal toxicity. Additionally, creating a blood formate profile (14.2 mM at 48 h) similar to that observed in methanol-treated rats by iv infusion of pH-buffered formate does not alter the electroretinogram as is observed with methanol treatment. These data suggest that intraretinal metabolism of methanol is necessary for the formate-mediated initiation of methanol-induced retinal toxicity.

Diethyldithiocarbamate methyl ester sulfoxide, an inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase and putative metabolite of disulfiram

S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) is a potent inhibitor of rat liver mitochondrial low Km aldehyde dehydrogenase (ALDH2) both in vivo and in vitro, and has been proposed to be the metabolite responsible for ALDH2 inhibition by disulfiram. Diethyldithiocarbamate methyl ester (DDTC-Me), a key intermediate in the metabolism of disulfiram, has been shown to be bioactivated by microsomal monooxygenases to diethyldithiocarbamate methyl ester sulfoxide (DDTC-Me sulfoxide). Studies were conducted to determine if DDTC-Me sulfoxide was also an active metabolite of disulfiram and inhibitor of ALDH2. DDTC-Me sulfoxide inhibited ALDH2 in vitro with an IC50 of 10 microM, and in vivo with an ID50 of 31 mg/kg (170 mumol/kg). Maximal ALDH2 inhibition in vivo was observed 8 hr after the administration of 45.2 mg/kg DDTC-Me sulfoxide, with ALDH2 activity returning to control levels after 48 hr. Although DDTC-Me sulfoxide inhibited ALDH2 in vivo, DDTC-Me sulfoxide was not detected in plasma from rats treated with either disulfiram (75 mg/kg), DDTC-Me (122.25 mg/kg), or DDTC-Me sulfoxide (45.2 mg/kg). However, DDTC-Me and S-methyl N,N-diethylthiolcarbamate (DETC-Me) were detected in plasma from rats treated with DDTC-Me sulfoxide. In rats treated with DDTC-Me sulfoxide and challenged with ethanol, a small increase of approximately microM in blood acetaldhyde and an inconsistent drop in blood pressure was observed. In conclusion, DDTC-Me sulfoxide inhibited ALDH2 in vitro and in vivo, was less potent than DETC- MeSO, and was not detected after disulfiram administration.

In vivo pharmacodynamic studies of the disulfiram metabolite S-methyl N,N-diethylthiolcarbamate sulfoxide: inhibition of liver aldehyde dehydrogenase

S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) is proposed to be the metabolite of disulfiram responsible for the in vivo inhibition of liver low Km aldehyde dehydrogenase (ALDH) in the rat. Studies were conducted in male Sprague-Dawley rats and also in vitro using both rat liver mitochondrial and purified bovine mitochondrial low Km ALDH to investigate further the pharmacodynamic and pharmacokinetic characteristics of DETC-MeSO. Administration of DETC-MeSO to rats produced a rapid and maximal inhibition of liver mitochondrial low Km ALDH within 2 hr, which was still inhibited 30% after 168 hr. After DETC-MeSO treatment, the maximum plasma concentration of DETC-MeSO was reached within 0.5 hr, with DETC-MeSO being undetectable 2 hr after DETC-MeSO dosing. Although a trace amount of DETC-Me was detected in the plasma 0.5 hr after DETC-MeSO administration to rats, this disappeared within 1 hr. When rats were treated with disulfiram, the maximal plasma concentration of DETC-MeSO was found within 2 hr, with only a very small quantity of DETC-MeSO still detectable after 8 hr. Rats also were given the disulfiram metabolites diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), and S-methyl N,N-diethylthiolcarbamate (DETC-Me), and plasma analyzed for DETC-MeSO 2 hr after the administration of these metabolites. DETC-MeSO was detected in plasma, further illustrating that DETC-MeSO can be found in plasma after the administration of either disulfiram, or the subsequent in vivo metabolites DDTC, DDTC-Me, or DETC-Me.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehyde dehydrogenase of mice inhibited by thiocarbamate herbicides

The herbicide S-ethyl N,N-dipropylthiocarbamate (EPTC) and three of its candidate metabolites (the sulfoxide, N-depropyl and S-methyl derivatives) inhibit mitochondrial low-Km aldehyde dehydrogenase (ALDH) in liver by 56 to 82% 2 hr after these thiocarbamates are administered intraperitoneally (ip) to mice at 8 mg/kg. They also greatly elevate the acetaldehyde level (determined as the O-benzyloxime ether) in blood (up to 500 microM) and brain (up to 3 ppm) 30 min after two ip treatments, the first with the thiocarbamate at 40 mg/kg and 2 hr later with ethanol at 1000 mg/kg. EPTC at 4 mg/kg inhibits liver ALDH activity by 50% and at 8 and 18 mg/kg gives half of the maximum ethanol-dependent elevation of acetaldehyde levels in blood and brain, respectively. The in vivo effects of other thiocarbamate herbicides at 8 mg/kg on ALDH activity and 40 mg/kg on acetaldehyde levels decrease in the order of thiobencarb, pebulate, vernolate and molinate > butylate and triallate >> cycloate. The percentage inhibition of liver ALDH activity generally correlates with the elevation in blood and brain acetaldehyde under these treatment protocols. B.W. Hart and M.D. Faiman (Biochem. Pharmacol. 43 403-406, 1992) have shown that the alcohol-aversion drug disulfiram is metabolized to S-methyl N,N-diethylthiocarbamate and its sulfoxide as the penultimate and ultimate metabolites inhibiting ALDH. Thus, the thiocarbamate herbicides and their metabolites are similar to the disulfiram metabolites not only in homologous structure but also in their potency range as ALDH inhibitors in vivo. On this basis some of the thiocarbamate herbicides may sensitize agricultural workers to ethanol intoxication.

Bioactivation of S-methyl N,N-diethylthiolcarbamate to S-methyl N,N-diethylthiolcarbamate sulfoxide. Implications for the role of cytochrome P450

Diethyldithiocarbamate (DDTC), diethyldithiocarbamate methyl ester (DDTC-Me), S-methyl N,N-diethylthiolcarbamate (DETC-Me) and S-methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) are all metabolites of disulfiram. All inhibit rat liver low Km aldehyde dehydrogenase (ALDH) in vivo, with the order of potency being DETC-MeSO > DETC-Me > DDTC-Me > DDTC. Studies were carried out both in vivo and in vitro to further investigate the role of bioactivation as a requirement for the action of disulfiram as a liver ALDH inhibitor. The cytochrome P450 inhibitor 1-benzylimidazole (NBI) was employed as a pharmacological tool to study the metabolism of DETC-Me to DETC-MeSO. Administration of NBI to rats prior to DETC-Me treatment blocked the inhibition of liver mitochondrial low Km ALDH by DETC-Me. This was accompanied by an increase in plasma DETC-ME and a decrease in plasma DETC-MeSO. Pretreatment of rats with NBI prior to DETC-MeSO administration did not block the inhibition of liver mitochondrial low Km ALDH by DETC-MeSO. In in vitro studies, the inclusion of NBI in an incubation containing rat liver microsomes, mitochondria and an NADPH-generating system blocked the formation of DETC-MeSO and inhibition of liver mitochondrial low Km ALDH by DETC-Me. DETC-MeSO was found to be a potent inhibitor of rat liver mitochondrial low Km ALDH both in vivo and in vitro. The data suggest that the metabolism of DETC-Me to DETC-MeSO is mediated by cytochrome P450, and that inhibition of cytochrome P450 by inhibitors such as NBI block the inhibition of low Km ALDH by DETC-Me.

Techniques to enhance compliance with disulfiram

Pharmacodynamic benefits of disulfiram in the treatment of alcoholism have yet to be clearly demonstrated. Nevertheless, research does suggest that disulfiram may well have positive effects on drinking if medicational compliance procedures are employed. This paper reviews research on four strategies for enhancing disulfiram compliance: implants, incentives, contracts, and patient information. Generalizations about the strategies are drawn and needs for future research are briefly addressed.

The pharmacology and toxicology of disulfiram and its metabolites

Disulfiram (Antabuse) is one of several aldehyde dehydrogenase (ALDH) inhibitors that raise the plasma level of acetaldehyde following ethanol ingestion. The usually pleasant reaction to ethanol is thereby changed to an unpleasant one, owing to a number of bodily reactions to acetaldehyde. Populations showing genetic polymorphism with a lack of some isozymes of ALDH have exhibited an intolerance to ethanol similar to that seen with disulfiram. A normal isozyme pattern seems to be a prerequisite for the development of alcoholism, which supports the principle of disulfiram treatment. Disulfiram is an irreversible ALDH inhibitor when administered in vivo. Diethylthiomethylcarbamate (Me-DTC) is formed from disulfiram in three metabolic steps. This compound and two further oxidized metabolites appear to be active metabolites of disulfiram. Measurements of plasma Me-DTC or the reduction of leucocyte ALDH 1 activity may be valuable markers for the proper dose titration of disulfiram and the rational use of this drug. Some toxicological points are discussed.

In vitro and in vivo inhibition of rat liver aldehyde dehydrogenase by S-methyl N,N-diethylthiolcarbamate sulfoxide, a new metabolite of disulfiram

In summary, these data provide the first evidence that DETC-MeSO is a natural metabolite of disulfiram, and a potent inhibitor of rat liver mitochondrial low Km ALDH both in vitro and in vivo. It is therefore proposed that, based upon evidence to date, DETC-MeSO appears to be the chemical species to which disulfiram must be bioactivated, and is the metabolite most likely responsible for disulfiram's inhibition of rat liver mitochondrial low Km ALDH in vivo. Characterization of the properties of DETC-MeSO as the metabolite responsible for disulfiram's action as an ALDH inhibitor is presently in the process of being completed.

Disulfiram metabolism as a requirement for the inhibition of rat liver mitochondrial low Km aldehyde dehydrogenase

In humans and animals, disulfiram produces a disulfiram-ethanol reaction after an ethanol challenge, the basis of which is the inhibition of liver aldehyde dehydrogenase (ALDH). Disulfiram and the metabolites diethyldithiocarbamate (DDTC), diethyldithiocarbamate-methyl ester (DDTC-Me), and S-methyl-N,N-diethylthiolcarbamate (DETC-Me) were studied in order to determine the role of bioactivation in disulfiram's action as an inhibitor of rat liver mitochondrial low Km ALDH (RLM low Km ALDH). In in vitro studies, disulfiram and DDTC (0.01 to 2.0 mM) both inhibited RLM low Km ALDH in a concentration-dependent manner. The addition of rat liver microsomes to the mitochondrial incubation did not further increase disulfiram-induced RLM low Km ALDH inhibition. However, DDTC-induced RLM low Km ALDH inhibition was increased further, but only at DDTC concentrations less than 0.05 mM. DDTC-Me and DETC-Me (2.0 mM) similarly exhibited an increased RLM low Km ALDH inhibition after the addition of liver microsomes. In in vivo studies, disulfiram (75 mg/kg), DDTC (114 mg/kg), DDTC-Me (41.2 mg/kg) or DETC-Me (18.6 mg/kg) administered i.p. to female rats inhibited RLM low Km ALDH. Inhibition of drug metabolism by pretreatment of rats with the cytochrome P450 inhibitor N-octylimidazole (NOI) (20 mg/kg, i.p.) prior to either disulfiram, DDTC, DDTC-Me or DETC-Me administration blocked the inhibition of RLM low Km ALDH. The in vitro and in vivo data support the conclusion that bioactivation of disulfiram to a reactive chemical species is required for RLM low Km ALDH inhibition and a disulfiram-ethanol reaction.

Effect of some thiocarbamate compounds on aldehyde dehydrogenase and implications for the disulfiram ethanol reaction

The effects of S-methyl diethyldithiocarbamate, S-methyl diethylmonothiocarbamate and bis(diethylcarbamoyl) disulphide on sheep liver cytoplasmic aldehyde dehydrogenase were investigated in vitro. The first compound has negligible effect. The second one is a weak inhibitor of the esterase activity of the enzyme and a weaker inhibitor of the dehydrogenase activity. A very low concentration of the third compound, however, acts as a potent inactivator of aldehyde dehydrogenase, similar in this respect to disulfiram, although somewhat slower to react. The possible involvement of these compounds in the physiological phenomenon known as the disulfiram ethanol reaction is discussed.

Pharmacotherapies for alcoholism: promising agents and clinical issues

The past 10 years have witnessed important advances in research on pharmacotherapy for alcoholism. Promising drugs are discussed under six headings: agents to treat alcohol withdrawal; anticraving agents; agents that make drinking an aversive experience; agents to alleviate concomitant psychiatric problems; agents to treat concurrent drug abuse; and amethystic ("sobering-up") agents. Research on the drug classes is summarized and clinical issues surrounding specific agents and alcoholism pharmacotherapy in general are discussed. Finally, long-range therapeutic implications of recent findings on the actions of alcohol on basic mechanisms of the brain are offered.

Dystonia and akinesia due to pallidoputaminal lesions after disulfiram intoxication

A case with segmental cranial plus crural dystonia of delayed onset and akinesia after acute intoxication with disulfiram is presented. Computed tomography showed bilateral pallidal lesions, whereas on magnetic resonance imaging additional small lesions of the putamen could be detected. Long-term observation with progression and a change of symptoms over a period of 10 years after the intoxication is demonstrated on videotape. Although other central side effects after intoxication with disulfiram are well known, movement disorders are uncommon. Carbon disulfide, a disulfiram metabolite, may be important in the etiopathogenesis.

S-methyl-N,N-diethylthiolcarbamate: a disulfiram metabolite and potent rat liver mitochondrial low Km aldehyde dehydrogenase inhibitor

S-methyl-N,N-diethylthiolcarbamate-methyl ester (DETC-Me), a proposed disulfiram metabolite, was investigated both in vivo and in vitro for its effectiveness as a liver mitochondrial low Km aldehyde dehydrogenase (L Km ALDH) inhibitor. Male Sprague-Dawley rats were treated intraperitoneally with DETC-Me, killed at various times and L Km ALDH determined. DETC-Me was found to be a more potent in vivo inhibitor of L Km ALDH than either disulfiram, diethyldithiocarbamate (DDTC) or diethyldithiocarbamate-methyl ester (DDTC-Me). The ID50 for DETC-Me, DDTC-Me and disulfiram was 6.5, 15.5 and 56.2 mg/kg, respectively. The ID50 for DDTC was similar to DDTC-Me. Maximal inhibition of L Km ALDH occurred 30 minutes after DETC-Me administration. DETC-Me was ineffective as an in vitro inhibitor. DETC-Me produced a marked disulfiram-ethanol reaction (DER) at one-quarter of the dose of disulfiram or DDTC. Plasma DETC-Me in rats was greater after DETC-Me administration than after DDTC-Me, DDTC or disulfiram. In conclusion, DETC-Me is proposed to be a metabolite of disulfiram, and may be the immediate precursor of the chemical species responsible for L Km ALDH inhibition.